Thursday, July 1, 2010

The Aesthetics of Space Travel



The deep space ship above (click on the image for full sized view) was inspired by the Travel Planner spreadsheet in the previous post, and modeled in the wonderfully simple and handy DoGA 3D modeler. The shuttle alongside is a rough approximation of the NASA shuttle, and thus a thorough anacronism in this image, but provided as a scale reference.

Of course you want some specifications of the ship. Even if you don't, you get them anyway:

Length Overall: 300 meters
Departure Mass: 10,000 tons
Propellant Load: 5000 tons (H2)
Drive Mass: 2000 tons
Keel and Tankage: 1000 tons

Gross Payload: 2000 tons
Flyway Cost: $5 billion (equivalent)

The payload includes a hab with berthing space for 50-200 passengers and crew, depending on mission duration, and a pair of detachable pods for 500 tons of express cargo, plus service bays and the like.

What this ship can do depends on its drive engine performance. If the drive puts out 2 gigawatts of thrust power - my baseline for a Realistic [TM] nuke electric drive - the ship can reach Mars in three months, give or take. (The sim gave 92 days for a 0.8 AU trip in flat space.) With a later generation drive putting out 20 gigawatts it can reach Mars in a little over a month, or Saturn in eight months.

The general arrangement of this ship is driven by design consideration - a nuclear drive that needs to be a long way from the crew, with large radiators to shed its waste heat; tanks for bulky liquid hydrogen; and a spinning hab section. Most serious proposals for deep space craft in the last 50 years have had more or less this arrangement - the movie 2001 left off the radiator fins, because in those days the audience would have been puzzled that a deep space ship had 'wings.'

A large, long-mission military craft, such as a laser star, might not look much different overall - replace the cargo pods with a laser installation and side-mounted main mirror, and perhaps a couple of smaller mirrors on rotating 'turret' mounts. Discussions here have persuaded me that heavy armor is of little use against the most likely threats facing such a ship.

Within these broad constraints, however, spaceships offer a great deal of design freedom, more than most terrestrial vehicles. Ships, planes, and faster land vehicles are all governed by fluid dynamics, and even movable shipyard cranes must conform to a 1-g gravity field. A spaceship, unless built for aerobraking, will never encounter fluid flow, and the forces exerted by high specific impulse drives - even torch level drives - are relatively gentle.

This ship might have had two propellant tanks, or half a dozen, instead of four. And the entire industrial assemblage of tanks and girders might be concealed, partly or entirely, within a 'hull' of sheeting no thicker than foil, protecting tanks and equipment from shifting heat exposure due to sunlight and shadow. Much of the ISS keel girder has a covering of some sort - in close-ups it looks a lot like canvas - that in more distant views gives the impression of a solid structure.

In fact the visual image of the ISS is dominated by its solar wings and radiators. The hab structure is fairly inconspicuous by comparison, like the hull of a sailing ship under full sail. This would be true to an extreme of solar electric ships; a 1-gigawatt solar electric drive would need a few square kilometers of solar wings. Even nuclear drives, fission or fusion, require extensive radiators - probably more than I showed - with other ship systems needing their own radiators, at varied operating temperatures. Unless the ship has an onboard reactor it must also have solar collectors for use when the drive is shut down.

All of which may do more to catch the eye than heavier but smaller structures such as the hab or even propellant tankage. And then there is color: the gold foil of the main ISS solar wings, for example.


Hollywood knows nothing of this (though I'm surprised they haven't picked up on the gold foil). Hollywood is no more interested in what real spaceships look like than it is in how they maneuver. This is only natural, even though we hard SF geeks complain. Hollywood doesn't care because its audience has almost no clue of what spaceships look like, or act like, getting most of their impressions from Hollywood itself.

The one actual spacecraft to have iconic visual status, the Shuttle, essentially looks like an airplane. The ISS has not yet acquired iconic status, though it may, especially after the Shuttle is retired. And perhaps it looks so unlike terrestrial vehicles that our eye does not yet know quite what to make of it.

As a point of comparison, watch aviation scenes in old movies, especially from before World War II. You'll see airplanes whooshing past (sometimes in pretty unconvincing special effects shots), but you will rarely see what is now a standard shot - a plane filmed from another plane in formation, hanging 'motionless' on the screen, clouds and distant landscape rolling slowly past, until perhaps the plane banks and turns away.

It is a standard shot because it is so very effective. But older movies rarely used it, because audiences would have had no idea what they were seeing. Everyone knew that airplanes were fast, and had at least some idea that their speed is what kept them in the air. A plane apparently hanging in midair would make no sense.

What changed all this, I would guess, is World War II. A flood of newsreel footage included many formation shots, and audiences gradually absorbed a feeling for what midair footage really looks like. When a postwar Jimmy Stewart enlisted for Strategic Air Command (1955), Hollywood - and its audience - were ready to see the B-36 and B-47 showcased in all their glory, including airborne formation shots.

I know what you bloodthirsty people are thinking - one good space war, and everyone will grok the visual language of space travel. Shame on you. Given enough civil space development, and time, people will get the hang of it.


The beauty of spaceships is in the eye of the beholder. The familiar aesthetics of terrestrial vehicles are as irrelevant to them as to Gothic cathedrals (which in some broad philosophical sense are themselves spaceships of a sort). General principles of design will provide some guidance. Even in making the quick thrown-together model above I found that slight changes in proportion could make the difference between a jumble of parts and a unity.

But the real visual impact of spaceships is something we will only learn from experience, by the glint of a distant sun.


Related posts: I looked at the characteristics - and overall conceptual elegance - of solar electric drive in On Gossamer Wings.

103 comments:

Cityside said...

Stewart certainly knew plenty about formation flying.

Rick said...

As a movie, Strategic Air Command is pretty lame, 50s schlock, but the flying sequences are AWESOME.

longbeast said...

I'm going to assume you know about Orbiter, the spaceflight sim. Have you ever tried converting models like this into ships usable as orbiter addons?

Making them work properly is sightly more complex than just listing mass, size, isp and so on, but not much more complex.

nqdp said...

I think this is a really great post to come right after the handy trip-planner one. I read it as something along the lines of "Hard SF geeks spend all of our time figuring out how much fuel our ships need to carry, but the only way to really connect to anyone else is through shiny pictures. If the pictures aren't interesting, then people won't be interested. Also, maybe more importantly, we need spaceships that look like they can't work in atmosphere, or water, or whatever, and then maybe people will start to figure out what's really going on." Or something like that.

For some reason, I've always been drawn to the aesthetics of the Soyuz spacecraft (I'm a horrible American, aren't I?), and hopefully they'll get some more time in the spotlight now that the Shuttle will stop flying. Maybe people could stop thinking that spacecraft=airplane in space. And maybe hard SF could become more popular. And I'd also like to mention here that I love the ISV Venture Star from Avatar, and I wish that it got more than about 10 seconds of screen time.

Anyways, I like designing various "midfuture realistic" spacecraft (and wouldn't mind if there was some future topic where we got to show off our ships to each other and brag a lot). Unfortunately, I'm still in the habit of designing them sideways, with the engines pointing backwards, even though the engines are always assumed to point down. Getting back to my point, I think it's helpful for both me and the viewers if the ships don't look anything like boats or airplanes. We don't really know what to expect or look for, but when we see a vehicle that's got lots of exposed structure, radial symmetry (rather than bilateral), funky heat radiators, and a tractor engine rig, we know that something new is going on. And then we start to figure it out and realize that this really is a design that we haven't seen before, because it's in the future and in space and these designs, though a few were sketched out before I was born, aren't the sort of thing that we see every day.

I just checked out "The Prefect" by Alastair Reynolds from the library, and it really bothers me that the ship on the cover looks like a high-tech airplane. I haven't started reading the book yet, so maybe there's some reason for the ship to look like that, but I think it looks a lot more like space opera than the hard SF I'm expecting. And I don't think that's a good way to market hard SF, nor will it drive the genre forward.

If you skipped all of that, what you missed can be summarized as "realistic ships should look realistic, but also different from airplanes, so that we really get what we're looking at."

Anonymous said...

2001 also appeared to omit propellant tanks on Discovery One, for some unknown reason. On the issue of a thin outer hull: as well as heat management, this could be a whipple shield to guard against meteoroid collisions.
Spacecraft-POV footage similar to the aircraft formation footage that Rick was talking about does already exist, such as the external tank camera footage from shuttle launches.
Perhaps one way that Hollywood could distinguish spacecraft from aircraft and watercraft would be to show an accelerating spacecraft moving up the screen rather than from left to right across it, helping the audience to intuitively understand that up and down in space is purely relative. This could be even more effective if several spacecraft were shown in a distant establishing shot moving in different directions, followed by a series of cuts showing each craft moving upwards in its own frame of reference.

R.C.

Citizen Joe said...

The gold foil is a good idea, but the implementation may be tricky. If the ship provides the sunshade, it might be set up like spools with an arm that pulls out gold tarps. That technique is used by the trash haulers in my parts. The other option is that cargo pods are responsible for their own sunshades. That means that those tanks would probably be gold instead of gray. The hab ring would probably be shaded as part of the vessel since it isn't removable.

Rick said...

Welcome to another new commenter! I've heard of Orbiter, but never tried it. Does it handle interplanetary missions?

Duplicate post duly removed! (Oddly, the duplicate was cut off, lacking the last two paragraphs of the first post.)

One reason we tend to portray spacecraft moving 'sideways' is simply the aspect ratio of computer monitors, not to mention TV/movie screens. If I had tilted the ship more upright, it wouldn't fit on the screen unless I backed off, and then the view would be less detailed.

If a ship has a spin hab, its internal 'up' gets even more confused. But note that as a concession to Romance I provided this ship with a Heinlein style penthouse control room at the forward end of the spin hub, just below the antenna mast. (This is the section with a dim red glow from internal lighting.)

I did also wonder about Discovery's fuel tanks, or lack of, in 2001.

Venture Star looks pretty cool - I might have gone if the movie had been more about it, instead of Dances With Wolves in space.

As an aside, compare the Noble Savages of Pandora with the just plain savages of Firefly/Serenity's Reivers, who are functionally the Hostile Injuns of its wild west setting.

Calsir said...

Long time since my last post. Just to tell you that yes, orbiter handles interplanetary flights pretty well. Or rather, it gives you a couple of computers that make the job possible. It is most definitely the kind of game that a SF enthusiast (hard or otherwise) would like.

Bye.

--
Calsir

Thucydides said...

You can have lots of fun with spaceship designs, depending on what sort of assumptions you want to make.

I can see ships which use aerobraking resembling high tech pine cones, with bristling radiators extending from the ship's spine but shielded by the aerobrake shield up front. Paper airplanes might also be a design aesthetic, with the triangular "wings" being the radiator fins and the various pieces of the ship filling the spine or nestled in the spaces between the "wings". Ships which make use of external power will have their designs dominated by laser or microwave receivers, huge gossamer assemblies surrounding the focus point.

Some ships will have to be streamlined, like shuttles and ramscoops, while others (like laserstars) might resemble huge sections of bridge truss with all the delicate components carefully packed inside.

I predict there will be quite the flurry of ship designs showing up on this blog in the near future (heh)

MRig said...

I must point out that the highest-grossing film of all time features a ship that looks rather like a much larger, interplanetary version of the one you've rendered here.

http://www.projectrho.com/rocket/rocket3ap.html#avatar

Realistic space stuff is not as far along, but it reminds me of the perennial soccer debate we have in this country. When will 'Murrica accept soccer? It already has.

Jnani said...

Being a worker in Hollywood, I do have a few things to say in defense of the realism we omit.

First off, I think the reason the radiator fins were omitted from 2001 the movie has less to do with the fact that the audience wouldn't understand them and more to do with the fact that without the fins Discovery was a more efficient thematic device for the film. A central motif for the film was circles - a circular space station, Discovery, made of circles, and shots of the Earth, Sun, and Moon over each other, all circles. In the end, the main character sees the circle of his own life and death, and then transcends it. So I think that was an artistic choice having to do with thematic cycles, and not with audience confusion.

Second, there some very good hard sci-fi films out there that Hollywood has produced. The one (yes, there are not many) that comes to mind is the recently produced "Moon". It may not seem like Hard SF, but mostly because the SF is mostly cast off to the side. The story mainly just deals with the few solitary characters on a moon-base, and doesn't really bring any science front and center.

I think one thing that we can all agree on is that in Hollywood, the science in SF does not come first, or even second. Telling a story through an effective visual medium comes first, so we tend to show what looks the coolest. A cool looking spaceship works, but only gets us so far. Since I've been keeping up with this forum regularly, I've watched Babylon 5 all the way through again, and have to say that there are a lot of things they use to keep the science of space warfare as realistic as possible while also keeping it visually interesting. Until about season three, when everyone just starts fighting with Magitech, a lot of the fights were shot with shot A: one warship fires, and then cut to shot B: another warship takes a hit. This is the way to film an action scene with two vessels that are thousands of kilometers away, and they did it often, though not all the time.

I guess what I am trying to say is that yes, your right to make the claim that science has been disregarded and oftentimes violated in film & TV portrayals of SF...but not all the time, and not by everyone. I will say, unfortunately, that the shows and movies that tend to be more scientifically accurate also happen to be less successful. Perhaps the only lesson to be gleaned is that in a visual medium, people don't want to watch a science lesson, they want to watch a story. You can make it as realistic as possible, the viewer probably won't even know the difference, but if you waste valuable story time explaining the science, you are diminishing the story.

Jnani said...

Comment Part A)

Being a worker in Hollywood, I do have a few things to say in defense of the realism we omit.

First off, I think the reason the radiator fins were omitted from 2001 the movie has less to do with the fact that the audience wouldn't understand them and more to do with the fact that without the fins Discovery was a more efficient thematic device for the film. A central motif for the film was circles - a circular space station, Discovery, made of circles, and shots of the Earth, Sun, and Moon over each other, all circles. In the end, the main character sees the circle of his own life and death, and then transcends it. So I think that was an artistic choice having to do with thematic cycles, and not with audience confusion.

Second, there some very good hard sci-fi films out there that Hollywood has produced. The one (yes, there are not many) that comes to mind is the recently produced "Moon". It may not seem like Hard SF, but mostly because the SF is mostly cast off to the side. The story mainly just deals with the few solitary characters on a moon-base, and doesn't really bring any science front and center.

Jnani said...

Comment Part B)

I think one thing that we can all agree on is that in Hollywood, the science in SF does not come first, or even second. Telling a story through an effective visual medium comes first, so we tend to show what looks the coolest. A cool looking spaceship works, but only gets us so far. Since I've been keeping up with this forum regularly, I've watched Babylon 5 all the way through again, and have to say that there are a lot of things they use to keep the science of space warfare as realistic as possible while also keeping it visually interesting. Until about season three, when everyone just starts fighting with Magitech, a lot of the fights were shot with shot A: one warship fires, and then cut to shot B: another warship takes a hit. This is the way to film an action scene with two vessels that are thousands of kilometers away, and they did it often, though not all the time.

I guess what I am trying to say is that yes, your right to make the claim that science has been disregarded and oftentimes violated in film & TV portrayals of SF...but not all the time, and not by everyone. I will say, unfortunately, that the shows and movies that tend to be more scientifically accurate also happen to be less successful. Perhaps the only lesson to be gleaned is that in a visual medium, people don't want to watch a science lesson, they want to watch a story. You can make it as realistic as possible, the viewer probably won't even know the difference, but if you waste valuable story time explaining the science, you are diminishing the story.

Jnani said...

Sorry for posting twice - google gave me a too large comment error the first time, so I broke it up.

Byron said...

Orbiter does handle interplanetary, but it takes practice, and there's only one actual interplanetary ship that I know of, the Deepstar. I tried to use it, but it didn't work on the Orbiter 2010 beta. It's incredibly realistic, and I object to calling it a game. It's a simulator. If you want good addons, try here.
Any ship that's aerobreaking will likely retract radiators, not try to shield them. And yes, we should have a ship gallery sometime. I've already shown mine, but I can get more renders, and I'm interested to see what everyone else has.

Citizen Joe said...

Now, would ships be like big trusses where cargo pods get attached? Would those pods have to be self sufficient? Would passengers merely dock their atmospheric vessel and live in there for the interplanetary trip?

Byron said...

I think somewhat. They would likely have an attachment point for a cargo bus, and what goes on that bus is up to you. A liner would be a single unit, while a cargo vessel might be a truss. But I doubt atmospheric vessels would be used as quarters. Too much extra stuff (engine, heat shield, etc.), and not enough radiation shielding or room.

ushumgal said...

I like your model! I do have one question: does the ring in the habitation section rotate, or does the whole ship rotate?

Which leads me to a more general question: I am quite familiar with objections to having rotating segments on spacecraft (how to seal the joint, how to get between the rotating and non-rotating sections, maintaining the strength of the spine of the ship through the area, and perhaps most importantly the problem of torque...there are more besides these, I am sure.

BUT, can anyone explain the objections to rotating the whole ship along its vertical axis? It would certainly make engineering the hab section easier, since there'd be no fiddly joint, and no torque either. I suppose large/fragile radiators might be a bit of a problem (especially if the project far from the axis, so that the centrifugal forces would be very strong at their outer ends).

Citizen Joe said...

If you spin the whole ship, then the whole ship has to be strong enough to handle that much acceleration. If those other parts of the ship stick out further than the hab ring, then those parts will be under even more stress. Now your ship is that much heavier because you need stronger supports. There are navigation, tracking and communication issues as well, which means sticking those bearings on the antennae instead of the hab ring.

Now, if we're talking Miligee accelerations, then it doesn't really matter what the orientation of the ring is. You could do sidewheelers or even a ring that runs on a tangential bearing. Transfer from the ring would involve stopping the ring so that the airlocks line up, and then moving across. Crew could operate in microgravity for a few days or weeks before being relieved by fresh crew from the hab ring.

But I'm still skeptical that a full sized ring would be justified just for people. If there were some other reason for artificial gravity (like some sort of refining process) then 'free' gravity for people would just be a plus.

Anonymous said...

Stewart didn't even have to act in that one...he really was a bomber pilot.

I like the image of your ship; it's realistic and yet stylish. My ships (either imagened or poorly rendered in MSPaint; I'm not an artist), usually come in three parts: the propulsion module, the hab module, and the mission module (cargo, passengers, weapons, scientific probes, etc). Some of my designs the whole thing spins; some of them only the hab section spins; a few of them the hab section doesn't spin at all; and some of my designs the spin hab is radial to the direction of thrust. I always try to make my ships have radiators, be balanced, and have those three elements I listed above. About half of my ships are mix-and-match; the other are 'unibody' designs. I'm partial to various fission drives; compact, lots of energy-to-mass, and has enough dangers to make it story-interesting. My ships tend to carry daughter craft and/or cargo pods (both aeroshells and basic boxes), because different ship types use different performance engines for different missions...you wouldn't send a ship from the surface of the Earth, fly across the Solar System, to finally land on Callisto, would you? I wouldn't; I'd have three ships and only have the second carry the third if that was the first visit to Callisto.

Well, that was a bit wordy, for me...

Ferrell

Thucydides said...

For rotating ships, the other factor is starting/stopping rotation when under acceleration. As well, there might be issues with the fittings and plumbing when transitioning between acceleration and station keeping rotation. The final straw is that the ship will need to have a rather wide diameter to reduce the Coriolis forces on the systems and crew.

This isn't totally undoable; The Mote in God's Eye and a lot of Jerry Pournelle's CoDominium work have detailed descriptions of just how such a ship would work (winching the curved wardroom table into the "wall" when under weigh is an interesting touch).

I might suggest an articulated ship, with the hab modules on booms which swing out from the central axis when rotating , but swing back to the central truss under acceleration so the floors ramain in the same orientation no matter if "Forward is up" or "Outward is Down".

If gravity and protection is key, the Neofuel giant ice donut is quite practical, with space in the middle for engines, shuttles and other carry ons.

And Byron, everyone has retractable radiators :), so the "pinecone" is just an attempt to find a new and different design aesthetic.

Looking forward to the picture gallery.

Anonymous said...

In Niven and Pournelle's Footfall, there's a scene where the alien mothership is decreasing its spin and accelerating at the same time, so down is towards one corner, then towards the aft wall. On ship diameter, Atomic Rocket's Artificial Gravity page has a link to a study suggesting that relatively high rates of rotation and therefore low diameters can be tolerated by crews if rotation is increased slowly, rather than going straight from freefall to 1g. On plumbing, this might be solved by having pipes running at 45 degrees to the directions of both spin gravity and thrust gravity, perhaps assisted by pumps, which would be necessary anyway if the ship was in freefall while docked to a station. On articulated habitats, the ISV Venture Star from James Cameron's Avatar uses this design, with the two crew habitats on arms that fold down when the ship is accelerating or decelarating via laser lightsail or its own engines, then fold out for spin gravity during the interstellar cruising phase.

R.C.

Rick said...

Welcome back to an occasional commenter!

Jnani's thematic explanation of Discovery's lack of big fuel tanks makes sense.

Also, our assumptions of what Realistic [TM] spaceships should look like were still taking form. My recollection is that 50s vintage illustrations of ships in this style often did not have radiator fins; probably the need was not yet clearly recognized.

For that matter, when I was a kid the 'standard' high specific impulse drive was ion drive, which would use a much denser propellant than liquid hydrogen.

A minor oddity of Avatar's Venture Star is that it thrusts in the opposite direction to what I would expect.

On spin, I didn't really specify even in my own mind whether only the hab section spins, or the entire ship - though I'd prefer to spin only the hab, if the coupling connection is not too problematic. But if the whole ship spins, the tanks and fins are under tension, and basically can hang from cables, with just a bit of stiffening bracing.

I used SpinCalc to determine spin radius, keeping everything 'green' except angular velocity (6 rpm), which I allowed to be yellow. There is still a lot of uncertainty about the limits for avoiding Coriolis nausea. See the Atomic Rockets section dealing with artificial gravity.

For the milligee accelerations I am modeling, ship acceleration is pretty much irrelevant to spin, as Citizen Joe noted. You wouldn't need to de-spin the whole hab to move between sections, just have a connector that spins to enter one side, and de-spins to exit the other side.

Whether spin is necessary depends (to current knowledge) on travel time - and on what passengers and crew are expected to do on arrival. If it is a military transport for gyrene/SWAT type guys, you had better have spin if the trip is more than a few weeks, or they will not be fit for action. If travel time is more than about 6 months, spin is needed to avoid more serious problems.

I think the advantages of spin are so great that it will be preferred for any travel time over a few days, depending on how expensive it is to arrange. (Remember the scene in 2001 with the zero gee toilet and its list of instructions?

Byron said...

I know that, but that's because that's the best design choice. I know I may be outnumbered here, but I think like an engineer, and your solution would add shielding mass with no discernible benefit. Looking cool is not a legitimate design parameter. I had that conversation with my friends about the Aurek at least half a dozen times. Finally I convinced them that it was close to optimum (surprising, as when I designed it, I didn't realize that.)

Byron said...

The Discovery's radiators were clearly described in the book, though.

Anita said...

Have to disagree about Joe and Jane Average Audience pre-WWII having no idea what an aircraft in flight at eye level looked like.

If feature films didn't show much (probably production costs circa 30's were the reason), the newsreels certainly did.

Ran across an invaluable site Criticalpast.com. It has thousands of newsreel and archive clips starting with bits from the 1890's. Lots of clips of aircraft in flight filmed from other planes, especially during the mid and late 30's.

Re Discovery 2001, wasn't it a nuke boat? What do I know about nuclear powered craft, but would it need propellant tanks?

MRig said...

Are you referring to the orientation of the Venture Star, or the fact that the ship looks like it's being pulled? The former is because it's on its deceleration burn. The second is because...aren't there engineering advantages to pushing vs. pulling? It seems plausible if you can get the exhaust to go where you want. We might see some ships that push and some that pull.

Citizen Joe said...

From what I read about the ship from Avatar, it used a tension structure because that was much lighter than a compression rig. So the drive fired off at a slight angle so that exhaust plumes went to either side of the habitat pod.

Rick said...

Blogger was being very odd today, resulting in me doing a triple post - I just got rid of the duplicates.

I stand corrected about 30s vintage newsreel showing footage of planes from other planes. It would be an interesting project for hard core film geeks to determine when this became familiar enough to be used in feature films.

There are engineering advantage to pulling IF you can keep both the exhaust plume and and waste-heat radiation away from ship structures. I'm conservative about that part, which is why my bias is to put the engine safely at the back/bottom.

Venture Star would need to have a 'true' badass torch drive, since it reaches 70 percent of C in a few months. Especially since it is a BIG ship, more than a km long; the departure mass could hardly be less than 100,000 tons.

I am too lazy to figure out how much drive power output would be required, but at a guess it would be on the order of 100,000 terawatts. (Whew!)

Discovery would need propellant tanks of some sort, even with a nuke drive. How big they would be depends on several factors. There are modules of some sort along the keel that might be propellant tanks.

Wikipedia has a pre-production draft drawing of Discovery that is a lot like my illo, including the tapered radiator fin and four big propellant tanks, though it has the familiar spherical hab section instead of the ring style I used.


There seems to be a growing demand for a place to post images - I'm open to suggestions as to the best approach!

Thucydides said...

Tension structures are much lighter and stronger (weight for weight) than compression structures, which is the reason the longest bridges are suspension bridges.

The downside is that the structure must always be under tension in order to reap the benefits. Once the tension members go slack, there is no support for the structure.

For most near term spacecraft, this might be best exploited during the coast phase, as Robert Zubrin suggested in Mars Direct. After injection into Mars transfer orbit, the trans stage is released on a tether and provides the counterweight for the Mars Direct hab to spin for gravity during the coast phase. Sensibly, the trans stage is "dead" and can just be cut loose when preparing to enter Mars orbit, if it were mission critical than failure of the cable or winch rig would mean no possibility to reach Mars.

Tension can also be used for other purposes. A compression spine could carry shuttles or other ships on tethers. The rotational energy of the mothership would be transferred to the smaller ships, providing a certain amount of launch energy.

Citizen Joe said...

The Venture Star from Avatar has (IIRC) 2 matter/antimatter drives plus a laser sail. Outbound, it uses lasers from Earth against a multi-km diameter solar sail to accelerate to .7c There is a reflective shield that is dragged behind to protect the habitat and rest of the ship during this phase. during coast, the sail is folded up and the whole ship spins around. The mirror shield is then positioned several thousand km ahead of the ship to act as a relativistic Whipple shield. During the deceleration phase, the shield is recovered and the antimatter drives fire up.

The Venture Star then produces enough antimatter for the return trip and uses the reverse method on the way back, using lasers from Earth to decelerate.

One issue I see with the spinal ships is that pulse drives would probably cause dangerous stresses. This could cause them to flex and continuous straining could cause the rig to fail. Again, not a problem with the continuous milligee acceleration but don't stick an orion drive on the end.

Rick said...

An Orion type of drive would need shock absorbers (and pretty humongous ones). Less extreme pulse drives would have less of a problem. I tend to assume pulse drives of some sort, but if average acceleration is 1 milligee, ship mass is 10,000 tons, and pulse rate is one kilohertz, each pulse is equivalent to hitting the back of the ship with a 10 kg sledgehammer - not so big a deal!

Anonymous said...

Rick; I don't think that the problem was with the audience;I'd imagine it was Hollywood's preception of what the audience would accept was more likely the reason.

Thinking about ship design, I don't see the need to have 'hard' (i.e. physical), connections between the different modules; each module (power/propulsion, command/hab, and mission) should have their own subsystems such as heat management and control systems (for instance), everything else can be 'wireless'; to move from one module to another, use airlocks and/or transfer boxes (like an elevator car). If mass is less important(mass is always important, but some design issue are more so) than passenger safety/comfort/health, then you might consider using an enclosed carousel design for your hab section. This relieves you of the burden of designing spinning bits to your airlocks and section/module connections. It probably brings up a bunch of other problems, but using very light weight material (semi-rigid balloons, for example), should alleviate many of those problems. What do you think?

Ferrell

Sabersonic said...

Might as well put in my two cents into this.

For Venture Star, well from what I've researched the Tensil Truss is durable enough so that it doesn't bend too much when the entire craft flips 180 degrees it doesn't get tangled up or loose its support. And though James Cameron ahd put some emphasis on "realism" and plausability on the interstellar STL craft, there seems to be a lack of radiators for the rest of the craft such as the hab modules and crew compartments energy systems. Pretty sure I read something on Atomic Rockets that warns of not putting radiators for the correct thermal output. Oh and before I forget, the engine of the Venture Star are matter-Anit matter/fusion rocket engines.

How that works, I have no idea.

As for the question of putting a spin hab on a spacecraft. Well my rule of thumb is if none of the following requirements are met by the Realistic (TM) spacecraft in question:

1) The total travel/flight time does not exceed a few days at most.

2) The onboard drive's acceleration does generate artificial gravity.

3) The onboard rocket drive is able to outrun the degenerative effect of the onboard crew's physical adaptation to a free fall environment.

Then a spin hab is a must, no matter the complications involved.

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Citizen Joe said...

Well, you could "simply" modify the human body so that it can sustain freefall without adverse effects. Then you could simulate gravity with magnetic fields where needed and then 'doping' the clothes with magnetic thread.

I'm not sure where the degradation comes from. If it is some sort of internal chemical reaction then the magnet-gravity simulation wouldn't work (although biochemistry might solve that). If it is simply muscle degradation from lack of resistance, then the magnetic fields would work. One definitive problem is that your inner ear wouldn't detect 'down'. Although you could get surgery to implant magnetic sensors (but that would seriously mess you up around the fusion plants). Eating food might be weird. Obviously, some people would not be able to handle microgees. You might be able to simulate a shower by using magnetic sandals and then stepping into a wind/water tunnel where the water is blown in from 'above' and sucked out from 'below'. It would even blow dry you afterward by simply turning off the water supply.

My point is that we don't know enough about what causes microgee problems to come up with a definitive answer. We have yet to test a spin hab in space so we don't even know for sure that it will solve the problems.

Thucydides said...

Thinking about a very old, schlocky "B" movie of yore (Silent Running), we could simply have the crew living in the biospheres and run the entire ship by wireless connections and teleoperated systems, with some airlocks reserved for emergency repairs.

The ship shown in Silent Running is not a practical design, but starting with the desire to have large habitat domes, we have them pointed "inwards" towards the spine with the radiation shielded bases facing space. A large mirror mounted on the bow directs sunlight down the truss to secondary mirrors which ensure the domes receive sunlight (and can be swiveled on order to create a day/night cycle). Tension structures keep the domes attached to the truss and allow spinning to keep the biomes under gravity at all times. Fuel tanks, engines etc. fill the truss "behind" the domes, and a shadow shield is provided if needed to protect the biomes (depending on the type of power plant being used).

This would actually be a small, mobile colony world, or could be used to deliver biomes to larger colony structures as they are being built. Ships of this type heading to deep space destinations beyond the asteroid belt would need huge primary mirrors to ensure enough sunlight is being gathered for the biomes. This might also be the form cycler spacecraft take so passengers can spend the years in flight living in a pleasant biome rather than a cramped spaceship hab.

Sabersonic said...

Citizen Joe: the idea of using magnets to simulate the sensation of gravity is a novel solution and within the plasible compared to the Space Opera staple of gravity plates/generators/whatever, though I forsee some complications with magnet doped cothing when one handles sensitive electronics onboard a spacecraft. That and the rather humerous, though potentially useful, effect when ferrite tools stick to one's clothing.

From what I remember of the degenerative effects of Free Fall adaptation, one likened it to being bed ridden. The muscles anthropied to become weak enough to require physical therepy, calcium leaches out from the bones, the blood pressue lowers to dangerous levels when under gravity, and a host of other problems that I cannot recall at the moment. True, one could fix it with bioegineering and all, but the census of this blog that warns against any alteration of the human body on the micro scale, even on the molecular scale. Less you want your colonists to grow unwanted tumors and cancers, infertility or worse, somehow become patient zero of a deadly plague.

The free fall shower idea is interesting, but I know someone is going to argue that a wet towel will do just as good a job and cost only a fraction of a free fall shower.

We may not know the extent of what causes microgravity problems, what is known is that they cause problems for those who wish to return to a gravity field of a planet, let alone Earth.

Thucydides: The redesign idea of the Vally Forge spacecraft is interesting, though for navigational stability at least one part of the craft would need to rotate the opposite of the rest of the spacecraft.

Though one must remember that As Atomic Rocket warns, windows let in more than sunlight in. Though I'm sure someone could find a way to create a window plane that'll only allow a certain frequency of the electromagnetic spectrum or better, exclude anything above a certain frequency, chances are it'll be some time before they're economical enough to be built as domes.

The distance from the sun relative to the spacecraft could also potentially require the use of internal lighting rather then large mirrors. Not really sure how effective a lightbulb is to plantlife compared to that of natural sunlight.

Still, the idea of biomes as a basis for cyclers isn't that bad of an idea, provided that there's a way to protect the passengers from the occasional solar flare and all.

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Citizen Joe said...

Re: magnetic clothes... I meant that the clothes would be readily affected by the magnetic field. So like 'iron' threads only more so.

Re: Windows on ships. You could just use fiber optics to let the light in.

Re: Spinhab biomes. I'm pretty sure that there will be times when they need to be de-spun for one reason or another. There needs to be some way of stowing everything for the microgee periods.

Re: Towels. Towels absorb water that needs to go back into the recycling system. To get it out of the towel, you have to let it transfer into the air first, then pull it back out. It would drive up the humidity which would also make it more difficult to air condition. You would also need to clean those towels. And those towels would eventually wear out, at which point you're potentially years away from the nearest linen shop. Considering the vast amount of power needed for the drive, running some fans for the shower is insignificant.

Anonymous said...

When I said that different parts of the ship might not need a 'hard' connection, I meant something like a sleeve-in-a-sleeve configuration; a lip and gate keeps the two from coming apart. Where the two connectors come together, there is a gap with a ring of radio/optical windows and a ring transformer for power transfer between the power module and the other modules. The airlock and/or hatch is in the middle.

Ferrell

Albert said...

Some time ago I farmed the net to get some decent images about realistic craft, and guess what?

Various concepts have the engine on the side of the truss.
(the ship flies "sideways")
http://spaceart1.ning.com/video/umbrella-ship-flyby

http://spaceart1.ning.com/photo/umbrella-ship?context=user

http://img412.imageshack.us/img412/599/ionf.jpg
(the image comes from http://homepage.mac.com/joebergeron/spaceart.html but for some reason has disappeared from the list)

A cool-looking concept with three nuclear power generators
http://img810.imageshack.us/img810/447

Also a pdf slideshow with various concepts http://fti.neep.wisc.edu/neep533/SPRING2004/lecture23.pdf

And a blog where a guy uses a pretty weird (but theoretically sound) solution to have a tumbling pidgeon ion ship.
http://selenianboondocks.com/2010/06/agnep2/

Having the engine lateral to the truss (and the main gun still spinal mounted) imho is a good idea for warships and even kinetics, after all what you need to do is thrust laterally to jink (or correct your course), not "forward" nor "backward".

Btw, even realistic designs don't seem to have enormous fuel tanks. That is an ion engine/plasma engine after all, and its high Isp is coupled with a probably denser fuel like noble gases (argon, xenon) or alkali metals (caesium, sodium).

Citizen Joe said...
I'm not sure where the degradation comes from. If it is some sort of internal chemical reaction then the magnet-gravity simulation wouldn't work (although biochemistry might solve that). If it is simply muscle degradation from lack of resistance, then the magnetic fields would work.

The degradation that worries pros is mostly the bone's.
And seems to be just a mechanical problem.
Still, the problem isn't living forever in freefall (there aren't adverse effects per-se), but stepping on Earth or on Mars with bones, muscles and cardiocirculatory system weakened by microgravity.

If you plan to live forever in a tin can orbiting things forever in a vacuum, there aren't health problems.

(if reproduction and gestation can work in frefall, of course. That's a major thing to know more about)

Last thing: Venture star in Avatar was designed by the guy that also designed the Valkyrie (antimatter interstellar starship, also the only ship ever imagined with tensile structure)
http://www.charlespellegrino.com/index.htm

-Albert

Albert said...

Some time ago I farmed the net to get some decent images about realistic craft, and guess what?

Various concepts have the engine on the side of the truss.
(the ship flies "sideways")
Umbrella ship flyby video

Umbrella ship

nuclear-powered Ion ship
(the image comes from here but for some reason has disappeared from the list)


A cool-looking concept with three nuclear power generators (although it doesn't generate gravity for the crew).

Also a pdf slideshow with various concepts

And a blog where a guy uses a pretty weird (but theoretically sound) solution to have a tumbling pidgeon ion ship.

Having the engine lateral to the truss (and the main gun still spinal mounted) imho is a good idea for warships and even kinetics, after all what you need to do in battle is thrust laterally to jink while still aiming at your target (or correct your course for KKVs), not "forward" nor "backward".

Btw, even realistic designs don't seem to have enormous fuel tanks. That is an ion engine/plasma engine after all, and its high Isp is coupled with a probably denser fuel like noble gases (argon, xenon) or alkali metals (caesium, sodium).

Citizen Joe said...
I'm not sure where the degradation comes from. If it is some sort of internal chemical reaction then the magnet-gravity simulation wouldn't work (although biochemistry might solve that). If it is simply muscle degradation from lack of resistance, then the magnetic fields would work.

The degradation that worries pros is mostly the bone's.
And seems to be just a mechanical problem.
Still, the problem isn't living forever in freefall (there aren't adverse effects per-se), but stepping on Earth or on Mars with bones, muscles and cardiocirculatory system weakened by microgravity.

If you plan to live forever in a tin can orbiting things forever in a vacuum, there aren't health problems.

(if reproduction and gestation can work in frefall, of course. That's a major thing to know more about)

Last thing: Venture star in Avatar was designed by the guy that also designed the Valkyrie (antimatter interstellar starship, also the only ship in fiction with tensile structure)



P.s. can you remove my previous post Rick? (the one without the clickable links)

-Albert

Citizen Joe said...

The magnetic clothes idea has the effect that everyone weighs the same and that weight is completely separate from mass. Another problem is heart atrophy since it isn't pumping as hard... unless the iron in the blood is sufficient to be magnetically attracted. Iron supplements in the diet?

Soldiers could train with varying magnetic fields so that they can learn to adjust to quickly changing gravity (like during landings). They can also use apps that detect the magnetic field and or gravity and then project an artificial horizon on to their glasses or visor. Eventually they'll learn to trust the artificial horizon for balance issues and it will virtually disappear.

The big problem I see with lateral thrusters is that people tend to move around. A little change in location out on the end of a long boom can significantly affect the course.

Luke said...

Sabersonic

Matter-antimatter/fusion thrusters are perhaps more properly termed antimatter initiated microfusion (AIM). By using antimatter annihilation, you can greatly reduce the compression needed to initiate fusion in a pulse drive. This will in turn cut down on the size and cost of your driver lasers, driver particle beams, Z-pinch machinery, or whatever you happen to be using. In practice, you will need some heavy element (probably uranium) at the center of your pulse fuel unit to react with the antimatter (otherwise, you get too many highly penetrating pions and not enough heat deposited in the fusion fuel).

Luke

Rick said...

The effects of microgravity seem to be like a hyper-sedentary lifestyle - a broad atrophy that would end with the subject not only unsuited to return to a gravity field, but just plain unhealthy. We have no idea yet what effects fractional-g spin would have, i.e. how much is enough.

A 'hard' connection between spin and nonspin sections may well be avoidable - which way things go may end up simply depending on which is less complicated in engineering practice.

'Sideways' keel arrangements look odd, but so long as you're dealing with milligee accelerations it isn't a problem - a 10,000 ton ship only produces a 10 ton load.

I'm rather skeptical of Charles Pellegrino, because he has put forth some pretty crankish archeological speculations. It may be that he has solid knowledge in one field, and is a crank in an unrelated one, but it does light a warning light.

Citizen Joe said...

OK, did some research... Ya, blood iron isn't ferromagnetic... and there's only 4 grams in a human body... so, there still needs to be something significant added to the bloodstream to provide the same effects of gravity by using magnetism.

Also blood tends to pool in the chest and face in microgees. Without something to fight against (like gravity) the cardiovascular system gets lazy.

Sabersonic said...

Something tells me that fractural G adaptation compared to Free Fall adatation to the human body would be expotnetially easier to recover from since the body experiences at least SOME level of gravity that it could adapt to. Up to a point anyway, and that's pretty much the million dollar question on the whole less-than-earth-gravity question.

In my honest opinion, although the so-called "Sideway Keel" arrangement of spacecraft have that interesting factor and emphasises the point that spacecraft are NOT surface vessels, such a desigh has to be urksome structurally. With either compression or tension design of spacecraft, the stress level of the vehicle is more or less parallel to the engine drive when it's on a burn. For a spacecraft whose "spine" (for lack of a better term) is perpendicular to that of the thrust of the engine, then that must cause disperportionate stress on the extremities of the spacecraft that could translate into wear and tear that must be taken into account even with mili-G acceleration.

Though then again, now that I think about it, "Sideway Keel" arrangements would only make logical sense on spacecraft that aren't expected to reach their destinations quickly or the acceleration period is measured in weeks or even days rather then minutes and seconds.

Now that I have that thought in mind, I'm now wondering if cycler stations could use such an arragement for engine drives or even if there is even a need for such engines on a cycler beyond getting into that initial orbit.

As for the Venture Star, Valkyrie design, and Charles Pellegrino, well as Atomic Rockets points out in this article on the aformentioned starcraft, every gram counts if one want's to have a meaningful payload for any STL Delta-V Starcraft on either end of the journey. Only possible way to have a compression-style design of a starcraft structure with a large enough payload allocation is potentially to go magi-tech and invent some kind of FTL drive. Either way, options are limited when one pulls in the Realistic (TM) card.

Oh, and before I forget.

Luke: The basic principle of the AIM Pulse Drive sounds interesting, but I gotta wonder if said heavy element must be around the same atomic number as Uranium or if "Heavy Element" could be translated the same way as the astronomy deffinition of metallicity?

Reason why I ask is that, as of late, uranium mining and uranium supply are pretty tight as of late and recent memory doesn't recall any uranium or any radioative elements among the asteroids. Even the moon is a poor location for uranium mining for the low numbers of the stuff, let alone the concentrations.

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Rick said...

Blogger is into duplicating comments lately! I've deleted a couple of dupes, along with the request to delete dupes. :-)

Rick said...

I'd guess that even 'modest' gravity would be a big health improvement over microgravity. But we won't have a clue how much is enough until we test it!

This has a bearing on planetary surface bases/colonies as well - in particular, whether lunar or Mars gravity is enough for health. If not, surface populations will have a stay limit. You could mount base facilities on a turntable, but this would be a major PITA.


Good question whether cycler stations really need a main engine. A drive bus might be mounted to put them on the desired orbit, then removed. Or, stationkeeping thrusters could be used to establish orbit - it would take a long time, but a cycler is a long-term facility in any case. I tend to agree that a sideways keel is a needless complication, unless some other factor of design convenience outweighs this.


'Heavy element' in the context of Luke's discussion probably means heavy in the usual sense - well up the periodic table. But its purpose here is as a sort of tamper, not energy production, so lead would probably be nearly as good as uranium, and depleted uranium would be fine. There must be a lot of depleted uranium around by now, and it probably makes up only a small fraction of propellant capsule mass.

Citizen Joe said...

The main drive on a sideways keel could be on tracks that run up and down the keel. That way the drive could balance itself out as fuel gets depleted or cargo is added on. It might be tricky, but the spin hab on the end of the keel could accelerate or slow down, which would induce spin on the keel. Once the proper attitude is achieved, the spin hab returns to normal and the keel stops spinning. That gives you yaw turning by moving the drive and climb/dive control by adjusting the spin hab. Neither one of which requires the use of remass.

Citizen Joe said...

Actually, the spinning hab, when acted upon by the thruster on one side would probably induce a roll (relative to the thrust vector). More thrust = more roll.

I'd hate to be the pilot on that thing. Although I'm sure everything would be computer controlled, and your view screen wouldn't even be pointing in the same direction as the ship. Still, if you ever had to manually control it you'd be pulling brakes, then accelerating spin, then sliding the drive about, then a few minutes firing the thruster, then cut power and slide the drive some more... It's like trying to fly a plane with one of those old RC cars that had forward (straight) and backwards (left).

Byron said...

I did see a NASA design for a sideways keel. The ship was a Mars craft with a nuke-electric drive. The hab was a transhab on one end, the drive was in the middle, and the reactor on the other end, and the whole thing was spinning. For that sort of design, it would be practical, but I don't think so for thrustgrav trips. (There's a link somewhere on atomic rockets.)

Thucydides said...

Going farther from the sun either involve getting even bigger mirrors (I have read speculation about setting up colonies in the Oort cloud using mirrors the size of continents), or boosting the amount of light the ship receives.

The ultimate extension of this engineering idea is to use the solar photosphere as a lasing medium (perhaps by using a platoon of mirrors orbiting in the photosphere and bouncing a seed laser beam around the circle, the plasma in the photosphere undergoes inversion then dumps the extra energy into the beam. In theory, you could illuminate entire planets this way (Potato crops on Triton or turning a tide locked planet orbiting a Red Dwarf into a tropical resort)

Luke said...

Sabersonic

No, heavy elements need to be pretty heavy. Basically, as soon as an antiproton touches a nucleus, it annihilates with one of the protons or neutrons in the outer layer. This produces pions. Some pions shoot away from the nucleus - you can't do much with these. Some shoot into the nucleus. These pions bounce around in the nucleus, adding their kinetic and (eventually) decay energy to the nucleons (protons and neutrons). The energy of the pion is so much more than the binding energy of the nucleus that the nucleus will shatter into fragments, and any excess energy goes into the kinetic energy of the fragments. If this happens in a light element, say carbon, you will only get a few light fragments with lots of energy per fragment. These will be fast moving and highly penetrating, and bust out of your fuel pellet without dumping much of their energy into it. This is not what you want. Really heavy atoms, on the other hand, either give you big heavy fragments or lots of light fragments with the energy spread out between them - in any case, they move more slowly, and dump most of their energy into the fuel pellet.

All the analyses I've seen for AIM used uranium. Perhaps because it is just heavier, or perhaps its low binding energy per nucleon helps. Lead or tungsten or some such might also work, but I don't know of anyone who's run the numbers. Fortunately, you don't need a lot of it.

Sabersonic said...

Byron: I believe that I saw something similar to what you've seen, though it used tethers to connect the distant "modules" that could even be wound back up. It certainly solves the little problem of perpendicular stress if the whole thing spins. Still, it'll probably need a reasonable amount of shadow shielding when the tethers are brought together. For what, I forget.

Luke: From your description, it seems that heavier elements would be the better choice then lighter for the AIM Drive design. Just earlier, the thought of lead and uranium particles accelerated out of a rocket engine and contunue at that velocity forever until it impacts something. A potential hazard that kind of urk me for a moment. But if it's more on the subatomic level then whole atoms or evem molecules, it doesn't seem to be all that lethal from what I could tell.

But I can't help but find that the shattering of uranium atoms seems a bit more like fission rather than fusion.

And before I loose this opportunity again I must ask, how does one find the accelation of a particular rocket engine in Earth Gravities from Newtons?

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UmbralRaptor said...

Sabersonic: to convert from Newtons to gravities, divide by 9.8. (Or 10 if you're doing purely back of the envelope calculations)

As for the pellets, I would imagine that the heat would turn them into plasma, so they'd disperse shortly after leaving the engine.

longbeast said...

re: venture star being the only ship in fiction with tensile structure

I can think of one other. Salt, by Adam Roberts had its interstellar ship on a tensile design. It was described as being something a bit like a space train - Nothing more than a huge engine at the head of a cable. There were lots of attachment points that people could use to have their in-system craft towed to another star. It didn't even provide power or life support.

The cable was for avoiding radiation shielding mass, not structural mass though.

Citizen Joe said...

While the idea of a shadow shield to protect the habitat from its own reactor/drive that still means that the ship is radiating all kinds of nastiness. Which means that when you pull up along side another ship or a space station, they aren't going to be happy. That would seem to imply some sort of non-nuclear tug or a shielded tug, that takes your habitat pod from your hot reactor to another ship and/or station.

Byron said...

Acceleration in gravities (G) from Thrust (T) and ship mass (m):
(T/m)/9.8=G. Newtons are a unit of force, while gravities are a unit of acceleration. UmbralRaptor, you're thinking of meters/seconds2.
The report is <a href="http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070023306_2007019854.pdf:>here</a>, and it's got a tensile truss, with engine in the middle, using that to cut down on shielding, and it's not designed to be reeled in.
The need for the tug depends on how hot the reactor is when not operating. If it's pretty clean (such as an D-He3 fusion reactor) you should be OK. If it's an old fission reactor, then yes, it would annoy the neighbors.

Byron said...

Oops, I screwed up the HTML tag. The link is here.

Elukka said...

Joe, I imagine you could include small chemical or other harmless kinds of thrusters on your habitat pod to take you to the station while leaving your hot reactor somewhere harmless.

Rick said...

Note to commenters - Blogger's commenting function is acting up today (the 6th), so if comments you posted earlier seem to be missing, that is why. Hopefully they'll get it straightened out!


Drive radiation poses rendezvous problems that rarely get mentioned! Even if the drive is not radioactive when shut down, you won't be able to use it in approach to and departure from a station.

Either tugs will be needed for that maneuver, or high ISP ships will take up parking orbits well away from stations, and 'lighters' will handle traffic between ship and station. If the drive is hot even when shut off, this will be the only option.

Thucydides said...

An interesting if rather brute force idea for creating fusion pulses is on NextBigFuture (http://nextbigfuture.com/2010/07/net-127-megajoulesgenerated-per-shot-of.html#more).

Slamming diamond pellets laced with frozen methane/D2 fuel into targets at speeds of 1000km/s would be pretty impressive on its own (have the Mythbusters tried this yet?), but the calculations indicate this would produce a decent amount of fusion energy (12.7 megajoules per shot).

A ship powered by this device would be built around one or more "gun barrels" to accelerate the fuel pellets, resulting in a long, slender core. Attach the rest of the ship modules and radiators to taste.

Citizen Joe said...

Wow. I had suggested a design like that for a super long (5 miles) laserstar that used D-He3 fusion. It needed the super long spine for the long linear accelerator to initiate the fusion. While most ships used a compact magnetically confined toroid D-T fusion reactor, the magnetic field needed for D-He3 was too great and would end up wrecking the ships. The 'fighters' in that setting also used a similar design but with Lithium Deuteride pellets instead. Those fighters would approach at 'ludicrous speed', then release a cloud of pellets. These fuel pellets would act as mines against the gravity based alien ships, but the LiD would simply burn up in an atmosphere.

Citizen Joe said...

Perhaps the shadow shield could be reconfigurable. During primary operation, the full shield is deployed between the habitat and the drive/reactor. However, once the drive/reactor is at idle, the shield then wraps around the whole core. Less radiation means less shielding needed.

Still, during the deceleration phase, you're pretty much pointing your completely unshielded fusion exhaust at the station. Likewise when you accelerate away. Seems to me that there would be good reason to maintain chemical rockets in space that would serve as rendezvous tugs.

Anonymous said...

I'm wondering if sending the mission/cargo/passenger module from the ship to the station (and back again) to where the ship is standing off at a safe distance, would be a way of getting around the whole dangerous radioactive drive problem. Either use your station-based tug or have some dedicated thrusters on the module you're transfering.

Ferrell

Albert said...

Why not ejecting the reactor?
After multiple months/years of voyage it will be tested and serviced while the main ship is docked.

The reactor, the plasma/ion engine and the big radiator remain (guarded) in a far orbit with a team of technicians radiocontrolling waldos to service it.

The ship mounts in its place a "orbital module" (that never leaves orbit) that is just a chemical rocket and some fuel cells to run the hab systems after the nuclear reactor is detached.

Hmm... wait a minute... a ship without the reactor/radiator/deep space engine is just the hab module, a few sensors and any cargo it may have. I'm detaching the drive bus and I'm moving around the payload.

Oh well. At least this stands true to the "modular construction" idea. :)

-Albert

nqdp said...

Hooray for modular construction! It's saved me a few hours of work when I've had to do something like triple the fuel a ship (er, a digital model of a ship) is carrying.

As for radiation shielding, isn't Earth the only planet where we don't need shielding? If we were orbiting Luna, Mars, or Ganymede, wouldn't our hab need shielding regardless of whether or not the Spacers used nuclear drives? Engines and Sol could produce gamma rays of similar frequencies, right?

Citizen Joe said...

Everyone needs to shield against ambient radiation. But you need extra protection when you're sitting next to a hot reactor.

Albert said...

Engines and Sol could produce gamma rays of similar frequencies, right?

Sol (or most habitable stars for that matter) produces mostly particle radiations, not gamma rays.
Also reactors emit neutrons, while Sol does not.

It is actually easier (i.e. less mass-intensive) to shield against Sol than against your engine/powerplant.

Galactic cosmic rays (high speed particles and gamma rays) are another matter alltogether.
It should be easier to heal the (few) damage they do than shield a ship/station from them.

-Albert

Citizen Joe said...

Aesthetically speaking, a rendezvous ship is going to be much different from something that isn't meant to interact with other vessels. So, interstellar ships might sacrifice docking safety in favor of a much reduced shield. Interplanetary vessels would need full shielding capability during rendezvous.

Rick said...

The whole question of protecting from other ships' drive radiation doesn't seem to get discussed much!

So long as you aren't going beyond Mars, you can avoid the whole problem by using solar electric drive, but solar power fades badly by the time you get into the asteroid belt, and is a nonstarter for the outer planets.

Ship to station taxis will need more extensive shielding, but the good news is that they only need airline-level passenger accommodation, much more compact than cabins.

Thucydides said...

The whole radiation argument seems to favour "cycler" spaceships for the long haul.

The added advantage is since the heavy shielding, life support and strengthened rotating mass is held in the cycler, the shuttles can get by with less mass and less capable engines (high thrust, low ISP engines to accelerate to the cycler and decelerate when matching orbits with the target planet. NERVA with an ISP of 800 would be suitable). The cycler itself would have a high ISP, low thrust engine to make adjustments since the planetary alignments will constantly change during the lifetime of the cycler, but long burns to correct the orbit will not be as taxing as straight shots with Torch, demi-torch or flashlight ships.

The cycler will most likely resemble the space hotel in "2001, a Space Odyssey", with an extensive "hub" assembly to house and service the various shuttles.

Rick said...

I think cycler stations look very good for the asteroid belt - much better than the traditional base ship orbiting permanently in the belt.

For Jupiter and Saturn I am iffier, because the cycler's orbit gets so long that it is only making a transfer pass at each end every few years, a very long 'season' for economic life.

But for these planets you might get big 'ships' that are not true cyclers, but have cycler-like properties, such as doing production work en route.

Look at my Travel Planner spreadsheet for a 'midrange' drive - the same drive engine can deliver 20 times the payload on a 1 year transfer orbit that it can deliver on a 200 day orbit. The specific numbers make grossly simplifying assumptions, but the differences will be on that order.

Citizen Joe said...

I'm good for nested cyclers. So, several that do the Earth-Mars Lagrangian points. Then more cyclers that go from the Mars Lagranian points out to various parts of the asteroid belt, inside and outside. I'd stick a physical station at those points so that you can gather everything for the months leading up to the rendezvous. I think that this is where massive momentum tethers would be very effective. Load up one ship at the rendezvous point, then the inbound ship hooks onto the tether and transfers its momentum to the outbound vessel. That can definitely make for a scary launch arrival. Missing the tether simply means that the inbound vessel continues to be the cycler. And you'd have to wait however long the cycle is to catch it again. Financial disaster, but the system keeps going.

I just saw an article on electrical analogs in gravity and they're trying to find the induced field analog. If that is found, then the physical tether could be replaced by a gravitic transformer

Albert said...

The whole radiation argument seems to favour "cycler" spaceships for the long haul.
Wait a minute, you say to place various cyclers around with shuttles cruising along them, right?
Like a series of fuel depots, and when the "night" comes (i.e. time to sleep for everyone on shuttles) the shuttle docks to the hotel it finds along the way.

That looks like a good reason to have loads of space stations.
Although the cost of it all will be pretty high.

-Albert

Thucydides said...

Albert,

The cycler is a huge spaceship (really a space station in free orbit around the sun in an orbit which intersects the orbit of the Earth and the target planet/asteroid etc. on a recurring basis), which provides the living quarters, gravity, radiation shielding and life support functions during the trip.

A shuttle in this case flies from the target planet/asteroid (or at least from LEO to a parking orbit at the target), and may or may not go with the cycler, although for practical reasons it is most likely to dock with and be carried by the cycler. Actually it would be more accurate to use the term lighter, since shuttles have the connotation of flying through the atmosphere from ground to orbit.

Once the cycler is in its established orbit, it may need to make orbital corrections, but not burns to radically change orbits. An Earth Mars cycler will cruise past each planet at interplanetary speed, and the lighters need to accelerate hard or make an impressive aerobraking manouevre to catch up to the cycler or slow down to mere orbital speeds.

Cyclers will probably not be going at torch speeds simply due to orbital mechanics, so several will be in established interplanetary orbits between the same planets o there will be launch windows at reasonable intervals. Esthetically, we are looking at huge wheels, tires or donuts in space, with the radiators, fuel tanks and other machinery scaled to the point of being small blisters protruding from the bulk of the main body.

Rick said...

I'd use 'ferries' for the vehicles that interchange between planet-orbital stations and passing cycler stations.

Citizen Joe said...

It seems to me that the ferries would have to go along for the ride. While the cyclers may have marginal acceleration/deceleration going on to match orbits, they don't end up stationary relative to the destinations. That means that much of the ferry's purpose is to accelerate its package to an intercept with the cycler as it passes. That package would (for the most part) then already be on the cycler path towards the destination. The benefit of the cycler is that it could house all of the specialty needs for the cargo and crew. So, power generation, spin hab, food prep/recycling, etc. All of that could be handled by the cycler and only needed to be accelerated once. That would free up a lot of mass for payloads.

It should also be pointed out that the cyclers tend to overshoot by quite a bit. So while the transfer time from Earth to Mars may be 85 days, it then shoots off into asteroid belt, only getting back to Earth after 9 years. That might be beneficial particularly if the recycling systems need a while to recover. Likewise, it could mean 'free' cycler space to the asteroid belt. Also, at the asteroid belt location, orbital speed would be much closer to the asteroid belt, thus latching on would be easier, particularly with large unprocessed loads of ore. Given the 5 year return trip to Earth or Mars (depending on which cycler) that ore could be processed in the pre-established spin hab, gravity sections for easier processing. Whatever is left could be used as remass for atmospheric injection.

I could see these cyclers becoming service industry colonies with people living their whole lives on them. During the short hop, the colonists act as stewards for the crews of ships. Then they act as farmers, recovering the recycling plants. Then they move on to refining ore (possibly manufacturing products). Depending on the specific cycle, that could be as much as 13 years.

Jim Baerg said...

Citizen Joe said:"It should also be pointed out that the cyclers tend to overshoot by quite a bit. So while the transfer time from Earth to Mars may be 85 days, it then shoots off into asteroid belt, only getting back to Earth after 9 years."

Such a long cycle seems the wrong way to go about it. In _The Case For Mars_ Robert Zubrin mentions 'free return orbits' for early Mars missions.

Zubrin recommends an orbit for the space craft that would take 2 years to go around the sun if for some reason it could not stop at Mars. This would take 6 months to go from Earth to Mars & it's aphelion would be 2.17 AU, in the inner part of the asteroid belt.

A 9 year cycle would have an aphelion of 7.6 AU (between Jupiter & Saturn), definitely not the way to go for a Mars cycler.
A 6 year orbit would be about right for an Earth-Jupiter cycler & a 13 year orbit for Saturn.

Citizen Joe said...

There are many different cyclers. Those long period ones usually mean they orbit the sun a couple times before they intersect Earth or Mars. In those cases you would have multiple sets of cyclers running so that you catch each synodic period. The Aldrin cycler runs off the single synodic period, but has the drawback of an Earth crossing speed of 6.54 km/s and Mars crossing at 9.75 km/s. The Aldrin cycler whips out into the asteroid belt (presumably automated and empty) out to 2.23 AU for about 16 months. Another problem is that it requires some course correction delta V.

An interesting cycler is the 6S7 and 6S8 which are about 13 year cyclers. However neither of them requires course correction delta V and the crossing speed is about half the Aldrin Cycler. Neither one gets out to the Asteroid Belt but that also means that solar power would be viable.

There are also some good belt servicing cyclers, but they usually blow by Mars kinda fast. That means aerobraking for drop offs. I really don't see throwing 12Km/s delta V at the cycler to hop a ride so they seem like outbound cyclers only.

Anyway a good paper on cyclers is here:
http://www.troymcconaghy.com/storage/AIAA_2002-4420.pdf

Albert said...

If I understood correctly the paper, the S1L1 one sounds cool too (the last one in table 6).

It is ballistic (no need for course correction) Low delta-v to reach it for "ferries", and relatively good travel times.

Follows a kinda weird trajectory but well...

-Albert

Sabersonic said...

"Of course, once we get torchships, we don't need cyclers anymore." - Byron

With the arrival of Torch Drive equipped spacecraft, one can postulate that Cyclers would take of the role of luxury tourist destinations, similar to the cruise line industry when air travel is readily available. The destination would not be the sole aim of such a ticket as would be the voyage itself. Not to mention that mass limits would probably not be so significant nor strongly enforced comparatively on a cycler then it would be on a Torch Craft that much reach a similar destination.

The construction of a cycler is a significant investment of resources and currency so it wouldn't make that much sense to dismantle one if an owner can find a way to utilize a cycler for a purpose that it may or may not be remotely designed to operate. A good example would be the Eiffel Tower that evolved from a rather hated exposition feature into a national icon.

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Citizen Joe said...

What would be the requirements of a torch drive? If it is still Newtonian then we're talking massive acceleration of the remass. That is the sort of thing that is going to be very radioactive. Which goes back to the question of how do you protect yourself from other people's radiation?

Once we get the gravitic analogs working, that's when the cyclers will go out of business.

Albert said...

Which goes back to the question of how do you protect yourself from other people's radiation?

In space this is pretty easy, because 100 or even 1000 kms is more than enough for about anything you can throw a stick at. And in space one megameter is close to nothing.

When they get into planetary orbit the radioactive engine/reactor/whatever is left in a very high orbit far enough from anything else. Eiter shielded orbit tugs will come and dock or the hab module detaches and goes down to dock to the station.

The problems of torch drives are how to protect you from your own engine radiation and how to keep the engine from melting.

Also, why throw away cyclers?
They are space stations after all, so they will be placed in orbits around something intersting and colonized permanently.

-Albert

Byron said...

My point is that even then, most people don't want a couple of months on a cruise, and even then that market is very limited. Cyclers are only practical when delta-V is expensive. As it gets cheaper, they will be phased out. The problem is that even if one way is fast, the other leg will take years, which accountants will see as a loss. Even if it is shut down, they won't build new ones, just use old ones.

Citizen Joe said...

You don't shut down, you re-tool. During that short hop, people are going to voraciously attack your resources, food, water, etc. In return, they'll leave vast piles of waste. During your X number of years on the turn around, you use it to reprocess that waste back into usable product (i.e. food and water). If you do it fast enough, you could possibly offload the prepared food to the Belters in exchange for their 'raw materials' which you then reprocess into useful goods, ready for sale when you hit your transport cycle.

Now what you have to keep in mind is that the cycler corporation doesn't have just one cycler, it will probably have as many as 12. One inbound and one outbound for each synodic cycle. That means that there will be like 6 outbound cyclers at various points along their path at any time and two (1 inbound 1 outbound) will be somewhere on the transport hop as much as 25% of the time.

Now if the corporation is willing to up the number of cyclers even more, they can use different cycles which could change the schedule from 1 flight every 25 months to two or more. Maybe there would be a cycler that transfers 3 months into the cycle while another hits at the 6 month mark and a third at the 9 month mark. After that, the window closes for 16 months (for a direct route).

Now, if you've also got cyclers going to the cloud cities of Venus, then there might be hops from Venus to Mars as well.

So I could see upwards of a hundred of these cyclers running between the inner planets and the asteroid belt. However, once you go outside the Belt solar power drops off too much and travel times (via cycler) become prohibitive. You might latch on to a cycler with your outer system ship for the first leg, but after that you'd really be on your own.

Byron said...

I'm not questioning the general utility of cyclers, just their use once delta-V becomes cheaper. The problem with your plan is simple. Cyclers are in use for their primary purpose a few percent of the time. Then they are on their own, and while they might do some good, I doubt moving "raw materials" is that good of a gig, and the processing means I need people on board. That all costs money. On the other hand, I can have a ship that's used say 75% of the time, and it's wastes can be processed at a permanent facility. Also, it's far more versatile. If demand for Mars falls off, then I can send it to Venus, or mothball it. A cycler is fixed, on the other hand. It will always be there at a certain time, and I can't make it come sooner if I have high demand, or stop it if there isn't any. Any cyclers in use might be steerage-class to Mars or wherever, but I doubt there will be any more launched when delta-V gets cheap (nuke-electric or whatever).

Citizen Joe said...

You still have to take into account all the life support needed for people. If you can get to Mars in a week, you've got a point. Most people can put up with a week of discomfort. But even a month is going to be horribly inconvenient for the general population. Although cyclers may take a long time to get to the destination, you will be riding in an artificial gravity setting with all sorts of luxuries that wouldn't be available to someone on a fast ship.

What will likely crash the cycler economy would be cheap lift offs. If getting something to orbit is expensive, then it might be provided much cheaper via space operations. Remass (water) might be shipped in from the asteroid belt. Manufacturing could be done on the cyclers during the 'inactive' cycle. It's like Datona Beach during Spring Break. Ya, the locals make a lot of money and there's wild parties, but they don't shut down once the students go back to college. So think of it as a working space station, that also moves around

Rick said...

An issue for cyclers will be balancing orbit periods with the social and economic life of the cycler population. Cyclers don't work well if there's a lot of down time where the people have no work to do.

Anonymous said...

Cyclers never did seem like "ships" to me...they seem more like railroads. They have a set route and a relitively fixed schedule. If you think of the cyclers more as railroads instead of steamships, then designing their "routes" should be easier; of course, cyclers have the advantage of being repurposed to different routes or even as space stations; or even as "mini-cyclers" (orbiting between the moons of one or another of the outer planets, or even the astroid belt), going from primarily transports to support vessels, to waystations, to mobile mining/refining ships, to agricultural stations. There are plenty of examples in fiction of updating or refurbishing spacecraft with new technology or different capabilities so it can be used in a new role.

Ferrell

Byron said...

The problem is that they're railroads with a fixed schedule and a lot of investment in each one, along with a low duty cycle. It's only going to work if we have a fairly high, reliable demand for transit to Mars or whatever, along with the ability to lift the cycler into orbit. Even then, you suddenly find that you have railroads that can be run at different times and that have a much higher duty cycle (high deltaV ships). You still have to explain why someone would build new cyclers in that environment. All they would be useful for is long cruises and steerage passage (maybe). Possible recycling isn't enough to justify their use.

Thucydides said...

I think due to the huge mass of the cycler, it may end up being a sort of "Flying Dutchman" of space, perhaps inhabited by marginal peoples looking for low rent living space and the ability to practice their religion, social order or whatnot in peace. The Authority will ensure the cycler cannot make large delta V changes and place itself on a collision course with planets, asteroids or large fixed space structures, while leaving warning beacons attached so fast packets won't collide with the cycler.

This makes the end of the 22nd century even better as a story setting, abandoned (?) cyclers orbiting between the Earth and Mars, Lunar "brownfields" of mass catchers in L2 abandoned as the Lunar 3He mines were shut down due to low cost 3He from the gas giants, new investment and colonies popping up in unexpected places (the "mirror rush" on Mercury to cash in on the solar photosphere laser project) and so on.

Ship design will probably still be constrained by the idea of minimizing mass and energy required for given payloads and destinations (at least commercial ships, purpose built military ships will have entirely different design considerations depending on how self contained they must be).

Citizen Joe said...

Again you're presuming that your duty cycle is just the trip to Mars. The cycler has to have artificial gravity, probably by spin. It will need solar power to keep the radiation levels down. It will need some sort of agricultural ability to regrow foodstuffs. Since it is basically isolated, it will need its own doctors and repair crews (although with the remote services nowadays, really they just need people or robots that follow instructions). All of this is in place and accelerated to orbit. Removing that will COST money/remass. So a company has a captive workforce for the 'idle leg' of the trip. This is when you do all the manufacturing and production work. If that isn't enough work, they can also telecommute to handle administrative jobs. While some manufacturing is great in microgee, some (most) needs the gravity that the spin hab can produce. In that aspect, cheap lifters would be the downfall. If it becomes cheaper to get something off of Earth than to transport it on the cycler, then they'll just build it on the ground and stick it on a rocket. I mean how much would it cost to send a pair of jeans into space? Like $300? If you have AstroCotton (tm) growing in the hydroponics, then you've got the raw materials to fabricate the clothes. And people will have time to grow, harvest, spin, weave and assemble a new pair of jeans for the inbound clients (or all the inhabitants).

Anonymous said...

Sometimes cost isn't the deciding factor...it's timeliness; so what if you can lift a whole medical team into orbit on the cheap if it takes until three days after you're dead to reach you. If the bread from Earth goes bad before it reaches you, you're better off getting it from next door...or the local "bread truck" when it comes past.

I don't believe that time sensitive cargos shipped directly from Earth will be practical for centuries; it will be much easier to have reserves of those time sensitive items and services much closer to the off-world locals that need them.

Ferrell

Rick said...

The railroad analogy applies in some ways to all spacecraft, at least until you have Truly Outrageous drive performance.

Compared to ships and planes, spacecraft are extremely constrained in their travel options, with very limited ability to 'change course.' A plane can fly to half its range, then turn around and come back, or go anywhere else within its half-range circle. A spaceship that heads for Mars is committed to going to Mars. In that sense all space traffic 'runs on rails.'

This has special relevance to military operations. You can perhaps build one abort option into the mission profile, with a defined window when you can choose it. Other than that you're pretty much stuck with Plan A, even if conditions change en route.

Jim Baerg said...

Rick: That was a crucial plot point in Kim Stanley Robinson's Mars Trilogy.

There was a 'revolt of the colony' on Mars & a force to supress the revolt was on it's way & about to aerobrake into Mars orbit. The rebels launched some rockets with explosive warheads to put lots of shrapnel in the path of the arriving force. This left the arriving force with the choice of a) get killed by the shrapnel, b) divert deeper into the Martian atmosphere & burn up or c) divert higher so no aerobraking occurs & they are on an orbit that returns them to earth or mars only years afte r the rebellion has been settled one way or another.

Rick said...

What I get for not having read KSR's Mars books! That sounds like an elegant and very believable analysis of the constraints that space motion puts on military operations.

Citizen Joe said...

I am skeptical about putting shrapnel in orbit of Mars. First, they conveniently had these rockets. Second, how would the inbound ship even KNOW the shrapnel was there to have the choice? Third, orbital space is BIG. A little tweak here and there and you're hundreds of miles from the planned entry window. If the colonists mined enough of Mars orbital space to be effective against the inbound military vessel, then they've pretty much quarantined themselves until they can figure out a way of sweeping that shrapnel out of the sky. This is directly analogous to landmines in various war torn countries.

Jim Baerg said...

The Mars rebels had learned from a previous failure & the rockets were made in advance. Also the rockets were lots of small ones to put the shrapnel into suborbital trajectories in the incoming forces path just as it was arriving. Also IIRC the rebels sent a radio message to the incoming force timed so that option c) was available but nothing else could be done in time to save the incoming fleet.

Citizen Joe said...

Still, the inbound ship needs to make an injection burn which could be hours or even days prior to the aerobraking maneuver. Until that burn is over (or you have prior knowledge, i.e. inside man) you don't know exactly where injection will occur. At that point, you don't have the option of changing course. I'm guessing the author had them turn back. But, more realistically, I suspect the military would have taken their chances. Destruction of a military ship at the hands of rebel rockets means the rebels lose... eventually. It doesn't matter if their rebellion works on Mars, they just started a war with Earth.

Albert said...

I'm skeptical too. If the shrapnels are not seekers, the attacking ships can dump some remass/water/whatever between them and the shrapnel to clear the path.

Or just evacuate (if it was manned in the first place) and kamikaze one ship while keeping the others all behind its cover. One gets shredded but clears the path, the others survive.

Unless the rebels have filled the whole Mars orbit with debirs.

-Albert

Rick said...

Not having read the books, I don't know how it is actually described, but I'd take the Martian defense to be, in effect, kinetic fragmentation missiles. They could be launched after any prior injection burn, and they only have to cover the lateral maneuver envelope.

And the books were published between 1992 and 1996 - effectively pre-Internet, and certainly long before the kind of online discussion and refinement done at SFConsim-l (and here!). Pretty good for the era!

And the broader point stands: Space maneuvers are constrained in ways quite different from terrestrial vehicles.

(I have an upcoming post on this point.)

Turbo10K said...

What about....

Ships in a ring, making a 'wheel', with a big heavy Interstellar drive in the hub?