Friday, June 26, 2015

The Weekly Moonship

Von Braun Moonship

The phrase sticks in my mind. I surely read it in an SF novel, or more than one, and perhaps in a variation like daily moonship. Since it is an evocative phrase, at any rate to me, let us evoke something from it.

The weekly moonship. Just the name tells us a good deal about Luna's place in human affairs: we go there every week, at least most weeks. It might be more; perhaps connecting flights depart from Cape Canaveral on Mondays, Baikonur on Tuesdays, and so on. But let us modestly stick to a single weekly moonship.

Not only do we know that we go to the Moon weekly, we can venture a broad guess as to how many people make the trip. Our moonship surely carries more than a couple of passengers, fewer than a thousand; a broad range might be 10-200. We will say fifty: our moonship has the seating of a 1950s airliner or transcontinental train coach.

Since the Luna round trip takes a week, weekly service probably means two passenger ships taking turns, with a third - perhaps an older model, less economical to fly - in reserve. For landing on the lunar surface, a shorter mission, one lander will do, with one in reserve. One or two ships suffice for other distant orbits, so altogether we have a generous half dozen passenger ships working the Moon and other locales in the outer reaches of Earth's orbital space.

And we will suppose that these ships mostly fill their seats, unlike the rather similar spaceliner in 2001 that carried Heywood Floyd to the Moon in solitary VIP splendor. So about 2500 passengers travel to Luna each year, at least to lunar orbit; most continue on down to the surface. At this stage nearly all are making the round trip; if most are serving six-month rotations we have about a thousand regular residents of Luna Base and its outliers.

Passengers making shorter stays nudge up the lunar population - as does anyone staying on past six months. Add a few hundred people in lunar orbit, or other distant orbits, for a total of roughly 2000 people in the outer orbital zone.

Beyond that zone we might suppose that about fifty people are on or orbiting Mars, with a similar number aboard exploratory missions elsewhere - perhaps a half dozen active deep space ships that carry human crews, plus some robotic freighters that can take slower orbits.

If the deep space missions use electric propulsion they depart from high orbits or at least refuel and take crew aboard there; if they use chemfuel or (properly shielded!) atomic rockets they blast straight out of low orbit for maximum Oberth effect. In that case the human presence in outer orbital space may still be confined largely to the Moon itself, and lunar orbit.

But we are not mainly concerned here with deep space. Anyway,  you cannot yet buy a ticket aboard the biennial Mars ship the way you can with the weekly moonship.

Looking inward, towards Earth, we can expect to find more people.

Geosynch is economically important but surprisingly difficult to reach - nearly twice as hard as jumping over the Moon, as Apollo 8 did. Geosynchronous orbits are awkwardly placed: High enough that it takes a big burn to get there, close enough, thus with high orbital speed, that it takes sizable burns to match orbit, then head back down. So geosynch traffic is purely utilitarian, and the human presence perhaps less than in lunar orbit. A single passenger ship can serve this route, with one in reserve.

Low Earth orbit is a different matter. It is the closest place in space, the easiest and cheapest to reach, and for many purposes and most passengers that is enough. Tourists can float and gawk as well here as anywhere. Virtual tourism is also served; Xollywood can and will use low Earth orbit as stand-in for the universe.

So ... taking a not too deep breath, let us say that there are 10,000 people in low Earth orbit at a given time, ten times the lunar population. For those who are staying weeks or months in space, this corresponds to a tenfold increase in traffic volume, about 25,000 people going up every year for fairly long stays.

But low Earth orbit allows quicker trips than the week-long journey to the Moon. So let us say that about ten percent of the people in low orbit are visiting for short stays of less than a week, adding about 50,000 annual trips, for a total of 75,000.

And let us round things out by adding 25,000 tourists who simply go up and down, never exiting the shuttle, but going back with memories.

Thus, 100,000 (!) passengers to space every year, a few hundred daily. If our passenger shuttles also carry fifty people, there are five or six daily flights to orbit worldwide. Allow, 'conservatively,' a one week turnaround, and there are about forty shuttles in the service rotation. Perhaps fifty in the active fleet, allowing for maintenance cycles, some in reserve, and so on.

In human terms this is some serious traveling. We can suppose that the baseline human lift cost to low orbit is perhaps $50,000 (in present day USD), but that is an average. Business travelers will pay another $20K for a reserved ticket and 'complementary' cocktail; most pay cheerfully because they aren't paying; their company picks up the tab.

Tourists fly standby and bring their own libations. They also benefit from the economics of unsold seats on the bus. The seats go into orbit whether or not any passengers are floating above them. The direct cost of lifting each passenger is really only a ton or two of propellant, at Earth industrial price, plus an airline meal.

Which means that some seats will be sold pretty cheap, and even us peasants can pass on that new car, and instead spend a day looking the universe in the eye.

The payload we care most about is us, but we must say a little about cargo traffic as well, especially since much of it also involves us intimately: food and shelter.

At this level of development, growing food in space is still in trial stage; daily sustenance comes up from Earth. My baseline 'cheap' orbit lift cost is $100,000/ton, $45 per old fashioned pound. That is roughly ten times the grocery store price of everyday goods, but not much more than the price of luxury items.

People in space will eat well, because the lobster doesn't cost much more than the rice you serve it with. In general, everyday economics has the boom-town combination of sky high all-around prices with peculiar twists.

You also need a place to stay. The most massive and crucial structural works in space are not ships but dormitory habitat modules: where you live, if you are living in space or on the Moon.

My baseline guesstimate for these is about 20 cubic meters and 10 tons per person. If you stripped all the laboratory equipment and such out of the International Space Station, beefed up life support, and fitted its pressure modules out like a Pullman train, it would have roomettes for some 45 people, which sounds about right.

(For really long term occupancy, including children and pregnant women, you need another 5-10 tons of radiation shielding. On the Moon you can just pile up regolith, AKA lunar dirt, over the hab structures. But at this stage we only need a few fully shielded habs.)

Booking a hab roomette as a hotel room might come to about $10,000 per night minimum - more inflated than the price of food, because the thing is so heavy. There may be bad hotels in space, but at this level of development there are not yet any cheap ones.

For 10,000 people in low orbit, thus about 100,000 tons of habitat, plus we might suppose another 100,000 tons of other facilities such as those Xollywood sound(less) stages. Annual orbit lift needed to support, maintain, upgrade, and expand it all might come to 30 percent of the total, 60,000 tons.

Suppose we have two main classes of cargo lifters. Most carry up about 25 tons, and are cargo counterparts of the passenger shuttles. About a fifth are heavy lifters, 100 tons to orbit, carrying about half the total load. Average payload is 40 tons, so 1500 flights per year, about five daily including one heavy lifter.

The fleet of cargo shuttles comes to about forty vehicles, so altogether our orbital shuttle fleet approaches a hundred (two-stage) vehicles.

The thousand people on the Moon, and the other thousand or so elsewhere in orbital space, also need room and board - coming to some 40,000 tons of imported structures, and about 12,000 tons per year in up-bound cargo traffic from Earth, half of it going to the Moon.

To carry this cargo up we will need a few more shuttles, and to take it on outward we need a small fleet of cargo ships. Let each carry 60 tons of cargo - comparable, for these longer trips, to the 50 seats aboard the passenger ships - and we have a couple of cargo moonships per week as well as the passenger ship. Altogether the cargo fleet working beyond low Earth orbit will number about a dozen ships - add the passenger fleet for a total of around 20.

So we come full circle to the weekly (passenger) moonship. A ticket will not come cheap, because lunar propellant is probably not yet competitive for use on low Earth orbit.

Propellant sent up from Earth to an orbital depot is a relatively simple bulk payload suited to maximum streamlining of operations, and the price might get pushed down to $50,000 per ton. A ton of lunar propellant delivered to low Earth orbit needs at least another ton or so to get it there, even with solar electric kites for the second leg of the trip, so the price point to match for lunar production is around $25,000 per ton at the source.

Moreover, rocket propellant uses a larger proportion of hydrogen than ice contains, thus perhaps two tons of ice per ton of propellant extracted. Altogether, to make lunar propellant competitive in low Earth orbit you may need to bring production cost down to $250 per ton of lunar regolith that must be crunched to obtain the ice - a pretty demanding order for mining on the Moon.

Lunar propellant is much more competitive in lunar space, versus propellant lifted all that way from Earth, but low Earth orbit will favor Earth-sourced propellant for a long time, even permanently if launch costs come down enough.

Our weekly moonship needs about four tons of propellant per passenger, costing $200,000 on orbit (and not counting, for Earth passengers, their ticket to orbit). All in all, upwards of a quarter million on average to fly to the Moon. Robert Heinlein, writing in 1949, pegged the full Earth-to-Moon lift at $30 per pound - equivalent, at current prices, to $299.75 (almost exactly 10x inflation), or $660,649 per ton. So we are beating Heinlein's price hands down.

That said, even filling that last empty seat will set you back a minimum of $30,000 in propellant to lift you and your baggage. But hey, a best-case total of maybe $50K or so to fly to the Moon? Not shabby.

Stepping back, the vision I have sketched here looks very much on the same scale as what Kubrick and Clarke gave us in 2001: A Space Odyssey. One estimate for the mass of Space Station V in the film comes to 68,000 tons, about a third of my estimate for total low-orbit presence.

The operating technology I've presumed - chemfuel rockets for all routine operations - is speculation-free, aside from the bit of magitech faerie dust needed to make space operations routine. We probably could have done it by 2001, had space development continued at the white hot pace of 1968.

The whole shebang - shuttles, orbital stations and habs, moonships and Luna base, all of it - has a combined mass somewhat less than 300,000 tons. By my million-dollars-per-ton guesstimate, which applies to commercial airliners - and expendable rocket stages - today, it would cost us not quite a third of a trillion dollars to build it all, and $100 billion or so to operate it each year.

In an earlier development stage, when spacecraft are still largely handbuilt prototypes, the same money will only buy about a tenth as much - still a respectable start: a thousand people in space, a hundred on the Moon, the cost falling and development expanding as experience is gained and economies of scale kick in.

But enough of the big picture, except for the biggest picture of all, the one outside the viewport. Ladies and gentlemen, moonship Henry Mancini is now ready for boarding at Airlock Ten-Alpha. Please glance at the ticket scanner as you pass by, and have a wonderful trip! Damy i gospoda, kosmicheskiy korabl' na Lunu Genri Manchini gotov ...

Kubrick's Moonship


I had intended to write about Ships for the Orbital Patrol. But the whole subject of 'local' space keeps expanding, and what can I do but expand along with it?

The first image, from an online model store, is a 3D rendering of the Von Braun moonship proposal of the 1950s. It carried about fifty people, but obviously did not aerobrake on the return trip. The second image, from Space Collective, shows the lunar liner from 2001.


Nyrath said...

Nicely scaled! You practically have a fully fleshed out economic model for a 2001 A Space Odyssey style cis-lunar transport system.

As always I'm sure the price bottleneck is the "halfway-to-anywhere" delta V cost of the boost to LEO. Things like space elevators always seemed a bit out of our current reach. Do you think some kind of laser launch system is realistic?

Rick said...

That was fast!

I felt really good about how the scaling worked out. It gives me a truly 'midfuture' picture of space - loosely speaking about midway between where we are now and the vision of full-fledged space colonies and interstellar missions.

The one thing lacking, awkwardly, is a clear economic reason for people to be in space, other than tourism. I do believe that, at some point, no amount of remote imagery can substitute for the insights that might come from the human eye and brain floating up there looking back at Earth, or wherever. (Though the classic 'blue marble' image was remote imagery to everyone but the crew of Apollo 8.) In any case, however, that is faith, not anything demonstrable.

Laser launch (probably) fits in the category of what I call electric railroad approaches to space - techs that shift the primary investment from 'spaceships' to fixed installations. (Though today's space launch complexes are hardly trivial investments!)

The ultimate electric railroad is an elevator, which really IS a railroad, a 40,000 km mainline highballing into space. All electric railroads face the challenge that they only really work well for very large traffic volumes.

Also, like some of the other electric railroad techs, e.g. mass drivers, laser launch is probably better suited to a steady stream of small cargo payloads, not big human-carrying vehicles.

That said, we will surely look at these techs as traffic grows!

Elukka said...

I think we haven't developed our use of the basic chemical rocket far enough to need to worry about the plausibility of more advanced systems. The technology, the engines and such, may be about as good as they will ever be, but to realize their full potential we need high launch rates and reusability. High launch rates alone would help but I think reusability is a must too if you're hoping for any sort of revolution.

The problem of high cost isn't a problem specific to chemical rockets, it tends to be a property of any highly complex thing you do in a very limited fashion, in limited numbers. Chemical rockets are actually pretty cheap; you could buy about four (partially reusable!) Falcon 9's for the cost of a 787. Switching to a more complex, presumably more expensive system for launch wouldn't necessarily help.

Chemical rockets appear to have a lot of potential left. SpaceX estimated a tenfold reduction in cost for a fully reusable Falcon 9. That was, I think, assuming optimistic but plausible near future launch rates. A fully developed, plausible midfuture rapidly reusable chemical launcher could very well exist in an airliner-like condition where fuel costs dominate. That might be somewhere in the low hundreds of thousands for a F9-sized launch. Call it a 200-fold reduction from current costs. I think this could comfortably carry us into the Weekly Moonship and beyond... Once we're there, we'll want to start looking at cheaper propellants, higher isp engines and/or alternate methods of launch.

That's not to say we shouldn't look at other alternatives before that. Maybe the positive takeaway is that in case laser launch and elevators and other advanced concepts don't work out, well, it looks like we don't strictly need them to have our space future. The high cost of launch is too often seen as a a sin chemical rockets, and their future potential sidelined in favor of more complicated propositions.

Nyrath said...

Yes, SpaceX is having a lot of trouble figuring out how to land their rockets in the quest for reusability. But they are close enough so it is brown-trousers time for their competitors. A tenfold or even fivefold reduction in cost for a fully reusable STO rocket will be an insurmountable advantage for SpaceX. The others will be forced to play catch-up.

I was initially puzzled as to why SpaceX was landing the rocket on a barge instead of in the ocean. Duh. Seawater is so corrosive that the engine would be ruined.

The problem Rick mentioned about the lack of an economic reason to be in space is the obnoxious elephant in the room, which I call "lack of MacGuffinite"
(featuring copious quotes from Rocketpunk Manifesto)
I've looked into a few options but none of them seem like realistic solutions to the problem. But I'm always on the lookout for more proposed solutions. said...

This would make for a great con game!

The Weekly Moonship!

You are the crew and passengers of the ISS Pavel Romanovich Popovich. It's the Monday run of the Popovich to Aldrin Moonbase. It's another milk run... really, it is. You have 3 metric tons of powdered milk. And you have to get it to Buzz Base to feed those hungry Loonies. (It's used as creamer for their coffee for the most part). You have your usual group of passengers, with some first timers. Nothing out of the ordinary.

What could go wrong!

Elukka said...

This is off-topic but Nyrath, since you're here, I feel I have to give some sort of acknowledgement for all the hours I've spent reading Project Rho. It's been fairly instrumental in helping me figure out my scifi stuff and spaceship designs.

As a shameless plug, have a spaceship:

Brett said...

Another great post on Local Space, Rick.

The tourists just taking a trip up into space without saying in a roommette might do a flyby close enough to see the larger space stations under construction in LEO. Unfortunately, they won't be close enough to see the swarms of robots being remotely controlled from Earth, but that's okay. By the time we're building them, remotely operated drones are ubiquitous for any line of work that would require heavy safety protection for the human workers who might otherwise be doing it.

I imagine humanity would live permanently in Earth-Space for a long, long time. Maybe, if or when off-world resource utilization gets good enough that a colony of folks who want to put some distance between themselves and Earth can do so, that will change - but Earth-Space is vast, the resources available are large, and it's always nice to have superb latency with the communications networks and Web back home.

I've looked into a few options but none of them seem like realistic solutions to the problem. But I'm always on the lookout for more proposed solutions.

It'll ultimately come down to whether people want to live in space colonies, or visit space for tourism reasons - and can afford either. It's possible to imagine a Local Space with no permanent residents at all, because Local Space is close enough that remotely-operated drones can be controlled in close to real-time (latency of less than a second, or a few seconds).


For farther out trips than Local Space, definitely - there's no substitute for human beings nearby, even if they're a few thousand kilometers away in space. The smartest probe still won't know why something is interesting aside from whatever parameters you put into it, so there's a loss of capability compared to having real-time control.

Nyrath said...

Nice ship Elukka! Offhand I'd say Orion drive, the pusher plate is a dead givaway.

Eth said...

Assuming a better economy (say, sustained 10% growth worldwide among other things) and a peaceful, prosperous world, there could be enough surplus that "because we can" is starting to become a good enough reason. After all, once resources aren't a problem anymore, a Kennedy-style speech may be a good way for a politician to attract voters, a megacorp to get good marketing or even an NGO to attract funds.
It doesn't need to make perfect economic sense anymore, because economy is fine - what is aimed at is prestige, ideals and such.
If economy is strong enough, prestige may become an affordable McGuffinite, if you will.

It would be kind of like the ancient Chinese great exploration fleets - before economy caught on them and they were cancelled.
And once there are enough people and infrastructure up there, it would hopefully reach a point where it starts creating enough of its own economy to be worthy of sustaining even without such prosperity. At the point described in this article, we may very well have reached it.

Now, our world isn't on that course at the moment, quite the contrary. But our world is also unstable, dynamic and fast-changing, so that's one (arguably optimistic) possible future. I wouldn't bet on it for the next century, but who knows?
In fact, if the Pentagon alone suddenly cut wasted money by half tomorrow and the amount was put into an efficiently-run space program, it may be just enough by itself to build such future on the long run. But I guess we're trying to stick to hard-SF here.

KraKon said...


Has there been any thorough analysis of laser launch systems done that you can link me to?

Elukka said...

Whoa. Looks like the schedule for reusability just got kicked back a notch, a Falcon 9 exploded rather spectacularly. My entirely unprofessional opinion is somehow the second stage exploded during the first stage burn, during which the first stage continued to perform normally until range safety blew it all up.

KraKon said...

Falcon9: Apparently, the first stage LOx tank underwent an 'overpressure' event, burst and exploded. The second stage detached, then autodestructed as is procedure.

Launch costs: I'd abstain from discussing the reasons behind a thousand person presence in space. That's a whole other, generally unsolvable, topic.

Rick: Thanks for providing numbers! I never realized how much regular space launches could come to resemble airline flights.

Geoffrey S H said...

Argh! wanted to post on the previous one, but was too late!

Some of the stuff wanted to post may be of use though.

Firstly, if spacecraft designs for 'coastal' lunar craft remain the same as speculated by Rick, you could get a situation where soyuz and apollo designs are recycled and changed over a millenia. Viking coastal and river craft left their mark in Norfolk Wherries and Portuguese fishing boats around a 1000 years after they vanished from the world stage. Looking at the type of lunar-transfer craft used by any particular nation might indicate the initial design influences when that nation first started a space program.

As far as infrastructure goes, I still hear about how such a thing would be difficult due to the lack of a need for zero-gravity for manufacturing. 1 g has too many uses.

Unless you used that zero-g as a'clean slate' and instead build massive centrifuge/ring stations (larger than any potential centrifuge on earth) to get *more* gravity than that on earth. Are there any uses for sch a thing? Uranium enrichment perhaps? The fashioning of ultra hard materials?

Lastly, assuming lasers become effective at 1 light second within the next century or two, I think there will be many defense stations pointed at troublesome enemy satellites in earth orbit for some time, any large scale space combat up to and beyond the pmf will be outside the earth hill sphere, and planet-side defenses will deter large military craft entering that sphere. So you will have these disposable kill-sats and installations within the sphere doing any heavy-duty military work.

Finally: I will post a random space craft (heavy duty "coastal" barge) as well, because I feel like it. Intended for a hard-sf space opera like setting.

fro1797 said...

I think that besides tourism, research and exploration would be the main drivers of humans in space, with building, maintaining, and expanding the infrastructure close behind it. The longer we have a permenant presence in local space, the more it will become entrenched and the more likely it will be that another economic reason will be discovered that will give a boost to human presence in local space. We have been sending people into space for half a century; we have been exploring under the seas for more than twice as long and even though there are several economic and scientific reasons to build permenately manned underwater outposts, we are only just now at the point where we can plan to build them. We are almost at the same point with building a presence in local space. We have three reasons to send humans into local space, let's capitalize on those and let them generate other reasons to expand our presence there.


Tony said...

While a neat intellectual toy, I'm not seeing the real world motivation. Even space tourism is probably not the answer. Even the manned exploration of the inner solar system is probably done better without much (if any) infrastructure in orbit, given that the payload tonnage one might expend on a large orbital infrastructure is probably better spent on the exploration vehicles and payloads themselves. Rick imagines a baseline 200,000 tons of on-orbit and lunar mining infrastructure, plus 30% annual replacement. If that much effort were all dedicated to going to Mars or perhaps the asteroids, it would probably be best, for practical reasons alone. But there are more than practical reasons. Since the primary motivation of people in space pretty much has to be sending them places where they can expand the frontiers of human existence, it's really tough to make a moral case for a manned orbital environment.

Now, all is not lost. There is one orbital platform that might make sense, both practically and morally, but it's not in Earth or Lunar orbit. It's a Mars cycler. There could be real value in reusing habitat and power systems for Hohmann-like transits to Mars and back.

Tony said...

WRT SpaceX and Falcon 9...grrr. It's hart to think of what to say that is both intellectually honest and fair. Why? Because it is entirely possible that SpaceX just wasn't sticking to its knitting as a launch service provider, instead concentrating on its reusability initiative. It is also entirely possible that they succumbed to client (i.e. NASA) pressure to get the mission off the ground. Or it could be both -- pressure to fly combined with pressure to beat the weather at the recovery site.

But at the same time it is unfair to say positively that either of these possibilities is the real issue. It's just too early in the process. And it could just be one of those things that happen with technologies as complex as launch vehicles.

What is fair to say is that this demonstrates that SpaceX really is just another launch services company. Whether they were culpable or just negligent, there's a reason that this happened -- there always is. SpaceX is now going to be evaluated like Boeing and LockMart on reliability. And that's going to affect their cost structure, because SpaceX is going to have to show the same kind of manufacturing and operations due diligence that other launch service companies have to. Additionally, insurance on SpaceX launches is now going to be based on a real world reliability model. The honeymoon is over.

Rick said...

The Falcon explosion sux, but the good news, for SpaceX, is that they seem robust enough to ride out 'routine' launch failures. The previous two attempts to supply the ISS, by other launch providers (one American, one Russian) also both packed up, so I don't yet see any special cause for heavy breathing about this particular failure.

And Musk has a brilliant business model. SpaceX will indeed be judged by the satellite biz as just another launch provider. But Musk does not need to hit his targets or even come close for SpaceX to make money - he just needs enough edge over the competition to claim 20 percent or so of the current launch market. And if he gets that far, he has the volume to aim for his marks.

The bad news for everyone is that space rockets do blow up, and too often - about 2 percent of launches are failures, even for mature launch systems. Unlike high costs this is not an artifact of low launch rates. Space boosters are just plain extreme designs, necessarily so because getting to orbit is so demanding. This might put the nix on my vision of operating spacecraft more or less like airplanes. But perhaps, as costs fall, designers can sacrifice some payload fraction to beef up the vehicles, and a little beefing up might go a long ways.

Otherwise I agree with Elukka that chemfuel rockets still have a lot of operational growth potential. And any launch tech will face the extreme-design challenge because, well, 7.9 km/s is really really fast.

Very cool designs from Elukka and GSH! Always love a little eye candy here.

Rick said...

Jumping out of sequence a bit, I don't think of my huge space establishment of 12,000 people as only or even primarily a staging base for a few deep space missions - that would indeed be grotesquely ill-suited and out of proportion to the requirement. What exactly all those people are doing in space is indeed a giga asterisk. But if space is ever going to have a big presence in human affairs it will surely involve a wide range of human activities, many of them only incidentally or accidentally related to space as such.

To some degree the very fact that we fret and argue about this is a byproduct of the current cost level. But as costs come down, they may eventually (or not) reach a level where they no longer are the elephant in the room. It is correctly observed that the Gobi Desert is about a thousand times more habitable than space. But hardly anyone thinks 'if only I could live in the Gobi Desert.' Whereas a lot of people would trade in their 5-bedroom houses for a roomette if they could open the window shade and see the Earth rolling by below them, or hanging above the lunar plain. Or go to the diner and flirt with Eva Marie Saint, or Cary Grant, according to preference.

The existence of a large city called Las Vegas shows that human habitation patterns are complex, and not always driven by obvious environmental factors.

Speaking of Earth above the Moon, look closely at the bottom image of my post. You'll notice that Earth does not quite look right. Simple reason: The film came out in 1968 - and until the last week of that year no human being knew what Earth looked like from the Moon. We went to the Moon and discovered ... Earth.

Milk runs and similar everyday adventures in space. 'Gravity' was not about everyday adventures, and I missed seeing it, but I heard it was quite good. The relevance is that it is a sort of benchmark - a space movie that was not 'about' space, but simply a human romance/drama that happened to take place in space, as it might have in any rugged and dangerous environment. As space certainly is today. But as (and if) space develops, the range of human activity there will grow.

I would love (and expect!) to see more movies/books that are not remotely SF, but happen to take place in a near- to midfuture space setting. From buddy cop movies to chick flicks, teen coming of age, whatever. Remember that horrible, sterile 'lounge area' in 2001's Space Station V. What a criminal waste of pressurized volume! At the development level I portray there IS a place for lavish, ostentatious open volumes in a space station, and not just Bigelow bags for bouncing around in. But how about a volume modeled on the grand saloon of a classic ocean liner, grandeur and elegance, a place where young women can have a drink and discuss their messy love lives in style. Sex in the Station!

Rick said...

Forgot to add that while I've never been a huge cycler fan - preferring faster travel speeds, which however require electric drive that may not scale the way I would like. In that case a cycler becomes an attractive option. Once in its orbit it needs only stationkeeping propellant, so it can basically be all hab, with local ships connecting at each end of the run. If the trip is going to take nine months, you really want comfortable accommodations.

Tony said...

Re: Musk

If SpaceX has and keeps 20% of the market, they're going to do so by servicing their launch services commitments. And if they do that, I'm not sure there's going to be programmatic space for reusability experimentation, not in the long run.

Tony said...

Well, as everyone knows, I'm all about removal of asterisks. Without the asterisks, large or small, the only economically justifiable motivation for large numbers of people in space is exploration. I also happen to think that it's the only morally viable one as well.

Also, I think Apollo 13 is obviously about people and not about space.

Elukka said...

The bad news for everyone is that space rockets do blow up, and too often - about 2 percent of launches are failures, even for mature launch systems. Unlike high costs this is not an artifact of low launch rates.

Are you sure? It seems like rockets are at the point where failures are invariably caused by some weird edge case, whereas airliners are at the point where they're caused by a perfect storm of really weird edge cases because we've flown so damn many of them we've ironed out most everything else. Rockets sort of feel they're at a terribly prolonged experimental stage still..

Tony: Their reusability experiments can be done on commercial flights. Currently it doesn't have the margin to do it on GEO margin but they're working on another revision of the vehicle to allow them to that. The customer presumably doesn't much care what tricks the detached first stage tries to pull after it's already done its job.

Nice ship Elukka! Offhand I'd say Orion drive, the pusher plate is a dead givaway.

Very cool designs from Elukka and GSH! Always love a little eye candy here.

Thanks! This is intended to be a centuries old clunker of a cruiser, essentially a missile platform with lots of endurance piled on. It's still effective at reminding worlds of their obligations by putting a lot of nukes on orbit, and when war comes it still throws a lot of warheads their way. Fueling a pulse drive might be an issue since the fuel/propellant is not something you'd dig out of a comet or something, but established tradition is you take from the locals. Keeps the supply lines short. They tend to comply when you park said nukes on their orbit.

Hop David said...

"If the deep space missions use electric propulsion they depart from high orbits or at least refuel and take crew aboard there; if they use chemfuel or (properly shielded!) atomic rockets they blast straight out of low orbit for maximum Oberth effect. "

The best Oberth benefit comes from high apogee, low perigee orbit. If you're in a high circular orbit it only takes a small tap of the brakes to drop to a near earth perigee. Falling from high up, the ship is traveling nearly 11 km/s at perigee. You get a much healthier Oberth benefit than the 7.7 km/s of low earth orbit. For more detail see What About Mr. Oberth?

Tony said...


Tony: Their reusability experiments can be done on commercial flights. Currently it doesn't have the margin to do it on GEO margin but they're working on another revision of the vehicle to allow them to that. The customer presumably doesn't much care what tricks the detached first stage tries to pull after it's already done its job.

Actually, the customer does care, for two reasons:

1. He doesn't want his mission compromised by divided attentions.

2. His potential payload mass is compromised by the inclusion of reusability features.

Now, I agree that neither of these need be show stoppers, but they both represent competitive disadvantages for SpaceX as a company trying to sell a service in a very limited market. So I'm skeptical of their competitive position with reusability experiments as part of their offering.

Tony said...

Oh, BTW, Las Vegas is the result of a wholly artificial competitive advantage, combined with the capability of the average person to patronize it. Hard to see how you're going to create the same thing in orbit.

Elukka said...

No, I really don't think the customer cares much, evidently not enough to severely bother them. SpaceX has a very robust manifest and they fully intend to test reusability on these flights. One of the customers (SES) expressed interest in using a reused first stage too.

SpaceX offers whatever fraction of payload to the customer that they like. If it's enough, the customer considers it, if not, they'll go to another provider. They only care whether it provides the payload they need, not how much is 'wasted' to something else. SpaceX is uprating the F9 (1.2?) so that they can lift a typical commercial GEO satellite in reusable mode. It's likely they'll continue offering heavier payloads for a pricier, expendable launch, but that won't be the average customer.

Geoffrey S H said...


Do you have any more designs in the pipeline? That missile cruiser looks very interesting!

Geoffrey S H said...


Do you have any more designs in the pipeline? That missile cruiser looks very interesting!

Thucydides said...

A few observations about costr effectiveness.

For the routine shipments of things like toilet paper, freeze dried fruits and all the other mundane items needed for space hotels/stations and any long term work force, the lowest cost shipper will come out on top. Dirt cheap and minimally reliable ships like "Aquarius", which is essentially a toilet roll pulled off a large diameter mandril and launched by rolling off a barge ito the ocean sionds like just the ticket; if you have already factored a potential 30% loss rate for non critical cargo items than everything is not only cheap, but any extra launches that get into space past the 60% you have accounted for is gravy.

As for the large assemblies, I will advocate for the same approach written large: using a "Sea Dragon" type launch vehicle so you can boost completed assemblies (including sheilding) into orbit in one lift. This has some obvious implications as well: less need for complex on orbit assembly, everything can be assembled and checked out in the factory on Earth. A full up Sea Dragon was designed to lift 550 tons into orbit, but lesser Dragons could be designed (using modern methods and materials) to lift fully assembled 200 ton modules into space.

This brings me to the final idea, a "utility" spacecraft which does not fall into a "tin can in space" trope, but more like a mobile home or camper. The "Stage Coach to the Stars" was more like a Bigelow inflatable module surrounded by a huge water baloon. The water provides rediatin sheilding, life support for the crew and even propulsion (heating the water in what is essentially an overgrown microwave. This might not have the "oomph" of a chemical rocket, but seems to have the sort of utility needed for longer duration space flights, and seems much less expensive than the traditional models (not to mention has much less expensive and delicate plumbing!).

This still does not really answer the issue of McGuffinite (and to tell the truth, I suspect that one of the drivers of space colonization will be simply to get away from Earth and not have to deal with Chinese hackers, Vladimir Putin, bankrupt Greek politicians or the annoying political class that is leaning on you at home). To that end, the setup in space will be rather different; fleets of orbital telescopes tracking NEOs, some real estate offices to stake your claim and orbital depots to fill up your "Space Stagecoach" with fresh water.

Thucydides said...

Forgot to mention one issue: it is also cheaper and more efficient overall (in terms of mass or energy) to use water rather than splitting the water into LH2 and LOX. This is true with nuclear thermal or the overgrown microwave idea. Carrying around the electrolizers, cyrogenic coolers and insulated tanks (as well as the spare parts and personnel to keep it running) is lots of extra mass which eats into the mass budget, even if you have higher efficinency engines using H2 or H2/LOX.

The trade offs will have to be carefully examined to see where the cutoff point for efficiency actually lies.

Eth said...

The bad news for everyone is that space rockets do blow up, and too often - about 2 percent of launches are failures, even for mature launch systems.

How long should we expect it to stay that way? And what could be done to make it fall below what is considered safe for general passenger transports?
Those are indeed certainly extreme systems, but so were early firearms: making stuff explode in a narrow tube closed at one end and shut at the other by a stone. No wonder they would regularly misfire or explode at the face of the soldier.
A few generations later and we were seeing firearms that would almost never fail when used in nice conditions (The Kalashnikov would even work in terrible conditions, but that's way later - and we probably don't need to send rockets through cyclones anyway).
What and how long would it take to get to that point for chemical rockets?

While we're at water, are there lighter molecules than H2O that would be liquid at (or at near-)room temperature? Or is water the best we got for 'simple' remass?

Also, it should be possible to use the energy of the Sun to directly heat remass, but I don't remember seeing much examples of such engine. I suppose it probably means it's pathetically inefficient, but would you have some info on those? It could be useful at some point as emergency engine in the right (read: very wrong) conditions.
Similarly, I suppose cracking water molecules using sunlight is impractical.

Geoffrey S H said...

What and how long would it take to get to that point for chemical rockets?

From the 1100s when firearms were becoming more prevalent to the 1850s (I can't think of breech explosions from 1600s onwards but I wouldn't be surprised if such a problem remained until the 19th century)?

At the very least there was around 500 years from invention to significant steps in reliability. Maybe the 26th century is when we get our "safe" passenger rockets?

Damien Sullivan said...

"Whereas a lot of people would trade in their 5-bedroom houses for a roomette if they could open the window shade and see the Earth rolling by below them, or hanging above the lunar plain."

Technically, a lot of people may now *say* they would. Actually doing so is another matter. And probably not many people have 5-bedroom houses unless they have big families (who won't fit in a roomette) or are pretty rich; I guess the latter could afford multiple flights to alleviate living in a roomette.

If there's 12,000 people in space, how many will be living in Antarctica at this time?

Will anyone be living in space or Antarctica as permanent residents raising kids?

Improvement in guns meant, among other things, improvement in metallurgy and machining, I'd think. We already have advanced metallurgy and precision machining; less room for improvement. Possibly process management is what needs to be nailed down.

Thucydides said...


Water is liquid, non toxic, and readily available throughout the solar system, which is a huge advantage. You can fill up on the Moon, restock at Ceres and then refill your tanks at Europa. Water is also massively useful for so many other things; the "Space Stagecoach" could still be livable even with an engine failure simply bacause the water protects you from radiation, thermal extremes, micrometeors and provides for your life support needs, so long as yor vegetable garden keeps going.

Using solar energy for thermal rockets is often called a "Solar Moth", and Atomic Rockets has some information about these and other types of engines. ISP is pretty terrible, and the mirror(s) provide a level of mass and complexity that you may or may not want to deal with. Puttering around Earth and Cis Lunar space, a Solar Moth wold probably fall under "good enough" for various low priority jobs; an old space pickup truck if you will.

As for using concentrated solar energy to split water, there is no reason you could not do so, but you would need a much larger mirror and the "cracker" in the mirror's focus would have to be able to withstand a temperature of 800-1200C, not to mention the corrosive effects of hot oxygen recombining inside the reactor. Once again, simplicity may win out, if the you can get access to refractory materials and enough aluminum foil to make a good mirror, rather than an electrical generator and some platinum electrodes.

Jim Baerg said...

If you put ammonia or methanol through a solid core nuclear rocket they would break up into hydrogen & nitrogen or carbon monoxide, so the exhaust would have a lower average molecular weight than water & so a higher exhaust speed for a given reactor temperature.

Water H2O mw= 18
2 NH3 -> N2 + 3H2 av mw = 8 2/3
CH3OH -> CO + 2H2 av mw = 10 2/3

Jim Baerg said...

for ammonia av mw = 8.5

Rick said...

Good questions about the fragility of space boosters. Probably both inherently extreme designs and relative lack of experience are factors. If you count the V-2 we have been launching space rockets as long as we have been flying jets, but the difference in flight numbers and therefore actual operating experience must be orders of magnitude. As for what is needed to make space rockets safe for ordinary passengers ... for that you'd have to ask a real rocket engineer, preferably a specialist in failure analysis.

Hop - I saw your discussion of the high apogee / low perigee ellipse ... alas, too late to incorporate in my remarks. I was somewhat aware of the neat properties of that orbit, thanks to Isaac Kuo at sfconsim-l, but had only thought of them in a demi-operatic military context, as an orbit for pre-positioned kinetic 'mines' defending Earth and its orbital space against a deep space attacker. A modest 3 km/s of Oberth boot at perigee serves a knuckle sandwich down the throat of an approaching task force at 9+ km/s. :>

Until now most of my detailed space thinking has been about deep space ships with a high specific impulse drive, for which orbital space is just a hill they have to spiral slowly up and down. It's fascinating to see the cool stuff that you can do with a little oomph and a lot of thinking ahead.

Low orbit as mecca for high rolling gamblers and lounge lizards? I love it, but agree that it could never remotely be an important driver, at most an amusing sideline like spoiled rich kids throwing wild parties on the Moon.

Truth to be told, Tony is probably right that the only good reason to go into space is to explore it, certainly at anything like current costs. I'd go a bit further and say that the time for actual human space exploration is not yet - it will come on the day that our probes send back data so exciting but so perplexing that the only way to puzzle it out is to send a geologist with a spade or a biologist with a Petri dish. This does still allow training missions, which is what the ISS is - testing long duration human spaceflight, and learning how to do lab work in space. So long as AI doesn't advance to the point where human exploration also gets screwed.

But RM does not pretend to be a Realistic[TM] space blog - there are excellent ones out there (and not so excellent). This blog is most fundamentally about Romance: what spaceships have in common with Catherine de Guienne. Which still doesn't totally get rid of the asterisk, because the SF setting game as I like to play it differs from fantasy in that it at least tries to fake realism. Plausible spaceships are easy. A rich and diverse story setting is tough, and so far I pretty much depend on an array of oscillating hands.

Antarctic exploration is as close as we can get to a real world equivalent. IIRC, Antarctica has a few thousand people in summer, including some tourists; a few hundred winter over. So it is close, seasonally, to the scale of my low orbit and lunar settings respectively. But at maybe 1 percent of my 'low' cost estimate. Antarctica is way cool (so to speak!) for experiencing an almost unearthly environment, but limited as a story setting.

A space 'camper' will be an interesting challenge. When (if) we get the sort of setting I portray, people fiddling in the boneyard will test the possibilities of really basic spacecraft that would never pass commercial rating but can still find a use, perhaps on the shadow side.

And a meta observation. It is wonderful to see so many familiar names here, and some new ones. Sorry I was gone so long!

Eth said...

Solar moth - thanks, with the name it's easier to find info (and Atomic Rocket to the rescue again!)

Jim Baerg
Interesting, ammonia seems relatively common in the Solar System, so it could make in some cases a better choice than water. Pipes and engines may be more expensive due to it being caustic, and its radiation shielding properties may be different. Also, as it is toxic, manned ships probably require a bit more precautions.
So while it's probably not superior to water in all cases, it looks like an interesting alternative in some cases.
Methanol is less caustic, but may not be as abundant for ISRU, or require more installations. Then again, maybe it can be made easily enough to not make much of a difference? Again, could be an interesting alternative, thanks!

About Antarctica, we must note that it is artificially slowed down: the continent has been declared a Sanctuary, so all you are allowed to do there is science. Once the time is passed and natural resources lobbies beat environmental and science lobbies to prevent renewing it, I expect to see way more people there.
At it stands, there has been children born there, and there are a few permanent installations. Even if it's individually for a short time, people already settle in Antarctica despite the adverse conditions (both natural and artificial)

In fact, Antarctica would be a parallel to the Moon or asteroids: a harsh, distant environment with both scientific and natural resource interests, while the Gobi desert would parallel deep space: a harsh, distant environment where pretty much the only 'resource' is that there's no one around.
People may not settle in the Gobi desert, but they do in Antarctica. If that's really a good parallel, well, that's good news!

Thucydides said...


The "Space Stagecoach" is a pretty serious proposition from what I have seen, and it combines the virtues of being rugged, low cost, simple and robust. The analogy might be between the "classic" British sports cars with their fussy hend welded tube frames, bespoke engines and fiddly Lucas electrical systems, and a 1963 Corvette "Stingray" with its loud and brutish V-8.

While the British car was theoretically much better (lightweight, excellent power to weight ratio and so on), it also required endless tinkering with multiple carburetors (or carburettor if you want to be British about it), the electical system, multiple other parts and systems; with a 'Vett you just turn the key and drive away.

One version on the link ( looks a lot like a kite; a diamond shaped solar array, 4 X bracing beams and a hab module on the end of two beams, with an engine at the center. This is about as minimal of a ship design as I have ever seen, yet it provides all the classic needs for long duration space flight (energy, protection from radiation and vaccuum, manouverability, artificial gravity) in one simple and rugged package. Add a "strongback" opposite the engine mount for carrying cargo pods and pallets and you have a real "space pickup truck". A utility vehicle like that would have a huge effect on making space operations cheaper, safer and simpler throughout the inner solar system. (Outer solar system would need a nuclear reactor to power it, rather than a kite shaped PV array).

Cererean said...

Re. Antarctica, I think it would be a really good idea for space enthusiasts to start colonising it. The social, technical, and political issues involved in doing so are very much like the ones faced by anyone wishing to colonise other planets, moons, and asteroids, so it may be very useful to get away from homo depot syndrome, and also get some idea of the political issues that will be involved. You won't be able to set up a mining operation there - at least, not one that will be able to export - but we'll allow you to import raw metal during the summer, plus a few low mass high value items... but if something breaks during the winter, you'll have to fix it yourself.

I think methanol can be synthesised relatively easily from hydrogen and carbon dioxide, much like methane can. I hadn't considered it before as a potential propellent in a thermal rocket.

Rick said...

Re 'spacewagon.' I am a big fan of solar electric propulsion (at least out to the main asteroid belt), but I wonder if trying to use water for everything is that helpful, wonderful substance though it is. You can indeed use it as a propellant for electric (or nuke thermal) drive, but it is a lousy one due to molecular weight.

From the life support page at Atomic Rockets, humans need about 4 kg of water per day, and NASA allows 26 kg for personal hygiene. With decent recycling, say conservatively 6 kg/day net consumption, a couple of tons per year. Ten tons per year if you just pump it all into the fuel tank, not trying to recycle. Even that won't put a big dent in propellant consumption when you consider the mass of the ship, fittings, payload, etc. And once you use it as propellant, of course, it is gone. Also I confess to being uneasy about living in a tent as primary habitat!

This need not rule out a fairly cheap space pickup truck, as such things go. But the features of one are probably something we'll only learn from operational experience, like the tradeoffs between passive systems for simplicity versus active ones for saving weight, etc. And on general principles I like to stick to (ostensibly!) conservative figures, like my $1 million/ton rule for spacecraft dry mass, as a minimal reality check too often lacking in space speculation. If, for example, people could build jet planes to automotive standards and save 90 percent of the cost, they would. They don't, so my guess is that it won't be practical for spacecraft either. As always, YMMV.

Cererean - welcome to the discussion threads! Overall, Antarctica - and for that matter its junior cousin, the arctic zone - probably deserves a lot more attention from space geekdom. Space is many times harsher (that whole O2 thing, for example), but arctic conditions are not a bad start for coming to grips with problems and possibilities.

Brett said...

I like solar electric propulsion, but I'm not really sold on it for anything except for non-time-sensitive cargo hauling in the inner solar system. I remember trying to do the math to see what kind of solar panel area you'd need to get a decent travel time to Mars, and they were pretty colossal - hundreds of square meters of solar panel area. Good old chemical propulsion will do very nicely for most purposes.

Now if we're sending a deep space mission to Jupiter (or even the Main Belt of asteroids), then that's another matter. Unless you're crazy enough to try aero-braking in Jupiter's atmosphere, which just sounds . . . absolutely terrifying.

Rick said...

Brett - From my own back of the envelope for solar electric propulsion, more like acres of solar panels. Hectares, outside of North America. It is sort of philosophically elegant, in a way - a ship's solar wings would be on the same order of size as the original - and still most important - solar power installations: farms. With the rest of the ship about the size of the farmhouse and barn.

The asterisk is obviously our ability to build such big structures in space, and make them lightweight enough that your performance isn't taken behind the barn and shot. For comparison, the sail area of the largest full-rigged ships was on the order of one acre/hectare. But if you can do it, it should be good for about 1 milligee, which gives you nearly 1 km/s per day; in a month you're booking along at 25 km/s. Out to the asteroid belt it will be hard to beat for fast deep space travel.

Brett said...

They are pretty magnificent looking. The first manned solar-electric ship would have to be named the Dragonfly. I bet you could see it from the Earth's surface as it spiraled outward.

I suppose any nuclear-electric propulsion system worth its salt would have some impressive "wings" as well, although they'd be radiator wings instead of solar panels. Good for the eventual trip to the Outer Solar System, with the ship sheltering in the shadow of Callisto.

Brett said...

Although. . . the Solar Dragonfly was moving about 35 passengers in your proposed Solar Electric Ship. If you already have the in-orbit chemical refueling facilities and assembly due to the settlement of Earth Space, then it's not a stretch to imagine the "slow cheap" service being a chem-ship ride taking six months to Mars. Not as fast or lovely as the Solar Ship, but cheaper and less bulky.

That comes later, though. In the mean-time, the Solar Ships are the way to go in Deep Space, and they can take you almost anywhere in the Inner Solar System without the need for refueling facilities at the destination.

Cererean said...

Re. the cheap chemical service, if you time it right, you can get to Mars in about 3 months using chemfuel, thanks to the Oberth effect and L1. Though deceleration may be difficult...

Though, it probably won't cost that much more to build a solar dragonfly than it will to build a chemfuel vehicle. You're dealing with less stress on the structure for it remember, and rocket engines cost money as well. It may turn out that the solar array (cells plus fresnel lenses) and engine may not be much more expensive.

Tony said...


No, I really don't think the customer cares much, evidently not enough to severely bother them. SpaceX has a very robust manifest and they fully intend to test reusability on these flights. One of the customers (SES) expressed interest in using a reused first stage too.

I really shouldn't have to point this out, but that was before Sunday. Starting Monday, you can bet that everybody on the manifest, as well as everybody in negotiations to go on the manifest, is reassessing every representation and promise SpaceX ever made to them. You can bet the accident investigation will be closely watched and its results combed very fine. If not entirely satisfactory -- and I don't see how it could be, given the circumstances of Sunday's launch -- you're going to see some pretty significant changes in what the customers will be demanding.

Tony said...

Thucydides: tell the truth, I suspect that one of the drivers of space colonization will be simply to get away from Earth and not have to deal with Chinese hackers, Vladimir Putin, bankrupt Greek politicians or the annoying political class that is leaning on you at home...

Anybody that can afford to get away into space has more to live for on Earth, and the resources to make life comfortable enough, if not perfect. If worse comes to worse, you can always bribe the right people.

BTW, the spacecoach has one very obvious weakness. Take a look at any picture of the ISS (any one you choose, as long as it shows the whole assembly), then think things through for about 30 seconds.

Elukka said...

So because of an apparent second stage (or, offchance, payload) failure, customers will push to prohibit SpaceX from testing first stage reusability because... their attention is divided or something? That really sounds like a stretch.

Tony said...

The second stage failure was just the proximate cause of the launch vehicle loss. Root cause analysis may -- and, in the case of aerospace, most often does -- reveal underlying systemic and/or programmatic problems. It's entirely possible, and maybe even likely, that Musk's little side project is a contributing factor. In any case, it's incumbent upon the customers at this point to demand a full accounting and insist that all unavoidable risks be reassessed.

Thucydides said...

The one claimed advantage of the electric propulsion systems in the "Spacecoach" is ISP's ranging from 800 seconds (similar to a NTR) to 2000 seconds, similar to exotica like VASMIR or other ion and plasma engines. Since the engine does not seem as massive or bulky as some of the other proposed systems (and so long as you stay away from nuclear reactors and the mass of shielding), the high ISP is very attractive. Assuming the thin film solar panels work as advertised, the system will be much less massive and have a very high performance compared to the competition.

Tony alludes to the lack of thermal radiators, but for the concept illustration I'll put that down more to artistic licence than anything else. Putting thermal radiators on the ends of the booms where the habs are is one possibility.

Using water simplifies things considerably, since if you have an issue you can always shunt the water from propulsion to life support to thermal control. This will be somewhat more involved if you have toxic fluids like Methanol or Ammonia, which have to ruthlessly segregated from the water.

Rick said...

Dragonfly versus chemfuel. I sort of took for granted that chemfuel could only do Hohmann-like orbits, since that is what is always discussed. But a little back of the envelope shows that with a high-ish but reasonable mass ratio of 4 (75 pct propellant fraction), the Oberth boot out of a long elliptical Earth orbit can hit or slightly exceed solar escape speed. That will certainly get you to Mars in less than 9 months, though my orbital mechanics fu is not up to saying how much less.

Aerobraking at Mars - more strictly 'aerocapture', since you're coming in above Mars escape velocity - would be nasty, because you're coming in WAY above escape velocity. Too low and you burn up; too high and you skip back off on a long, long solar orbit to nowhere. (Or even a solar escape orbit, which takes even longer to get nowhere, for very large values of nowhere.) And even just right, deceleration and heat load will be brutal.

We don't know whether solar electric can scale to the Dragonfly requirement, dozens of megawatts and a milligee or so. (The Dawn probe is in the microgee range.) Finding out will no doubt cost a bundle. But if it does scale, there's no obvious reason why Dragonfly would cost more per payload.

One thing, electric drive is not an efficient user of lunar ice, since the oxygen would only reduce propellant performance. So you'd just have to throw it away, whatever Luna Base can't use.

Falcon 9 loss. I am still not seeing cause to heavy breathe. An 'overpressure event' in the second stage, per early buzz, can ruin your entire day. But what is the Falcon failure rate so far? Maybe 20 percent? That is 10x the industry standard for mature launch systems, but seems about in line for a new stack in its first dozen or so flights. And an 80 percent success rate is about 80 percent better than you'd expect from alt-space flakes. Presumably the market already priced in the new kid on the block factor. it will price it in a bit more, and SpaceX will either roll with the punch or go on the ropes.

I have not followed SpaceX or Elon Musk at all closely. My judgment of them is based purely on Falcon, which looks overall like a sensible shoes conservative approach. No aerospike engines or SSTO jive, or even fancy schmancy hydrogen, just lots of kerosene and a single engine type in sea level and vacuum varients. Yes, trying to recover the first stage IS fancy, but unless that did in fact compromise the launch, for which zero evidence so far, the customers don't care what happens to those stages after they are done with them.

I looked at the ISS for more than 30 seconds, and the specific problem for Spacecoach eludes me. But I do see another subtle problem with carrying around huge amounts of water. Blackbody temperature at 1 AU is about 255 K. If your water freezes, it will still provide shielding, but it won't come out of the tap or go into the propellant feed lines. Heat management is one of the bigger devils in the details of space travel.

Nyrath said...

Rick: From my own back of the envelope for solar electric propulsion, more like acres of solar panels.

Agreed. This ion-drive design has just a bit more than 150 acres of solar cells.

Large solar powered orbital transfer vehicle

Geoffrey S H said...

"I looked at the ISS for more than 30 seconds, and the specific problem for Spacecoach eludes me."

Perhaps spacecoach is too simple to work? Its internal systems might be so simple and bare-bones that the various dangers and problems travelers will regularly face cannot all be accounted for? Perhaps it would have to be so large to properly support the passengers that it would take too long and too much money to construct?

Rick said...

Nyrath - Another cool link! And I like their 'plumber's guide to starships' series.

Perhaps spacecoach is too simple to work? That is sort of my gut feeling, without analyzing the design. The answer to complexity is probably not to take an ax to it, and stuff like using water for everything and living in a Bigelow bag may be more creative than practical. But still ideas worth exploring!

Thucydides said...

Being a blog, the amount of detailed discussion on things like Spacecoach are limited by space. Some of the advantages of Spacecoach's simplicity can translate into savings for the more complex stuff like life support and so on.

Based on the published figure of 40 tons for a basic Spacecoach, two Falcon launches to bring everything into orbit and keeping to Rick's cost estimate for aerospace hardware, we get a $40 million dollar flight article and $100 million to put all the pieces in orbit ($50 million/launch). A $140 million deep space capable craft, or general purpose "pickup truck" for operations from LEO to cis Lunar space seems pretty reasonable. If/when lunar ice or water from NEO's becomes available, then the second Falcon flight isn't needed (how much water costs in orbit from Lunar or NEO sources isn't going to be obvious, maybe it will be cheaper to truck it up from Earth for a while!)

Thermal management of the water to keep it from freezing up will be one issue, although it doesn't seem insurmountable (worst case scenario: the huge solar panels are powering water heaters in the tankage when they are not powering the engines). The heat of the spacecrafts systems could also be dumped into the water tanks rather than external radiators.

This does sound like a topic worth expanding on.

Brett said...


Thanks for that info on aerobraking. Another little difficulty that Zubrin has been eliding over with Mars Direct while slamming VASIMR.

Tony said...

The problem with the spacecoach, as illustrated in the io9 link, is that the thruster cluster is apparently mounted rigidly, with its axis normal to the plane of the solar collection array. While not an unworkable arrangement, one that makes more sense is like the arrangement of current solar-electric interplanetary spacecraft -- and ISS -- where the arrays are on gimbaled wings that can be pointed constantly at the sun.

Tony said...


Falcon 9 loss. I am still not seeing cause to heavy breathe.

I agree, no cause to heavy breathe. Just cause for due diligence on the part of the customers, both existing and potential. Also, let's not forget that the second stage is not a subcontracted module, like second stages on most American launch vehicles. It's a SpaceX product. That means that SpaceX technology and procedures -- all of their technology and procedures -- has to be under scrutiny, simply as a matter of prudence. Just because it was the second stage that failed doesn't mean that's the only place that needs to be reviewed.

Put yourself in the shoes of a customer getting ready to lay down $100M for a launch campaign that (necessarily, but also inescapably) puts hundreds of millions of dollars more of spacecraft and years of future revenue at risk. Now your intended launch service provider has had a total vehicle loss carrying a revenue payload. You're going to want complete and believable answers before carrying on. You are also going to look at competitors, maybe not to switch up your game, but to see what you would like to see in SpaceX for risk mitigation. You're going to notice that none of these other companies is screwing around with side projects that increase technical and operational complexity. It would only be prudence, as a fiduciary of your financial backers, to question unnecessary risks. Reusability experiments, even if they weren't the cause this time, are still an unnecessary risk in the context of getting your payload in orbit.

Thucydides said...


Point taken about the positioning of the engine in the diagram (although since this is an artist's conception there may be things like engine gimbaling which are not really delved into). Oddly enough, on the Spacecoach's own website ( the artwork they chose is entirely different (and rather less plausible in my mind). In terms of adapting existing design ideas, a truss with "wings" like the ISS, with some Bigelow "bags" and water balloons strung along the side, the "microwave" in the back and a wakesheild up front is easily doable based on current practice and experience. This is going to be bigger and heavier than the 40 tons they estimate.

WRT people getting away from it all, while wealthy people may be able to bribe or otherwise insulate themselves from opressive bureaucrats and the like, historically middle class people are the ones who take the step of moving out. The settlers aboard the Mayflower, for example, would be considered "middle class" by today's standards, and many of the early settlement groups were middle class people looking for a new start away from religious persecution. Commercial settlements would also consist of "middle class" tradesmen and their families, who could be expected to be able to do the work needed or expected in the New World for their wealthy patrons and expedition sponsors back home. So if there is a relatively cheap and reliable means of transportation and the ability to "live off the land" to make a real settlement, then I think there will indeed be a push of sorts for people interested in settling where they can practice their own social, religious of economic beliefs without outside interference.

Tony said...


WRT people getting away from it all, while wealthy people may be able to bribe or otherwise insulate themselves from opressive bureaucrats and the like, historically middle class people are the ones who take the step of moving out. The settlers aboard the Mayflower, for example, would be considered "middle class" by today's standards, and many of the early settlement groups were middle class people looking for a new start away from religious persecution. Commercial settlements would also consist of "middle class" tradesmen and their families, who could be expected to be able to do the work needed or expected in the New World for their wealthy patrons and expedition sponsors back home. So if there is a relatively cheap and reliable means of transportation and the ability to "live off the land" to make a real settlement, then I think there will indeed be a push of sorts for people interested in settling where they can practice their own social, religious of economic beliefs without outside interference.

No such means are likely ever going to exist. Things may get cheaper, but not to the point that any recognizable analog of Mayflower. I know you grew up on the highly optimistic space fiction of the 70s and 80s. Well, we have to leave that all behind and get serious. Nobody's going to go live in space for political reasons. Few, if any, are going to go live in space for economic reasons. (Even subcontractors for foodservice and things like that are probably going to have to provide highly qualifies and competitively selected personnel, who will serve one or perhaps two multi-year tours, but eventually return to Earth.) The human future in space belongs, probably for many centuries, to explorers and a minimal amount of vitally necessary logistical support personnel, all of who will want to come home to Earth.

Rick said...

Tony -

SpaceX. I imagine that the actual negotiation of launch prices would make Constantine Porphyrogenitus throw up his hands and say 'too Byzantine for me'. Presumably SpaceX is underpricing its short term costs, like anyone breaking into a market. Now it may have to do so a bit more, and convincingly show that the failure was 'normal,' not a sign of systemic flaws.

It does turn out that I lo-balled Falcon's performance to date: 19 launches, 17 successes, one partial failure (the primary payload reached its orbit, a secondary payload - in effect filling an empty seat on the bus - did not); and the blowup. A success rate of 89-95 percent, depending on how you rate the partial - the 98 percent estimate for 'industry standard' may be deducting only complete failures.

The human future in space belongs, probably for many centuries, to explorers and a minimal amount of vitally necessary logistical support personnel, all of who will want to come home to Earth.

In the language of the old style Left this might be called 'enhancing the contradictions' of Rocketpunk Manifesto. In an earlier reply I disclaimed being 'realistic', but I probably belabor the practicalities, especially costs, more than most space speculation blogs. And in truth I do play with contradictory or at least inconsistent premises, since I am interested in both real possibilities and operatic conceivabilities.

Even my optimistic long term cost ballpark (which presupposes enormous traffic volume) is still way pricey in everyday human terms - $10,000 per night for the most cramped accommodations that have ever had luxury status, and people didn't ride Pullman trains for months on end. A group of billionaires might get their version of Galt's Gulch IN SPAAACE, but I doubt that is what Thucydides really has in mind.

In human terms I have no complaint about a space future essentially confined to exploration, since that is profoundly cool in its own right. And the moralist in me is not sure of the need for reprising all our human follies and sorrows in outer space. The writer in me has somewhat different priorities. Which means that I foresee an upcoming post looking more into whether and how a demi-plausible cost structure might yield, if not opera, at least a little song and dance.

Rick said...

A new post is up: The Space Authority and the Orbital Patrol.

Calvin said...

Hello everyone,
I started reading this blog about when it started to die down and am really excited to join the conversation.

I’d like to bring up magbeam propulsion as a really interesting technology for getting around in earth orbital space and beyond. A platform could fire a self-focusing plasma beam at a spacecraft equipped with an M2P2 or plasma magnet to push it, applying a few km/s for a 10 ton spacecraft and a helicon antenna in the hundred megawatt range. Unlike most beamed power concepts, the propellant is onboard the beam platform as well as the powerplant, which in this report is a solar array with a huge amount of battery storage.

Link from atomic rockets:

Conceivably, you could send 10 ton payloads from LEO all the way to the moon with one platform in LEO and another based on the surface of the moon to slow down the payload from the transfer orbit and do most of the dV involved in landing. The range is much better in weaker parts of earth’s magnetosphere. If the beam on the moonbase could push the spacecraft back into a transfer to LEO, then you could have your weekly moon-Xpress shuttle be little more than a small cabin with life support and a set of magnetic coils.

(One more reason to have a moonbase at one of the poles is that it could fire a beam retrograde to the moon’s orbit all month-long)

Another platform in a higher orbit could give the payload a boost big enough to do a 50 day transfer to Mars or Hohman to main belt asteroids, except that you need another platform at the destination before you can ferry supplies.

This opens up another possibility for the rugged individualist’s “stagecoach IN SPAAAACE.” A few tons for a transhab and the coils for a plasma magnet, the rest inert gas for inflating the magsail and water for life support and RCS. It would get a one time boost from the megacorp’s magbeam out to the frontier where the magsail would protect the pioneers from space weather and complete the rendezvous with the asteroid claim.

Rick said...

Welcome to the discussion threads! Readers and commenters like you are the main reason I have re-launched (so to speak!) Rocketpunk Manifesto.

An interesting twist on beamed propulsion - especially the part about the propellant also coming from the beam station, being (I gather?) bank-shot, so to speak, off the spacecraft being hustled along.

I don't think this tech would be a great fit for the 'spacecoach', though, for a bit of a roundabout reason. It falls into the class of 'electric railroad' approaches (see top of thread) that are optimized for heavy, steady traffic. Not a drive for heading into the back of beyond. Of course you could fit the spacecoach like those trucks the railroads use for inspection - raise the pantograph and zing along, then start the onboard engine, lower the rubber tires, and head into the boondocks.

But since the spacecoach is mainly for the boondocks, no reason for it to carry gear (whatever deflects the beam to scoot the ship along) that it rarely uses. So more likely the spacecoach would simply be shipped as a freight payload to the 'railhead', then proceed on its way from there.

fro1797 said...

A 'spacecoach' sounds like, at minimum, it would just be a hab, logistics module, and a power/propulsion module. Cheap, simple, just enough to get a few people and some cargo to an already established site. Maybe use them to support far-flung research bases scattered throughout the system. Much fodder for stories.


Jim Baerg said...

Calvin: "One more reason to have a moonbase at one of the poles is that it could fire a beam retrograde to the moon’s orbit all month-long"

You could do that from anywhere on the trailing hemisphere of the moon. The advantage of putting the magbeam at one of the poles is that it could turn 180° to point forward or backward. You want forward to bring the earth to moon shuttle up to the velocity of the moon in orbit around the earth or to speed up an interplanetary craft to over earth escape speed. You want backward to send the shuttle from moon to earth.

Jim Baerg said...

Here is something to make the regular moonship a lot easier.