Comments on Rocketpunk Manifesto: Space Warfare IV - Mobility

Hosing down an enemy ship with micro-second pulses...

2010-10-05T06:07:30.437-07:00

Hosing down an enemy ship with micro-second pulses?! Okay. We have GW lasers but only enough heatsink and radiator to absorb half a second of 'hosing'. You do the maths.

Bookmarking...

Jean - The uber-range laser is Citizen Joe's i...

2009-08-06T20:47:41.902-07:00

Jean - The uber-range laser is Citizen Joe's idea, not mine, but my guess: You can hold down the firing button so long as your power supply holds out, forcing any target within Incredible Range to maneuver constantly, gradually eating away at its delta v.

And if the laser is powerful enough you can sweep it through the target's evasion cross section like a hose, and sooner or later you will hit it.

I guess I am new here so I am unfamiliar with the ...

2009-08-06T13:43:18.093-07:00

I guess I am new here so I am unfamiliar with the 5-mile ship with the "badass Xaser" that has a range in the light minutes but...

It has a range in the light-minutes? Unless the object you are targeting has no way of creating Delta-V for itself, and therefore follows a predictable orbit, how are you supposed to aim and hit anything when it takes several minutes to spot the object. Let's say that you even have FTL sensors (gasp!) it also takes several more minutes for the weapon to hit. It seems like a good weapon to dislodge asteroids from inconvenient orbits (ie: on a collision course with a certain planet whose ecosystem we have a vested interest in) but utterly useless against a hostile foe who presumably knows about said "badass Xaser" and is very likely to alter its course, and at those ranges they wouldn't even need to eat to deep into their Delta-V budget. Close might count in horseshoes and hand grenades, but definitely not with a laser.

As Mr. Spock would say, fascinating! This seems to...

2009-08-03T13:52:10.753-07:00

As Mr. Spock would say, fascinating! This seems to be my day for interesting news/media items. (See my latest post.)

I just watched the show Defying Gravity on Hulu an...

2009-08-03T11:20:34.096-07:00

I just watched the show Defying Gravity on Hulu and sure enough, they used the magnetic clothes trick that I described earlier to simulate gravity.

Rapid attitude changes probably go hand in hand wi...

2009-07-10T13:39:10.690-07:00

Rapid attitude changes probably go hand in hand with high combat acceleration, but might well require a separate fuel supply. (Probably the same chemfuel as ordinary attitude thrusters, but a lot more of it.)

True that the super X-ray ship does not have to do a lot of 'gyrating' in combat, given its enormous weapon range.

Large internal rotating bodies can act as a gyro. ...

2009-07-10T12:52:25.485-07:00

Large internal rotating bodies can act as a gyro. They normally stabilize things, but if you apply some friction, you can rotate your ship along the axis of the gyro. You can also push perpendicular to the axis in order to turn the ship. Now the forces we are talking about are minuscule compared to what is needed for combat maneuvering, but they don't require re-mass to maneuver.

The 5 mile xray laser ship has ranges in the order of light minutes, so even microradians of adjustment are thousands of miles. Fortunately, the fine tuning and aiming is done with an array at the end of the ship, so once you get in the right area, you don't have to re-orient the ship. Likewise, being able to target at that range means that you don't have to worry about maneuvering from return fire.

"Ferrell - also attitude-change maneuvers, if...

2009-07-10T12:08:23.790-07:00

"Ferrell - also attitude-change maneuvers, if those are combat relevant, as for Citizen Joe's 5-mile ship with the badass X-ray laser. You pretty much have to de-spin a ship for attitude maneuvers, or it will go all haywire on you. (Which could be a good way to make Bad Things happen to spin bearings.)"

You're right, a military or "space watch" space crusier should have a huge set of maneuvering thrusters...with lots of fuel, perhaps even a seperate supply from the main engine supply...

Ferrell

Ferrell - also attitude-change maneuvers, if those...

2009-07-09T20:31:06.407-07:00

Ferrell - also attitude-change maneuvers, if those are combat relevant, as for Citizen Joe's 5-mile ship with the badass X-ray laser. You pretty much have to de-spin a ship for attitude maneuvers, or it will go all haywire on you. (Which could be a good way to make Bad Things happen to spin bearings.)

"Yes, though size would also be a factor, esp...

2009-07-09T19:38:39.303-07:00

"Yes, though size would also be a factor, especially between 'spinnable' and 'permanently spun'."

Yes, or maybe thrust...a military interceptor or a Space Watch Asteroid Deflector may be spun-when-needed AND be a High Endurence space crusier...
Ferrell

Yes, though size would also be a factor, especiall...

2009-07-07T14:11:03.701-07:00

Yes, though size would also be a factor, especially between 'spinnable' and 'permanently spun'.

Future spacecraft might be classified into low, me...

2009-07-07T13:56:42.781-07:00

Future spacecraft might be classified into low, medium, and high endurance... no spin, spinable-when-needed, and permanently spun...

Ferrell

Plus, it is really funny to have the command cr...

2009-07-07T13:15:19.639-07:00
Plus, it is really funny to have the command crew talking like Mickey Mouse. ... Well, yes. :-)

As for which spacecraft will use spin, I suspect the main factor will be mission duration. For missions of a few days it is hardly needed, but for spacecraft intended for permanent habitation (stations, or ships that function as 'mobile stations') it is essential. Where the dividing line is will depend on a host of secondary features, but I'm inclined to think that mature interplanetary craft will have spin.

I suspect that most spacecraft will use the full mix, because it is the simplest approach, e.g., you can open both doors to the docking collar. Spacesuits will probably use pure O2 to minimize pressure and resulting joint stiffness, but other than that I think the standard mix is preferred.

Plus, it is really funny to have the command crew ...

2009-07-07T11:52:52.340-07:00
Plus, it is really funny to have the command crew talking like Mickey Mouse.

I suppose on a more serious note, what kind of ships would have some sort of artificial gravity and why? What sort of ships would make do without? What sort of ship run with the full pressure Nitrogen/Oxygen mix and which use a 'lesser quality' air?

Citizen Joe - Just considering the tech issues by ...

2009-07-07T08:55:39.597-07:00
Citizen Joe - Just considering the tech issues by themselves, I still think the simplest approach would be to use the breathing mix for the whole pressurized volume. The 'dead space' between the pressure shell and the spin structures inside is is probably small compared to the volume of the drums themselves, plus the volume of nonspun micrograv working spaces.

But story requirements do pretty much trump all other considerations!

Joe: If you have some technology that can get stu...

2009-07-07T08:08:14.718-07:00
Joe:

If you have some technology that can get stuff out of the atmospheres of the gas giants in large quantities at reasonable cost, that technology can more easily get stuff from Earth or Venus. I note that Venus has over 3x as much nitrogen as earth in its atmosphere (mixed in with a *lot* of CO2) http://en.wikipedia.org/wiki/Atmosphere_of_Venus

If helium is readily available, so is nitrogen.

Argon is 25% denser than oxygen, which means that ...

2009-07-07T07:22:38.603-07:00
Argon is 25% denser than oxygen, which means that leaks from the microgee environment into the spin habs could result in a deadly stratification as the argon builds up on the outer edge of the habitat. Should you pass out on the floor, that means no oxygen.

That being said, there are many uses for argon. I just don't see it as being easier to get and use than nitrogen, thus less likely to be used as a buffer gas.

Helium-4 is about 50 times more abundant than oxygen, and 250 times more abundant than nitrogen and almost 3600 times more abundant than Argon. If you can solve that atmospheric dive problem it just stands to reason that Helium-4 is well suited to the microgee buffer gas. Even more so when you consider that it is the impurity you're pulling out of the hydrogen scoops, and thus would otherwise be waste.

One of the driving forces in my proposed setting w...

2009-07-07T06:38:45.078-07:00
One of the driving forces in my proposed setting was fusion power, which requires Deuterium and He3. Diving into the upper atmospheres of the gas giants was to be the primary source. That of course requires a specialized ship. However, once you're in the atmosphere, you can use it for propulsion rather than burning your remass. I had even envisioned deep plunge vessels that used multiple pressure hulls and the crew operated in hardshell suits to harvest ammonia from Uranus at around 100 atm pressure. That is an incredibly dangerous job that requires people on board because the dense atmosphere pretty much cuts off external communications, like during the blackout phase of re-entry. But the nitrogen is needed to support plants, so in the end, it is worth it.

The operations around Saturn were intended as an attempt to have a self sustaining ecosystem in case we found another habitable system. Titan was the primary source of nitrogen for the agriculture industry there. Meanwhile large chucks of frozen ammonia were lofted into space and then chucked towards Mars. With some course corrections near the end, these ammonia asteroids were driven into thin atmosphere of Mars in an attempt to build it up, part of the terraforming project there.

All of this was part of a scifi setting and not something I truly expect to happen. Much of it was designed around the notion of creating a compelling story and explaining why people would be out there doing this stuff when you could otherwise just send a robot. So, yes, I'm invoking the Zeroth Law of SciFi a bit, but I do try to keep the rest of physics intact.

Now, if you get into the likely events, space warfare drops off the playing field entirely in favor of OMG! We just hit WHAT?

Joe: I think nitrogen would be much easier to get...

2009-07-06T21:39:07.133-07:00
Joe:

I think nitrogen would be much easier to get than helium. IINM there is reason to think the ices on the moons of Jupiter & Saturn would include ammonia (NH3) ice. Also the organic crud in carbonaceous chondrite meteors probably includes nitrogen bonded to carbon atoms.

Meanwhile unless you have some way to get stuff out of the atmosphere of gas giants, helium will be only available from gas absorbed from the solar wind in regolith on airless bodies like the moon & will be a minor byproduct of mining the regolith.

How about argon as a nitrogen substitute? It's...

2009-07-06T21:06:23.732-07:00
How about argon as a nitrogen substitute? It's not dirt common, but probably not too hard to find locked into ices anywhere beyond the snow line. I'm nearly certain it is easier to come by than helium.

Rick, I would pressurize that area with a breathab...

2009-07-06T20:29:17.246-07:00
Rick, I would pressurize that area with a breathable mixture, but I'd use helium as a buffer gas since it is more readily available than nitrogen in space. But I wouldn't use helium in the habitat section due to the centripetal force causing it to stratify. The helium will want to leak towards vacuum not into the pressurized nitrogen/oxygen areas. Losses of helium and oxygen aren't that big a deal, since oxygen can be cracked out of the ice stores and helium is easy enough to find in space. Nitrogen is harder to find (at least in our system) and requires lifting it off the surface or penetrating into gas giants to crush depths (Although I have concept ships for that too). That leaves Earth, Titan (at Saturn) and Triton (at Neptune) as sources of nitrogen.

Yep, I've seen those. I extrapolated on that ...

2009-07-06T20:11:36.524-07:00
Yep, I've seen those. I extrapolated on that suit for the command crew of the ship I've suggested. The command pressure suit includes biomonitoring, cooling via perspiration, magnetic linings and it relaxes when a charge is applied. Thus, it is easier to get into. Without the charge, the fibers tension up to apply pressure. The command crew operate with configurable gloves that operate the controls virtually. In case of an emergency, the command crew need only don their helmets rather than try to suit up entirely. Meanwhile, operating between two magnetic plates simulates gravity for operation in an otherwise microgee environment.

Citizen Joe - The one real question I'd have i...

2009-07-06T18:28:09.170-07:00
Citizen Joe - The one real question I'd have is why not simply pressurize the whole volume with a breathable mix? The spin sections are then just Really Big counterparts of the Discovery centrifuge in '2001', and you can dispense with pressure hatches entirely. (Of course you'll have emergency gastight hatches, but any large spacecraft will have those.

Jim - Presumably the entire suit does not have to be on this principle (the helmet obviously isn't. That would alleviate the complications of fitting it to the torso, and the struggle of getting into it.

At minimum this approach would be great for the gloves, which seem to be much the worst aspect of working in present day spacesuits - imagine trying to do handwork wearing a baseball mitt or boxing gloves. Arms and shoulders are the next priority. I don't think the hips are a big issue in space, though more of one for people working on planets.

"Working in zero-g is difficult. Working in z...

2009-07-06T17:45:16.107-07:00
"Working in zero-g is difficult. Working in zero-g vacuum requires a bulky space suit."

Though considerably less bulky if this works:
http://en.wikipedia.org/wiki/Space_activity_suit

I realize that atmospheric friction could slow thi...

2009-07-06T06:25:13.645-07:00
I realize that atmospheric friction could slow things down, but compared to the energy needed for the drive, a little bit of friction is negligible. My proposed rings within a shell had the greater purpose of providing a construction environment. Working in zero-g is difficult. Working in zero-g vacuum requires a bulky space suit. If you pressurize the shell, you only need respirators (assuming you pressurize with non-breathable). Also pressurizing the shell means that you need LESS material to pressurize the actual habitat rings. So the weight requirement is a wash. The rotating rings also provide gyro stabilization for the whole ship. Which is useful since it is basically a gigantic laser. This sort of arrangement is admittedly unfeasible in sizes under 'Mobile space station'.

With the two tethered ships idea, you pretty much have to expend reaction mass to increase or decrease spin.