Nautilus-X: the Space Station With Rockets 121
astroengine writes "So we have a space station, now what? We've heard some rather outlandish ideas, but this is one concept a research group in NASA is taking seriously. By retrofitting the ISS with rockets, Nautilus-X will act as an interplanetary space station of sorts, including room for 6 astronauts, an artificial gravity ring, inflatable habitats and docking for exploration spaceships. When can we take a luxury cruise to Mars? 2020 by the project's estimate. It all sounds very 2001, but the projected costs of retrofitting the space station seem a little on the low side."
Comments on TFA (Score:4, Interesting)
He says:
The Nautilus has a huge deep-space antenna where laser transmission may make more sense. It also has a shuttle-derived remote manipulator arm which also seems like excess weight.
As for the manipulator arm, yes, it is excess weight. Excess weight isn't necessarily a bad thing if you are already going to be lifting a lot of mass to orbit. If, say, one launch for constructing this vehicle required a Dragon, HTV, Progress, or some other supply vehicle to be lifted (for the purposes of a lifeboat, or some such thing), one could piggy back the manipulator arm on as an extra payload and outfit it to the new spacecraft. If the arm would require an extra launch then, yes, it is an expensive addition. However, in the event that this spacecraft would be landing a crew and then picking them back up again, the manipulator arm would not be unnecessary mass, but, in that case, a critical system for redocking surface-to-orbit ferries.
The oddest thing about that assessment by the author is when he says this previously in the article:
To significantly lower mass and therefore reduce transit time, why not simply send unmanned landers ahead and put them into a parking orbit to wait until the crew arrives.
If the spacecraft is supposed to be linking up with landers in a parking orbit at the destination, you can bet your sweet ass that a manipulator arm will be necessary to capture the landers. Of course, alternatively, the crew could also take a ferry to the on-orbit lander modules instead, but then you'd be carrying around the crew ferries rather than the landers and/or the arm, which means, again, a trade study should be conducted and the folks at NASA have probably already done so.
One other thing to consider is that while a higher mass requires a higher delta-v to hop from orbit to orbit, if the excess mass is a small enough fraction, it may not make a practical difference. Rocket engines that are in production produce a certain amount of thrust. If that thrust can boost "up to X many kg of mass to this delta-v" then reducing your mass below X is somewhat unnecessary, unless you need or want a higher delta-v margin.
It's important to remember that the first European colonists to North America didn't land on the East Coast and then drag race to the Pacific. Rather, they established a colonial foothold in the East first (like we should in LEO) and then, after developing their on-continent infrastructure some, they set off to explore further. Baby-steps lead towards progress. One off, epic publicity stunts lead to debt.
The ring would have to be huge (Score:0, Interesting)
Imagine a small rotating ring, as seen in 2001. Imagine yourself crouching near the floor, then suddenly standing up. Conservation of rotational momentum would accelerate you in the direction of rotation, hard, and maybe give you vertigo as well. So you'd puke, fall down, slide in it for several feet. To be practical the ring would have to be about a mile in diameter.
Re:Neat (Score:5, Interesting)
Hahah, alright so. You construct an 11km high tower/launch ramp, a compressive tower the same as cell towers as a truss of smaller elements. A reasonable height-to-base ratiomight be 20:1. So a 10 km tower would have 3 base points 0.5 km apart, assuming you have a triangular cross section for the tower as a whole.
Each principal column would in turn be a truss with 3 sub-columns spaced 25 meters apart, which in turn are made of tertiary columns 1.2 meters apart and 0.06 meters in diameter each. The tertiary columns have a wall thickness of 0.03 meters. This puts you above the denser elements of the atmosphere. Its not nearly as hard as it seems, Frank Lloyd Wright designed mile-high skyscrapers back in the 30's.
Then you run maglev/railgun type vacuum tubes up the length of it, therefore using extremely cheap electrical energy to power the vessel through the first stage, which I think should put the ship into LEO at 7g, althoughyou'd probably still need a booster stage.
If you could launch at 10000 ft above sea level, you could reduce your velocity change to get into orbit by approx. 250 m/s. However, you need about 8000 m/s to get into orbit. A 3% improvement, which would actually be a serious improvement. A RL-10A has an Isp of about 450 seconds; thus, exhaust velocity Ve is about 4400 km/sec. Structure and payload mass fraction is exp[deltaV/Ve]; a RL-10A powered vehicle could achieve a maxium amount of structure plus payload to 8km/sec of 16.3%. Typically about 5% of this is actually payload. A 3% decrease in delta-V to orbit increases this to 17.3%. This increases the *payload* to 6% of the gross lift-off mass -- a 20% increase in payload.
Imagine the benefits of launching higher and a lot faster.
This has the effect of vastly reducing the cost to get to LEO and from there to proper orbit and eventually escape; if it was as cheap to get to orbit as it is to cross oceans, we'd already be on Mars.
So lets talk mineral wealth. The most detailed study of an asteroid, Eros, collected by NEAR shows that it contains precious metals worth at least $20 trillion. If Eros is typical of stony meteorites, then it contains about 3% metal. With the known abundance's of metals in meteorites, even a very cautious estimate suggests 20,000 million tonnes of aluminium along with similar amounts of gold, platinum and other rarer metals.
That is just in one asteroid and not a very large one at that. There are thousands of asteroids out there.
So once you make it economical to get up there, you need to build out an infrastructure. There are lots of theories on how to do this by aseroid resource extraction, I'm wavering towards the "rubble pile" asteroids which come pre-demolished, I can go into more detail if you like.
Let's be clear though, unless a launch tower would drastically lower costs to space, the initial buildout has to be for space and by space. Then once orbital manufacture has reached a sufficiently advanced level, you can send manufactured goods, worth many times their wieght in gold, straight back to earth markets.
/borrowed from many sources, I haven't the time to do the maths right now.