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SCI-FI Spacecraft that can be constructed now


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A fusion reactor would be ideal to use as a method of superheating plasma and ejecting that to provide propulsion. Just need to tank up on liquid hydrogen.

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Fusion is still one of those "soon" technologies, and generating the power necessary to start the reaction would be better suited to powering the spacecraft and generating propulsion.

Using hydrogen as a coolant for the reactor and ejecting it out the back was studied as part of the NERVA program, the theory is sound, but there were problems due to the materials of the time.

Project Daedalus was proposed using inertial confinement fusion as the propulsion source:

Instead, Daedalus would be propelled by a fusion rocket using pellets of deuterium/helium-3 mix that would be ignited in the reaction chamber by inertial confinement using electron beams. 250 pellets would be detonated per second, and the resulting plasma would be directed by a magnetic nozzle. Due to the scarcity of helium-3 it was to be mined from the atmosphere of Jupiter via large hot-air balloon supported robotic factories over a 20 year period.

However, inertial confinement fusion at the moment requires a long setup time, and the beams have to be timed to the picosecond and aimed precisely on an ultra-smooth target. Even then errors can creep in, causing problems with the ignition. This is for one pellet, not the 250/second in Project Daedalus.

The simplest fusion drive would be to use hydrogen bombs to drive an Orion ship, they're 'cleaner' than fission bombs in terms of byproducts.

Ken

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Greetings!

The Eagle Transporter may LOOK easy enough for us to do, until you get to the Anti-Gravity part.

This ship had gravitational compensators in those four big pods at each corner (and those nuclear bottle rockets in back are another story!). Point 25 of C may not be warp drive, but it would be perfect for the solar system. I always wondered what an aerodynamic, flying version of the Eagle would be like...probably more feasable.

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Point 25 of C may not be warp drive, but it would be perfect for the solar system.

Except that you have to decelerate from 0.25C, taking basically the same amount of fuel it took to accelerate to 0.25C (depending on orbital characteristics)

Project Daedalus was expected to hit 0.12C after nearly 4 years of acceleration using 50,000 metric tonnes of fuel, it would then cruise for 46 years until reaching Barbard's star. It would not slow down at the target star system simply because there was no fuel left to slow down.

Ken

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Even the most "realistic" sci-fi spacecraft invariably understate the need for propellant. You need a lot of reaction mass to make the spaceship go places, and these spacecraft usually don't have big visible fuel tanks. Therefore they must (1) use some kind of super-dense propellant, meaning a lot of reaction mass can be kept in small tanks, or (2) they have some kind of super-efficient engines, so that a small amount of reaction mass is all that's needed. Neither fits the "can be constructed now" criterion.

The "Orion" nuclear-pulse approach exists only on paper, so I'm not sure if we should count it as "possible now".

Nuclear-thermal rockets have been tested (if only on Earth), so we could probably count those. I've toyed with the numbers and for a round-trip to Mars (with aerobraking upon Earth return) requires that propellant makes up about 6/7ths of the total mass. That's assuming nuclear thermal propulsion with anhydrous ammonia propellant (I'm skeptical about long-term storage of liquid hydrogen), aerobraking at Earth return, and about half the dry mass being shed before Mars departure (landers, empty tankage, etc.) You can play with the assumptions and get different numbers, but we're still talking an awful lot of propellant per unit of payload. That's something sci-fi ships almost never have.

Short of a major technological breakthrough, I think real spacecraft are likely to be more analogous to rockets than to ships, planes or space stations. That is, they'll be big things but mostly propellant, expendable rather than reusable, shedding stages as they go until all that's left is the relatively tiny payload at the end.

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One SF design I can think of from film that could be done with today's technology (albeit it has some impractical quirks) is the ESA shuttle Churchill from Lifeforce (for those that have seen the film, it only appeared in maybe the first ten minutes of it, as most of the film involved a naked Matilda May going around sucking energy out of people and turning them into energy vampire zombies). It was a lengthened space shuttle with a NERVA nuclear rocket engine strapped to the belly and two giant solar arrays. The craft was designed for a manned mission to Halley's comet. The NERVA has been tested and it works, plus a lengthened shuttle proposal was on the drawingboard at one time as well.

The only oddball bit in the film was it implied that the solar arrays would be extended while the NERVA was running, which is not a good idea since the stress would probably rip them apart. But, such arrays would potentially work for the coast phase and such a craft might be good for a Mars flyby. Due to the NERVA, it could perform missions in a few months that might take a year with just chemical drives. All one would need is reaction mass for fuel. Plus, the canard foreplanes on the shuttle also seemed like a not so good idea as well, due to the hotspots on reentry they might cause. Then there is also the notion of dragging around the dead weight of three SSMEs and a pair of wings on interplanetary flights when they would be pretty much useless for anything else after the shuttle was launched into space. And without a lander vehicle of some kind attached, it wouldn't really be able to do much except collect data in orbit or a planet or a celestrial object.

But, it could be built (not necessarily that it should be built).

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As a hard core fan of all things space exploration it is unfortunate that I most certainly won't be here for a major breakthrough in propulsion. I love reading books on FTL space flight. Here is an interesting article on hyper-drives from starshipmodeler. Maybe it is a possibility:

http://space.newscientist.com/article/mg18925331.200

Edited by afterburner
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