[Spaceships] getting into orbit without superscience?

[Rupert]

Originally Posted by fdsa1234567890

Orion drives would also work, but they also involve deliberately setting off nuclear weapons within the atmosphere, which make them extremely impractical as a common launch system. NTRs have a similar radiation flaw and are also no better than metallic hydrogen in terms of delta-v with even less thrust.

NTRs need not leak radioactive materials.

As for the overall question - yes, getting off Earth (and similar planets) with realistic rockets is a pain. Non-super science fusion is a no-go. Antimatter Thermal using high-thrust and/or water versions is workable at very high TLs, but isnt really any better than HEDM chemical rockets. On top of that, unless antimatter production is extremely cheap any antimatter rocket is going to cost an enormous amount to run. On the plus-side, antimatter-catalysed hydrogen (or water) fuel doesn't count as a volatile system.

There is another option from Spaceships 7 - the laser rocket. It gives the same performance as an HEDM rocket, but is cheaper and doesn't involve volatile fuel. The catch is that it depends on powerful laser systems at the launch facility, so it's not a low-infrastructure option. Also, the propellant is really cheap.

[Emerikol]

I guess it all depends on how you define super science.

Since current scientific theory affirmatively declares FTL travel is not possible, anything allowing for FTL travel would be super science in my book.

But there are things that many scientists would not be surprised if they happened. So if you took a scientist 100 years into the future and we had FTL drives, that scientist would be surprised. One of the foundational theories he was taught as fact has been overturned in some way. This happens in the world of science. Newtonian mechanics were overturned by Einstein's relativistic mechanics. Scientists in Newtons day would be shocked by that. So even super science breakthroughs are not completely off the chart.

For me the next big scientific breakthrough that will change the very nature of space travel, and I expect it to happen at some point, is some sort of unified theory. Scientists are pursuing it right now. So while such an approach is "impossible" today, many think it is not forever out of reach. Unlike FTL drives. So I wouldn't call this super science. I'd call it speculative science for sure. We may never discover that theory. If we do though we can turn electrical power into gravitical thrust. We can probably bond new materials using strong and weak forces that we could never imagine creating now.

I suspect though that many would call the above super science because it is not yet possible. So your definition matters.

[Stormcrow]

Originally Posted by Emerikol

I guess it all depends on how you define super science.

GURPS clearly defines what it means by superscience, and it marks all equipment as to whether it is considered superscience or not.

"'Superscience' technologies violate physical laws... as we currently understand them" (page B513).

Superscience equipment has a "^" for its TL or, if the writer decides that it appears at a certain TL, the "^" appears after the TL number.

So the original question can be restated as: what is the most efficient way to get from the surface to orbit using only equipment that doesn't have a "^" on its TL? (And there is an implicit "also not magical" in there.)

[RogerBW]

Originally Posted by Stormcrow

So the original question can be restated as: what is the most efficient way to get from the surface to orbit using only equipment that doesn't have a "^" on its TL? (And there is an implicit "also not magical" in there.)

It's not in Spaceships; it's in Ultra-Tech, p. 224. "Space Elevator (TL9)".

Seriously – because of the problems with rockets that other people have already pointed out, any spacefaring society that can use beanstalks probably should. So spacecraft that can get to orbit may be quite specialised, not your general-purpose freight and passenger haulers.

That said, in GURPS Spaceships terms and avoiding speculation about real-world drives, assuming a vaguely earthlike planet, you want:

• TL is not ^
• number of fuel tanks needed to get to orbit is as low as possible

Spaceships 1 p. 37 says that there's no constraint on thrust if your vehicle has wings, so by a strict reading of the rules an antimatter pion drive will get the job done. But at 0.005G per drive I feel it would have some trouble overcoming air resistance (and even ignoring that, at the end of a 10,000 foot runway it's doing a mere 38 mph, not to mention the runway has been vaporised). Maybe you can loft it off a balloon or high-altitude carrier aircraft?

But let's also say we need at least 0.1G performance. TL11 high-thrust fusion pulse drive, then, with 20mps per tank of pellets. A bit marginal? External pulsed plasma will unambiguously get the job done, and you don't even need wings. Then you're down to antimatter thermal rockets, HEDM, nuclear thermal, and chemical.

[thrash]

Originally Posted by RogerBW

TL11 high-thrust fusion pulse drive, then, with 20mps per tank of pellets.

I question whether fusion pulsed drives will even function in an atmosphere, which will interfere with the "laser beams, particle beams and/or miniscule amounts of antimatter" needed for ignition and with the control of the plasma that results.

[tshiggins]

Originally Posted by RogerBW

It's not in Spaceships; it's in Ultra-Tech, p. 224. "Space Elevator (TL9)".

(SNIP)

Also, the Solar System has only one planet where humans live -- or might want to live -- in large numbers, which also has a gravity well deep enough to require exotic material for the beanstalk.

On Mars, with only 38 percent of Earth's gravity, you could probably build the elevator cable out of Kevlar or current technology carbon fiber, or something.

Every other place would only need steel cables.

[Emerikol]

Originally Posted by Stormcrow

GURPS clearly defines what it means by superscience, and it marks all equipment as to whether it is considered superscience or not.

"'Superscience' technologies violate physical laws... as we currently understand them" (page B513).

Superscience equipment has a "^" for its TL or, if the writer decides that it appears at a certain TL, the "^" appears after the TL number.

So the original question can be restated as: what is the most efficient way to get from the surface to orbit using only equipment that doesn't have a "^" on its TL? (And there is an implicit "also not magical" in there.)

I did not realize this but I did wonder about the ^ on some items.

[RyanW]

Originally Posted by Emerikol

I did not realize this but I did wonder about the ^ on some items.

It could be noted that superscience ranges from "It's magic, don't question it" to "The math works out but we don't pretend to know how it works" to "Completely realistic except for the part where it doesn't instantly melt itself at this sort of energy density."

[Varyon]

Originally Posted by Rupert

NTRs need not leak radioactive materials.

The important thing to keep in mind about NTR's is that it's the thermal bit that's crucial, it's just that said thermal energy is generated by a nuclear (fission) reactor. It should be possible to avoid making the exhaust radioactive at all, although I assume you'd lose some thrust in the mix (as you're essentially making more of the drive's mass consist of shielding). It's also possible that, even with radioactive exhaust, it's rather short-lived radiation, unlikely to cause any environmental issues. While the delta-V of NTR is decent (IIRC), I feel what makes it a real contender is the ram-rocket option, where the drive doesn't use any reaction mass so long as it's in an atmosphere above Trace. That lets you get (partially) up to speed at essentially zero cost, so you should be able to deliver a greater mass fraction into orbit. The big issue with NTR is what happens when you have a serious accident.

Originally Posted by Rupert

There is another option from Spaceships 7 - the laser rocket. It gives the same performance as an HEDM rocket, but is cheaper and doesn't involve volatile fuel. The catch is that it depends on powerful laser systems at the launch facility, so it's not a low-infrastructure option. Also, the propellant is really cheap.

As I've mentioned before, you can actually help justify the expense of the launch lasers in that they can readily double as defensive systems - if it's powerful and accurate enough to launch a spaceship into orbit, it can probably take out almost any ICBM over the same hemisphere. Of course, this also means you need the permission, or be powerful enough you don't have to ask for permission, of the other polities in the same hemisphere, as you could also readily shoot down any commercial flight or similar in that area.

[Prince Charon]

Space elevators are tricky to build and potentially dangerous if things go wrong, but do seem to be possible, and might end up being an efficient solution to the issue of getting into orbit, compared to rockets. There are also a few other methods of non-rocket spacelaunch that might work.

Atomic Rockets has a fairly long list of realistic Surface to Orbit concepts, both rocket (not limited to atomics) and otherwise.