08-20-2021, 07:57 AM | #11 | |
Join Date: Aug 2004
Location: Wellington, NZ
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Re: [Spaceships] getting into orbit without superscience?
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Rupert Boleyn "A pessimist is an optimist with a sense of history." |
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08-20-2021, 08:33 AM | #12 | |
Join Date: Jun 2006
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Re: [Spaceships] getting into orbit without superscience?
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The truth is that even a lot of spacecraft engines and power plants that aren't "officially" superscience really are, it's just the required superscience is the somewhat invisible "requires parts that still work at temperatures too high for chemical bonds to exist".
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-- MA Lloyd |
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08-20-2021, 10:02 AM | #13 |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: [Spaceships] getting into orbit without superscience?
Well, you can use hydrogen as reaction mass instead of combustion byproducts; that allows an ISp of around 1,400 without being any hotter than current rocket. The problem is that reactors can't generally run anywhere near as hot as a current rocket engine.
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08-20-2021, 11:11 AM | #14 |
Join Date: Aug 2007
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Re: [Spaceships] getting into orbit without superscience?
Free neutrons don't constitute any sort of long-term radiation hazard. All of the major components of Earth's atmosphere are still harmless after absorbing a neutron. The neutron hitting a nucleus but not being absorbed does transfer some energy but it's pennyante stuff. You're in much more danger from the heat of the exhaust.
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Fred Brackin |
08-20-2021, 11:55 AM | #15 |
Join Date: Aug 2004
Location: Ronkonkoma, NY
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Re: [Spaceships] getting into orbit without superscience?
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.) |
08-20-2021, 11:57 AM | #16 |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: [Spaceships] getting into orbit without superscience?
Mean free path of a neutron in air near is something like half a mile at 1 atmosphere, so it's a bit of a direct radiation hazard and also can activate materials on the ground.
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08-20-2021, 12:17 PM | #17 |
Join Date: Aug 2007
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Re: [Spaceships] getting into orbit without superscience?
....and dispersing these enutrons over an area of half a mile in radius doesn't reduce the concentration to negligable numbers?
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Fred Brackin |
08-20-2021, 12:34 PM | #18 |
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Join Date: Sep 2004
Location: Southeast NC
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Re: [Spaceships] getting into orbit without superscience?
A ton of heat producing equipment (i.e. reactor) will heat a lot less reaction mass to those sorts of temperatures than a ton of chemical rocket engine can burn. In other words, you can have Isp or thrust (with current or near future technology), take your pick.
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RyanW - Actually one normal sized guy in three tiny trenchcoats. |
08-20-2021, 01:33 PM | #19 | |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: [Spaceships] getting into orbit without superscience?
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A 5 ton (SM+6) chemical rocket produces 300 tons of thrust (3 MN) with an exhaust velocity of 3 mps, for a total power output of 7 GW. A 5 ton (SM+6) fission power plant produces 1 EP, sufficient to power a beam weapon that emits 30MJ/10s or 3MW. There's probably inefficiency there, but even if you set beam weapons to 10% the rocket is more than 200x as powerful. You can get around that, but it generally requires open cycle. Which means you're spraying fuel out the back. |
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08-20-2021, 03:50 PM | #20 |
Join Date: Jun 2020
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Re: [Spaceships] getting into orbit without superscience?
The SABRE engine is also relevant. It has two modes, acting like a ramjet at low altitudes and switching to closed cycle mode at high altitudes. Wikipedia It works really well in Kerbal Space Program. It wouldn't be suitable for a trip around the solar system though, but you could fly crew and cargo to orbit and rendezvous with a craft constructed in orbit. Another drawback is that it requires an atmosphere with oxygen (or possibly some other oxidizer?).
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