TL7 Spaceship Design

[scc]

Originally Posted by Ulzgoroth

All NERVA tests were done on the ground, though, so what difference are you pointing to here?

Rocket engines and 'fuel economy' is weird, but in simple terms the faster the re-mass, that is fuel, leaves the rocket nozzle the more delta-v you have, the problem that this is not a linear equation, to get a delta-v increase of say x10 you'd have to decrease re-mass flow by say x100, which means thrust drops by x10 as well. Now exp-atmospheric this doesn't matter but in atmosphere you NEED to generate more then 1G of thrust.

Take NERVA and compare it to the F-1's powering the Saturn 5, it gets a thrust to weight ratio of 1.38 to their 94.1, but gets more then twice the delta-v per unit weight of fuel.

[Ulzgoroth]

Originally Posted by scc

Rocket engines and 'fuel economy' is weird, but in simple terms the faster the re-mass, that is fuel, leaves the rocket nozzle the more delta-v you have, the problem that this is not a linear equation, to get a delta-v increase of say x10 you'd have to decrease re-mass flow by say x100, which means thrust drops by x10 as well. Now exp-atmospheric this doesn't matter but in atmosphere you NEED to generate more then 1G of thrust.

Take NERVA and compare it to the F-1's powering the Saturn 5, it gets a thrust to weight ratio of 1.38 to their 94.1, but gets more then twice the delta-v per unit weight of fuel.

...And what's the connection between that and the "environmental disaster, spewing radiation everywhere" assertion?

[Rupert]

Originally Posted by Ulzgoroth

I've always heard radioactive exhaust on Project Pluto declared a feature. On the other hand, the wiki writeup argues that Pluto's engine wouldn't deliver particularly much fallout - though that may have been intended in comparison to the multiple nuclear warheads it was supposed to drop.

Pluto wasn't a space rocket, isn't even properly a rocket at all. It's a nuclear ramjet cruise missile/unmanned strategic bomber.

It wasn't the irradiation of the air that was the thing with PLUTO, it was that the pile was unshielded, so anything that came near it got fried and that after all its payload was delivered it was to crash into yet another target site, making for a very radioactive mess to clean up. The exhaust was radioactive, but not by enough to count in a nuclear war.

[Ulzgoroth]

Originally Posted by Rupert

It wasn't the irradiation of the air that was the thing with PLUTO, it was that the pile was unshielded, so anything that came near it got fried and that after all its payload was delivered it was to crash into yet another target site, making for a very radioactive mess to clean up. The exhaust was radioactive, but not by enough to count in a nuclear war.

I have literally never seen a discussion of Project Pluto that didn't make reference to it acting as a radiological weapon.

(Not by irradiating the air, but by shedding radioactive particles from its exposed core and/or direct irradiation by said core. Neither of which is likely to have much noticeable impact in an environment where the nuclear ramjet drone bombers are flying but nonetheless it always comes up. And frequently, as here, is the reason for Pluto being brought up in the first place.)

[Fred Brackin]

Originally Posted by scc

S

Massively complicated flying machines are very much in genre for steampunk.

I didn't say that your spaceplane was "massively complicated". I said it was "very sophisticated". These two things are not interchangeable. Indeed, in terms of Steampunk they often mean opposite things.

At any rate, the Cinemaitc Gadgeteer in question is going to be a lot closer to Tony Stark than anyone seen in Verne or even H.G. Wells.

If your setting is a lot more like TL9 with TL7 (or TL5) military weapons than TL5+2 Steampuunk all of this might make more sense.

[Geomax]

One SSTO method that'd be very in genre for Steampunk would be airship-to-orbit a la JP Aerospace. 12 fuel tanks + NTR + 4 gasbags (from SS7) gives you 5.04 mps (more than the 4.67 required here) and 3 more systems to play with - cram things in with Smaller Systems if need be. This isn't actually any more than you'd get with chemical, but you have a bit more delta v in orbit and can save on the need for a soft landing system by braking very slowly at high altitude. Since thrust isn't too important you can use a Smaller Systems NTR for a bit more payload as well.

Pretty sure TL7 material science wouldn't really be up to the task, but it's TL 5+2 with magsails and it's at least feasible in game.

[AlexanderHowl]

Spaceships with gasbags should really be treated as unstreamlined for Air Performance calculations because of their massive surface area. Additionally, they should tear apart over 250 mph.

[YankeeGamer]

Spaceships seems to make no adjustments for atmospheric density, yet a denser atmosphere means more lift for wings/parachutes for landing. On the other hand, thinner air means a faster speed of sound--useful for the gadget below.

Another option that seems very steampunk-like:
There is a long and wide track on the ground, and the ship rides on a rail vehicle--probably electrically powered--that provides the first boost--almost a first stage that doesn't leave the ground. That has the plot issue, for good or ill, of a long object that needs to be protected from baddies.

[AlexanderHowl]

That would need to be a really high TL rail. For example, a first stage disposable chemical booster would give 3.12 mps of delta-v. A train would need to accelerate at 5g for 102 seconds to reach that level of velocity. Assuming an equal amount of line for deceleration as accleration, the train would need a rail 511 kilometers. You would want it to crest at a height of 50 km at 255 km (maximum velocity), in order to reduce air resistance.

[Agemegos]

Originally Posted by YankeeGamer

On the other hand, thinner air means a faster speed of sound

Does it? I seem to remember back in freshman physics deriving a result that the speed of sound in a gas depends on its temperature and mean molecular mass but not on the number of molecules per unit volume.