Real SSTO design

[Transits]

Could you please post designs (it can be pictures or descriptions) of an SSTO that could get into an orbit around Mars from its surface. I am writing a book which needs to have the SSTO and I would like to learn from the community what features I should add.

[SargeRho]

Getting into orbit from Mars' surface isn't hard, most proposals to go to Mars have a single stage to orbit Mars Ascent Vehicle.

But if you insist...

That's a Nuclear Lightbulb powered SSTO designed by William Black.

[Klingon Admiral]

Wouldn't a space gun be quite sensible on Mars? I mean, lower atmosphere density, lower velocities that need to be achieved, huge mountains which one could build the barrel into.

[SargeRho]

It'd be useful for decreasing the fuel needed to get into orbit, but might be too complicated to be feasible, a "normal" rocket powered SSTO might be more viable.

[Transits]

I doesn't need to be big, but it does need to carry 20 people to low orbit. I cannot use a space gun as the technology in my book is not very advanced yet.

[Nibb31]

Do a google image search for "Mars Ascent Vehicle". You'll find boatloads of MSTO and SSTO concept designs.

[Guest]

A chemical-powered hydrolox or methalox (if you want ISRU) SSTO, maybe with a nuclear OMS should do it. It would look like your bog-standard passenger rocket, only smaller and with big vacuum nozzles (atmo pressure is much lower on Mars) instead of SL ones.

Or try something like this: http://www.wired.com/images_blogs/wiredscience/2012/10/mars-excursion-module.jpg

[Idobox]

You need 4.1km/s deltaV to reach Mars orbit.

With a LOx/LH2 engine, that means a mass ratio of 3 will be more than enough.

For reference, the first stage of the Ariane 5V, which uses that fuel, has a mass ratio of 14.6.

It could reach orbit and come back with a payload of 14t (with a perfect burn, no gravity loss, no friction). With a 12t payload, you have a decent safety margin. Also, it should be noted that a Mars rocket could have a much better mass ratio than this because it wouldn't have to be strong enough to support a second stage while accelerating on Earth.

If you just want to reach orbit in a single stage and ditch the rocket, that same rocket could carry a 55t payload.

And that's a current rocket, weighing 12.7t dry, 186 t fueled, 30.7m high, 5.40 m in diameter.

[Transits]

It should be a space plane though. Sorry for not being clear, but the colony which uses it needs to be able to reuse it quickly, which means that I cannot use ablative heat sheilding or staging.

[SargeRho]

Then the one I posted might be a good choice. It's able to be reused quickly, as long as you got significant stockpiles of Uranium, Neon and Hydrogen.

[Transits]

Hydrogen yes, Neon and Uranium no, but I could swap out the nuclear engines for areospikes and turn it into a spaceplane (with the same features).

[SargeRho]

Using Methalox aerospikes is probably your best option. Methane is a lot denser than Hydrogen, easier to store, and doesn't have too much of an Isp drawback.

[Transits]

Thanks for the tip, although I don't know where I would get an easy source of meathane on Mars.

[SargeRho]

The air...and some Hydrogen from the permafrost underground.

[sgt_flyer]

Thanks for the tip, although I don't know where I would get an easy source of meathane on Mars.

You'll need to find some form of water (ice, for example) Then, with the water from the ice and co2 you could scrub from atmo, you can make methane + o2 with the help of electricity. (Basically, 2H2O + CO2 = 2O2 + CH4) - so you could make both methane and oxydizer

Edited March 26, 2014 by sgt_flyer

[Transits]

I didn't know that there was much Meathane in Mars' atmosphere. So thank you. The colony is based near a large aquifer, so this will be perfect.

[SargeRho]

There is almost no Methane in Mars' atmosphere actually. But you can make Methane and Oxygen from Water and CO2.

[SuperFastJellyfish]

I didn't know that there was much Meathane in Mars' atmosphere. So thank you. The colony is based near a large aquifer, so this will be perfect.

There isn't any methane in the atmosphere according to Curiosity. You have to gather co2 and source of hydrogen to create it on site AFAIK.

[Transits]

Well I can use the aquifers for that!

[SargeRho]

If (and that's a rather big if) Mars has a biological history, you might even be able to find Oil and Natural Gas underground.

[Nibb31]

It should be a space plane though. Sorry for not being clear, but the colony which uses it needs to be able to reuse it quickly, which means that I cannot use ablative heat sheilding or staging.

A space plane on Mars is a silly idea. Why would you waste mass on wings and hydraulics and tires when the atmosphere is too thin to provide any significant lift ? Why waste precious colony resources on building a beefy runway several kilometers long that can withstand the weight of a 200 ton spaceplane ?

There's nothing wrong with having fast-turnaround shuttle-like reusable thermal tiles on a VTVL vehicle. This is science-fiction after all, and VTVL is more realistic for a mars ascent vehicle.

Edited March 27, 2014 by Nibb31

[Accelerando]

you can also use regenerative cooling with cryogenic propellants. if you want hydrolox fuel for one, LH2 is a nice coolant. VTVL single-stage designs like phil bono's ROMBUS would have used regen cooling pumping LH2 through the aerospike plug during ballistic reentry.

[Skyler4856]

It should be a space plane though. Sorry for not being clear, but the colony which uses it needs to be able to reuse it quickly, which means that I cannot use ablative heat sheilding or staging.

I'd imagine it would be a VTHL

[CaptRobau]

A lot of 60s SSTO designs used aerospikes as the engine of choice, but that technology never got very far past the drawing board. They must've been up to something. Maybe those designs could work if aerospikes had all the kinks worked out of it?

[Ralathon]

Why is everyone talking about aerospikes? This is for a Mars SSTO, Mars has a surface pressure less than 1% of earth. The main appeal of an aerospike is that it maintains near optimal ISP regardless of pressure. On mars you can just use vacuum nozzles and ignore the atmosphere, losses will be minimal.