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I know that Single-Stage-to-Orbit is quite challenging from the surface of Earth, but it's relatively straightforward from the moon (as demonstrated by the Apollo LM). What about Mars? Let's assume in-situ fueling of methane-LOX.

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  • $\begingroup$ A follow up question could be "Is it desirable ?" $\endgroup$ – Antzi Apr 28 '16 at 16:27
  • $\begingroup$ There isn't a point in having an SSTO for mars right now. LEaving debris isn't a large concern and a two stage rocket is far more efficient. $\endgroup$ – SSTO Oct 26 '20 at 14:41
  • $\begingroup$ @SSTO Reusability on a planet with scarce resources an no "natural outcroppings" of steel an aluminum to mine. Currently there are no opportunities for non-destructive splashdowns and no highway infrastructure to bring a first stage landing back to the launch site. So there really can be a good point to considering this! $\endgroup$ – uhoh Oct 27 '20 at 1:59
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It's definitely viable. By the rocket equation:

$∆v = v_e \ln \frac {m_0} {m_f}$

Methane-LOX gives an exhaust velocity around 3500m/s. Mars surface to orbit requires the expenditure of about 3800 m/s of ∆v.

So the ratio of initial (fully fueled) mass to final (fuel spent) mass need only be around:

$e^{\frac {3800} {3500}}$

or

$e^{1.09}$

or about 3:1 -- 2 tons of propellant per 1 ton of empty ship/payload.

This is as compared to an Earth-launched SSTO, which needs about 9500 m/s, about a 15:1 mass ratio for methalox!

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  • $\begingroup$ How does atmospheric drag factor in? $\endgroup$ – kgutwin Apr 29 '16 at 16:18
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    $\begingroup$ Drag is included in the needed ascent ∆v figures. The exact ∆v required for ascent to orbit will vary substantially with the rocket's thrust-vs-time profile (faster ascent incurs slightly more drag, but much less gravity loss). The figures above are "typical", but Earth ascents will vary from something like 9200-10000 m/s with different launchers. The drag penalty portion is fairly small; for the Saturn V, drag accounted for around 50 m/s of the ∆v budget, and on a Mars ascent it will be far less due to the thinner atmosphere. $\endgroup$ – Russell Borogove Apr 29 '16 at 17:30
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Yes. Though one vs. two stages is always a trade. From what I've seen from Mars Sample Return studies anyway, two stages is usually the winner, mainly due to mass and volume constraints.

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  • $\begingroup$ Likely SSTO wouldn't be much of trade-off. SSTO-and-anywhere-else though definitely would be. Even back to the surface. $\endgroup$ – SF. Apr 28 '16 at 19:32
  • $\begingroup$ If you're designing a one-time system to return samples or even astronauts from Mars once, then the only reason not to go two stage would be complexity. On the other hand, if you are designing infrastructure for a colony then SSTO (and back) is hugely advantageous because of the reduced manpower and support needed to reuse the vehivle. $\endgroup$ – Steve Linton Oct 26 '20 at 15:23

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