The Coming SSTO's: Applications to interplanetary flight.

Copyright 2012 Robert Clark

Credit: NASA image of an Orbital Transfer Vehicle with aerobrake. From David S.F. Portree's page: Shuttle-Era Manned Mars Flyby (1985).

 Note also a key fact about SSTO's is that the delta-V requirement for
a round-trip mission from LEO to the lunar surface is a little less
than that for flights from Earth's surface to LEO. Then if you could
do orbital refueling, you could have a single, reusable vehicle that
does lunar missions. This important capability about SSTO's is
mentioned in G. Harry Stine's very nice book Halfway to Anywhere:
Achieving America's Destiny in Space :

"...an SSTO that is refueled in orbit has the capability to fly to the
Moon, land, lift off, and fly back without additional refueling."
Halfway to Anywhere: Achieving America's Destiny in Space, p. 220.
http://www.amazon.com/dp/0871318474

A table that gives the delta-V budget for trips in the Earth-Moon
system is given here:

Delta-V budget.
Earth–Moon space.

 http://en.wikipedia.org/wiki/Delta-v_budget#Earth.E2.80.93Moon_space

  From this you can calculate that the delta-V for a round trip from
LEO to the lunar surface is less than that for getting to LEO.
It has been argued that SSTO's are not economical. But that such a
vehicle with orbital refueling could also be used for lunar missions
changes the economic equations significantly.

 Surprisingly such SSTO's could also be used for Mars missions.

Elon Musk has argued in favor of promoting creating a self-sustaining

colony on Mars:

Elon Musk "Mars Pioneer Award" Acceptance Speech - 15th Annual

International Mars Society Convention.

 For such a colony he proposes reusable vehicles and getting propellant for

return trips from Mars. Musk proposes cutting the costs to space by two

orders of magnitude by reusability. Then there would be also a dramatic drop

in the cost to lift the large amount of propellant to space.
 So let's suppose there are propellant depots at LEO. Since Musk proposes a

self-sustaining colony on Mars, lets also suppose propellant depots in low

Mars orbit for return trips.
Here's a map of delta-v's between Mars/Moon/Earth:

 If you add up the delta-v's from low Earth orbit to low Mars orbit you get

6.1 km/s. Now use the same specifications for the Falcon 9 v1.1 first stage

as estimated before, 13 mT dry mass and 375 mT propellant load. Then

you could transport 45 mT from LEO to low Mars orbit:

311*9.81ln(1 + 375/(13 + 45)) = 6,130 m/s.


   Bob Clark