This was generated by the Spacecraft Control Toolbox function DVHoh.m. 255.2 days is a long time for a crew to be exposed to cosmic radiation. NASA has proposed using a nuclear thermal engine to speed things up. The best combustion engines, like the RL10B-2, use hydrogen and oxygen and have a specific impulse of 465 seconds. This is obtained by running them hydrogen-rich. Nuclear thermal, which is only heating hydrogen, can reach 900 seconds. The higher your specific impulse, the less fuel you use for a given velocity change.
A mission to Mars consists of an Earth escape segment, a heliocentric segment, and Mars entry. You can do them all with the same rocket or use separate stages or methods. For example, you could depart from low-Earth orbit (LEO), do the transfer, and enter low-Mars orbit (LMO) with one stage. As an alternative, the launch vehicle could take the Mars transfer vehicle into a heliocentric orbit. Instead of using the transfer stage to do a powered entry into Mars orbit, you could use aerobraking. Aerobraking could be used, in theory, for both Mars entry and to replace the burn into Mars heliocentric orbit (that is, to match the heliocentric velocity of Mars).
Specific impulse nuclear thermal 900.00 Specific impulse H2/O2 465.00 Tank Fraction 0.10 Time Hohmann 255.23 days Time Fast Transfer 150.23 days Mass fraction Nuclear Thermal Hohmann 0.30 Mass fraction Nuclear Thermal Fast 0.12 Mass fraction H2/O2 Hohmann 0.05 Mass fraction H2/O2 Lambert Only 0.03 Total Delta-V Hohmann 9.03 km/s Delta-V Hohmann 4.41 km/s Total Delta-V Fast Transfer 14.35 km/s Delta-V Fast Transfer Lambert 9.73 km/s Departure 4.43 km/s Arrival 5.30 km/s Delta-V Earth Escape 3.19 km/s Delta-V Mars Entry 1.43 km/s
The Tank Fraction is the fraction of the spacecraft’s dry mass that is proportional to the fuel mass. This is composed mostly of fuel tanks. The mass fraction is how much mass is left when the spacecraft reaches Mars, not including the fuel tanks. The total Delta-V assumes one stage is used to go from LEO to LMO. Lambert’s law is used for the fast transfer. We break up the Lambert maneuver into departure and arrival velocity changes. In principle, you could aerobrake 5.3 km/s + 1.43 km/s.
The fast transfer is shown below. Contrast it with the Hohmann transfer.