People from Earth to Mars in 30 days

It is possible using a combination of electric and chemical propulsion to send people in a rocket from Earth to Mars in 30 days. The electric portion of the system would accelerate nine refueling depots to prepositioning orbits. The chemical rocket with a human crew would rendezvous with each of the nine refueling depots, adding about 3056 meters per second in each of ten burns. The nine refueling depots would be in nine independent orbits. The first would pass Earth at 3,056 m/sec, the second at 6,112 m/sec, the third at 9,168 m/sec and so on. The spaceship to Mars would accelerate to 3,056 and rendezvous with the first tanker just as it passes and likewise with each of the others in turn until it finally achieved the delta v for fast transfer to Mars This would follow an orbit of the same same aphelion and perihelion as a Hohmann transfer orbit between Mercury and Saturn, but with the inclination, longitude of ascending node and argument of perihelion needed to intersect Earth's and Mars' orbits. The change in velocity (delta v) necessary to change from Earth's orbit to the transfer orbit is 30,561 meters per second. This is just an example trajectory and there are probably transfer orbits that more efficiently use delta v and can make the 30 day transfer with less than nine refuelings. The fuel transfer technology still needs to be developed and practiced to be sure that the fuel transfers and rocket restarts are accomplished without fail, lest the crew be stranded en route. To address the possibility of difficulties with timely, reliable transfer of fuel and difficulties with engine restart, the fuel could be transferred complete with a fresh set of tanks, fresh engine, plumbing and wiring in a stage swap with the tanker. In using this technique, there would be only a mechanical connection between the rocket stage and the Mars bound spaceship. The rocket stage would have its own electrical power and be controlled by radio signals over a short gap. The prepositioning of the fuel depots would begin long before the human crew is launched, on the order of ten years before.

A spaceship for a 30 day voyage could be smaller than one intended for a 180 day voyage because not as much air, food and water would need to be carried. Provision for refueling would add some mass and there would need to be a substantial heat shield for slowing down at Mars. The 30 day mission to Mars may be limited to a fly-by unless other refuelings are scheduled near Mars to cut down the velocity of the spacecraft some before it begins atmospheric braking at Mars. There is a limit to the peak deceleration loading that it is reasonable for humans to endure. The refuelings near Mars and the atmospheric braking in excess of human tolerence could both be done away with if one is willing to settle for a 38 day transfer when Earth and Mars are closest. This uses a modified transfer trajectory with only seven refuelings.