Martian mission profile for the interplanetary expedition vehicle 800У533 (78 499 bytes)		The classical manned planetary landing mission profile is as follows. The elements of the vehicle are first delivered to low Earth orbit where they are assembled into a single vehicle. Then, using propulsion units, this vehicle is injected into the interplanetary trajectory, and over the next few months the vehicle transits to Mars. When it is near Mars, the vehicle decelerates and goes into a low Mars orbit. A special lander separates from the main section of the vehicle to take to the Martian surface the mission crew or a part of the crew. Upon completion of their work, the crew returns to the vehicle on an ascent module included in the lander, and heads for Earth.
Overall view of the interplanetary expedition vehicle 640У431 (30 472 bytes)
		In accordance with the above concept the interplanetary vehicle consists of the following major components:

	an interplanetary orbiter where the crew lives and works throughout the entire mission and which houses all the primary equipment;
	solar array-powered electrical propulsion unit to support transit from Earth to Mars and back;
	a lander with an ascent module which takes a part of the crew down to the planet surface and brings them back to the main vehicle.

There can be alternative configurations for the vehicle. The key objective is to assure a high probability of the crew return to Earth. That is why it is important to adopt a mission profile and engineering solutions that are simple and reliable.
The key decision, which drives both the vehicle configuration and all the subsequent decisions, is the choice of the propulsion system for the interplanetary transit.
Various approaches could be used: for example, one could use liquid-propellant engines, the most widely used and mature space technology. But a vehicle with such engines, because of their low efficiency, will have a huge mass, and as a result, it will be very expensive, but the most important point is that, in spite of high maturity of liquid-propellant engines, the mission reliability and safety requirements will not be met.
A more efficient solution, from the standpoint of the vehicle initial mass, would be to use a nuclear engine, where the energy of nuclear reactions heats up a gas providing the required thrust. But it turns out that this engine does not meet crew safety and cost requirements either. Considerable costs would be incurred by the ground developmental testing facility for the propulsion unit.
Among the existing engines, the most efficient ones for the use on a Martian vehicle are electric propulsion engines. These are high reliability and low-cost engines. A vehicle using such engines would have the minimal mass. It is easier to construct in low Earth orbit than any other type of engine.
The proposed concept for the Martian mission has he following major advantages:

• High probability of safe crew return. It is difficult to imagine a mission concept, where this probability would be higher;
• Preliminary evaluations show minimal mission costs, both for the vehicle itself and for its ground developmental testing facilities;
• The use of electrical propulsion engines and solar arrays allows to make the vehicle reusable, which would allow to expand the in-flight developmental testing program and considerably reduce the costs of the Mars exploration program;
• The program of flight developmental testing of the lander/ascent module during an unmanned mission to Mars, besides increasing the safety, will also allow to conduct a comprehensive Martian surface research program;
• The desire to achieve environmental safety of the interplanetary vehicle will increase the likelihood of support for the project from the world public opinion.