NASA has been wrestling over how to actually mount a human expedition to Mars in the 2030s for decades. NASASpaceflight.com describes the latest concept, using the heavy lift Space Launch System and a nuclear powered propulsion system.
The complete Mars mission would be the most complex space mission ever attempted by NASA. The space agency is looking at a plant that would involve the launch of seven SLS rockets to assemble three different spacecraft.
“During a campaign the first two HLV launches are focused on sending up the two major elements known as propulsive stages. These stages are placed into LEO, in order to wait for the rest of the vehicle elements to arrive for rendezvous.
“HLV launches 3 and 4 are used to deliver the Habitat and Cargo Landers, large elements of hardware which are depicted as sitting on top of the HLV without the need for a fairing.
“Each of these elements rendezvous and dock with their propulsion stages in LEO and depart en route to Mars.”
Next the ship that would take the Mars astronauts to Mars is assembled in low Earth orbit.
“The next phase of the campaign would involve three SLS’ tasked with launching the major elements of the Mars Transport Vehicle (MTV), with the hardware deployed and rendezvous in LEO. This vehicle would include a DSH and the Orion the crew will eventually splashdown in upon their return to Earth.
“The crew would then launch to the assembled vehicle on another Orion, which is undocked as the crew ingress the MTV.
“Arriving at the Red Planet aft first – to allow for deceleration – the MTV would carry out a propulsive Mars Orbit Capture manuever. The crew would then enter the attached Orion, undock from the MTV and dock with the orbiting Habitat Lander waiting for them in Mars orbit.
“The Orion would then undock unmanned and redocks with the MTV, as the Habitat Lander – now containing the crew – begins its descent to the Martian surface.”
The Mars astronauts would spend about 500 days on the Martian surface, exploring and conducting experiments, before returning to the MTV which would take them back to Earth.
Of course this plan, of which there are a number of variants, if just the latest NASA has developed. A Mars expedition is at least 20 years away and with uncertain budgets and likely changes in policy with new presidencies and new congresses, the final plan may or may not resemble what has been set forth.
In the meantime, planetary geologist Paul Spudis has pointed out that 80 percent of the Mars of the referenced Mars mission is fuel. If American astronauts return to the moon before going to Mars and developed Earth’s nearest neighbor as a refueling stop, using water that has been discovered in surprising abundance there, the number of heavy lift SLS launches and thus the complexity of the Mars mission would be reduced. Thus far, pursuit to President Barack Obama’s directive, NASA is foregoing a return to the moon in favor of missions to asteroids before heading for Mars.