Earth Return Vehicle

The Earth Return Vehicle (ERV) forms a part of the Mars Direct humans-to-Mars mission concept first developed by Doctor Robert Zubrin and David Baker in the early 1990s. cite book |author=Glen Holden; Hanlon, Michael |authorlink= |editor= |others= |title=The real Mars |edition= |language= |publisher=Carroll & Graf |location=New York, NY |year=2004 |origyear= |pages= p117|quote= |isbn=0-7867-1413-1 |oclc= |doi= |url= http://books.google.com/books?id=XzplaSzE5nsC&pg=PA117&dq=%22Earth+Return+Vehicle%22+zubrin&as_brr=3&ei=XC3NSObSOZLkywS1zPWUAw&sig=ACfU3U3TUkDvYyuGkN5TrXUMzpf1FjZDZw|accessdate=]

It is a vehicle designed to return a crew of astronauts from the surface of Mars to Earth at the conclusion of their stay on Mars. It is used in conjunction with the Mars Habitat Unit to enable the human exploration of Mars.

Description

The ERV is a two-stage vehicle, with the upper stage comprising the living accommodation for the crew during their six-month return trip to Earth from Mars.

The lower stage of the ERV contains the vehicle’s descent / ascent engines and a small chemical production plant.

The ERV is launched atop a heavy lift launch vehicle, possibly derived from the space shuttle. It is unmanned, and only carries sufficient fuel to safely reach the surface of Mars following aerobraking in the planet's atmosphere on its arrival in orbit.

Once on the surface of Mars, a small nuclear generator is used to power the chemical production plant carried by the ERV. This in turn uses some six tonnes of hydrogen feedstock aboard the ERV. together with the carbon dioxide of the Martian atmosphere to generate up to 112 tonnes of methane and oxygen, to be used as propellants for the return trip to Earth. These are manufactured through a number of simple chemical reactions, e.g., the Sabatier reaction or water electrolysis. On the way back to Earth, the lower stage is used as a counterweight to generate artificial gravity.

pecifications

Round trip payload
Crew compartment	7,100 kg
Reaction control system	400 kg
Biconic brake	2,450 kg
Stage 1(dry)	6,330 kg
Stage 2 (dry)	1,770 kg
Mars-bound payload
Hydrogen for propellant production	5,810 kg
SP-100 Reactor	4,500 kg
Earth-bound payload
Crew	450 kg
Suits	300 kg
Consumables (dry food)	2,000 kg
Soil Samples	150 kg
Stage 1 propulsion system
Usable propellant (methane / oxygen)	70,160 kg
Dry mass	8,850 kg
Total engine thrust	85,237 kgf (835.89 kN)
Specific impulse	373 s (3.65 kN·s/kg)
Stage 2 propulsion system
Usable propellant (methane / oxygen)	25,000 kg
Dry mass	2,560 kg
Total engine thrust	9,059 kgf (88.84 kN)
Specific impulse	373 s (3.65 kN·s/kg)

Notes