DRM 1 Vehicles Credit - © Mark Wade

The Design Reference Mission 1.0 was the Space Exploration Initiative's last gasp. The plan, unveiled in May 1993, was a NASA version of Zubrin's Mars Direct, using larger spacecraft, but compensating for this by using nuclear thermal instead of chemical propulsion. Six crew would be sent on a conjunction class trajectory to Mars, with propellant for the return trip being obtained by an ISRU propellant plant on the surface.

In the original Mars Direct scenario the Earth Return Vehicle would lift off directly from the Mars surface toward the trajectory toward earth. In the NASA version a Mars Ascent Vehicle would rendezvous with a Mars Orbit way-station, which would provide more space for the crew on the long return.

A 240-metric ton payload heavy lift launch vehicle would be required. In September 2007 three HLV launches would each place an unmanned payload and a nuclear thermal rocket stage into low earth orbit. Payloads on the three launches would be the Cargo Lander, the ERV Orbiter, and the Unmanned Habitat Lander, each with a mass of 60 to 75 metric tons. NASA felt these figures were more realistic than Mars Direct's 30 to 40 metric ton estimates. The Cargo Lander consisted of the Mars Ascent Vehicle, an ISRU facility, hydrogen feed stock, and 40 metric tons of cargo, including a surface rover. The ERV and Habitat Common Module were similar to the Mars Direct 'hockey puck' aerobraked package.

The spacecraft would arrive at Mars in September 2008. The ERV would aerobrake into orbit, while the other elements would aerobrake directly to a landing on the surface. The Cargo Lander would begin manufacture 5.7 metric tons of methane and 20.5 metric tons of liquid oxygen from the atmosphere.

One cycle later, in October-November 2009, another triple launch would occur, this time with a crew of six aboard the Habitat Lander. The duplication of spacecraft provide back-ups for the first set, or if not needed, then spacecraft for the next crew. They would land near the first Cargo Lander and Habitat, both of which were equipped with wheels to allow them to be joined together into a single pressurized base. A 600 day stay would include several 10-day traverses up to 500 km from the lander. In October 2011 the crew would ride the Mars Ascent Vehicle portion of the first Cargo Lander rockets to Mars orbit using propellants generated on the Martian surface. It docks with the Earth Return Vehicle, which the crew then lives in during the coast back to earth. At earth the crew would enter the Mars Ascent Vehicle command capsule, then separate the ERV, re-enter the atmosphere, and land below parachutes on earth.

After this study, the NASA Mars Manned Space Office was again dismantled.

• Summary: NASA's "Design Reference Mission" based upon previous studies; good focus on operations and science return
• Propulsion: Nuclear thermal
• Braking at Mars: aerodynamic
• Mission Type: conjunction
• Split or All-Up: split
• ISRU: ISRU
• Launch Year: 2007
• Crew: 6
• Mars Surface payload-metric tons: 63
• Outbound time-days: 150
• Mars Stay Time-days: 610
• Return Time-days: 120
• Total Mission Time-days: 880
• Total Payload Required in Low Earth Orbit-metric tons: 900
• Total Propellant Required-metric tons: 340
• Propellant Fraction: 0.37
• Mass per crew-metric tons: 150
• Launch Vehicle Payload to LEO-metric tons: 240
• Number of Launches Required to Assemble Payload in Low Earth Orbit: 3
• Launch Vehicle: DRM1

• Cargo Lander Reference Version 1.  Class: Manned. Type: Mars Lander. Destination: Mars. Nation: USA. Agency: NASA.

  The first version of the NASA Cargo Lander for the design reference mission would land an Earth Entry/Mars Ascent Capsule, an ascent stage, and an ISRU plant on the surface that would produce propellant for the crew's return journey from the Martian atmosphere. It had a typical mass of 90,190 kg on approach to Mars and 60,920 kg on the surface.

  Cargo Lander 1 Reference Version 1.0 Mass Summary Earth Entry/Mars Ascent Capsule: 5,500 kg Ascent stage dry mass: 2,550 kg ISRU plant: 4,802 kg Hydrogen feedstock: 4,500 kg PVA keep-alive power system: 300 kg 160 kw nuclear power plant: 12,498 kg 1.0 km power cables, PMAD: 1,900 kg Communication system: 820 kg Pressurized Rover: 15,500 kg 15 kwe DIPS cart: 1,100 kg Unpressurized rover: 440 kg 3 teleoperable science rovers: 1,320 kg Water storage tank: 1,220 kg Science equipment: 3,800 kg TOTAL CARGO MASS: 56,250 kg Terminal propulsion system: 4,670 kg TOTAL LANDED MASS: 60,920 kg Propellant: 11,970 kg Forward Aeroshell: 17,300 kg TOTAL ENTRY MASS: 90,190 kg NTR Propulsion System: 28,900 TMI Propellant: 86,000 kg TOTAL INITIAL MASS: 205,090 kg

  Length: 40.30 m (132.20 ft). Mass: 205,090 kg (452,140 lb).

• Crew Lander Reference Version 1.  Class: Manned. Type: Mars Lander. Destination: Mars. Nation: USA. Agency: NASA.

  The first version of the NASA Crew Lander for the design reference mission would land the crew and a Mars surface habitat on the surface near the previously-landed cargo lander. The crew would have to use the ascent stage and return capsule of the cargo lander to get back to earth. The crew lander had a typical mass of 89,980 kg on approach to Mars and 60,710 kg on the surface.

  Crew Lander Reference Version 1.0 Mass Summary Habitat element 2: 53,400 kg Life Support System: 6,000 kg Health Care: 2,500 kg Crew Accommodations: 22,500 kg EVA equipment: 4,000 kg Comm/infomanagement: 1,500 kg Power: 500 kg Thermal: 2000 kg Structure: 10,000 kg Science: 900 kg Spares: 3,500 kg Crew: 500 kg 3 kw PVA keep-alive power: 1,700 kg Unpressurized rover 3: 440 kg TOTAL PAYLOAD MASS: 56,040 kg Terminal propulsion system: 4,670 kg TOTAL LANDED MASS: 60,710 kg Propellant: 11,970 kg Forward Aeroshell: 17,300 kg TOTAL ENTRY MASS: 89,980 kg NTR Propulsion System: 28,900 kg Shadow Shield: 3,300 kg TMI Propellant: 86,000 kg TOTAL INITIAL MASS: 208,180 kg

  Mass: 208,180 kg (458,950 lb).

• Portree, David S. F., Humans to Mars: Fifty Years of Mission Planning, 1950 - 2000, NASA Monographs in Aerospace History Series, Number 21, February 2001. Excellent overview of American plans for sending men to Mars.

• NASA Report, Mars Design Reference Mission 1, . Accessed at: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980037039_1998037039.pdf. -right click to download pdfs!

• Hoffman, Stephen J, and Kaplan, David I, Editors, Human Exploration of Mars: The Reference Mission of the NASA Mars Exploration Study Team, NASA Special Publication 6107 July 1997.