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Combo Lander Mission

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Combo Lander Credit: NASA

AKA: Three-Magnum Mars Mission. Status: Study 1998.

The design team was directed to employ a solar electric propulsion (SEP) stage for delivering the Mars mission elements to a high apogee Earth departure orbit and to not employ nuclear propulsion for any maneuvers. The study was unusual in the approach of designing to a fixed constraint for Earth launch mass. The most significant result was the identification of the technology challenges that had to be met to achieve the launch mass goal.

The reference launch vehicle used in the study was the Magnum, so this mission concept was also referred to as the "Three-Magnum Mars Mission". The capacity of the Magnum launch vehicle defined for this study was 89.5 metric tons for launch packages which employed the launch shroud as an aeroshell, and 85.5 metric tons for payloads which did not include the shroud as payload. The payload capability quoted was for launch from the Kennedy Space Center to a circular orbit of 400 kilometers at an inclination of 28.5 degrees. The dimensions of the Magnum shroud were defined as an outer diameter of 8.4 meters and a length of 28 meters.

The mission defined included a crew of four people, a scientific payload of 1770 kg and two unpressurized rovers with a mass of 650 kg each. The missions were conjunction class with outbound and inbound transit durations of 180 to 200 days and Mars surface stay times of 520 to 580 days. The elements were designed to accomplish missions in six out of the eight opportunities in the synodic cycle. The other two opportunities would require an additional propulsive stage of approximately 16 metric tons.

Several different mission scenarios were considered and two were documented for the study: a Combination Lander Scenario in which all elements were sent to Mars in a single opportunity, and a Split Mission Scenario in which some elements were deployed at Mars in the first opportunity and the crew traveled to Mars in the next opportunity. The Split Mission Scenario was similar to the Design Reference Mission 3.0 whereby propellant for Mars ascent were produced at Mars.

Several strategies were used to constrain the total mission mass with respect to the Design Reference Mission and to achieve the launch mass target.

• Crew reduced from 6 to 4 persons
• Initial departure orbit apogee raised from 39,000 km to 120,000 km
• Hydrogen fuel was used for all maneuvers.

Several technology development challenges were identified as necessary to achieve the launch mass target:

• Structures, tanks, and aeroshells with a reduction in mass of up to 50% over current technology
• High performance power generation system for space and surface operations (100 kg/kWe)
• Long-term hydrogen storage with near zero boil-off for up to four years
• Lightweight chemical propulsion engines with a specific impulse of 480 seconds.
• Deployable solar electric propulsion system with a megawatt-capacity solar array

Combination Lander Scenario

The mission scenario was as follows:

• Three launches from earth by the Magnum launcher orbit the SEP spacecraft (85 metric tons), the Combo Lander, and a Transhab/TEI (89 metric tons each with integrated payload shrouds/aeroshells). The payloads dock in low earth orbit
• Slow acceleration spiral of the three payloads, unmanned, by the SEP to high earth orbit
• Launch from earth of a small taxi vehicle with the crew
• Rendezvous and docking of the taxi with the Mars spacecraft in high earth orbit
• Transmars injection of the Transhab/TEI stage with the crew. The SEP was left in high earth orbit.
• On approach to Mars, the Transhab/TEI and Combo Lander separate. Each separately aerobrakes into Mars orbit.
• In Mars orbit, the Transhab/TEI and Combo Lander rendezvous and dock. The crew transfers to the Combo Lander.
• The Combo Lander descends to the Martian surface.
• The long surface mission was accomplished.
• An ascent vehicle with the crew separated from the rest of the Combo Lander and rockets into Mars orbit
• The ascent vehicle and Transhab/TEI rendezvous and dock in Mars orbit
• The crew transfers to the Transhab/TEI and cast off the ascent vehicle
• The Transhab/TEI burns into trans-earth injection
• On approach to earth, the TEI stage separates. The Transhab aerobrakes into low earth orbit
• A shuttle from earth and the Transhab rendezvous and dock in earth orbit. The crew was taken by the shuttle to a space station or returned to the earth

Mass breakdown for the baseline mission was as follows:

Launch 1: SEP, 85,500 kg

Launch 2: 88,742 kg, consisting of:

• Transit Habitat: 27,403 kg
• Aeroshell: 8,750 kg
• TEI Stage: 40,017 kg
• TMI Stage:12,572 kg

Launch 3: 89,258 kg, consisting of:

• Ascent Crew Module: 2,704 kg
• Ascent Stage: 10,681 kg
• Surface Habitat: 20,293 kg
• Surface Payload: 3,070 kg
• Surface/Transit Power: 3,025 kg
• Lander Stage: 13,166 kg
• Aeroshell: 6,901 kg
• TMI Stage:29,418 kg

A Split Mission Scenario was sketched out as a means of reducing the payload to under the 75 metric ton payload of the baseline Magnum launch vehicle design. The Split Mission used the ISRU propellant generation on the Martian surface and Mars surface rendezvous concepts of the Design Reference Mission, but also included all of the strategies and technology challenges of the Combo Lander study. The major differences in this scenario were 1) the predeployment of the return vehicle in Mars orbit, 2) pre-deployment of the ascent vehicle on the surface of Mars, 3) the production of propellant on Mars, and 4) the use of methane rather than hydrogen for Mars ascent. The scenario was still constrained to three launches (two at the first Mars launch opportunity, a third two years later at the next opportunity), but reduced the payload requirement for the Magnum vehicle to 75 metric tons.

Each scenario also required a Space Shuttle launch at the beginning of the mission to deliver the crew and their high-Earth orbit taxi and also a Shuttle mission at the end to recover the crew in low Earth orbit. This three-launch strategy was reliant on the key technologies described previously.

Mass breakdown for the split mission was as follows:

Launch 1: 72,931 kg, consisting of:

• SEP: 53,220 kg
• MI Stage: 19,711 kg

Launch 2: 72,209 kg, consisting of:

• Ascent Vehicle: 9,105 kg
• Ascent Lander: 5,044 kg
• ISRU Plant: 4,868 kg
• Ascent Aeroshell: 3,203 kg
• Return Habitat: 25,458 kg
• Surface Payload: 2,420 kg
• Hab Aeroshell: 6,184 kg
• TEl Stage: 15,927 kg

Launch 3: 75,150 kg, consisting of:

• Surface/Transit Power: 3,025 kg
• Hab Lander 7,958 kg
• Rover: 650 kg
• Aeroshell: 5,124 kg
• TMI Stage:12,874 kg
• SEP Refueling propellant: 23,282 kg

Combo Lander All-Up Mission Summary:

• Summary: Focus on single Mars lander to transport crew & also support on surface; all-up and split mission scenarios
• Propulsion: Solar electric/Lox/LH2
• Braking at Mars: aerodynamic
• Mission Type: conjunction
• Split or All-Up: all up
• ISRU: ISRU
• Launch Year: 2011
• Crew: 4
• Mars Surface payload-metric tons: 4
• Outbound time-days: 200
• Mars Stay Time-days: 580
• Return Time-days: 190
• Total Mission Time-days: 970
• Total Payload Required in Low Earth Orbit-metric tons: 280
• Mass per crew-metric tons: 70
• Launch Vehicle Payload to LEO-metric tons: 90
• Number of Launches Required to Assemble Payload in Low Earth Orbit: 3 Magnum + 2 Shuttle
• Launch Vehicle: Magnum plus

Combo Lander Split Mission Summary:

• Summary: Focus on single Mars lander to transport crew & also support on surface; all-up and split mission scenarios
• Propulsion: Solar electric/Lox/LH2
• Braking at Mars: aerodynamic
• Mission Type: conjunction
• Split or All-Up: split
• ISRU: ISRU
• Launch Year: 2011
• Crew: 4
• Mars Surface payload-metric tons: 40
• Outbound time-days: 210
• Mars Stay Time-days: 590
• Return Time-days: 220
• Total Mission Time-days: 1020
• Total Payload Required in Low Earth Orbit-metric tons: 230
• Total Propellant Required-metric tons: 110
• Propellant Fraction: 0.47
• Mass per crew-metric tons: 57
• Launch Vehicle Payload to LEO-metric tons: 225
• Number of Launches Required to Assemble Payload in Low Earth Orbit: 3 Magnum + 2 Shuttle
• Launch Vehicle: Magnum