Human Exploration Mission Scenario
The Case for Mars II, 1984

This design for a human Mars mission accommodates a crew of fifteen which would rendezvous on Mars with supplies and equipment sent on ahead. The aim of this concept would be to utilize Martian resources by deriving water, air, and fuel from Mars' atmosphere and to live off the land by farming for food. Such a scenario would not only establish a base for later crews to expand upon, but would also create a self-sufficient safe haven on Mars not entirely dependent on the success of interplanetary flight schedules. This Case for Mars concept incorporates a flyby cycler spacecraft, and the use of aerocapture as means of reducing the large fuel penalties for commuting into Mars' gravity well. As a whole, these features distance this Case for Mars mission scenario from all previous concepts by allowing more extensive surface operations and a larger crew for the same amount of initial mass launched from Earth.

1. Mars Spacecraft are Assembled at Space Station

The planned U.S. Space Station in Low Earth Orbit (LEO) could serve as a platform for collecting all the components necessary for the first human expedition to Mars. Each part would be carried there by the existing Space Shuttle and, or currently conceived Heavy Lift Launch Vehicle. The hardware has been figured largely from available Shuttle and Space Station systems, such as habitability modules and truss-beam construction seen at the top being integrated. A cone shaped Mars landing vehicle is seen poised next to a rectangular satellite hanger. Offloading residual fuel from a Shuttle's External Tank is depicted filling orange liquid hydrogen and white liquid oxygen tanks for the Mars boost.

2. Interplanetary Spacecraft Depart from Earth Orbit

Once assembled, three identical spacecraft (only two depicted here) each with five astronauts aboard, depart Earth orbit on a Mars bound trajectory. This maneuver, called Trans-Mars Insertion (TMI), uses two Space Shuttle main engines per spacecraft fueled by liquid hydrogen and liquid oxygen. Two umbrella like solar collectors concentrate solar energy to run thermal electrical generators. The truss supported shield ahead of the craft is an aerobrake used upon return to Earth to slow the craft to orbital speed through friction with the upper atmosphere.

3. Booster Engines and Tanks are Jettisoned

Following TMI out of LEO, the spent fuel tanks and attached engines are jettisoned. This exposes three docking ports at the end of the beam which houses a crew transfer tunnel.

4. Rendezvous, Docking and Spin-up

Three days out and just past the orbit of the Moon, the crew maneuver their spacecraft to rendezvous and dock in a pinwheel configuration. A third, central port allows for just two vehicles to join dumbbell fashion in the event a third spacecraft wasn't necessary on a future mission, or in the case of emergency where one didn't make it. Once secured with tension cables, the assembled structure is spun to produce artificial gravity. Retractable radiator panels are deployed through doors in the aerobrakes.

5. Habitat Module and Crew Quarters

This transparent view shows one of the six habitat modules, crew quarters of one of the three landers, and part of the crew transfer tunnel. Each habitat module provides the living and working volume roughly equivalent to one mobile home. Spread over six such modules, this gives the total crew of fifteen men and women adequate accommodation. The smaller compartment of the lander is nested by tanks of fuel and consumables in order to provide enough bulk shielding in the event of intense radiation from occasional solar flares. A pressurized tunnel connects the other spacecraft via the docking ports which are large enough for crew and equipment transfer. In the event of systems failing in one module, multiple module redundancy gives added safety for the long voyage beyond help.

6. Cycler Approaching Mars

After a six to eight month voyage, the spinning cruise configuration approaches Mars. A spin rate of just below three revolutions per minute avoids rotational motion awareness by the crew. This constraint dictates the length of beam from habitat to spin axis to simulate Mars gravity which is one third that of Earth's. The red rocket engines are proven Space Shuttle Orbital Maneuvering System (OMS) engines which are used at Mars flyby to trim the interplanetary trajectory back towards Earth. Only the conical landers will go into Mars orbit and subsequently land. Visible tension cables stabilize the spinning structure. The hexagonal pieces are electronically steerable phased array antennae which keep a constant aim toward Earth throughout rotation axially aligned with the Sun.

7. Landers Detach from Cycler and Head for Mars

Nearing Mars, the crew first slows and then stops the rotation of the structure. Boarding the three landers, all fifteen astronauts depart the assembly and fire their engines to encounter the planet. Now unoccupied, the large mothership will perform automated firing of its engines at Mars flyby to put it on an Earth return path. Back at Earth, it will be refitted to carry another crew outbound and pick up those ready for return. Orbital mechanics dictates at least two of these interplanetary assemblies would be required to service crew rotation for each launch opportunity from Earth.

8. Aerobraking into the Mars Atmosphere

The landers penetrate the Martian atmosphere making use of a shape derived from nuclear weapon delivery systems. This well understood technology developed for ICBM reentry vehicles allows for accurate targeting at extreme velocities through an atmosphere. After first braking against the Martian atmosphere from interplanetary speed into Mars orbit, the three craft would regroup formation and perform a small deorbit thrust maneuver. Reentering the atmosphere, the landers would accurately home in on a landing site by gliding just like the Space Shuttle does on Earth. Aerobraking at both Earth and Mars greatly reduces the need for braking fuel which in turn greatly reduces the amount of initial mass which must be launched from Earth. Additional savings are shown later in manufacturing return fuel from Martian resources. Every bit of mass saved on initial delivery to Mars decreases the extremely expensive launch cost from Earth, and thus increases affordability of such a mission.

9. Final Descent onto Mars' Surface

Final descent is slowed by parachute and controlled by five rocket engines to home in on three unmanned cargo vehicles. Sent ahead of the crew, the cargo ships determine the landing site. The flat terrain depicted is considered safe compared to more dramatic sites.

10. Crew and Cargo Landers on Mars

Similar shapes, the manned and unmanned landers have different purposes. The unmanned cargo ships land on their sides whereas the crew landers remain upright for future liftoff.

11. Unloading Cargo on Mars

The cargo landers are unloaded through a large door and later towed to a permanent base location by a drag line. Visible in the foreground are rolled up inflatable greenhouses.

12. Assembling the First Mars Base

The base is assembled near, but at a safe distance from the crew landers which will launch in place at the end of the first stay. On a cleared site, the cargo vehicles are resealed to hold pressure, then oriented nose to tail and connected together for use as the dwelling. Airlocks are installed in sides as well as the rear of the vehicles by removing one engine in each for access to greenhouses. Redundant, trash can sized nuclear power generators are placed at a safe distance, seen in the background with blue radiators to distribute excess heat. Adjacent equipment, called a "gas extractor", processes Martian atmosphere into a breathable air supply, as well as creating a fuel mixture for liftoff and driving rovers.

13. Greenhouses for Food Production

Inflatable greenhouses are erected to supply food and provide a partially closed biological system with the crew. Advanced intensive agriculture methods have been shown to be productive at reduced pressure levels. This allows for ultra lightweight inflatable growing areas to quickly service the base.

14. Interior of a Mars Habitat

Interior view of one of the dwellings shows fresh food in the multi use kitchen-dinning area. Total living volume of each vehicle is slightly greater than one mobile home. Low power fluorescent lighting illuminates the interior. Spacesuit and airlock are seen within the boundary of the resealed cargo door. Double height space in the rear provides crew with sleeping area and storage.

15. Covering the Habitat for Radiation Protection

Drag lines are used to scoop soil and cover the habitat for protection from solar flare radiation which the thin Martian atmosphere and weak magnetic field only provide minor shielding.

16. Gas Extractor Makes Air, Water and Fuel

Close up of the gas extractor. This machine, operating like a jet engine, sucks in the thin Martian atmosphere safely above the surface dust. Compressing the mostly carbon dioxide air, it separates out oxygen, nitrogen and argon for breathing, and carbon monoxide which is used as a return fuel with oxygen. Small amounts of water may also be extracted from the air, but underlying ice in permafrost may also be a source of water.

17. Landers are Refueled with Propellant Made on Mars

Tanks of carbon monoxide and oxygen are hauled out to refuel the crew landers throughout the duration of stay. It takes just over one year to completely fuel the three vehicles, roughly the same amount of time before the next interplanetary spacecraft flies by to bring the crew home. In case of failure of the next outbound spacecraft, the crew is safe on Mars, being self-sufficient until another launch opportunity.

18. First Crew Departs Mars as the Next Crew Arrives

As the next crew arrives, the first crew blasts off and drops a lower stage on its way to catch up with the large pinwheel spacecraft making its pass on its way back to Earth.

19. Return to Earth

Approaching Earth, the large spacecraft fires its OMS engines one last time to be captured by Earth's gravity into a high elliptical orbit. After dividing again into three vehicles and retracting their radiator panels, the spacecraft slow their speed and lower their orbit with the aerobrake. Successive passes will wear down its orbit to within range of the Space Station in a period of a couple weeks. The crew, on the other hand, can re-board the top half of their landers for a similar, yet quicker maneuver, ending their mission.

With the support of more cargo shipments, and a continuous cycle of crew, this scenario would establish a self-sufficient, permanent, expanding, scientific outpost on Mars similar to our research bases in Antarctica. The importance of this design shows such a mission could be done soon and relatively cheaply using available technology and equipment.

Drawings © Copyright, Carter Emmart 1986, 1995