MARS LAB: JOURNEY TO MARS
You and your colleagues have been selected by NASA to help design the first manned mission to Earth’s neighbor Mars. The trip will be much more difficult than the Apollo missions to the Moon, which lies much closer to Earth. The Moon could be reached in a few days, even the quickest journey to Mars will take months.
NASA has put together a proposed mission to Mars that be viewed by going on the internet to www-sn.jsc.nasa.gov. This mission takes advantage of the Earth-Mars alignment that occurs roughly every two years to develop a “least energy” high speed orbit that will minimize the amount of time the astronauts will spend in flight between the two planets. The mission will be multipart: cargo rockets will take supplies to Mars orbit in advance of the first manned flight, cargo rockets will continue to bring supplies while the humans are on the surface, and a second and third crew will in turn take over from the first crew when they are ready to leave Mars to return to Earth. The following mission parameters have been selected.
MISSION TO MARS: MISSION PARAMETERS
Crew Size 6
Outbound Flight Time 4-6 months (worst case 150 days)*
Surface Time 600 days (worst case 619 days)
Return Flight Time 4-6 months (worst case 110 days)
* Worst case assumes an unfavorable opposition between Mars and the Earth.
The mission assumes the flight crew will take all of their consumable supplies with them. It is also assumed that the return journey fuel will be manufactured on Mars, from components available on Mars and from components taken from Earth on the outbound journey.
- Flight Path
The most energy efficient pathway between two orbiting bodies is known as a “Holmann transfer orbit.” To go to Mars, the spacecraft is initially placed in a circular, low Earth orbit (LEO). Then, using a single rocket burn, the spacecraft is placed in an elliptical orbit that has a perigee identical to that of the LEO and an apogee that will loop around Mars. As the craft loops around Mars the rocket is fired again to produce the necessary acceleration change to enter Mars orbit. In a variation, the craft can use aerobraking in the Martian atmosphere to allow a landing on the surface without entering Mars orbit, eliminating the necessity of a second rocket burn.
Since the Earth is closer to the Sun than Mars, it travels in it’s orbit at a faster rate than does Mars, in accordance with Kepler’s third law. Thus the Earth periodically catches up with and passes Mars. When the an exterior planet is lined up with Earth this way it is called “opposition.” The flight path from Earth to Mars can be minimized by timing the flight to take advantage of these times, when Earth is catching up with Mars, which recur about every 26 months.
The orbits of Earth and Mars are elliptical (in accordance with Kepler’s first law), not circular, and the closest approach distance of the two planets will vary depending on the orientations of the two ellipses. Some oppositions of the two will therefore be more favorable and others less favorable for the journey. It should be noted that the flight path takes the spacecraft not to where the final destination is at the time of the journeys beginning, but rather where the destination will be at the journeys end. It should also be noted that the space craft does not follow a straight path, but a curved path like Earth and Mars.
MARS LAB: JOURNEY TO MARS EXERCISES
- Use the internet (Google Mar’s Oppositions) to determine the oppositions of Mars for the next 20 years. Determine the distance from Earth to Mars at each opposition. Make a table that shows the date and the distance between the two. Which dates would be favorable for an Earth-Mars journey, which unfavorable? Remember that the astronauts will have to return to Earth at the next opposition. Therefore the best times to make the journey will be when the Earth-Mars/Mars-Earth distance is minimal.
- Crew Selection
It has been determined that there will be enough room on the spacecraft to carry six people. The selection of the flight crew is important because due to the length of the journey (nearly 3 years) there will be no way to get aid from Earth. Crew must be capable of maintaining both themselves and their equipment in a hostile environment. The crew should also have enough expertise so that once they arrive on Mars they can carry out scientific research-the ultimate purpose of the voyage. The crew will also be confined in very close quarters for a long time. Therefore the group dynamics will be important.
- Determine what the makeup of the crew should be. Consider the technical expertise needed from the crew members. Should there be pilots, engineers, research scientists, technicians, medical doctors, etc.? Should a vital member of the crew become incapacitated, who will take over his duties. List the types of crew members chosen and rank them in order of importance to the mission.
- Should the crew be multinational or all from one nation? What are the benefits and detriments of each type of crew?
- Should the crew be all female, all male, or a combination of the two? What are the benefits and detriments of each type of crew?
- How should the crew be organized? Should there be a single, clearly delineated leader, or should different phases of the mission have different leaders who are more suited to lead that particular phase (i.e. should a pilot lead the flight to Mars and back to Earth while someone else leads the ground phase of the mission? Since Earth cannot be returned to for such a long period and while on Mars communication with Earth will be delayed due to the distance of the planet, how should problems among the crew members be resolved?
- Determine the biohazards to the crew during each phase of the journey, and rank them in terms of severity. How will you provide for each of these hazards? See the Discussion forum regarding this subject and post there.