CS272 – Tech A

A manned mission to Mars is widely viewed as the present long-term goal of space exploration.  At their absolute closest, Earth and Mars are roughly 55-million kilometers apart.  Pointing a rocket at Mars and launching, however, isn’t the answer to getting there.  Due to the obvious desire to reduce the amount of time and fuel necessary to make the trip, a transfer orbit is the most realistic way to successfully get a spacecraft from the Earth to Mars.  A transfer orbit uses the orbital velocity of an object (usually a planet or moon), along with powered propulsion, to get from point A to B.  Because of the differences in the orbits of Earth and Mars, the optimal time to make a trip happens only once every 25 months.  Add to that the estimates that the voyage would take 6 months each way, and the challenges of sending a human crew to Mars become evident.

One way to shorten the time issue would be to change the propulsion method.  The main method used in the past and still today is chemical rockets.  They consume a large amount of fuel and are relatively slow when considering an interplanetary scale.  They’re what we’ve been using for decades to launch space vehicles, they’re very well tested, and they’re fairly safe when used correctly.  If a mission to Mars was going to be performed tomorrow, chemical propulsion is probably the method that would be used.

A possible alternate propulsion method would be the use of nuclear thermal rockets.  Anything with the word “nuclear” is often viewed skeptically, but in theory nuclear energy is remarkably powerful and efficient.  The spacecraft could use the nuclear power to produce electricity and to create artificial gravity.  There have been numerous cases of muscular atrophy and bone loss associated with astronauts who spend long periods of time in a microgravity environment.  Aside from the living conditions, the nuclear thermal rockets could propel the spaceship faster and for longer periods of time, accelerating the ship to Mars in roughly half the time of a traditional chemical rocket.  Nuclear propulsion would only kick in once in space, so the use of a chemical rocket would be required to launch the vehicle from the surface into orbit.  Because of this, no radiation is emitted into the Earth’s atmosphere.  The idea of using nuclear power in space exploration has been around for decades, but hasn’t ever really “taken off” due to the health and safety concerns of all of those involved.  With the relatively recent resurgence of interest in the human exploration of Mars, all the benefits of nuclear power have come back to scientists as a realistic propulsion possibility.

Ion engines are another propulsion method being considered to send a manned spacecraft to Mars.  Ion thrusters are used today in unmanned space vehicles because they are extremely efficient and can be run on very little fuel.  The downside is that they produce very little thrust.  The Ad Astra Rocket Company is developing an ion engine that is much more powerful.  In fact, they claim people could reach Mars in as little as 39 days, which is well inside the “comfortable” range of what humans have been exposed to.  Sending astronauts to Mars in a matter of weeks rather than months is obviously a benefit to this propulsion method, but still there is much testing and technology development that needs to be done before this method could be implemented into manned Mars exploration.

All things considered, nuclear power is the way to go.  The technology involved isn’t that far off.  There is an understanding of how to safely use nuclear power that is already in place today.  The United States Navy has a fleet of nuclear powered aircraft carriers that are said to operate more than 20 years without refueling.   The rocket technology isn’t here yet, but they aren’t as far off as the high-powered ion engines.  Ion engines are the long-range future of the manned exploration of Mars, but if a manned mission is going to be run in the next 10-20 years, this is the kind of high-speed, long-lasting, and efficient propulsion that’s going to be necessary to get the job done.

Sources:

http://www.universetoday.com/14841/how-long-does-it-take-to-get-to-mars/

http://www.wired.com/wired/archive/12.12/mars.html

http://www.space.com/scienceastronomy/solarsystem/nuclearmars_000521.html

http://www.newscientist.com/article/dn17476-ion-engine-could-one-day-power-39day-trips-to-mars.html?full=true

http://www.public.navy.mil/usff/nctamspac/Pages/AboutUs.aspx