Robert Zubrin is premature in his call for commitment to a trip to Mars (“A Space Program We Can Believe In,” Commentary, May 21, page 19). He is premature for three reasons:
- There is no knowledge that life in space can be sustained for the 18 months’ duration of a trip to Mars.
- We do not have efficient rocket engines necessary to provide an economical trip to Mars.
- We do not know whether the United States can afford the cost to build and operate a system for travel to Mars.
If we wish to travel to Mars, each of these problems needs to be addressed.
The first is easily handled. Volunteers could undertake living on the international space station for the duration of a flight to Mars.
The second could be handled by building an efficient rocket engine for use in traveling to Mars. Unfortunately, this has been impeded, for 50 years, by pseudo-science that claims fuel-rich mixture ratios are optimum.
With proof of ability to support life in space for the duration of a flight to Mars, and an efficient rocket engine in hand, the cost of building vehicles and operating them during a trip to Mars could be estimated to determine if the United States could afford such a trip.
A trip to Mars could be accomplished the same economical way that we went to the Moon using what is called a Hohmann transfer. It requires a rocket impulse to put a vehicle on a trajectory to martian orbit, and another rocket impulse at Mars to put the vehicle into orbit.
Mr. Zubrin apparently does not approve of this simple, economical way to go to Mars, because he advocates for a more expensive approach: the so-called direct transfer. This method requires using a rocket engine continuously during flight, first to gain velocity against the Earth and sun’s gravity, and then to decelerate to remain in orbit about Mars. While it reduces the travel time to Mars, direct transfer requires an exorbitant amount of additional rocket fuel, chemical or nuclear powered.
Dale Lawrence Jensen
Lawndale , Calif.
