by Grant Palmer

April 23, 1999

The idea for a Mars Airplane has been around since the 1960's. The purpose of it would be to explore the Mars countryside over a much wider range than a rover could and much closer up than from an orbiting satellite. Someone had the idea of flying a Mars Airplane to commenorate the 100th anniversary of the first powered flight on Earth, the Wright Flyer at Kitty Hawk. The NASA Administrator embraced the idea. This set off a frenzy of activity with several NASA centers trying to come up with the best idea for the Mars Airplane.

Here at NASA Ames, there were three separate concepts that were analyzed. The first two were low-speed vehicles that would be flown to Mars inside a conventional space capsule. The capsule would enter the Martian atmosphere and when it had decelerated enough, the airplane would deploy.

The third concept was for a supersonic airplane, meaning one that would fly faster than the speed of sound. The supersonic Mars Airplane would enter the atmosphere itself using advanced materials to keep the outer skin cool. This is the concept that I was asked to help analyze.

I work in computational fluid dynamics. I write computer programs that calculate how the air, or in this case Martian atmosphere, flows over the body when it enters the atmosphere. Friction between the atmosphere and the surface of the vehicle causes the outer temperature of the vehicle to heat up. Part of my job is to see if the temperature will exceed the maximum temperature of the vehicle.

The first thing I do is to generate a grid. The surface of the vehicle is broken up into individual squares. The computer program will compute the pressure and temperature in the center of each one of these squares. What I really is to generate a 3-D grid, meaning that the Mars Airplane is surrounded by cubes.

Once I have my grid, I'm ready to run the program. I get the atmospheric conditions, velocity, density, temperature, from a trajectory expert. I set up the input parameters and start to run the computation. It takes a lot of computer time. The solution will require about 50 hours on the Cray C90 computer. The C90 is the world's largest supercomputer.

In the old days, airplanes were built based on experiments and flight tests. With futuristic concepts such as the Supersonic Mars Airplane, you can't design it that way. There's no way to test the vehicle by experiment and you can't flight test it since Mars is so far away. The design of this type of vehicle will largely be done on computer.