Aero/astro alum airs satellite stories


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Denise Brehm
Email: brehm@mit.edu
Phone: 617-253-8069
Department of Civil and Environmental Engineering

Talk about attitude.

That's exactly what Paul Tompkins (SB '92) of Hughes Space and Communications did in his presentation describing some of the unpredictable obstacles he's encountered when hurtling commercial spacecraft off the planet and into a targeted orbit 22,000 miles from Earth.

One of the keys to maneuvering these satellites is keeping the crafts' axes aligned with inertial space in just the right attitude. A bad attitude can bring down a mission.

"Spacecraft are the archetypal systems engineering problem," he told a group of aerospace students last week in a talk titled "Spacecraft Mission Operations: Murphy's Law in Action" sponsored by the Massachusetts Space Grant Consortium.

"Sometimes this work is a dream and sometimes a nightmare. You always hope for a boring mission. Even though you want to have adrenaline when you're working at four in the morning, the best mission is still a boring one," said Mr. Tompkins, a mission analyst for Hughes who started working at the company as an intern the summer after his junior year. That internship led to a job following his graduation from the aeronautics and astronautics program in 1992.

While missions to Mars still capture the nation's attention, tons of machinery are put into orbit each year without much notice. These satellites orbit our planet at the same speed that Earth turns, so they appear to be at a fixed point in space. He said Hughes plans 16 launches this year alone -- satellites for communications (telephone, video and TV programming), meteorology and other scientific purposes.

But for Mr. Tompkins and the other engineers planning and designing these missions, each launch holds as much excitement as the Mars landing did for the rest of us.

As his audience watched a videotaped launch of a flaming rocket headed straight up into the sky, Mr. Tompkins told them, "At this point, we're just sitting and praying 'God, I hope this is gonna work.'

"Bad things happen all the time. You try to analyze and plan to the best of your ability, but there might be something you didn't take into account," he said.

For each mission, a team spends several years planning and building the spacecraft and testing it "in a giant cylinder" for its ability to withstand the extreme temperatures and other conditions of space. But the true test comes when they launch the spacecraft, position it into orbit and spend a few weeks putting it through test maneuvers.

If all goes well, they turn it over to the client, who will operate it for its 12- to 20-year life span. If something goes wrong, they attempt to guide the spacecraft from their control room on Earth. Mr. Tompkins told an anecdote of one spacecraft they launched but then couldn't get into orbit.

"In terms of operation, you'd almost rather have the spacecraft explode. In this case, you've got a perfectly healthy spacecraft in a totally useless orbit," he said. It took weeks of maneuvering to get it into the targeted orbit.

Occasionally a more dramatic rescue is required. He said they once sent a shuttle up just to bring home two ailing satellites and keep them out of the path of other vehicles. Even worse than bad attitude, those two satellites had identical, but faulty, rocket motors.

A version of this article appeared in MIT Tech Talk on March 4, 1998.


Topics: Aeronautical and astronautical engineering, Alumni/ae

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