seal  Purdue News

May 2003

Columbia tragedy proves need to overhaul shuttle program

By James M. Longuski

As a NASA veteran and longtime aerospace engineer, I watched the unfolding space shuttle disaster in horror, not only because of the obvious human tragedy, but also because this was an accident that could have been prevented. The NASA family -- and I consider myself to be a part of that family -- is devoted to the space program.

We couldn't ask for a greater commitment from the astronauts -- they are willing to risk their lives. We should refuse, however, to accept Columbia's demise and the loss of its precious human cargo as an unavoidable consequence of the fact that space exploration is inherently dangerous.

The disaster has prompted me to think long and hard about where our space program has gone wrong in the past and what we need to do in the future.

The shuttle is fundamentally unsafe for humans because it has no viable escape systems. It is riskier than the Mercury, Gemini and Apollo spacecraft, the last of which carried our astronauts to the moon. These capsules employed a simple "blunt-body" design, which made heat shielding far less complex than that of the winged vehicle design of the shuttle. All three of these earlier designs also had credible abort systems to save the crew. The shuttle has no such capability.

The Apollo capsule safely delivered astronauts from the moon, 240,000 miles away, entering Earth's atmosphere at a speed of 25,000 miles per hour. In comparison, the shuttle enters the atmosphere at 17,500 miles per hour from an orbit of about 300 miles, and the slightest error in its reentry angle can be fatal.

What we need is a major rethinking of the space shuttle program. The weakness of the shuttle design is that it tries to serve two masters: ferrying astronauts and carrying cargo. Unfortunately, this all-purpose vehicle does not perform either of these roles optimally.

We should consider building two new vehicles. One should be an unpiloted heavy-lift version of the shuttle, and the other should be a "human-rated" space vehicle with escape systems.

A space cargo vehicle can be constructed with parts from the existing shuttle, including its two solid rocket boosters and the large external tank. This approach will allow us to take the shuttle vehicle itself off-line and replace it with a pilotless cargo container.

The second vehicle should be designed to carry very little cargo and maximize the safety of the astronauts. This vehicle could be launched on top of an Atlas V or Delta IV rocket.

While we are waiting for these two new vehicles to enter service, we can do something right now to reduce the dangers to shuttle astronauts. In order to reduce the risk, we should fly fewer missions, but they should last longer. We can put a crew on the International Space Station for a four-month mission with three shuttle flights per year. In this way, we can do just as much science with fewer launches and reentries.

If the interim period lasts three years, then we will have taken about a 17 percent risk of losing another crew. On the other hand, if we fly another 100 missions with the 2 percent failure rate we have with the current space shuttle, there is an 87 percent chance of losing another crew.

By designing two vehicles, we will greatly improve both safety and lifting capability because a pilotless vehicle eliminates many design elements needed for a human crew, providing additional room for cargo.

How much will it cost to replace the existing shuttles with two different types of vehicles? The short answer is, I don't know. But we do know how much it will cost if we do nothing: another crew will be killed in the next hundred flights or so.

Such a high failure rate is unacceptable, and we should demand better for the brave men and women who choose to become astronauts. Yes, space exploration is inherently dangerous. This is why extraordinary safeguards must be built into each and every human-rated spacecraft.

What we need today is a 21st century space transportation system that places the highest priority on the lives of our astronauts. We already know how to do this, but only the White House can provide the direction that is so desperately needed today for America's space program.

Our leaders should seize upon the Columbia tragedy as a catalyst for meaningful change, the creation of a long-term goal that goes far beyond the redesign of the space shuttle. That overarching goal should be the exploration and colonization of Mars. If we are to risk the lives of our astronauts, we must have a lofty goal that makes the risk worthwhile.

The establishment of a second home on another planet is a vision that gives all of humanity greater opportunity and greater hope for the future. It's a bold vision that will allow Americans and the NASA family to once again set our sights on the stars and focus on future achievement instead of past loss.

(James M. Longuski is a professor in the School of Aeronautics and Astronautics at Purdue University in West Lafayette, Indiana, where he teaches courses in dynamics, aerospace optimization, and spacecraft design. He holds a doctoral degree in aerospace engineering and worked for nine years at NASA's Jet Propulsion Laboratory, where he was a maneuver analyst and a mission designer. He is an associate fellow of the American Institute of Aeronautics and Astronautics and has written more than 100 conference and journal papers in the general area of astrodynamics, including such topics as spacecraft dynamics and control, reentry theory, mission design, space trajectory optimization and a new test of Einstein's theory of general relativity. He also has worked with Dr. Buzz Aldrin on a human transportation system to Mars.)

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