In a letter to NASA Administrator Charles Bolden, he writes:
Loss of control of the space station would mean a catastrophic reentry into the Earth's atmosphere of the massive structure - the largest object ever placed in orbit around the Earth, measuring over three football fields long and weighing more than 400 tons.
The tons of falling debris that would survive reentry would pose an unprecedented threat to populated areas around the world.
Such an international catastrophe would have significant ramifications for foreign relations and liability for the United States, Russia and the other countries who participate as partners on the space station.
To be sure, the space station has numerous, triple-redundant life support and control systems that makes such a total technical failure unlikely. However, to say that it is so redundant that it could never happen ignores the tragic lessons learned due to the overconfidence in fail-safe technology in disasters throughout history, from the sinking of the Titanic to the nuclear reactor crisis in Japan.
The capability of the Space Shuttles to provide the independent repair spacewalks, critical for restoring operations on a disabled ISS, would also be vital for protecting the ISS cargo and crew transport business of the emerging commercial space industry. Keeping the shuttle fleet in service would also comply with a new, internationally accepted flight criteria that we believe should be established: Any object placed in orbit that is too large for an uncontrolled reentry must have a spacecraft available to support independent EVA repairs.
The list of endorsers on this letter is virtually a catalog of my personal heroes. They are making a serious request for a serious issue. Is it too late?
Robert L. Crippen, Pilot STS-1, Commander (STS-7, STS-41C & STS-41G)
Frederick H. Hauck, Pilot STS-7, Commander (STS-51A & STS-26)
Walter Cunningham, LM Pilot, Apollo 7
Neil A. Armstrong, Commander, Apollo 11
James A. Lovell, Jr., Commander, Apollo 13
Eugene A. Cernan, Commander, Apollo 17
Gene Kranz, Director of Mission Operations - Flight Director
Tom Moser, NASA Space Station Program Director
John W. Robinson, Chairman, Space Propulsion Synergy Team