The commentary by Mike Griffin and Scott Pace on fuel depots [“Propellant Depots Instead of Heavy Lift?” Oct. 31, page 17] is another one of those cases of excellent engineering analysis reaching the wrong conclusions. Too many times in the aerospace industry the brilliant engineering solution was the right answer for the wrong problem (the space shuttle being the most obvious).

The basis of their article is: “Heavy-lift launch is a strategic capability for a spacefaring society, and its absence severely constrains any plans.” Both clauses of that sentence are incorrect. Heavy lift has one application — taking humans into the solar system. I wish that was a required strategic capability. It may be one in the future, but it is certainly not one now. Even we optimists who want humans on Mars before 2030 don’t need to start a heavy-lift development for at least five years. And what plans do the authors think are being constrained? The only constraints on plans are lack of budget — and those constraints are getting tighter! Starting on the Space Launch System (SLS) plan now without any missions for at least 10 years guarantees it will be overly expensive and unsustainable — doomed to go down the path of previous false starts, including that travelled by Constellation.

It isn’t fuel depots that are premature, it is heavy lift. We need to put our existing fleet of U.S. launch vehicles — Atlas, Delta, Falcon, Taurus — to work for humans. Let the path to deep space begin now with what we have, and in a few years we can decide on the trades between the heavy-lift booster and in-orbit refueling. Allowing a few years for the commercial rocket development might also introduce other trades — permitting us to do more with less cost. Starting the SLS prematurely will likely cause delays in the commercial rocket program and will certainly cause a near-term abandonment of solar system exploration. Those will hurt the future of American space exploration far more than will a couple of years’ delay in the SLS.

Louis Friedman
Pasadena, Calif.


Louis Friedman is the co-founder and Executive Director Emeritus of The Planetary Society. Prior to that he was Manager of Advanced Programs and the post-Viking Mars Program at JPL.