February 27, 2010
Wild claims are being tossed about regarding the future U.S. space program. Recipes for success are touted and e-mailed around – concepts based more on wishful thinking than on solid science and engineering. My friend Rand Simberg refers to those who would replicate anew the means we devised to go to the Moon several decades ago, as having an “Apollo cargo cult” mentality (i.e., Pacific islanders waiting for parachutes to once again drop wondrous things in crates from planes, as they did during World War II). A counterpart to the so-called “Apollo cargo cult” also exists in the space community and they rely on their own talismanic thinking – a belief in some technique or item that allows us to go farther and longer in space, with incredible new capabilities. The talisman takes different forms for different groups, but in all cases, they ward off the evil spirits of physical and bureaucratic reality.
Early in the history of the Vision for Space Exploration, talismanic thinking was apparent with Project Prometheus. This was a program to develop an advanced space nuclear reactor for missions to the outer Solar System – where the Sun’s rays are too weak to provide enough energy to power systems. Used anywhere, such a capability enables activities to take place in a power-rich environment, making many necessary and routine operations easier, safer and more efficient. Former NASA Administrator Sean O’Keefe was enamored of Prometheus, so much so that he often unintentionally overstated its capabilities. For him, Prometheus was a talisman – a unique capability that enabled the otherwise unobtainable.
NASA Administrator Charles Bolden fancies his own talisman – the technology to “go to Mars in days and weeks, rather than months.” Bolden is probably referring to VASIMR, the plasma rocket engine designed and undergoing testing by former astronaut Franklin Chang-Diaz. In principle, a VASIMR-powered vehicle could go to Mars on non-minimum energy trajectories, thereby cutting transit time between planets to a fraction of that required for a chemical rocket.
VASIMR is an interesting concept and some form of it will be very useful when we are ready to travel to the outer planets. However, one aspect about it that I have not heard mentioned by Bolden is the low mass, high power system needed to run it. The only known systems approaching the necessary power density needed are nuclear reactors. Which brings us back to Project Prometheus, a joint NASA-Department of Energy (DoE) effort.
Prometheus was canceled in the FY2006 budget. It was deemed too complex and too costly for its proposed use, the Jupiter Icy Moons Orbiter. This was a robotic spacecraft designed to tour the Jupiter system and obtain data on its satellites during multiple flybys. Note well: this power system was thought to be both too complex and expensive for a robotic mission. A similar system for human missions – which involves many more systems, power requirements, and propulsion – would be even more complex and expensive. Tack on international participation and – well, you get the picture.
So where does this leave VASIMR? Chang-Diaz notes that nuclear reactors can be launched empty and then assembled and fueled in space, presumably by human astronauts. Thus, there are no safety considerations associated with its launch. The problem is that the pieces of this reactor don’t exist and aren’t even being thought about being built. For decades the DoE community has talked about a space reactor of the 100 to 1000 kW class; a VASIMR-powered Mars vehicle would need a 10 megawatt reactor. Billions of dollars went into the SP-100 program in the 1980s and 1990s and still the reactors needed to power VASIMR exist only in the mind’s eye of some space dreamers. The United States Navy has been building and operating nuclear reactors for over 60 years, so one would think that building a space reactor would be achievable, but practice has proven otherwise.
VASIMR is Bolden’s talisman, the magic beans that will grow a stalk that we can climb to Mars. Such a rocket engine would be a technological breakthrough promising capabilities well beyond our current reach. But for now, a Mars craft using VASIMR is imaginary. Reality will not come about by spending massive amounts of money on general technology investment. When VASIMR is finally built, it will be because it is needed for a specific application or mission. Once again, the ends will drive the means, not the other way around.
Talismanic thinking is common in much of the current discussion about the new path for NASA. Other talismans include cheap access to low Earth orbit, commercial transport replacing Orion, and an “exciting space goal” to engage the public. These new dogmas (all of them means, not ends) clearly illustrate that there is no strategic thinking or thoughtful leadership guiding America’s space program. Those at the top need to know where they are going and understand why; the fact that they currently do not bodes ill for the future of our country.
NASA Administrator Charles Bolden recently said that “he is trying to find middle ground between groups “radically” in favor of keeping the Constellation program and others lobbying for reliance on commercial space entities.” But he is still confusing the means with the ends. We should re-affirm that our mission is to use the resources of the Moon to build a transportation infrastructure whereby all can travel to wherever they choose as often as they want. Our direction in space goes through the Moon or we go nowhere.
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