Los Angeles - Jan 21, 2003
It seems to be the week for excessive hype where space is concerned. Over the last few days, three separate stories about developments and problems in space exploration have made a considerable splash -- but on more detailed inspection, all three have been overblown.
The first is Peter Pae's story in the January 17 Los Angeles Times, "NASA Sets Its Sights on Nuclear Rocket to Mars". As a result of an interview with NASA Administrator Sean O'Keefe, Pae reported: "Hoping to pave the way for human exploration of Mars within the next decade, NASA is expected to announce that developing a nuclear-powered rocket is its top research priority.
The space agency is expected to request 'significant resources and funding' to design a nuclear-powered propulsion system to triple the speed of space travel, theoretically making it possible for humans to reach Mars in a two-month voyage.
The Bush administration has signed off on the ambitious nuclear-rocket project -- though not specifically for the Mars landing -- and the president may officially launch the initiative during his State of the Union address on Jan. 28...
The project, dubbed Project Prometheus, would greatly expand the nuclear propulsion plans that NASA quietly announced last year when it said it may spend $1 billion over the next five years to design a nuclear rocket."
The latter part of this statement may well be accurate. NASA officials have refused to officially confirm any enlargement of planned spending on the development of nuclear propulsion and have said flat-out that Pae incorrectly interpreted O'Keefe as saying that Bush would definitely announce the plan in the State of the Union speech.
However, Brian Berger reports in "Space News" that an official who has seen NASA's Fiscal Year 2004 budget request confirms that there will be a considerable expansion of the program: "There is significant money in the budget for Prometheus... more than I expected to see."
However, this -- to put it mildly -- is not the same thing as saying that NASA plans to try to develop a very large nuclear rocket engine capable of launching a manned ship to Mars within a decade.
Pae quotes O'Keefe as saying: "We're talking about doing something on a very aggressive schedule to not only develop the capabilities for nuclear propulsion and power generation but to have a mission using the new technology within a decade."
But O'Keefe has spent the past year talking constantly about his hopes for a deep space mission using nuclear-powered propulsion within a decade or so -- while making it clear that he is talking about an unmanned, relatively small probe. NASA's Nuclear Electric Propulsion program -- for which it included $46.5 million in its FY 2003 budget request -- would have been just such a system.
Like the already-existing Solar Electric Propulsion (SEP) system first successfully tested on the Deep Space 1 probe, and scheduled for its first operational deep space use on the 2006 "Dawn" asteroid probe, its actual rocket engines would be ion thrusters using several kilowatts of high-voltage electricity to electromagnetically hurl a trickle of ionized vapor out of the thrusters at extremely high speed, thus producing at most a few ounces of thrust, but for years rather than minutes.
This allows a spacecraft to gradually accelerate itself to very high velocities using a far smaller amount of onboard ejectable propellant mass than any chemically powered rocket engine can do.
But the Achilles' heel of solar-electric propulsion is that -- since it requires large amounts of sunlight converted into electrical energy by huge solar-cell arrays -- it can only be used in the inner Solar System.
The very high acceleration levels achievable through ion drive, however, are far more useful in the vast spaces of the outer Solar System, where the sunlight levels are much too low to power it. To run ion engines in the outer System, an alternative source of high levels of electrical power is needed.
A spacecraft with a nuclear-electric propulsion (NEP) system would therefore carry a miniature nuclear reactor weighing several hundred kilograms, and capable of turning out kilowatts of power for years on end, like the solar arrays of a SEP spacecraft -- but anywhere in the Solar System. It could thus accelerate itself to very high speeds in the outer System -- and also decelerate itself later to enter orbit around outer planets.
It could also then carry out very extensive and high-powered maneuvers in such planetary orbits, greatly increasing its ability to survey such a planet and the system of moons, rings, and magnetosphere that surrounded it.
For instance, a NEP-powered Jupiter orbiter could easily enter orbit around each of Jupiter's four major moons, survey each in detail before leaving it to travel to the next one -- while a spacecraft equipped with a chemical rocket engine would have great difficulty entering permanent orbit around even one of Jupiter's moons.
O'Keefe is a great enthusiast for such nuclear deep-space propulsion systems and has advocated them constantly since taking office, saying that NASA hoped to spend a billion dollars over the next five years to develop them.
But this is an enormous distance from the tremendously larger and more powerful nuclear-powered rocket engines that would be necessary to accelerate a manned ship to Mars.
Indeed, these would probably not use NEP at all, but would instead use some form of "nuclear thermal propulsion" in which a large reactor would heat the propellant gas directly to thousands of degrees in order to blast it out of the rear exhaust.
Such a huge nuclear-powered manned ship would certainly take tens of billions of dollars to develop, and it is utterly ridiculous to say that there is any chance that NASA could develop a manned Mars ship (nuclear-powered or not) quickly enough to launch it within a decade.
Peter Pae, in his Times article, seems to have been completely confused by O'Keefe's references to the fact that such a vastly larger nuclear-rocket system could indeed send a manned ship to Mars in only a couple of months, and so falsely connected them to O'Keefe's simultaneously declared indications that the Bush Administration does intend to considerably increase the current spending level on the NEP program while renaming it "Prometheus".
Indeed, one can argue that even the tremendously more modest unmanned NEP program that O'Keefe apparently was talking about is a very unwise choice for NASA right now, given the agency's increasingly serious fiscal problems.
Nuclear-electric exploration of the Solar System has tremendous scientific potential in the middle-range future -- and such reactors would use uranium-235, which is far more expensive than plutonium but also thousands of times less radioactive when a reactor is shut down, thus being virtually totally safe to launch into orbit.
But developing such miniature spacegoing reactors, as mentioned, will still be a difficult task, costing one or two billion dollars -- and there is simply no unmanned Solar System scientific mission planned for flight within the next 15 to 20 years that needs such a powerful propulsion system badly enough to be worth that expense in such a short time.
It would make vastly more sense to stretch out the development of an NEP system over 20 years rather than 10 (let alone even less time), and instead use the money saved for the important nearer-term non-NEP space science missions which are currently likely to go begging for want of funding.
One such mission is the Pluto flyby probe, which has been the subject of a bizarre political tug of war for the past few years. NASA, under former administrator Dan Goldin, was very reluctant to fund it -- but the planetary science community strongly supports it, especially since there is a good chance that Pluto's scientifically important atmosphere will freeze out some time during the next two decades as the planet moves further from the Sun.
Moreover, if its launch is delayed beyond 2006, it won't be able for another decade to utilize a gravity-assist flyby of Jupiter to greatly accelerate its trip to Pluto without any deep-space propulsion system.
Even after O'Keefe replaced Goldin, NASA and the Bush Administration refused to support any such near-term probe. Indeed, O'Keefe (who has no formal engineering background) embarrassed himself by testifying entirely falsely to Congress that a Pluto probe should wait until an NEP system had been developed, because such a probe -- even though it couldn't possible be launched until about 2012 -- would still reach Pluto before a simple, vastly cheaper Jupiter-assisted probe.
He also stated erroneously that such a late-launched NEP Pluto mission would be far better than the simpler probe because it could use its NEP system to brake into orbit around Pluto for protracted study.
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Europe's Great Leap Upwards
Los Angeles - Jan 06, 2003
There have been several interesting developments in the past month where the space science programs of the European nations are concerned. They're a mixed bag -- although, on the whole, they're rather discouraging. Funding remains a serious problem for space science in virtually every country, given its very high cost relative to other forms of research.
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