VASIMR and Honor
As I was working on providing a follow up to my article on the new Lockheed Martin fusion technology breakthrough, I thought it would be good to familiarize myself on the recent history of VASIMR technology. In that pre-story preparation, I ran across an interesting discussion of a jousting match between the Mars Society’s Robert Zubrin and Franklin Chang-Diaz, the president of Ad Astra, and the inventor of the VASIMR system, written by Space News correspondent Chuck Black. Apparently, Zubrin considers VASIMR to be a fraud, and called Chang-Diaz out to debate the value of VASIMR in a Mars mission. Black’s article argues that the debate challenge and the back-and-forth banter surrounding it is a present-day analog for the 1890’s feud between Edison and Westinghouse over supremacy of AC versus DC electrical power.
Personally, I think Black is trying too hard.
Zubrin’s cause for outrage seems to stem from an opinion that VASIMR is “only useful as a smokescreen for those who wish to avoid embracing” real initiatives which could start in the near term, using a list of current technologies advocated in Zubrin’s Wall Street Journal essay “How We Can Fly to Mars in This Decade—And on the Cheap”. Zubrin also explicitly calls VASIMR a “total falsehood” which “must be exposed.”
I have seen the engine in operation, and heard the laments of the team from way back in the late 1990’s as to the hurdles to achieving each new Tech Readiness Level (TRL). It could be argued that Franklin has been fighting inertia at least as long as Zubrin in regards to moving forward with ANY real Mars exploration plan. Dithering by NASA is definitely not a new behavior for the agency, and VASIMR propulsion would help break up any inertia to manned Mars exploration, just as committing to Mars Direct would. For Zubrin to single out Ad Astra’s work as a roadblock to Mars Direct and somehow by an extension a drag on any humans-to-Mars program indicates a certain myopia.
Zubrin, and Mars Direct groupies in general, are unfair in such pronouncements. I think that Franklin’s characterization of his team’s work in this way as slander is entirely accurate. VASIMR has had a consistent (albeit slow) development track, as has Mars Direct, and in both cases, the proponents for both were essentially forced out of the NASA structure to continue development. Frankly, the fact that Ad Astra has continued to move forward technologically while Mars Direct has not seems to be of some irritation to Zubrin.
Zubrin even invited Chang-Diaz to a panel discussion titled “VASIMR: Silver Bullet or Hoax” at the 2011 Mars Society international convention to debate a false argument about the validity of the technology. Indeed, Zubrin said:
“To achieve his much-repeated claim that VASIMR could enable a 39-day one-way transit to Mars, Chang-Diaz posits a nuclear reactor system with a power of 200,000 kilowatts and a power-to-mass ratio of 1,000 watts per kilogram. In fact, the largest space nuclear reactor ever built, the Soviet (era) Topaz, had a power of 10 kilowatts and a power-to-mass ratio of 10 watts per kilogram.”
The issue here is that the 39-day mission is openly described as possible someday, but not now. The bulk of the various mission plans described by Ad Astra are not nearly so fast, but are still sportier than Mars Direct. The criticism of the extreme edge of speculation as if that was the near-term goal, well, that is dishonest in itself.
On the other hand, recent developments in fusion technology from Lockheed’s Skunk Works division, as discussed here, bring the kg/KW ratio in line with what is needed to serve the energy needs of the 39-day journey. From the Lockheed article:
“An advanced fusion reactor version, the International Thermonuclear Experimental Reactor (ITER), being built in Cadarache, France, is expected to generate 500 MW … The ITER, for example, will cost an estimated $50 billion and when complete will measure around 100 ft. high and weigh 23,000 tons… for the same size, the CFR [Compact Fusion Reactor] generates more power than a tokamak by a factor of 10. This in turn means, for the same power output, the CFR can be 10 times smaller.”
Let’s do some simple math:
23000 tons equals 208.7x 105 Kg
500MW equals 500,000 KW
Calculations with the above figures shows that the ITR has a ratio of about 42 Kg/KW. Given that result, an equivalent CFR system would weigh in at about 4.2 Kg/KW.
However, we don’t need an ITR-equivalent CFR, as we only need 200 MW of power, not 500MW. More calculations:
200 MW/500 MW =0.4
0.4 * 4.2 Kg/KW equals 1.68 Kg/KW
In regards to energy requirements to serve a 39-day mission, the wall to climb becomes lower as this CFR technology comes online. Of course, this doesn’t quite hit the arbitrary goal of 1.0 Kg/KW performance, so we would need to accept a slower cruise. However, if you do a very rough calculation of 1.68 * 39 days, the mission duration comes in somewhere around 65 days, and that is still with only one CFR unit in service. If two CFR’s are powering the engines, the transit time resets to the range that Zubrin finds so fantastical. Any way you look at the problem, the concept of VASIMR-based Mars missions with fast trip times is in no way a hoax.
Black also points out:
But while Zubrin is also correct in his assessment that the current administration is “not making an effort to develop a space nuclear reactor of any kind” he omits to mention past and current efforts by the US and others, some of which are outlined in a November 2009 Wired.com article titled, “Russia Leads Nuclear Space Race After U.S. Drops Out.”
This insightful thought about the state of space nuclear power research is only improved upon, and greatly too, by the new Lockheed CFR power system. Russia, nor anybody else, has left behind American ingenuity, it appears.
Another important idea brought up by Black, tangential to the power density hurdle to be vaulted:
Of course, we can’t forget that there are also substantial difficulties testing and assessing electrical propulsion systems. For example, the theories covering the behavior of the magnetic nozzles used by the systems are a complex mash-up of theory and guesswork, which often provides unreliable predictions at variance from any measured, real world performance… For instance, testing the magnetic nozzle requires a test volume that’s large enough for the plasma to fully separate from the magnetic field so as to insure that the outer fringes of the field aren’t dragging on the plasma and killing most of the thrust that the inner parts of the field are producing. This means you need a huge vacuum chamber to perform any sort of accurate test… you could test the engine in space, which is big and has vacuum pretty much everywhere. But the only place presently available for this sort of testing is aboard the International Space Station (ISS), which has been considered and hinted at by the US and NASA, but is not yet formally scheduled for the VASIMR…
This is a phenomenon that I have heard of, where the exit plasma tries to follow the magnetic field lines of the engine, which in effect “curls” the ejected plasma back around towards the forward direction. Since you have not sent as much plasma aftward, the resulting effective thrust is then lower than desired. The last time I talked with anyone on the team about it, they were working on a nozzle subsystem to break the field lines at the end of the nozzle. I do not know what the status of that effort is at this time.
However, we do know that electrical propulsion systems in general work. The ion thruster developed for the Japan Aerospace Exploration Agency (JAXA) “Hayabusa” mission, which is a small scale, low powered electrical propulsion engine similar to VASIMR has demonstrated its feasibility during interplanetary flight under real world conditions for over a thousand hours of continuous use… The NASA launched Dawn spacecraft… uses xenon ion thrusters pioneered during the Deep Space 1 probes, a part of the NASA New Millennium Program focused on testing high risk technologies. There are others as well, which means that VASIMR is certainly not a hoax, but it also suggests that perhaps Chang-Diaz is a bit more optimistic in his claims for this specific propulsion system than the existing evidence warrants.
In essence, both Zubrin and Chang-Diaz are exaggerating their present case. Why would they be doing this? That’s easy. Both realize that science and engineering are starting to take a backseat in space exploration to public relations and entertainment.
I’m not going to agree with this evaluation. The success of previous electric propulsion systems and their missions suggests nothing about quick VASIMR-based trips being optimistic, and certainly not exaggerated. As of the time this article was written, back in 2011, I would agree that the needed power source wasn’t really on the horizon yet, but that has no bearing on earlier electric propulsion missions’ successes. As such I think the author is striving for an equivalence in position between Zubrin’s and Chang-Diaz’s claims, playing to the middle of the road. In particular, Zubrin’s comments and subsequent challenge to debate were offered in a crass and technically undisciplined way. Zubrin basically said that Ad Astra was perpetrating a hoax, and even if it was a real technology, it was a stupid one. As a twist on the old fable, there are no grapes, and even if there were, they’d be sour? No wonder Chang-Diaz didn’t accept that juvenile debate under those conditions!
I’m not going to go into a full reprint of Black’s description of the Edison-Westinghouse battles over the future of electrical power, though it is an interesting synopsis of the history. I think this draws up his views neatly:
Are we entering a new era where showmanship, entertainment, political glad-handling, pork-barreling and hyperbole will each be necessary in order to suitably move forward new technologies? Only time will tell. But the idea of Bob Zubrin calling out Franklin Chang-Diaz for the modern day equivalent of a public gunfight at high noon for perpetrating a “hoax” doesn’t seem to strike anyone as being silly. So maybe the next “gilded age” has already arrived.
Really? We’re talking about finding mission architectures and visions to leave the Earth to explore and claim the rest of the solar system. In a fit of pique, a major space advocacy organization picks an illogical fight with a private company that is developing technology to facilitate one of those visions. How is that in any way NOT silly? I’m all for a new Wild West period in space, but knifing each other in back? Not so much. The appeal to the idea of this being two showmen hawking their products is a bit too pat an explanation for the circumstances.
Beyond all of that, the real shining moment today is that it seems that one of Zubrin’s major detractions of the VASIMR 39-day mission, copious electrical power, will likely be brushed aside within the decade.