Zubrin Challenges Chang Diaz to Debate Over Mars Exploration, VASIMR Engine

There seems to be a trend of prominent space experts challenging each other to debates.

First, New Horizons Supremo Alan Stern challenged Neil deGrasse Tyson to debate whether Pluto should be restored to planetary status. Stern, whose mission will explore Pluto next year, believes it should be elevated from dwarf planet status. Tyson, the driving force behind Pluto’s demotion, refused to debate the subject.

Now, it’s Robert Zubrin’s turn. The Mars Society president has challenged Ad Astra Rocket Company Founder Franklin Chang-Diaz to a debate over how to best explore Mars. Near as I can tell from the press release, it would give Zubrin a chance to demonstrate that Ad Astra’s plasma-based VASIMR engine, which Chang Diaz is promoting for rapid trips to Mars, is pretty much a fraud.

Wow, who could turn down an invitation like that?

So far,  Chang-Diaz hasn’t responded to the invitation, which was sent on June 13. If he doesn’t accept, Zubrin plans to pull a Clint Eastwood  by debating an empty chair. Actually, that’s a pretty good incentive not to show up. The video of that could be hilarious.

I’ve reproduced the Mars Society’s press release, so you can learn all the details.

Zubrin Challenges Chang Diaz to Debate at Mars Society Convention in Houston

Mars Society President Dr. Robert Zubrin has challenged Ad Astra President & CEO Dr. Franklin Chang Diaz to a debate at the 17th Annual International Mars Society Convention, which will be held in Ad Astra’s hometown of Houston, Texas August 7-10, 2014. The proposed debate proposition is: Resolved “Electric Propulsion in an Enabling Technology for Human Mars Exploration,” with Dr. Chang Diaz representing the affirmative side and Dr. Zubrin the negative side.

Commenting on the challenge, Dr. Zubrin said, “This debate is critically necessary. Dr. Chang Diaz has been actively propagandizing an argument combining three claims. First, that cosmic radiation hazards dictate that current day propulsion, which enables six month transits from Earth to Mars, is too slow to enable
human mission to Mars. Second, that therefore much faster forms of interplanetary propulsion are necessary before we dare undertake human Mars exploration missions. Third, that his VASIMR propulsion system would uniquely enable such quick trips.

“In fact, all three of these points are false. First, the roughly 60 Rem cosmic ray dose that would be received by astronauts over the course of a round-trip Mars mission using 6 month transits involves about a 1 percent risk of cancer later in life, and has already been experienced by half a dozen cosmonauts and astronauts who have conducted extended stays on the ISS or Mir without any radiological causalities. Second, it is thus the case that interplanetary transits faster than six months are not necessary or even desirable, because the six month transit to Mars also provides the crew with a two-year free return trajectory, which would be lost if a faster outbound transit were attempted. Therefore if a superior propulsion system, like nuclear thermal rockets, were available that could, in principle, speed up the transit, competent mission planners would use it to increase the payload, and thus the redundancy of mission critical systems, while keeping the transit time the same, as this would do far more to increase both the safety and capability of the mission. Thirdly, it is simply not true that Dr. Chang Diaz’s VASIMR drive or any other electric propulsion system is capable of enabling the quick trips that Dr. Chang Diaz promises. Such claims are based on assuming nuclear electric power systems with 10,000 times the power and 1/100th the mass per unit power as any that have ever been built. In reality, using realistic numbers, electric propulsion systems would require much longer transit times to the Red Planet than what we can already do today.

“So Dr. Chang Diaz’s argument for the critical necessity of his technology is false end-to-end, and simply amounts to a claim that the nation cannot attempt its program unless it funds his program. Furthermore, by making a false argument for the critical role of high power electric propulsion in enabling Mars missions, the Chang Diaz line serves not only as a rationale for avoiding the challenge of Mars, but also provides justification undertaking irrelevant activities, such as the proposed mission to use a large electric propulsion system to tow a 500 ton boulder from interplanetary space into lunar orbit. This exercise threatens to divert NASA’s human spaceflight program from other objectives, thereby delaying human exploration of Mars (or the Moon or the Near Earth asteroids) for another decade, while the taxi meter on the parked human spaceflight program continues to run at a cost of many billions of dollars per year.

“So Dr. Chang Diaz either needs to come forth and publicly defend his assertions or else clearly disavow them. We have challenged him to come and debate twice before at other locations, and he did not appear. Now our conference is being held in his hometown of Houston, so there is no excuse for him not to show up.”

Dr. Zubrin’s challenge was sent to Dr. Chang Diaz on June 13th. In the 13 days since, Dr. Chang Diaz has not replied. According to Dr. Zubrin, if Dr. Chang Diaz does not appear at the Houston convention, he will be forced to accept an empty chair as Dr. Chang Diaz’s representative and conduct the debate on that basis.

Dr. Zubrin’s letter to Dr. Chang Diaz containing the challenge and proposed terms of the debate is presented below.

June 13, 2014

Dear Franklin,

As you probably know, the Mars Society is holding its annual convention this year in Houston, at the South Shore Harbour Resort, not far from NASA’s Johnson Space Center, August 7-10.

I would like to invite you to debate on the following question: “Electric Propulsion is an Enabling Technology for Human Mars Exploration.”

I suggest a true formal debate, one on one. You for affirmative, me for negative. Each side would have 20 minutes to present an opening statement, affirmative then negative. This would be followed by a 10 minute rebuttal by each side, affirmative then negative.

The debate would then be opened for 30 minutes of questions from the audience, which could be directed to either panelist, for a one minute answer and then a one minute response from the other.

I believe that this would be an excellent way to bring to light all sides of this issue and the broader challenges facing human Mars exploration in general.

The debate could be on August 7, 8, or 10 during the day or on August 7 or 8 as an evening event.

What do you say? Are you in?



The 17th Annual International Mars Society Convention will be held at the South Shore Harbour Resort, League City, Texas, just outside Houston near the NASA Johnson Space Center, August 7-10, 2014. Online registration is now open. In addition to the Zubrin-Chang Diaz debate, the conference will also feature plenary talks by many prominent speakers, as well as the final face-off competition of the International Inspiration Mars Student Design Contest for proposed designs for a two-person human Mars flyby mission to be conducted in the near future. Those wishing to present papers at the conference should submit 300 word abstracts by 5:00 pm MDT, June 30, 2014 to abstracts@marssociety.org. Also, please note that discount advanced registration for the conference expires June 30, 2014. For further information about the Mars Society, please visit our website.