jump to navigation

Dr. James Dewar, Sunday, 2-12-12 February 12, 2012

Posted by The Space Show in Uncategorized.
Tags: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,

Dr. James Dewar, Sunday, 2-12-12



Guest:  Dr. James (Jim) A. Dewar.  Topics:  Nuclear Thermal Rocket (NTR), changing paradigms to use the NTR from Earth launch, nuclear economics.  You are invited to comment, ask questions, and discuss the Space Show program/guest(s) on the Space Show blog, https://thespaceshow.wordpress.com.  Comments, questions, and any discussion must be relevant and applicable to Space Show programming. Transcripts of Space Show programs are not permitted without prior written consent from The Space Show (even if for personal use) & are a violation of the Space Show copyright.  We welcomed Dr. Dewar back to The Space Show to further discuss the Nuclear Thermal Rocket (NTR) and his paradigm changing approach to use the NTR to launch from Earth rather than using it only in space.  During this nearly 2.5 hour discussion, Dr. Dewar makes the case for the NTR based on probable economics, the previous history associated with NERVA, and the assumed benefits flowing to private companies engaged in public private partnerships along the lines Dr. Dewar described.  In the first segment, Dr. Dewar started out describing the existing barriers to using the NTR to LEO rather than only in space, plus he referred us to his 29 page introductory paper which is available on The Space Show blog for your download and review.  During this segment, we fielded many listener emails and calls wanting to discuss the NTR ISP, possible fuels, testing, and legal issues impacting the use of the nuclear rocket. Michael called and talked about the discussions for a new treaty, the Fissile Material Cut-Off Treaty (FMCT) and how that would adversely impact using the NTR.  Dr. Dewar talked about treaty issues over the years and suggested that treaties are not that easy to establish in this era while suggesting that they could also be modified.  Near the end of the first segment, questions about thorium came up as did questions about additional commercial uses for the nuclear engine here on Earth. 

In the second longer segment, we talked about winning over the public and the media.  Charles Pooley called in with a set of questions and we talked about reentry vehicles, highly enriched uranium, and more.  Jim described a Titan missile accident in Arkansas as an example of the safety controls even in a very large explosion.  Another listener asked about cooling and Jim told us about pulse cooling.  Dr. Dewar’s air launch idea was brought up again by another caller andMarshall sent in an email inquiring about the nuclear engine replacing coal in our terrestrial power plants to make electricity.  I asked Dr. Dewar about risk assessment for the nuclear rocket and reprocessing given terrorism, etc.  He said the reprocessed material would be carefully guarded but also weighed against the environmental risks associated with burying waste, burning it, or even dumping waste in the ocean.  Dr. Dewar was asked about using the nuclear rocket only in space rather than attempting to use it to launch from Earth.  He compared using it only in space to the Pony Express. Don’t miss his full response in replying to this question.  Later in this segment, I asked Jim for his first step in advancing the NTR.  He said the first step was to get people talking about the subject.  Tom called in and also wondered how to get people to rally to the cause.  Near the end of the program, Jim talked some more about potential economic benefits along with secondary commercial products such as heat pipes.  As our program was ending ion engines came up as did Vasimr.

Please post your comments/questions on The Space Show blog.  If you want to contact Dr. Dewar, send your note to me for forwarding.

To download and read Dr. Dewar’s paper, see below:

A Technical and Economic Introduction to Nuclear Rockets

A Technical Note on Nuclear Rockets-1



1. Rick Kwan - February 21, 2012

If you want a well-informed adversary to nuclear rockets on the show, you might try physicist Michio Kaku, who is gaining a lot of ground in popular culture. Lots of people turn to him for explanations of science. He is one also one of the people who protested the launch of Cassini-Huygens because of the plutonium it carried in its RTG. I imagine that he could come of with credible scenarios for what might make nuclear thermal launches to LEO objectionable. And if by chance he thinks it’s doable, you may have a remarkable ally.

James A. Dewar - February 21, 2012


I would appear with him in any forum and believe you are right: he would be a remarkable ally. I also think the greens would be remarkable allies. I believe both would be open to my arguments: the many benefits far outweigh any risks.

I hope you read Appendix C in The Nuclear Rocket to begin thinking about the technical aspects of this launch sequence and get back to me if you see any show-stoppers. I also hope you read my 29-page paper that is attached to this blog to get a intuitive feel for the potential of nuclear rockets. Get back to me on this if you have questions.

Thanks for writing.

Jim Dewar

Rick Kwan - February 21, 2012

Having stuck my foot in my mouth, let me see if I can avoid chewing it off… On second thought, a debate or discussion makes much more sense when there has been a prototype demonstration that shows technology that meets the criteria of safety, non-proliferation, and non-radioactive exhaust/debris. Otherwise, we are basically going to be accused of simply presenting PowerPoints and hot air, a common problem with many aerospace projects.

I’ll get hold of the material and attempt to educate myself. I’m still digesting this show as well as the one with Steve Howe. Thanks for the good information.


James A. Dewar - February 22, 2012

I don’t think you’ve stuck your foot in your mouth at all. What I’ve done in my books, article on the blog, and appearances is outline the technical aspects and many benefits of breaking the ban on using nuclear rockets to reach and return from LEO. No one has looked at this for over 50 years, so it’s very much like having dinner with a business partner and doodling on a napkin on a business plan. You are thinking conceptually at this point and here it’s good and useful to consider the objections to a proposal. So I would have no problem in discussing this with the greens or others. To do it later, after there has been a prototype demonstration, almost requires the program to be kept secret and secret programs once exposed normally are cancelled. Witness the Air Force’s Project Timberwind. Rather, I maintain the greens would become the strongest supporters of this launch sequence, as it opens up space to achieve many if not all of their goals of having a green earth. So I would want to talk to them ASAP and get their views.

I look forward to having a discussion with you after you read the material I suggested, particularly Appendix C of The Nuclear Rocket.

Jim Dewar

2. pritchie (@pritchie) - February 15, 2012

One more quick comment, given you are looking at air launch a partnership w/ StratoLaunch seems like it would be a great fit.

James A. Dewar - February 15, 2012

In my opinion, the first launches would be conducted by the Air Force because the nuclear rocket would have a lot of highly enriched uranium (HEU) in it. HEU is used in many nuclear weapons. However, after experience is gained, I could see private companies, such as StratoLaunch, launching nuclear rockets. They would, of course, require a government license to do so and some might object to a private company handling weapons useable materials, but the nuclear weapons complex has had private security firms guarding the various sites. I see no real technical problem in doing that here, but only after experience is gained. Not at the beginning.

Alistair - February 16, 2012

All US launches with nuclear materials are required to go through INSRP (Interagency Nuclear Safety Review Process). This is no easy task for launches on land. INSRP, in a nutshell, analyzes what would happen if there was a catastrophic event during launch. Streamlining this process would not be easy until you have a standard configuration of the materials and rocket.

Thus, I would think a standard configuration and launch in open ocean would be the easiest way to implement NTR (used for launch) in the near future.

You’d have to ensure that your instantenous impact point (i.e. where the stage would fall if it failed prematurely (or even if it succeeded)) is always over deep water. Typically, this is true of most launches, but some launches do have a small window where they will cross a land mass (typically a sparsely populated region).

I’m not sure how much of a difference (w/rt INSRP) there would be for a NTR launch, vice NTR in deep-space (i.e. not used for launch).
Politically, I think you’d have an easier time convincing the public that an NTR in deep space is less risky than one used for launch.

While I think the NTR engineering challenges are manageble, I’ve seen too many engineers say that the worse case scenario is not possible, only to eat those words later. Having said that, I’ve also seen too many safety experts trying to avoid risk instead of managing the risk. Knowning what risks there are (vice being ignorant or in denial), gets you a long way towards a good program.

Good program. I still need to finishing reading through Dr. Dewar’s paper, though (so take the above with a grain of salt).

James A. Dewar - February 16, 2012

You raise several points.

1. The interagency review process and approval by the president for launches is not a real barrier. It is a bureaucratic creation and like all such, if you can create it you can also de-create it. Moreover, in creating a corporate-government entity that I call NucRocCorp to develop and launch nuclear rockets, the Congress would be deeply involved, as legislation would be required. Such a structure cannot be created by executive order. As this is debated, the approval process for actual launches and recovery of nuclear engines would be discussed thoroughly. I can see a vastly streamlined process coming into being, replacing the cumbersome one now in place.

The why is simple. Breaking the taboo means getting to $100 per pound, or less, to LEO. This is a paradigm shift not only for the space program but also for a lot of technologies and industries that would develop from breaking the ban. If you agree with that, you should see the potential to make a lot of money, where new industries are created, particularly ones with high paying jobs, where new tax bases are established, particularly in rust belt areas. So if the direction of my thinking is correct and I think it is (though I won’t necessarily agree with all I have said once I see what others have to say), then things are streamlined. You must remember, in Washington particularly, money talks and BS walks.

2. On the technical aspects of a launch and recovery of nuclear engines, I can see an extensive period of analysis and R&D to pick out the best solutions. You have an extremely wide launch corridor, starting perhaps off the coast of Australia to North and South America. That’s about half the globe, though you could probably launch a bit earlier, say in the Indian Ocean, and pass over some lightly inhabited regions before getting into the wide Pacific. Then you would have to factor in the US controlled islands in the Pacific that would be used as staging or recovery areas.

Then you would have to devise your cocoon to enclose the nuclear engine. This has never been studied. I pointed out the Mark-6 was the RV for the W-53 and withstood an extremely violent explosion and contained the nuclear materials. So I hold a cocoon can be devised to hold a nuclear engine in its launch to and return from LEO. There appear to be three or four shapes: an RV type structure, an Apollo type capsule, a flying bathtube/space shuttle type structure or a clamshell type rig. I hold this cocoon would have all types of accident prevention/mitigation gear that would reduce the risks of an accident to manageable levels. I hope you read my Appendix C in The Nuclear Rocket to begin thinking about the risks and how to manage them. I don’t see any show-stoppers, but note it will take time to sort through the options. I do agree that many safety experts believe doing nothing is the safest course of action. That of course is unrealistic as life has risks.

3. I agree with you that the public would be fearful, but I view that as an obligation upon people who think like I do to convince them. I don’t think their views are cast in concrete the same way that I don’t think the greens are against nuclear rockets – in fact, I think they will become the program’s strongest supporters. All have to be shown the benefits far outweigh the risks. That’s why I call for debate and dialogue. As you air out these views, you start to build support and once you have some support, once people see the benefits – jobs, industries, tax bases, money and so forth – then you have something with which to go to Congress. See how different this justification for a nuclear rocket program is from the manned Mars approach. There’s something in it for the average person, that’s why I call it a democratic space program.

3. pritchie (@pritchie) - February 15, 2012

Great program! Very much enjoyed it.

The potential for nuclear rockets is obviously there, but the roadblocks in the US seem significant. Do you know what the laws in France or Japan (bad timing) would be?

James A. Dewar - February 15, 2012

I do not know what French or Japanese law is, but in my view they would not be able to have a nuclear rocket program because they lack isolated land areas for testing. France might be able to use some of its territories in the Pacific, but that surely would cause a PR problem and their sheer isolation would hinder the speedy conduct of the program.
If you read my second book, you will see I provide for foreign corporate participation in a US nuclear rocket program both in developing as well as launching them. I hope you will read my argument, think about it then add your voice and opinion as to whether it makes sense.
The roadblocks in the US are significant, but as more and more people enter the debate and dialogue on breaking the ban against using nuclear rockets to reach LEO, then things not only can but will change – once people see the benefits. Jobs, new high tech industries, money and profit and a range of options with which to green the planet.

4. Andy Hill - February 14, 2012

Excellent program David, I really enjoyed listening to your guest.

I was wondering Dr Dewar what you thought about the use of ceramic instead of graphite or tungsten as was proposed for project Pluto in the 1950s.

Also would it be possible to create a smaller engine core from Plutonium for use in space (I think you mentioned that the amount required for a critical mass is much less than for Uranium.

James A. Dewar - February 14, 2012

There are many fuel possibilities for a solid core nuclear rocket and I support research and development on them all. However, I recommend the B-4 core be developed into a flight rated system because it is the nearest to being rated as operational. The program needs flight experience, where everyone beings to have confidence in the new technology, including the public and greens, and not starting over research that might be the case with a new fuel. Please read my 29-page intro: the hardest thing with a solid core is keeping it inside the pressure vessel. Los Alamos studied dozens of different core concepts after the program started in 1955, but didn’t have one that stayed inside the pressure vessel until 1964. That’s nine years.
I urge you to read both of my books for a fuller picture of the potential of nuclear rockets as well as the 29-page summary.
Thanks for your email and interest.
Jim Dewar

James A. Dewar - February 14, 2012

Plutonium 239 has a bare sphere critical mass of around 10 pounds or kilograms, I forget which. This makes it attractive as you can have a small core size, thus saving thousands of pounds. However, it is more difficult to handle than U-235 and more important, does not form compounds that can operate over 2000 or more C. So it doesn’t make sense for the solid core, you aren’t likely to gain real specific impulse advantage. As you investigate other core concepts, such as gas cores, it might make sense, but even here I doubt it. But that is what you would find out in any advanced R&D effort.
Hope this answers your question.
Jim Dewar

5. James A. Dewar - February 14, 2012

Doubling is only the start, with about 825 seconds of specific impulse. It goes up from there. That’s the entire point in my paper where I project 10 generations of solid core nuclear rockets. Each generation has an improved capability and that changes the payload costs. So $100 per pound will not be fixed in concrete, but can go even lower. I hope you read the paper and my books. All will give you a clearer picture of the benefits of nuclear rockets and of breaking the taboo against using them to reach LEO.
Jim Dewar

Terry in Corpus Christi - February 14, 2012

Dr. Dewar, thanks for your reply. Nuclear rockets just sound great! I just don’t know why there isn’t more interest if we are serious about lowering the cost to LEO and travel to Mars and beyond. Do you remember if Dr. Von Braun had any interest in nuclear? I know he had a low opinion of solid rockets.
Thanks for your time! Got to get one of your books soon.

James A. Dewar - February 14, 2012

If you read my first book, you will see that von Braun was deeply involved in the nuclear rocket program and was in charge of the RIFT program. If the nuclear rocket and Saturn had not been cancelled, he would have operational control over the program.
Jim Dewar

6. Terry in Corpus Christi - February 12, 2012

I really enjoyed hearing from Dr. Dewar this afternoon. Doubling the weight to LEO should be worth getting someones attention.
I hope to have him back on the program soon.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: