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The NRC Pathways HSF Study Panel Discussion, Sunday, 10-12-14 October 13, 2014

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The NRC Pathways HSF Study Panel Discussion, Sunday, 10-12-14

Featuring Dr. Jim Logan, Dan Adamo, Dr. John Jurist


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Guests:  Dan Adamo, Dr. Jim Logan, Dr. John Jurist.  Topics:  Our three guests reviewed the NRC “Pathways To Exploration HSF study.  Please direct all comments and questions regarding Space Show programs/guest(s) to the Space Show blog, https://thespaceshow.wordpress.com.  Comments and questions should be relevant to the specific Space Show program. Written Transcripts of Space Show programs are a violation of our copyright and are not permitted without prior written consent, even if for your own use. We do not permit the commercial use of Space Show programs or any part thereof, nor do we permit editing, YouTube clips, or clips placed on other private channels & websites. Space Show programs can be quoted, but the quote must be cited or referenced using the proper citation format. Contact The Space Show for further information. In addition, please remember that your Amazon purchases can help support The Space Show/OGLF. See http://www.onegiantleapfoundation.org/amazon.htm.  For those listening to archives using live365.com and rating the programs, please email me as to why you assign a specific rating to the show. This will help me bring better programming to the audience.

Welcome to this 2.5 hour Space Show Classroom discussion with Dan Adamo, Dr. John Jurist, & Dr. Jim Logan regarding the recently released NRC “Pathways To Exploration: Rationales And Approaches For A U.S. Program Of Human Space Exploration.”  You can download the report for free at  http://www.nap.edu/catalog.php?record_id=18801.  In addition, the project referred to in the last part of this discussion by Dan and Jim, the “Aquarius interplanetary HSF transport” paper can be freely downloaded at  http://www.spaceenterpriseinstitute.org/2014/07/aquarius-a-reusable-water-based-interplanetary-human-spaceflight-transport.  Please note that our panel members used cell phones which caused audio issues which you may hear during the discussion.  Finally, as this program will also be archived on both The Space Show and The Space Show Classroom blogs, there will be two papers uploaded to each blog, one by Dan Adamo & the other by caller Dr. James Dewar. I will mention both in the summary below.  In the first segment, our panel members opened with their perspective on the NRC Pathways HSF study.  While there were similarities in their perspectives, there were also noteworthy differences.  After this comprehensive introduction, I asked our panel members about the study and space settlement or pioneering.  Each panel member had much to say on the settlement issue, including the need to solve the gravity prescription for long duration HSF or settlement.  Our panel members  said that for the most part, space settlement was out of scope for this report.  In this part of the discussion much was said about microgravity issues & the need to do on orbit experiments to determine the HSF gravity prescription.  Deimos was discussed as an initial better choice that the surface of Mars re microgravity issues.  Our guests spoke to the need of a short arm centrifuge on the ISS.  Jim spoke to the specifics of such an experiment such as 1 G at the head., 2.5 g’s at the feet for two hours a day to see how it serves as a microgravity countermeasure.  Our panel members mentioned that there already was such a short arm centrifuge built years ago by NASA and Wiley, http://www.nasa.gov/centers/johnson/slsd/about/divisions/hacd/laboratories/short-arm_centrifuge_laboratory.html.  The guests talked about unknown human factor challenges for going to Mars and long duration spaceflight.  Jim provided us with interesting statistics on human spaceflight totals since the beginning in 1961.  The panel members had much to say about the budget issues discussed in the NRC study.  Another point brought up was the study’s assumption that if we are not going to the surface of Mars, why even do HSF?  Near the end of the first segment, listener Carl brought up the well known plans for Mars settlement with Elon Musk & SpaceX.  This sparked quite the discussion so don’t miss it.

In the second segment, our panel talked about the value of the Pathways study, international partnerships and what they saw as contradictory statements, especially regarding the mission cost impact of such partnerships.  John mentioned the study’s reference to NASA education & public outreach which he thought was more focused on STEM & the development of more engineers rather than on educating the general public to be more knowledgeable about science.  The panel members  noted that there was little attention paid to the societal impact of not even having a human spaceflight program.  Dan & Jim agreed on the importance of educational outreach and shared their experiences with us from the employment with NASA.  Adrian in San Diego sent in an email suggesting the panel was being pessimistic and that China would not overthink issues and just do missions without full disclosure.  All three panel members had much to say in response to Adrian’s charge of being pessimistic.  They talked about being reality based, not pessimistic & why it was so important to be reality based.  The panel hit back hard on the charge of being pessimistic.  Dan & Jim said to be other than realistic was reckless and irresponsible.  Jim also said that being called pessimistic suggested to him that reality had violated the person’s ideology.  Jim would be happy to debate the issues with anyone in open forum.  This discussion brought Jim and Dan to talking about their Aquarius project which you can download at the above URL.  They spent some time discussing the benefits of their approach, noting how it addresses & mitigates many of the problems associated with a HSF mission to Mars.  They also spoke to the need for nuclear propulsion and talked about using water as fuel and very high ISP ratings with high temperatures.  During this discussion, Dr. Jim Dewar called in to suggest their ISP ratings were low, he explained why, and he talked about starting small to start flying and then improving as you go.  We did not know it but we lost John from the connection but Jim, Dan, and Dr. Dewar spoke to the NERVA project, and specifics about nuclear propulsion.  This advanced nuclear propulsion discussion was close to a half an hour near the end of the program.  Dr. Dewar was a guest on the program in 2008 & 2009 regarding nuclear propulsion & its history. He also authored two books on the subject.  Use the GuestSearch tool on our website to find his interviews which I suggest you listen to if you have not already done so.  I will also upload to both blogs the paper Dr. Dewar referenced in his discussion.  After the nuclear discussion, Adrian sent in another email titled “rebuttal.”  He challenged the panel members to do the experiments, not just to talk about them.  Jim, Dan & I challenged Adrian for his solutions to doing many of the needed & essential experiments. All of the panel members supported doing the needed experiments & have said so for decades.  Getting funding for the experiments, NASA approval, etc. is a challenge.  I then challenged Adrian to come to The Space Show as a guest with his solutions for doing the essential work & experiments rather than his just talking about how badly they are needed per his second email.  I hope Adrian does have answers and will contact me about coming on the show to discuss them with us.  Jim & Dan each provided closing comments focusing back on the study report.  They thought the report was worth it from the taxpayer perspective and that it would be used for references.  Jim did think the report was not as good as other government studies he had seen because it was so speculative, something all three guests addressed in their opening remarks.  An 11th hour call came from SLS John to talk about the ISP formula & temperatures Dan and Jim used in their paper Aquarius paper.  Dan authorized me to upload to the blog his written comments on the NRC Pathways study so you will find that document on both blogs as well.

Please post comments/questions on The Space Show blog.  You can reach the panel members through me.

A Technical Note on Nuclear Rockets-1



1. Amnon Govrin - November 19, 2014

I have a question and admit I know nothing about rocket engines, so please, just tell me if it’s impossible, no need to belittle me about my ignorance 🙂
I understand that it is desirable to use hydrogen due to its low atom mass. However, it sounds like the heavier Oxygen doesn’t contribute much. Is there any possibility to trap (filter) the Oxygen after the disassociation process and use it for life support rather than vet it into space?

2. The Space Show - October 16, 2014

Posted on behalf of Matt:

Hi John,
I think the simple Isp-formula, which uses the T/M ratio as a paramter does not apply in our case, because the average molecular mass is not constant during expansion process due recombination of dissociated radicals in the nozzle. Furthermore, significant heat is added during expansion process due to recombination. Your simple Isp formula is only valid for a heated gas, which is adiabatic expanded in a nozzle without chemical reactions during expansion, with a constant ratio isentropic exponent and without heat addition in nozzle.
If the formula would apply (what is not the case) you should also calculate the Isp using the average molecular mass of the gas species that you regarded (there are three molecules/moles:one moles oxygen atoms, two moles hydrogen atoms,weighting together 18 grams, therefore M= 6 g/mol).

Here is a link, that shows required temperature to achieve water dissocication (figure 3):


3. John (in Fort Worth) - October 15, 2014

The question that I had about the Isp = 900 sec at 3000 degrees C with water as the propellant is the following. In James Dewar’s book “To the End of the Solar System: The Story of the Nuclear Rocket” an Isp of 1000 sec is cited at 3000 degrees C for H2 is given. Using the sqrt( T/M) rule where T is temperature in Kelvin and M is the molar mass were can estimate Isp for other propellants. H2O has a mass of 18 in atomic mass units. So scaling is the rule which is Isp (water) = Isp (H2) x sqrt(2/18) = 1000 sec x 1/3 = 333 seconds. This assumes no disassociation of the water and puts water as propellant in the same Isp class as chemical rockets.

If one goes to the best case for Aquarius which is 100% disassociation then the result is two monotonic H particles mass = 1 and one monotonic O particle mass =16 produced for every molecule of H2O. Using the scaling approach above was have
Isp (H) = Isp (H2) x sqrt (mass of H2 / mass of H) = 1000 sec x sqrt (2 / 1) = 1000 sec x sqrt (2) = 1000 sec x 1.414 = 1,414 sec.

Similarly, the Isp (O) = Isp (H2) x sqrt (mass of H2 / mass of O) = 1000 sec x sqrt (2/16) = 354 sec. Here is the part I’m not sure about but I assume that the specific impulse of the disassociated H, H, and O is the mass weighted average of there specific impulses. There for Isp (Aquarius) = 2/18 * 1414 sec + 16/18 * 354 sec = 472 sec. So this leaves Aquarius at a specific impulse that is only slightly better than the best chemical system but only slightly more than half of the proposed 900 sec.

I’m not sure that this is the correct way to approach this problem as there can be some complexities that this basic weighted average approach misses. On the other hand I have made a favorable assumption for Aquarius in the I’ve assumed complete disassociation of water at 3000 degrees C or 3273 Kelvin.

Matt - October 16, 2014

Hi John, I will write a more detailed comment to the subject of Isp calculation. Did you take meanwhile a look in the thesis mentioned below?

John (in Fort Worth) - October 16, 2014

Yes. Note in my last paragraph I pointed out my doubts about this basic approach. But, also I assumed 100% disassociation as a purposeful optimistic assumption versus your charts 35%. I see your point that recombination would release energy but the question is how much before the propellant flow leaves the nozzle? Also, when you get recombination in the nozzle you lose the high Isp H atoms.

If you use the average of 6 for the mass you get Isp = 577 which is better but a lot less than 900. I’m very doubtful that is the correct approach (I had considered it). I think we need a more sophisticated analysis.

One thought is that even if the Isp is much lower than 900 it can still have a major advantage in that it avoid the issue of long term boil off issue of a chemical Mars mission, i.e. the LH2.

Also, someone wrote a book back in 1965 about a nuclear engine that used water. I can’t remember the name of either book or author. I never got many hands on a copy either.

Matt - October 17, 2014

Hi John, thanks a lot for reply. The figure 3 is valid for 1 atm. That is the reason that Dr. Logan proposed to use much lower pressure (0,01-0,1 atm ?) to achieve more complete dissociation. However, I see practical problems to build such a high thrust engine with such a low chamber pressure.

If you operate at “normal”, much higher pressure and 3000 K you get just only a steam rocket. However, also that case may be of interest, because you can refill the tanks at the target planet and reuse the reactor many, many times.

It is very much energy required dissociating the water completely, it must be the objective to regain this energy (stored in the electronic configuration of the atoms?) to heat and speed up the molecules during expansion, also if the mean molecular mass is increased. The theoretical achievable Isp performance for this case is shown, if you use (theoretically) the dissociated H and O atoms as propellants for its own (which is practically not yet possible, according that was told in the PhD thesis) and “burn” / combine it again to water.

In our a bit different case arises the question: Is there enough time during expansion flow though nozzle, that the combination can happen before the dissociated water has left the nozzle?

The whole analysis regarding a nuclear heated “free radical”/dissociation” water engine is a PhD thesis worth. It was maybe already done, because there is not much new under the sun. But a first search brought no results. It may be a sign that the idea does not function at all.

Kirk - October 27, 2014

John, I agree with your mass weighted average approach for calculating the ISP of disassociated H2O, and gave a short proof in reply to your comment on #2336, the Audition-Open Lines Program, of Tuesday, 10-14-14. This does, of course, assume complete disassociation and no recombination.

4. Joe from Houston - October 15, 2014

Dr Logan and I like using a small arm centrifuge on the ISS to study the POSITIVE effects of a non-zero gravity environment in space. Even if it is for a couple of hours a day. We have a big hill to climb. We are just two small voices among billions of people on this planet. The likelihood of anyone powerful enough to take action on this idea is extremely remote. In reality, ideas only exist in one’s mind. It is the actions taken that bear the fruit of something meaningful. Something of purpose and benefit to all humankind.

What we have here is a lack of communication of this extraordinary idea that would essentially pave the way to extending human presence in space in the least expensive and safest way. Never mind about doing this next with a multi-billion dollar tethered space vehicle in space that creates thousands of jobs and put humans in extreme danger. Do it in the lab. The lab we built in space designed precisely to do such things.

This idea should be the primary directive coming directly from NASA. It requires a 180 course correction, however, because right now and until the end of the ISS program, it is all about going to and from the ISS with politically motivated justifications. 99% of the money spent is for this purpose. Rockets and recovery systems are built. The space station and its operators are expensively maintained as the rocket’s only destination. Most of the training is spent on what could happen when going to and from the ISS using semi-automated systems which could take perhaps a few hours even though they are going to live there day-in and day-out for 6 months conducting experiments and maintaining their health and the systems up there.

True; they are putting up people willing to stay a year. It could simply turn out to be an endurance test of the deleterious effects of zero-gravity on the human body. Boy, I can’t wait to see that experiment result in 2-5 years from now.

When you spend 6 hours a day operating and maintaining the ISS, 2 hours of physical fitness exercising, 2 hours of eating and hygiene duties, and 8 to 10 hours of sleeping and relaxing, how much do you have left over for personal time and conducting experiments? You have just 4 to 6 hours left. Which do you suppose gets a bigger share of the hours left over? My guess is “personal time” since you must understand these people are cooped up for months on end in a can in the most extreme and hazardous environment. They would likely go stir crazy if they did not have free time to spend by themselves to recharge their purpose for being there.

NASA knows it. Their partners know it. Their launch service companies know it. The US and Russian governments know it and they are ALL unwilling to budge from this strong and powerful position. Life goes on so to speak and the status quo stays undisturbed. Sometimes, all it takes is a 180 degree course change when you realize you are headed for a thunderstorm when out at sea. It starts with just a simple bend of the wrist holding the boat’s tiller or rudder.

Instead, we have experiments up there to study, over and over, the deleterious effects of zero-gravity on human activities. The main hope is to discover some scientific finding that benefits people on the ground. We do all we can to “Keep Hope Alive” since this mantra is proven to work for admirable people such as Jesse Jackson. This is a self-perpetuating prophecy with no end in sight until, like all NASA programs, the funding gets suddenly yanked and abandoned like what happened during the Apollo era, and the Shuttle era.

Right now we have a 3D printer up there to see if it works in zero-G. If it does, they will likely print out NASA logos in 2D relief on a rectangular plaque labelled as priceless souvenirs destined for museums across the globe. If is does not work, they will likely spend more time and money to fix it over and over until it does work when they could be spending that type of money on finding a way to cheaply and safely extend human presence in space; the primary barrier to sending humans to Mars and returning them some time later.

Why should we spend time thinking and dreaming about going to Mars when our orbiting laboratory is not dedicating any time whatsoever in finding a way to extend human presence in space by using Dr Logan’s admirable idea of applying a small amount of artificial gravity to the human body and measuring the effects on the human bone?

I know this sounds like a rant but an effective rant is how things get done in Washington. If you do not rant, no one in Washington is going to take notice. No one holding any real power, that is. Have you ever noticed that? If not, you are likely not interested in true innovation and change. Taking notice of controversy, emotion, and skin-in-the-game is how the hearts and minds are swayed away from a collision course with program cancellations.

5. Matt - October 15, 2014

Hi SLS John and elsewhere,

I added a link to a German doctoral thesis, which contains tables (see page 28) about the specific impulse, which can be realized by combination of different free radicals (which might be produced by dissociation). In case of the combination OH and O to water we get for example an ideal theoretical impulse of 700 s (6871 m/s). There are seems to be further, even more energetic reaction ways to recombine water (see table) from radicals. I think it can be understood, even it is written in German language.


The question of the day is, under which condition is possible to achieve this complete dissociation of water. If we heat water to 3000°C at chemical rockets like (high) chamber pressures we get mainly only heated steam and a quite low Isp. At a former discussion with Dr. Logan and Dr. Jurist it was said that a nearly complete dissociation at 3000°C temperature can be achieved by assuming very low chamber pressure (1 atm is too high for 3000°C, at this condition just 35% are dissociated). I try to use a NASA thermodynamic rocket code (based on SP-273) to calculate (w/o knowing exactly the limitations of the code) examples, which seems to support the need of very low chamber pressure (fractions of atmospheric pressure?). Assuming this is correct, the question arise, how the heat can be transferred from nuclear reactor core to liquid water at this low pressure levels?

6. B John - October 15, 2014

It was suggested on this show to send a manned mission to Mars orbit in order to remote control rovers on Mars’ surface in real time. NASA once had a paper mission of that kind called HERRO. But one of the most ingenious and doable ideas in space flight today, in my opinion, makes that kind of manned missions completely unnecessary.

The concept is explained in this presentation by Dr. Jeff Norris at JPL, between 5:00 and 22:30 if you have a few minutes to watch it: https://www.youtube.com/watch?v=EeSGuGw4aJU#t=302

With SIMULATED REAL TIME, Mars rovers can be controlled from Earth as if there were no time delay to Mars. There’s no new physics involved, one simply assumes that the rover will execute its commands as planned and the future outcome is simulated in the control room. It works because Mars rovers are sloths. Only rarely will something unexpected occur and the simulation will then go back to its last true state.

Imagine if a manned orbiting telerobotics mission was launched, and only afterwards did people figure out that they could’ve done like this instead, and save $100 billion or so…

/Best regards

Matt - October 15, 2014

Hi B John, the robot must be very autonomous and intelligent to compensate for the time lag between Mars and Earth (about 10 to 40 minutes). This seems mot feasible for while. On the other hand, a manned mission to Deimos would be significant cheaper as mission to Mars surface and also much less risky. It woud be a natural evolution from ISS, a NEO mission to the final objective of manned mars.

Dr. Fred Singer explains the Deimos plan in detail here:

B John - October 15, 2014

No, you are wrong, Matt.
By simply simulating real time, there’s no need at all to send people to the vicinity of Mars. That entire concept becomes completely worthless. Any robot can be better controlled from Earth in simulated real time, than from a Mars orbit.

From Earth, a rover on Mars can be directed 24/7 by different teams working shifts. 4 or 6 astronauts circling Mars could do only a fraction of that work, at 100 times the cost. It would be very much more inefficient to send humans to Mars orbit, than to have scores of humans here do the same job much more cheaply and better.

Autonomous robots will be REPLACED by simulated real time when instead humans are controlling the robots. Simulated real time means less dependence on autonomy.

Dr. Fred Singer is a fool if he doesn’t understand this paradigm shift. It is completely meaningless to send humans to Mars orbit. No point at all in doing that.

Matt - October 15, 2014

Hi B John,

I am just watching your “video game” video, it is very interesting and may be applied for future robot mission. However, the concept seems to need a fairly complete knowledge of the to be simulated environment, which is on the other hand subject of exploration. This is a contradiction.

You may move faster easier from point to other, but if you ould like to make a special operation, where do not know what the result will be in advance, or you hvae to to react without any delay and also if surprises can happen, you will be lost by this approach.

B John - October 15, 2014

Certainly “simulated real time” won’t work where for example humans are involved. We are unpredictable. But a rover like Curiosity has a theoretical top speed of 200 meters per day. In 20 minutes delay that’s 3 meter. That is very predictable in the stale Martian desert. I think they stopped to drill only three times. On Mars nothing surprising ever happens.

It is today’s concept of “only once a day” which requires almost total knowledge of the terrain. Simulated real time instead allows for new information to be accounted for, in real time.

Matt - October 17, 2014

What we really need are real intelligent robots, which can make its own decision in real time based on a large pool of experiences and exhibit a large varity of behavior modes.

7. Matt - October 13, 2014

Hello Dr. Logan, hello Dr. Jurist,

I enjoyed the show very much, but I have an important comment (in addition to “John” comment). I missed a major point in discussion about thermal nuclear rocket propulsion for Aquarius, namely that using water as propellant required to reach the Isp of 800 seconds a complete different working scheme of the engine, which is a very , very low chamber working pressure, which is very different to normal nuclear thermal rocket . I was a bit disappointed that that point was not further discussed together with Dr. Dewar, who was not might not aware of the relevance of the water propellant usage.

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