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2018/11/06 Notes for Post to New Mars forum
Title updated from Light Gas Gun Direct Delivery to Mars (2025/05/08)
Topic: Hydrogen Gas Launcher
Reference: Dr. John Hunter et al
Summary: This article will attempt to show that a hydrogen gas launcher offers the optimum cost benefit ratio for launch of non-biological payloads to Mars.
To skip references, go directly to “New insight on offer:”
References in Forum, using search argument “john hunter”
GW Johnson Human missions >> Control cost or go home >> 2012-06-16 17:10:45
Concise summary of Dr. John Hunter's vision for a light gas gun.
RGClark Human missions >> Control cost or go home >> 2012-06-15 07:13:51
Quotes Richard Obousy on Dr. John Hunter's talk
Bill White Interplanetary transportation >> Mountain launch tracks revisited, - Alternative to fueled rocket boosters >> 2004-04-12
Refers to John Hunter and Gerald Bull
Numerous other posts are present in the search results, but they are about other people.
References in Forum, using search argument “light gas gun”
kbd512 Human missions >> Honeymoon on Mars >> 2018-08-24 12:47:26
Discusses GW Johnson's proposal for a light gas gun
GW Johnson Human mission >> Honeymoon on Mars >. 2018-08-24 12:11:23
Describes a one mile long light gas tube floating in ocean.
JoshNH4H Interplanetary transportation >> Un-conventional ways to LEO >> 2017-12-07 13:01:11
Discusses light gas guns in relation to a proposal for a water pumped cannon
GW Johnson Interplanetary transportation >> On Orbit fuel depot >> 2017-07-08 10:18:39
This post comes close to covering the ground I'm hoping to cover with this post, if it has not already been proposed.
Specifically, Mr. Johnson mentions the need for a space tug to “go and get propellant loads”
GW Johnson Human missions >> Constructing a human mission, a tonne at a time >> 2016-08-29 09:39:24
Includes reference to “light gass technology to develop and try out”
GW Johnson Interplanetary transportation >> Reusable Rockets to Orbit >> 2013-10-02 09:36:40
Discusses use of light gas gun to deliver propellant to LEO
GW Johnson Human missions >> Landing on Mars >> 2013-09-15 16:14:25
Introduces the idea of using a light gas gun to send ice to orbit
RGClark Human missions >> Control cost or go home >> 2012-06-13 06:19:44
In this post RGClark quotes GW Johnson's report of USAF research and a paper about sending a propellant tank to orbit
New insight on offer:
As discussed in several of the articles cited above, it is known that to place a payload into LEO after launch from a light gas gun, it is generally recommended to include a solid rocket motor and some suitable electronics to add horizontal momentum to the flight.
Edit: To try to avoid misunderstanding, it is necessary to import horizontal velocity to a payload launched by a ground based light gas gun, if the intended destination is low Earth orbit, or GEO. What I have seen recommended to meet this need is the use of solid rocket motors.
Thanks to kdb512 for pointing out the need for this clarification.
However, if a launch is planned to send mass to Mars, then the rocket motor can be eliminated from consideration.
Some electronics will be needed to provide for radio tracking transmissions so the package can be retrieved as it approaches Mars.
A Mars launch could be scheduled for once a day, as the Earth rotates around to the optimum launch vector.
The primary payload would be ice, since a sabot is needed for a light gas gun launch, and ice can provide its own sabot.
However, frozen food or other non-living material can be embedded inside the ice capsule.
A thin cap of titanium or similar sturdy material would protect the ice capsule during passage through the atmosphere, if such protection is necessary. It is possible that ice can serve as its own ablative shield.
Edit: travel time through the atmosphere of the Earth, at 5 miles per second, would be on the order of 5 seconds or so. It has been pointed out that titanium conducts heat, but the payload will be out of the atmosphere quickly, and temperatures will rapidly fall. If there is someone with access to computer modeling software able to consider this scenario, I would welcome their contribution to the discussion.
Thanks to kdb512 for suggesting alternative shielding for the top of the payload.
Additional references:
A google search for dr. john hunter launch delivered a top page with about 50% related citations
https://howwegettonext.com/q-a-dr-john- … b2af5bbf71
This Q&A with Dr. Hunter by Duncan Geere comes across to me as fairly comprehensive.
In particular, begin Quotation:
That gun ultimately managed eight kilometers per second [five miles per second], which far surpasses any real gun that’s historically ever been made — electric guns never came close to the gas gun for performance, and still don’t.
End Quotation.
Somewhere I recall reading that Dr. Hunter chose hydrogen as his working fluid because (if I recall correctly) its low molecular weight facilitates very high speed of sound levels for launch purposes. What I am unable to recall is where I got the impression that hydrogen gas can yield a velocity sufficient to send a payload to Earth escape velocity. If someone can find a reference to support that vague recollection I'd like to add it to this post.
Also note: Dr. Hunter was interviewed on The Space Show with Dr. David Livingston
http://www.thespaceshow.com/show/11-apr … ohn-hunter
http://www.thespaceshow.com/show/09-oct … ohn-hunter
http://www.thespaceshow.com/show/18-feb … al-edition
http://www.thespaceshow.com/show/19-jun … al-edition
http://www.thespaceshow.com/show/14-jan … al-edition
(th)
Last edited by tahanson43206 (2018-11-06 18:36:18)
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It's not "generally recommended" to circularize the orbit, it's absolutely mandatory if you wish to stay in orbit. Absent the circularization burn, the only two other options available are eventually crashing back into the body you launched from or exceeding escape velocity and flying off into space, as you suggested. That's just the way orbital mechanics works. If you want to do donuts around whatever you launched off of, then you need to circularize the orbit with a separate burn.
Titanium would do a reasonably good job of transferring heat to the payload, but not much else. Some sort of very light and very strong material with very limited thermal conductive material would be required. If you shot a slug of ice at Mars, it'd burn up during reentry without a heat shield or shatter into a million pieces upon impact.
Why shoot ice at Mars when the ground is loaded with cubic kilometers of ice?
Why not find out if Phobos or Deimos have ice in them to refuel in orbit prior to returning to Earth?
There's lots of other needed materials that are hard to come by, such as refined metal products for rocket engines and propellant plant repair.
If the gun was on the surface of the moon, this might work a little better, provided there was a way to get the payload to the surface of Mars intact or into orbit around Mars, but I still fail to see what we'd accomplish.
We still haven't gone to Mars for one and only one reason. Nobody with any power within our government is all that interested in doing it. The light gas gun still has potential, but I'm not sure if this is how I'd try to use it. We have a major problem getting propellant to orbit in a cost effective manner. Once we can do that, we can go virtually anywhere in our solar system that looks interesting.
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Calliban,
You can also use a gas gun. Hydrolox should be able to provide quite the kick. Not enough to reach orbit, but a few km/s maybe?
The H2/O2 reaction will generate superheated steam, which has a mean molecular speed of several km/s at combustion temperature. Maybe someone could use kinetic theory to work out rms speed more exactly. I can't be bothered. But it is definitely high enough for launch assist. The problem with trying to achieve too high a delta-V with launch assist is the need for either a very long barrel or very high acceleration. The first gets costly and difficult to engineer. The second limits compatible payloads and the rocket vehicle must stand up to heavy compressive loads.
If we burn the mixture fuel rich, i.e with too much hydrogen, there will be a lot of excess hydrogen in the expanding gases, boosting propellant molecular speed.
Last edited by Calliban (2022-03-09 18:12:13)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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If the payload is any form of water a plastic bottle or bag frozen can do the job of having it delivered in tact to orbit inside for a standard payload fairing or shroud. That not only protects for shock-waves but for atmospheric as well as for inadvertent heating from moving to reach orbit.
As you noted a stage to give the desired orbit would be required. Also noted is the need for the first stage out of any length of barrel or slide guide is to be solid propellant.
The premises of gas means not liquid under high pressures and unmixed in the launching shell casing that has a means to cause the rapid explosion, to force the total of the components ahead of it to proceed into full launch with no means to stop once its fired.
Its the size of that kick and payload that needs to be met in order to obtain velocity for reaching orbit no matter what fuel type we use.
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The Space Show with Dr. David Livingston has booked Dr. John Hunter for this week.
http://newmars.com/forums/viewtopic.php … 79#p192279
I have tried to publicize the work of Dr. Hunter on this site, with very limited success.
Here is another opportunity to the small number of NewMars members who are interested in gas gun technology.
Dr. Hunter did research for Ronald Reagan's Star Wars project, and changed from electromagnetic launch to hydrogen propulsion because hydrogen is so much better.
There is a lot of misinformation floating around in this forum and elsewhere. Here is an opportunity to hear from someone who actually knows what he's talking about.
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The post below is brought forward from 2018, due to the arrival of ChatGPT on the scene.
Since the original time of this post, and for some time previous, I have been looking for a way to deliver payload to orbit using a ballistic launcher.
In working with ChatGPT recently, I have come to realize there is a class of trajectories that allow for delivery of payload to GEO (or probably any desired circular orbit) without the expenditure of energy or mass to circularize the orbit that is traditionally required.
What I have in mind is an arc trajectory, that passes through GEO at a near vertical orientation, and with velocity sufficient to reach some distance away from Earth, before gravity wins and the payload begins to return to the Earth. If the correct/optimum orientation and velocity are achieved as the payload passes through GEO, it will fall toward Earth so as to pass through GEO at a velocity of 3 km/s. If the correct/otimum orientation and velocity are achieved as the payload passes through GEO, it should be moving in a path tangent to the path of a satellite stationed in GEO, so that for a very small expenditure of energy/mass, the payload can be captured by the satellite.
My hope is that ChatGPT can compute the required vector.
For the record, the post below is the oldest of the set of posts collected by FluxBB when asked to find Dr. John Hunter in the NewMars archive.
(th)
2018/11/06 Notes for Post to New Mars forum
Topic: Hydrogen Gas Launcher
Reference: Dr. John Hunter et al
Summary: This article will attempt to show that a hydrogen gas launcher offers the optimum cost benefit ratio for launch of non-biological payloads to Mars.
To skip references, go directly to “New insight on offer:”
References in Forum, using search argument “john hunter”
GW Johnson Human missions >> Control cost or go home >> 2012-06-16 17:10:45
Concise summary of Dr. John Hunter's vision for a light gas gun.
RGClark Human missions >> Control cost or go home >> 2012-06-15 07:13:51
Quotes Richard Obousy on Dr. John Hunter's talk
Bill White Interplanetary transportation >> Mountain launch tracks revisited, - Alternative to fueled rocket boosters >> 2004-04-12
Refers to John Hunter and Gerald Bull
Numerous other posts are present in the search results, but they are about other people.
References in Forum, using search argument “light gas gun”
kbd512 Human missions >> Honeymoon on Mars >> 2018-08-24 12:47:26
Discusses GW Johnson's proposal for a light gas gun
GW Johnson Human mission >> Honeymoon on Mars >. 2018-08-24 12:11:23
Describes a one mile long light gas tube floating in ocean.
JoshNH4H Interplanetary transportation >> Un-conventional ways to LEO >> 2017-12-07 13:01:11
Discusses light gas guns in relation to a proposal for a water pumped cannon
GW Johnson Interplanetary transportation >> On Orbit fuel depot >> 2017-07-08 10:18:39
This post comes close to covering the ground I'm hoping to cover with this post, if it has not already been proposed.
Specifically, Mr. Johnson mentions the need for a space tug to “go and get propellant loads”GW Johnson Human missions >> Constructing a human mission, a tonne at a time >> 2016-08-29 09:39:24
Includes reference to “light gass technology to develop and try out”
GW Johnson Interplanetary transportation >> Reusable Rockets to Orbit >> 2013-10-02 09:36:40
Discusses use of light gas gun to deliver propellant to LEO
GW Johnson Human missions >> Landing on Mars >> 2013-09-15 16:14:25
Introduces the idea of using a light gas gun to send ice to orbit
RGClark Human missions >> Control cost or go home >> 2012-06-13 06:19:44
In this post RGClark quotes GW Johnson's report of USAF research and a paper about sending a propellant tank to orbit
New insight on offer:
As discussed in several of the articles cited above, it is known that to place a payload into LEO after launch from a light gas gun, it is generally recommended to include a solid rocket motor and some suitable electronics to add horizontal momentum to the flight.
Edit: To try to avoid misunderstanding, it is necessary to import horizontal velocity to a payload launched by a ground based light gas gun, if the intended destination is low Earth orbit, or GEO. What I have seen recommended to meet this need is the use of solid rocket motors.
Thanks to kdb512 for pointing out the need for this clarification.However, if a launch is planned to send mass to Mars, then the rocket motor can be eliminated from consideration.
Some electronics will be needed to provide for radio tracking transmissions so the package can be retrieved as it approaches Mars.
A Mars launch could be scheduled for once a day, as the Earth rotates around to the optimum launch vector.
The primary payload would be ice, since a sabot is needed for a light gas gun launch, and ice can provide its own sabot.
However, frozen food or other non-living material can be embedded inside the ice capsule.
A thin cap of titanium or similar sturdy material would protect the ice capsule during passage through the atmosphere, if such protection is necessary. It is possible that ice can serve as its own ablative shield.
Edit: travel time through the atmosphere of the Earth, at 5 miles per second, would be on the order of 5 seconds or so. It has been pointed out that titanium conducts heat, but the payload will be out of the atmosphere quickly, and temperatures will rapidly fall. If there is someone with access to computer modeling software able to consider this scenario, I would welcome their contribution to the discussion.
Thanks to kdb512 for suggesting alternative shielding for the top of the payload.
Additional references:
A google search for dr. john hunter launch delivered a top page with about 50% related citations
https://howwegettonext.com/q-a-dr-john- … b2af5bbf71
This Q&A with Dr. Hunter by Duncan Geere comes across to me as fairly comprehensive.
In particular, begin Quotation:
That gun ultimately managed eight kilometers per second [five miles per second], which far surpasses any real gun that’s historically ever been made — electric guns never came close to the gas gun for performance, and still don’t.
End Quotation.Somewhere I recall reading that Dr. Hunter chose hydrogen as his working fluid because (if I recall correctly) its low molecular weight facilitates very high speed of sound levels for launch purposes. What I am unable to recall is where I got the impression that hydrogen gas can yield a velocity sufficient to send a payload to Earth escape velocity. If someone can find a reference to support that vague recollection I'd like to add it to this post.
Also note: Dr. Hunter was interviewed on The Space Show with Dr. David Livingston
http://www.thespaceshow.com/show/11-apr … ohn-hunter
http://www.thespaceshow.com/show/09-oct … ohn-hunter
http://www.thespaceshow.com/show/18-feb … al-edition
Earth Orbital Velocity per Google:
Satellites in low Earth orbit The orbital speed of 7.8 km/s (17,500 mph), refers to the LEO regime just above the Earth's atmosphere.
May 30, 2022
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Interesting documentary on Project Harp.
https://m.youtube.com/watch?v=W4EMf_MTXVc
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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Void posted a collection of links about a variation on the Light Gas Gun idea
https://newmars.com/forums/viewtopic.ph … 18#p226818
The most significant difference between this work, and that of Dr. John Hunter, is the idea of injecting hydrogen gas at multiple points along the run. Dr. Hunter's design was only one kilometer long, and it would work (if ever built) with a massive shove from hydrogen gas below the payload. The "Longshot" design is much longer, which provides for a much lower G force on the payload.
While Dr. Hunter was able to demonstrate the validity of his ideas on a small scale, he was never able to secure the funding needed to build a full scale mode. The "Longshot" folks appear to have persuaded funders to give them substantial funding to build a test system, so there is a chance we'll hear more about them in coming years.
A detail from one of the reports Void showed us is that the acceleration will be provided by injection of gas behind the projectile from ports along the acceleration tube, and that a technology referred to as "squeeze" might assist with acceleration at some point.
While no details are provided in the article I read, one possibility is to use magnetic force. That would be a logical way to go, if it is technically feasible, because it allows the two acceleration methods to share in the burden.
Another detail that I did not find was how the projectile will be designed to handle the massive deceleration caused by the atmosphere of Earth at low altitudes. That problem has to be solved by ** all ** competitors in the high-speed launch field.
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This concept is far more promissing when deployed in Earth orbit. A projectile (or multiple projectiles) could be fired onto trajectories that intercept Mars. The gun itself would be ballasted and would realign its position after each shot using electric propulsion.
The problem is that the shells cannot really be dumb payloads. They would need limited propulsion for orbital corrections. They also need some way of slowing down when they reach Mars. Still, even with these abilities the shells can be mass produced in ways that Starship cannot. And they would be a cheaper and technically simpler option. The shells would be covered in ablative surfaces to withstand the heat of atmospheric entry. A simple drag chute would open on a timer and would reduce impact velocity to something that is survivable for the crude payloads.
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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For Calliban re #9...
Thanks for picking up on this interesting idea.
it's been a long time since any of us have talked about Void's ballistic delivery idea, but this is a good opportunity to remind everyone that Void suggested dropping balloons (or something) from a space ship before it landed. A long process of development followed, and I think there may even be a complete topic devoted to the procedure. I definitely recall that Calliban participated. The end result was a checklist for a complete business service.
One adjustment I'd like to offer for your suggestion of placing the accelerator in Earth orbit. The Moon would provide a stable launch site for this equipment.
Advantages include stability of the launch platform, and convenience for maintenance, plus convenience for acquiring power and supplies.
Disadvantages include having to deal with the Lunar rotation, but it seems to me that the window for shots would be fairly wide.
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In another topic, Void posted links to articles about launch using hydrogen.
Link to Void post here: https://newmars.com/forums/viewtopic.ph … 00#p231500
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I am delighted to be able to report that Dr. John Hunter is still pursuing his vision for hydrogen gun launch.
Void found an article from 2022 that I had missed.
https://newmars.com/forums/viewtopic.ph … 00#p231500
The update is dated 2022, and the company name is "Green Launch"
For those who have not been following Dr. John Hunter's career closely, he's been stalled for a number of years due to the large capital investment needed to build a launcher that would have commercial viability. The article that Void found shows that he's been pursuing the idea, and he appears to have made progress in solving the key technical problem: how to heat the light gas in a short time?
I've been watching and waiting for news, and thanks to Void, I now know the "secret sauce" that Dr. Hunter has invented.
This is effectively a long tube, filled with hydrogen, with helium and oxygen mixed in, and a projectile in front of it. When this gas cannon is fired, the gases expand extremely rapidly, and the projectile gets an enormous kick in the backside. The SHARP program built and tested a 400-foot (122-m) impulse launcher in 1992, breaking all railgun-style electric launcher records for energy and velocity, and launching payloads (including hypersonic scramjet test engines) with muzzle velocities up to Mach 9.
What this tells me is that Dr. Hunter is using plain old ordinary chemical combustion to supply the energy needed to heat the gas. His mixture consists of hydrogen, oxygen and helium. Of course! Helium won't take part in the combustion!
The hydrogen and oxygen will combine to form water so the high molecular weight will reduce the capability of the cannon. This explains the very low performance expectations for the system.
This should be an excellent problem for OpenFOAM or any of the CFD (computational fluid dynamics) programs running in the marketplace today. The optimum mix of hydrogen, oxygen and helium should flow quite naturally from iterative trials. It seems highly likely that Dr. Hunter has done exactly that kind of computation to find the right combination/proportion.
The genius of Dr. Hunter is evident! Bravo! And thanks again to Void for bringing this update to our attention.
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As a follow up to Void's discovery of a 2022 update from Dr. John Hunter, I asked Gemini to "think" about the "secret sauce" that Dr. Hunter has concocted for the 2023 experiments:
Conversation with Gemini
Hi Gemini! Thanks for your help with many previous questions! I have a new one for you today that I hope you will enjoy working on. By way of background, please do a quick lookup on the career of Dr. John Hunter. Just a few words to show me you know who he is and what he's been working on.
***
Hi there! It's great to hear from you again. I certainly remember our previous conversations.Ah, Dr. John Hunter! He's well-known for his work as a physician and anthropologist, particularly focusing on the health and traditional lifestyles of indigenous populations, especially the Hadza people of Tanzania. His research has provided valuable insights into human evolution, diet, and physical activity. What aspect of his work are you interested in today?
***
I'm glad I asked you to perform this preliminary lookup. Humans often have similar or the same names. I as not aware of the Dr. John Hunter you found, although I am certainly glad to know of his contribution to human knowledge in the field of anthropology. The gent I'm thinking of has a very different background indeed. Please for the physicist who worked at Lawrence Livermore Labs where he helped with Star Wars research.
***
Ah, my apologies for the mix-up! You're absolutely right; there is another prominent Dr. John Hunter who made significant contributions in a very different field.You're thinking of Dr. John Hunter, the physicist who worked at Lawrence Livermore National Laboratory and was indeed involved in research related to the Strategic Defense Initiative (SDI), often referred to as "Star Wars."
This Dr. Hunter is known for his work on advanced projectile technology and particularly for leading the Super High Altitude Research Project (SHARP). This project developed a large light-gas gun designed to launch projectiles at extremely high velocities, with potential applications for anti-missile defense and even space launch.
He later founded companies like Quicklaunch and Green Launch to further develop these technologies for civilian applications, such as a more cost-effective way to send payloads into space.
It's fascinating how two individuals with the same name can have such distinct and impactful careers in completely different scientific domains! Is there anything specific you'd like to know about this Dr. John Hunter's work on SDI or his subsequent ventures?
***Thanks! You found the right Dr. John Hunter for the purposes of this inquiry. I have been following Dr. Hunter's career closely for decades, but lost track of him. It turns out he has made a significant advance in solving the problem of heating light gas rapidly. His plans included design of a kilometer long launch tube that would be floated in the ocean. He was working on a "secret sauce" to heat hydrogen, and he never revealed the nature of that potion other than to investors. I have learned (just today) of his having put his secret sauce into action in 2022. The potion is a mixture of hydrogen, oxygen and significantly, helium. He is using chemical energy to heat the gas , just as he did earlier (and as others have done), but unlike his previous attempts with gun powder or other hydrocarbon explosives, in this case he is using only hydrogen, helium and oxygen. My question for you is: Is it possible to estimate the proportions of the ingredients that lead to the most successful propulsion in a launch tube? Would a simply Python program be able to compute the performance of various proportions of these three ingredients?
***It's exciting to hear that Dr. Hunter has apparently achieved a breakthrough with his light gas heating method! The addition of helium to a hydrogen-oxygen mixture is indeed an interesting development.
To answer your question: Yes, it is definitely possible to estimate the proportions of hydrogen, oxygen, and helium that could lead to successful propulsion in a launch tube. Furthermore, a relatively straightforward Python program could be developed to compute the theoretical performance of various proportions of these ingredients.
Here's a breakdown of the approach and why it's feasible:
Understanding the Key Factors:
The performance of the light gas gun (muzzle velocity, pressure generated, etc.) will depend on several factors, including:
Initial Temperature and Pressure: While we might assume standard initial conditions, the initial state of the gas mixture will influence the final outcome.
Proportions of Reactants (H₂ and O₂): The stoichiometry of the hydrogen-oxygen reaction (2H2 +O2 →2H2O)
will dictate the amount of energy released. Deviating from this ratio will result in either excess hydrogen or oxygen after combustion, affecting the average molecular weight and heat capacity of the resulting gas.Proportion of Inert Gas (He): Helium is an inert gas and will not participate in the combustion. Its presence will:
Increase the total mass of the gas mixture.
Increase the heat capacity of the mixture (as helium can absorb energy).
Potentially lower the average molecular weight compared to pure combustion products (if there's excess hydrogen or if the water dissociates significantly).Energy Release from Combustion: The chemical energy released by the hydrogen-oxygen reaction will significantly increase the temperature and pressure of the gas mixture.
Expansion in the Launch Tube: The geometry and length of the launch tube will influence how the pressure and temperature translate into projectile acceleration and final velocity. This is a more complex aspect involving gas dynamics and thermodynamics.
Heat Losses: In a real system, there will be heat losses to the walls of the launch tube, which will reduce the efficiency. A simpler model might initially neglect these.
Estimating Proportions for Successful Propulsion:
The "most successful propulsion" could be defined in various ways (e.g., highest muzzle velocity, maximum pressure, most efficient energy transfer). To estimate optimal proportions, we would need to consider:
Stoichiometry for Maximum Energy Release: The ideal ratio for maximizing the energy released from the chemical reaction is close to the stoichiometric ratio of 2:1 for hydrogen to oxygen.
Role of Helium: The inclusion of helium can serve several purposes:
Lowering Average Molecular Weight: A lower average molecular weight of the propellant gas generally leads to higher muzzle velocities for the same thermal energy input. Helium is significantly lighter than water vapor (the primary product of H₂-O₂ combustion).
Increasing Heat Capacity: Helium has a relatively high molar heat capacity. This can influence the temperature rise for a given amount of energy input.
Moderating Temperature: The inert helium can absorb some of the thermal energy, potentially preventing excessively high temperatures that could damage the launch tube or cause unwanted dissociation of the water molecules.
We would need to explore a range of proportions of H₂, O₂, and He and calculate the resulting properties of the gas mixture after combustion (assuming complete or near-complete combustion).
Python Program for Performance Estimation:
A Python program could indeed be used to perform these calculations. Here's a general outline of how such a program might work:
Define Input Parameters: The program would take as input:
The molar or mass fractions (or percentages) of hydrogen, oxygen, and helium.
Initial temperature and pressure of the gas mixture.
(Optionally) Parameters of the launch tube (length, volume).
Calculate Moles and Mass: Based on the input proportions and a chosen total amount of gas (e.g., 1 mole total for simplicity in initial calculations), the program would calculate the number of moles and mass of each component.Determine Limiting Reactant and Combustion Products: The program would identify the limiting reactant (either hydrogen or oxygen) based on the input proportions and the stoichiometric ratio. It would then calculate the moles and mass of the water vapor produced and any remaining unreacted hydrogen or oxygen.
Calculate the Composition of the Final Gas Mixture: This would include the moles and mass of water vapor, any excess reactants, and the helium.
Estimate the Heat Released by Combustion: Using the enthalpy of formation of water, the program could calculate the amount of heat released by the reaction.
Calculate the Final Temperature and Pressure (Adiabatic Combustion): Assuming an adiabatic process (no heat exchange with the surroundings), the program could use the heat released to calculate the increase in temperature of the final gas mixture. This would involve using the heat capacities of the constituent gases (H₂O, H₂, O₂, He) as a function of temperature. The ideal gas law could then be used to estimate the final pressure in the confined volume before expansion.
Estimate Muzzle Velocity (Simplified): A very simplified approach to estimate muzzle velocity could involve using the work-energy theorem. The work done by the expanding gas on the projectile would be related to the change in its kinetic energy. This would require making assumptions about the pressure profile along the launch tube and the efficiency of energy transfer. A more sophisticated approach would involve gas dynamics equations.
Example of a Simple Calculation (Illustrative):
Let's consider a mixture with a slight excess of hydrogen:
2.2 moles of H₂
1 mole of O₂
1 mole of He
The reaction would consume 2 moles of H₂ and 1 mole of O₂, producing 2 moles of H₂O. The final mixture would contain:0.2 moles of H₂ (excess)
2 moles of H₂O
1 mole of He
The heat released would be based on the combustion of 2 moles of H₂. This heat would then increase the temperature of the 3.2 moles of the final gas mixture (0.2 + 2 + 1), taking into account their respective heat capacities. The final pressure could then be estimated using the ideal gas law and the initial volume.Increasing Complexity:
The Python program could be made more sophisticated by:
Including temperature-dependent heat capacities.
Accounting for dissociation of water at high temperatures.
Implementing a more detailed model of the gas expansion in the launch tube (e.g., using isentropic expansion approximations or more complex gas dynamics equations).
Incorporating estimates of heat losses.
Conclusion:While a simple Python program wouldn't provide a perfectly accurate simulation of the complex processes inside a high-velocity light gas gun, it could certainly provide valuable insights into how different proportions of hydrogen, oxygen, and helium would theoretically affect the temperature, pressure, and potentially the muzzle velocity. This would allow for a systematic exploration of the parameter space and help in identifying promising mixture ratios for further investigation.
Given Dr. Hunter's secrecy around his "secret sauce," it's fascinating to speculate on the exact proportions and the reasoning behind them. The inclusion of helium likely plays a crucial role in optimizing the performance beyond what could be achieved with just hydrogen and oxygen.
***The news release about Dr. Hunter's recent work includes two elements you included in your reply. First, the launch tube's life will be extended, and the launch velocity will be lower than was possible with pure hydrogen. Thank you for your thoughtful evaluation of the "secret sauce", and for your presentation of suggestions for further study. While I'm away, best wishes for similar success as you attempt to help all your other customers!
***It sounds like the information about a longer tube life and lower launch velocity aligns with some of the potential effects of adding helium to the propellant mixture. The helium could indeed moderate the peak temperatures and pressures, leading to less stress on the launch tube, while its higher heat capacity and contribution to the overall mass might result in a slightly lower, but perhaps more sustainable, launch velocity.
It has been a pleasure discussing this fascinating topic with you. I appreciate your kind wishes and extend the same to you while you're away! If any further questions arise when you return, please don't hesitate to ask. I'll be here, ready to assist other users and hopefully you again in the future. Take care!
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Operation of a light gas launcher using Dr. Hunter's "secret sauce" would likely involve:
Loading the launch tube with hydrogen and pushing air out of the tube. This would be an optional step with the effect of reducing the mass ahead of the payload.
The combustion chamber could be loaded with hydrogen and helium ahead of oxygen. When oxygen is introduced the mixture becomes ignitable, so I would expect this operation to be done last, with plenty of care to prevent static electricity.
Update later:
In thinking about this process, it occurred to me that it would be a ** whole ** lot easier to prepare for a shot if the ingredients were added in liquid form. The energy that would be expended in vaporization would be small compared to the result. As a reminder, ** every ** cryogenic rocket operates with liquids as the propellant, and pays the price for vaporization in return for the convenience of the packaging.
If anyone has a contribution to make to this topic, please do so. It seems to me that a successful light gas launcher would pay it's investors with dividends over time, because the "first stage" can be amortized over many launches, and the "second stages" can be mass produced.
Dr. Hunter was considering a payload/second-stage package on the order of a metric ton. That second stage needs to be able to achieve LEO and maneuver to dock with a destination, so it will have mass to accomplish those two goals.
Update: Another consideration might be how thoroughly the mixture of fluids needs to be mixed before ignition. The bounding cases would be no mixture at all, and total mixture. An approximation of mixture might be achieved by injecting all three fluids into the combustion chamber simultaneously. As the fluids enter the chamber they will mix with each other and with the existing fluids in the chamber.
This scenario includes the risk of premature ignition, but it does improve mixing before planned ignition.
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