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#1 2018-11-06 12:11:02

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 11,960

Light Gas Gun Direct Delivery to Mars

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

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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#2 2018-11-06 17:00:48

kbd512
Administrator
Registered: 2015-01-02
Posts: 6,205

Re: Light Gas Gun Direct Delivery to Mars

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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#3 2022-03-09 18:06:44

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 2,210

Re: Light Gas Gun Direct Delivery to Mars

Terraformer wrote:

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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#4 2022-03-09 18:44:32

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 26,733

Re: Light Gas Gun Direct Delivery to Mars

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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#5 2022-03-14 18:25:35

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 11,960

Re: Light Gas Gun Direct Delivery to Mars

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.

(th)

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