New Mars Forums

Official discussion forum of The Mars Society and MarsNews.com

You are not logged in.

Announcement

Announcement: We've recently made changes to our user database and have removed inactive and spam users. If you can not login, please re-register.

#201 2020-02-24 07:16:40

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 351

Re: Un- conventional ways to LEO

Terraformer wrote:

We have to bear in mind that bulk commodities are far less fragile than human beings. If we can launch fuel, food, water etc into space for $10/kg, then it doesn't actually matter that much that humans and electronics have to go up on significantly more expensive rockets. Almost all of the mass we need to do stuff is in the former group. Though we might need orbital tugs to capture it on-orbit, if it's launched dumb.

Plasma cutter torches heated by electric arc have typical temperatures of about 20,000K.  An electrical arc could be used to generate atomic hydrogen at 12,000K, which would have average velocity of 10km/s.  The acceleration of a bullet can be upwards of 100,000g.  A plasma arc cannon accelerating a robust projectile to 10km/s would have a barrel length of 50m.  To protect the barrel from erosion in the extremely high temperature plasma, a strong magnetic field would be needed.  I suspect that the plasma pressure will be huge, so barrel lifetime may be short.

The projectile would lose a lot of mass travelling through the Earth atmosphere.  But if it is made from cheap materials, it would hardly matter.  The projectiles would need to be intercepted in high Earth orbit, as the gun would need to fire vertically to minimise the column density of air that it passes through.  Maybe we would park a large bag in GEO, directly above the launch site and fire projectiles at it continuously.

If the plasma gun fires empty, the charge will clear the barrel of all air.  The air will be cleared around the muzzle of the gun as well and it will not reenter until plasma pressure has declined to less than 1 bar.  If the gun fires continuously at a high cyclic rate, air will not re-enter the barrel before the next round has fired.  So it would be sensible to operate the gun like a machine gun.  The barrel will need to be cooled in operation.  Maybe we could pump water through channels and bleed steam out of pores in the side of the barrel.

Last edited by Calliban (2020-02-24 07:27:05)


Interested in space science, engineering and technology.

Offline

#202 2020-02-24 15:28:57

tahanson43206
Member
Registered: 2018-04-27
Posts: 2,202

Re: Un- conventional ways to LEO

For Calliban re #201

Your post here is awesome!  I hope it survives scrutiny << grin >>

The idea of launching to GEO is intriguing.  I'd like to remind you (in your enthusiasm) that the horizontal velocity needed for the object heading through Geo is considerable.  I've looked into it in the past, and this is a good time for forum members to remind us (all) of that velocity.

The catcher at GEO must not only catch the object travelling past, but it must do so while losing momentum to the object, as it brings the object up to orbital velocity at GEO.

Dr. Hunter is planning to not lose any mass at all due to travel through the atmosphere.  His experience doing Star Wars research showed him, and those who read his papers, that the shape and materials he used can travel without damage at 3 km/second.  The 20 miles of appreciable atmosphere are crossed in seconds.

Please develop your concept further!  Your's is the most optimistic vision for a ballistic launcher I have read in years.

Edit #1: Notes on velocity of satellites in Geosynchrous Orbit of Earth

Report on Geosynchronous Satellite velocity along orbit.

For those forum readers who may be following the discussion of ballistic launch methods.

Semi-major axis: 42,164 km <<== Distance of satellite from center of the Earth at apogee

https://en.wikipedia.org/wiki/Geostationary_orbit

C = PiD

264924 km per day <<== Circumference of orbit if it were a circle

Divided by 24 hours: 11038 km / hour

Divided by 3600 to give km / second: 3 km/second

(th)

Last edited by tahanson43206 (2020-02-24 18:59:31)

Offline

#203 2020-02-24 17:54:01

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 18,368

Re: Un- conventional ways to LEO

The hydrogen in the barrel will ignite once the rocket exits the barrel as it has oxygen to burn until gone with those temperatures....The volume of hydrogen is quite large.

500 °C
Hydrogen gas forms explosive mixtures with air in concentrations from 4–74% and with chlorine at 5–95%. The explosive reactions may be triggered by spark, heat, or sunlight. The hydrogen auto ignition temperature, the temperature of spontaneous ignition in air, is 500 °C (932 °F).

Online

#204 2020-02-24 19:18:58

tahanson43206
Member
Registered: 2018-04-27
Posts: 2,202

Re: Un- conventional ways to LEO

For SpaceNut re #203

There are at least two scenarios under discussion here, and there may be more << grin >>

For a while, Calliban was talking about launching a rocket with steam, and he offered a way of producing steam that I had not heard before.  In that proposal, Calliban described heating rocks slowly over time, until they contained enough thermal energy for a launch.  Calliban than proposed injecting liquid water into the mass of rocks at a rate sufficient to lift a second stage rocket vehicle as though it were being lifted by a first stage launch vehicle.

I was reminded of work done by Dr. John Hunter, and it is that subtopic that involves hydrogen.

However, Dr. Hunter's work did ** not ** involve ignition of a rocket motor shortly after launch.  Instead, the capsule contained a solid rocket that would be ignited at Apogee, to circularize the orbit.

In addition, unlike Calliban's later posts, Dr. Hunter's design plans to spend more time in the atmosphere, by aiming the launch at an angle.  The angle chosen would be selected based upon optimization of the factors at hand.  Among the tradeoffs are:

1) Time spent in the atmosphere leading to loss of momentum
2) Amount of propulsion deliverable by the onboard solid rocket (mass spent here reduces payload mass)
3) Total mass of the capsule
4) Size of the bore of the launcher
5) Length of the barrel of the launcher
6) Working fluid chosen (eg, Hydrogen)
7) Working temperature and pressure planned for the launch
8) Energy availability
9) Time required for applying energy to the working fluid

There may be other factors ...

In Dr. Hunter's design, while you are correct to anticipate some Hydrogen would escape before a cap slams over the muzzle after exit of the capsule, there would be no source of ignition at the muzzle.

What there ** could ** be is a loud, thunderous roar as the capsule flies through the atmosphere, creating a partial vacuum behind the vehicle, which would close dramatically in a manner similar to lightning.

However, that prediction is pure speculation on my part, because I have not seen (or heard) mention of that in any discussions about Dr. Hunter's design.

What I ** have ** heard is a description of the tremendous noise created by early ballistic launcher experiments in the Barbados Islands.

Wikipedia has a lengthy article on the subject, NOT including mention of the sound.  The report on the sound comes from a friend who (I think) got the reports from unofficial channels.  If anyone is interested in learning more the gent is still with us and potentially available for a question or two.

https://en.wikipedia.org/wiki/Project_HARP

The HARP experiments were true artillery shots using traditional munitions, so all the sounds associated with artillery were present, but in greater degree, due to the tremendous size of the equipment.

Edit #1:  On the ** other ** hand, if Calliban's vision of a plasma launcher ever comes to pass, the hot exhaust from ** that ** launcher would surely put on quite a fireworks display, as it interacts with the molecules in the atmosphere.

(th)

Last edited by tahanson43206 (2020-02-24 19:51:47)

Offline

#205 2020-02-24 19:54:51

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 18,368

Re: Un- conventional ways to LEO

We are trying to change how we deliver rocket or there mass to orbit that can finish on there own power to achieve optimal conditions for circling the earth for an extended period. We want it to be as capable as possible and still be safe to use.
https://en.wikipedia.org/wiki/Internal_ballistics
study of the propulsion of a projectile while controling the exit speed.
https://en.wikipedia.org/wiki/Muzzle_velocity
All while being a rocket with a no propellant fuel or mass stage
https://en.wikipedia.org/wiki/Rocket
https://en.wikipedia.org/wiki/Rocket_engine
For the purpose of lofting the rockets up through the atmospheric drag as well as the drag of gravity trying to pull it back down.
https://www.grc.nasa.gov/WWW/K-12/rocket/rktaero.html
https://en.wikipedia.org/wiki/Gravity_drag
with the final aspect to achieve a velocity approaching escape
https://en.wikipedia.org/wiki/Escape_velocity
http://www.qrg.northwestern.edu/project … ocity.html

Online

#206 2020-02-25 06:10:49

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 351

Re: Un- conventional ways to LEO

Many thanks Tahanson and Spacenut for the links.  I wasn't aware of Project HARP until now.  It would seem that conventional cordite allows a muzzle velocity of about 2000m/s.  With hydrogen-oxygen chemical propellant, rocket exhaust velocity is typically reported as being 4500m/s.  So it would appear that even without rail guns or plasma arc technology, chemical propellants can boost a shell to orbital altitude.  Could we collect shells that reach that altitude in some sort of orbital bag and use ion propulsion to maintain the bags orbital velocity?  That is an interesting question.

In terms of human tolerance to g-forces, the evidence is that most unconditioned humans can tolerate 17g in a couched position for up to several minutes without long term effects.  Could they tolerate even more for a period of a few seconds, if seated in a padded couch, say?
https://en.wikipedia.org/wiki/High-G_tr … ite_note-3

Whilst high-g is tolerable for dumb payloads, designing an upper stage to withstand high-g loads would presumably increase structural mass.  I doubt that it would be free.  At accelerations of 20g for 10 seconds, muzzle velocity would reach 2km/s.  That is enough to eliminate the need for a lower stage.  But the barrel length would be 10km, which is too large to be practical.  Reducing barrel length to 2km, would reduce muzzle velocity to 894m/s.  That is still enough to reach a height of 13.3km, assuming a third of energy is lost to drag.  That is well into the stratosphere.

Last edited by Calliban (2020-02-25 06:26:07)


Interested in space science, engineering and technology.

Offline

#207 2020-02-25 07:03:25

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 351

Re: Un- conventional ways to LEO

A cold gas thruster embedded within the sabot may be a way of boosting the velocity of the upper stage, after its exit from the barrel.  A very simple device - just a pressurised tank, a valve and a nozzle.
https://en.wikipedia.org/wiki/Cold_gas_thruster

Carbon dioxide would be a good choice, because it can be stored as liquid in a pressure vessel.  Mass ratios greater than 2 would appear to be possible.  This could boost velocity by several hundred metres per second.

Last edited by Calliban (2020-02-25 07:14:20)


Interested in space science, engineering and technology.

Offline

#208 2020-02-25 07:45:05

tahanson43206
Member
Registered: 2018-04-27
Posts: 2,202

Re: Un- conventional ways to LEO

For Calliban re #206

Thanks for taking a look at HARP.  Gerald Bull is the key player in that story.  He was eventually assassinated, reportedly because he was working with Saddam Hussain to continue development of long range artillery. 

It would appear that Dr. Hunter has launch to LEO using Hydrogen figured out.  I am hoping you will take a few more minutes to see if you can extend your insight about a plasma launcher.  I've not heard of anyone contemplating something so ambitious, so would guess you have the field to yourself to explore for feasibility.  I think your suggestion that a magnetic field would be a factor in the design is most interesting.

***
I've been thinking about your shot to GEO and the problem of giving the arriving mass a 3 Km/second horizontal impulse.  Your suggestion of using an ion drive to make up the loss has a number of advantages.  In my own thinking about this in an earlier time, I allocated 50 percent of the payload mass to the horizontal impulse process.  Dr. Hunter allocated a portion of his planned launch to LEO capsule mass to a rounding rocket.  I don't know what percentage of the capsule mass was allocated to that function, and indeed, as noted in a recent post, there are many variables at play to determine an optimum solution.

***
I do have an alternative concept to offer for your evaluation.  If your plasma launcher idea proves feasible, it would be used (I am confident) for supplies of material that can withstand momentary high G force.  If you are willing to launch once per day, then the Moon could provide the orbit adjustment function that the capture bag would provide.  The payload would be returning from the Moon with a momentum that would be (with correct navigation) compatible with the orbit of a capture device in GEO.  Payloads would need to be equipped with radio beacons at a minimum and ideally, some navigation capability.

The problem to be solved is not too different from the earlier discussion of launching material from the surface of the Moon.  I liked your magnetic sled idea when you brought it up, and still do. 

***

My understanding is that electronics for use in artillery shells exists, so I would extrapolate that electronics could be shipped to GEO.  However, a ** very ** useful payload would be simple water.  Simple carbon delivered to GEO would be useful for a large number of applications.

Edit#1: The operator of a collection facility at GEO would be dealing in momentum transfers.  A payload arriving from below would require a 3 km/second horizontal impulse in the direction of orbit, which would decrease the momentum of the capture facility by an equal amount.  A payload arriving from the Moon would have positive momentum in the direction of the orbit of the capture station.  It would be interesting to see an analysis of the amounts of momentum that would be involved. 

(th)

Last edited by tahanson43206 (2020-02-25 07:51:31)

Offline

#209 2020-02-25 10:18:13

tahanson43206
Member
Registered: 2018-04-27
Posts: 2,202

Re: Un- conventional ways to LEO

For Calliban re topic ...

This reply is from a friend who wrote back by email when I described the discussion in this topic.  It includes mention of sound produced by various ballistic launch devices, including the World War I "Paris" guns deployed by the Germans.

If you have questions for the author, I'll pass them along.

Gerald Bull’s space guns were very loud; the gun in Barbados could be heard across the island.  Contemporary news accounts (early 60’s) claimed a rise in the birth rate when the gun was fired around the clock launching projectiles studying the ionosphere.  The reporter theorized that the loud discharge of the gun woke the islanders through the night, leading to a lot more sex!

The Paris Gun was also loud.  Whenever the three were in action, 3,000 standard large-bore guns would open up to “cover” the report from the long range pieces to reduce the chance of the firing position being given away by their unique blast.  A French Air Force officer devised a method to locate the guns by their muzzle blast, employing children from a school for the blind to listen to the cannonade using large horn receivers to determine the azimuth to each of the gun positions.

The officer could not get official approval or support for his efforts, but the children did locate all three firing positions.  This was confirmed after the Germans were pushed out of the salient allowing firing on Paris in August of 1918.  In addition to the noise of the blast, the extreme muzzle velocity of the projectiles produced strong shock waves that went booming across the land as the shells headed for the stratosphere on their way to Paris.

Conventional gun powder can only achieve about 10,000 ft/sec muzzle velocity due to the low speed of sound in the gasses produced by the deflagration at firing.  Light gas guns use hydrogen as the working fluid because of the high sonic velocity it supports, as you noted.  Pressure waves can only advance through a gas at the sonic velocity, so muzzle velocity of a gun can only approach this speed.

Dr. Hunter developed a gun called “Super HARP” in the 80’s and early 90’s during the BMSDO hey days (“Star Wars”).  This system was basically a very large version of a light gas gun.  Common light gas guns (there are two in Dayton) fire small diameter projectiles.  Conventional gun powder is used to drive a plastic piston into a bore filled with hydrogen to compress it to very high pressure.  A burst disk constrains the gas until its rupture pressure is achieved. When the dusk bursts, the high pressure hydrogen pushes against a sabot-mounted projectile, which then accelerates down a smaller bore tube towards the target.

The whole system downstream of the rupture disk is evacuated to allow extreme velocities to be achieved, up beyond earth escape velocity.  Light gas guns are used theses days to study armor for satellites.

The guns in Dayton were used to develop protection for the ISS, and I’m sure the Air Force uses them to aid in the design of protection for military satellites as well.  The larger gun in Dayton uses a three-inch naval gun breech mechanism and conventional shell to propel a nylon piston down the large bore into the waiting hydrogen.  The gas is compressed by the piston until it ruptures the disk, then the sabot is blasted down the bore of a 20 mm cannon barrel that has had its rifling machined out.  After leaving the muzzle of that barrel, the sabot and (usually) spherical projectile encounters a three inch thick steel plate with a hole in it that allows the projectile to pass through, but it restricts the sabot, causing it to evaporate with only a small part of it traveling through the hole into the rest of the test chamber.  The object getting blasted sits down range of the separator plate, inside the evacuated chamber.

Super HARP was one of the only light gas guns developed to fire projectiles into the atmosphere.  It was used to test hypersonic projectiles for the “Star Wars” program, but Hunter also wanted to use it to launch items into the air.  It was designed with a pivot joint between the driver section and projectile tube to allow elevation, but it was never swung up from the horizontal.  It only ever fired into a butt beyond the test range, like Bull’s gun at the Highwater range straddling the US/Canada border in Maine.

Apparently, Dr. Hunter acquired the remains of Super HARP when the government junked it, but he never re-assembled the system.  It may still be languishing in San Diego somewhere.

Dr. Hunters latest design uses hydrogen heated not by compression, but by external heating.  Thus he is on the same path you have been discussing with the guy from Scotland when it comes to increasing muzzle velocity capability by heating the hydrogen.  Dr. Hunter was supposed to demonstrate his new idea on one of the Bull guns at Yuma Probing Grounds a few years ago, but I’ve heard nothing about that attempt.  The Army allowed him to modify the seven inch Bull gun, which has not been used for a long time.

The new method devised by Dr. Hunter uses a large reservoir of hydrogen gas that is heated to extreme temperatures by electric means, and once the desired pressure is achieved, a disk would be rupture remotely, allowing the hydrogen to push in the sabot in the projectile bore of the gun.

I’m sure Dr. Hunter’s target hydrogen temperature is a secret, but I doubt if it is to the point of dissociation.  Achieving such temperatures is a tough row to hoe, because it is difficult to insulate the chamber well enough to keep the heat in, and the temperature is so high that the heating elements would be difficult to keep intact during the heating process.

Light gas and gun powder systems use high temperatures to transmit energy from the powder to the projectile, but the process happens very quickly.  The very high temperatures exist for extremely short intervals, so the materials are not stressed as highly as they would be if the hydrogen was heated and held in a steady state inside a vessel.  The chamber temperatures inside the Paris Guns may have reached levels of dissociation, because the chamber would advance six inches per shot, due to evaporation of the steel in the area of the forcing cone, where the rifling starts.  Think of that.  Really tough tool steel just evaporating!  And the muzzle velocity of the Paris Guns was about one mile per second. Bull’s gunpowder guns achieved just under two miles per second, using sabot-equipped projectiles and no rifling.

I am also skeptical of using dissociated hydrogen, because I think it will be very tough to get the hydrogen to high enough temperatures, and to keep it there as the pressures drop while the gas expands and pushes the projectile down the tube.  I’m also not sure how you would apply magnetic containment of the plasma, because the gun tube would have to be made of ferrous steel, which is also magnetic.  Maybe a strong stainless steel (non-magnetic type) could be used, or a thin tube could be surrounded by a glass composite reinforcement that would add strength but let the magnetic fields through.  This would yield a hybrid of the light gas gun and plasma driver.

Maybe?

(th)

Offline

#210 2020-02-25 14:15:14

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 351

Re: Un- conventional ways to LEO

Tahanson, that is excellent feedback.  Many thanks.  I will read in more detail later.

The plasma arc idea begins to sound like something that would destroy the barrel.  The magnetic field is unlikely to contain the plasma regardless of the permeability of the barrel, as even superconducting magnets cannot contain plasma pressure of more than a few bar.

The powder propelled gas gun is a concept that is proven to be successful, at least on a small scale.  One way of preheating the hydrogen would be to inject a small quantity of oxygen that would ignite on compression.  The remaining hydrogen would be heated to 2000K and would expand faster than the water molecules.

As for the steam cannon idea, one option would be to launch the vehicle at high sub sonic speed, say 300m/s and then ignite a solid fuelled ramjet engine.  This would essentially be a hollow steel tube, lined with butyl rubber, with a compression cone mounted on top.  These would be strap on boosters.  These would need to be travelling above Mach 0.5 to provide thrust.  The cannon can provide the necessary boost.

Last edited by Calliban (2020-02-25 14:24:19)


Interested in space science, engineering and technology.

Offline

#211 2020-02-25 16:02:18

tahanson43206
Member
Registered: 2018-04-27
Posts: 2,202

Re: Un- conventional ways to LEO

For Calliban re topic ...

I'm hoping the computations posted here will be useful for future discussion.

If you have a moment (knowing you're working full time and have family) please check the figures I've posted here.  In addition, if you would like to see content added to this reference post, please let me know what to add.

You are doubtless aware of the FluxBB search tool, but others who happen across this web site may not be.

To find this reference post in future, enter the search term into the search window and tahanson43206 as author.

Most of the time the text past the colon is all that is needed.  However, upon occasion, it is necessary to add the colon to break a tie that can occur.

Reference Ballistic Launch Specification for NewMars forums

SearchTerm:BallisticLaunch
SearchTerm:LaunchBallistic

The factors given in this post are derived from a concept published by Dr. John Hunter for his Quicklaunch system.  They are adjusted slightly to provide a common framework for discussion of alternative ballistic launch methods.

Payload capsule: 1 metric ton  (includes sabot, payload, rounding rocket, electronics)

Launcher length: 1 kilometer

Launcher barrel diameter: 2 Meters

Target launch velocity: 6 km/second or greater

Computed values:

Acceleration rate:

a = (v2 − u2 ) / 2s
This applies to constant acceleration only, and a stands for acceleration, v means final velocity, u means starting velocity and s is the distance travelled between the starting and final velocity.May 4, 2018

How to Find Acceleration With Velocity & Distance | Sciencing
sciencing.com › Science › Physics › Fundamentals

s is 1 kilometer
u is 0
v is 6 km/second

36 – 0 / 2 >> 18 kilometers per second squared

G force experienced by payload capsule in vertical launch configuration.

The standard Earth gravity of 9.8 meters/second squared is assumed.  The launch tube is assumed to be vertical.

The payload capsule would experience G force of 18,000 meters per second squared, divided by 9.8 meters per second squared, or 1837 G’s, plus 1 or 1838 G’s.

(th)

Offline

#212 2020-02-25 16:11:41

Terraformer
Member
From: Lancashire
Registered: 2007-08-27
Posts: 3,240
Website

Re: Un- conventional ways to LEO

I wonder if we could mount a cannon on a massive stratospheric airship...? That would let us launch where the air is far thinner, and horizontally (well, diagonally). There would be a lot of recoil from it though, but perhaps we can use sails to brace it against the atmosphere.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

Offline

#213 2020-02-25 16:28:27

tahanson43206
Member
Registered: 2018-04-27
Posts: 2,202

Re: Un- conventional ways to LEO

For Terraformer re #212

Your suggestion here is interesting and a nice addition to the mixture of ideas at play.

I've not seen the specific suggestion before, but others in the forum may have seen a variation or two on the idea.

The closest I can think of off hand is the idea of mounting a launcher on the side of a mountain.  Your suggestion has the great advantage of mobility.

A possible solution to the recoil problem is to plan for a recoil in the opposite direction.  The Earth usually plays the role of shock absorber, but equal and opposite could do as well.  The tradeoff is mobility for twice the energy.  There could well be situations where the benefits win the decision.

For Calliban re #210 ... please keep thinking for a bit longer!  It would be a shame to lose such a promising idea without a thorough scrubbing, although I'll admit things don't look as promising now as they did (to me at least) at first.

JoshNH4H had me on the ropes when he pointed out that a plasma of pure Iron atoms without electrons would destroy any material enclosure, and I'm doubtful there is a solution to the containment problem with known physics.

We were discussing the idea of JoshNH4H to use iron atoms as a "convenient" dense energy storage medium. 

(th)

Offline

#214 2020-02-25 18:30:16

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 351

Re: Un- conventional ways to LEO

Your maths is sound.  1800g doesn't sound too bad.  Some rifle bullets have acceleration 2 orders of magnitude greater.  To achieve a velocity of 9km/s, enough to get to GEO say, acceleration would need to be 4100g in a 1km barrel.  Still quite modest by the standards of munitions.  The larger the projectile is, the less it will be affected by air resistance.

Ionised materials have particle energy beyond melting point of most container materials.  A relatively cold plasma could be trapped by a magnetic field.  But the energy density would be poor, due to the low density of plasma at achievable magnetic pressure.

Last edited by Calliban (2020-02-25 18:34:03)


Interested in space science, engineering and technology.

Offline

#215 2020-02-25 18:54:00

tahanson43206
Member
Registered: 2018-04-27
Posts: 2,202

Re: Un- conventional ways to LEO

For Calliban re #214

Thanks for taking a look at the "reference" numbers for a (somewhat generic) ballistic launcher.

I'm hoping to add the correct numbers for energy needed and work done in the near future.  I did all that in years past, and probably can no longer find the notes.  The "reference" post should also include the pressure needed to drive the launch.

Here is a detail I may not be able to work out with the resources at hand ...

One of the programs for "computational fluid dynamics (CFD" should be able to solve for the dynamics of a ballistic launch of the type we are describing.  There (appear to be/are) multiple commercial CFD packages, and I know of at least one Open Source package.

The concern I have is the drop off of pressure on the capsule as it ascends the launch tube.  I am anticipating that the pressure on the capsule will drop off as the capsule ascends, so the starting pressure needs to be greater than whatever value is needed at the muzzle to achieve the particular launch goals.

***
Details of operation of an actual launcher in a business situation remain unclear (to me at least).

Dr. Hunter (as I recall) talked about capturing Hydrogen after the capsule leaves the muzzle, but there will be losses.

The Hydrogen needs to be collected, purged of molecules of air which will inevitably contaminate the collected gas, and restored to whatever condition is needed for the next shot. 

If solar power is used to provide the energy for this operation, the amount of power required will be significant, and the performance of the solar collectors will need to match the requirement.

As a reminder, the launcher needs to be located well away from land where significant numbers of people reside, and even with that restriction, the firings may well be audible over hundreds of miles.

(th)

Offline

#216 2020-02-25 19:58:43

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 18,368

Re: Un- conventional ways to LEO

The door to exit the rocket can not close fast enough as its going to be open long before it goes past the lip of the barrel and that means the in rushing air will allow for it to ignite....So keeping that temperature below that flash point is critical. So possibly a blow of cyrogenic hydrogen just behind the exit to keep the flash point down.
So can we make use of cyrogenic hydrogens rapid heating curve. At cryogenic temperatures of 17 K, hydrogen is liquid and can be formed into a rapidly expanding jet. Cryogenic hydrogen has a density nearly twice that of compressed hydrogen at 70 MPa. Liquid hydrogen is stored in specially insulated cryogenic tanks under pressure, which have provisions for cooling, heating, and venting.

http://conference.ing.unipi.it/ichs2011/papers/253.pdf
MODELING OF SUDDEN HYDROGEN EXPANSION

https://ntrs.nasa.gov/archive/nasa/casi … 014185.pdf
Methodology for Assessing a Boiling Liquid Expanding Vapor

Hydrogen%20phase%20diagram.jpg

Online

#217 2020-02-26 08:49:52

tahanson43206
Member
Registered: 2018-04-27
Posts: 2,202

Re: Un- conventional ways to LEO

For Calliban re topic

A few years back, an education software company published a tool for computing various physics problems.

The Internet (by now) provides all the computations (and more) that were embedded in Physics 101, but I like having the tool on my hard drive.

I brought it up to reconstruct computations for the ballistic launcher problem we've been discussing in recent days.

Here is a set of computations I ran this morning.  I had forgotten the brief time needed to generate the force for the proposed launch.

For SpaceNut ... I've been skeptical of your concern about ignition of Hydrogen, but upon seeing the numbers I'll be pasting below, I've decided there is almost no possibility of capturing the gases used for the launch, any more than there is a chance of capturing gases expelled from a large artillery piece.

Since the launcher will be located well away from land where populations of people reside, I've come to the conclusion the hydrogen can be allowed to burn off to yield a bit of rain down wind.  The time of 1/3 second for the launch precludes any possibility of placing a cap over the muzzle.  This will definitely be a case of closing the barn door after the horse escapes.

***
Tool: Physics 101 SE (version 8) by Praeter Software

Version 8.0 (9/15/2010)

www.praetersoftware.com/products/physics101/

Also see: www.praetersoftware.com/about/

Formed in 2001, Praeter Software is the industry leader in the educational software market. Our flagship application, Physics 101 SE, is one of the most highly rated software programs of all time and is used by students and teachers everywhere to save thousands of hours from mundane busywork.

Given:

Desired velocity: 6 km/second (6000 meters/second)

Capsule mass: 1 metric ton (1000 kg)

Length of launch tube: 1 Km (1000 meters)

Activity planned:
1) Derive Time
2) Derive Acceleration
3) Derive Energy required
4) Derive Work done

1) Derive Time:

Given initial velocity of 0
Given final velocity of 6000 m/sec
Given acceleration of 18,000 m/sec per second

Time of launch is: 0.333 seconds

2) Derive Acceleration

Given initial velocity of 0
Given final velocity of 6000 m/s
Given time of .333 seconds

Acceleration is 18018

3) Derive Kinetic Energy:

Given mass of 1000 kg
Given velocity of 6000 m/s
KE is 18,000,000,000.0 Joules

4) Derive Power required:

Given energy in Joules: 18000000000.0
Given time: .333 seconds
Power in watts: 54,054,054,054.054

***
For Calliban ... back to you at this point.  I'm hoping you can think of a way of delivering that much energy into the system.

My sense of how Dr. Hunter planned to do that was by building up pressure behind a pressure release port of some kind.

Some time ago I had imagined a pressure plug consisting of frozen water.  The plug would be released of its own accord when the pressure in the feed chamber exceeds the strength of the electron bonds holding the water/ice to the steel barrell.

(th)

Last edited by tahanson43206 (2020-02-26 08:50:46)

Offline

#218 2020-02-27 05:58:37

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 351

Re: Un- conventional ways to LEO

Tahanson,

If you look at the light gas gun design (wiki gives a good enough illustration) the driving charge is usually gun powder or some other propellant.
https://en.wikipedia.org/wiki/Light-gas_gun

So that is where the 18GJ will need to come from.  In principle, there are other ways of providing that energy.  But a chemical propellant is cheap and well understood.  Alternative chemical propellants are numerous.  We could experiment with liquid propellants, which may be cheaper than gun powder.  Also from Wiki:

'The hybrid electrothermal light-gas gun works on similar principles of the standard light-gas gun, but adds an electric arc to heat the light gas to a higher temperature and pressure than the piston alone. The arc is applied in the chamber containing the light gas, raising the temperature and pressure to the point where the gas both breaks the bursting disk and ignites the propellant behind the piston, which is perforated to allow ignition. The resulting combination of electrical heating and piston compression provide higher pressures and temperatures, resulting in more power and a higher potential speed than a standard light-gas gun.'

Electricity is actually quite tricky as an energy source for the gas gun, because it must be delivered at very high power levels.  There are ways of doing that, but they are expensive: Flash capacitors, explosively propelled linear electric generators, flywheels, etc.  This is why I suggested the idea of mixing in a little oxygen with the hydrogen, which would then ignite under compression and rapidly heat the hydrogen up.

The energy efficiency of a gun is about 30%.  So for every 3 joules of energy transferred to the projectile, about 10 joules of propellant energy is needed.  The efficiency will presumably be slightly better for a large bore gun, as there will be proportionately less heat transfer to the barrel.  So the primary charge will need to provide about 60GJ of energy.  If hydrogen and oxygen are used as propellant, then each kg of bipropellant will contain 14.7MJ of stored chemical energy.  To provide 60GJ of chemical energy, we would need some 4000kg of H2-O2 driving propellant.  So the system mass ratio to reach orbit is about 5.  Much better than any chemical rocket.

Regarding the problem with hydrogen igniting on contact with air.  This would only be a problem for any hydrogen that is expelled ahead of the projectile.  However, if this does occur, there is concern that the shockwave from the ignition could alter the trajectory of the shell.  We could evacuate the barrel ahead of the projectile.  But I suspect that wont be necessary.  Remember that the hydrogen needs to mix with the outside air in order to ignite.  The hydrogen will escape from the barrel as an expanding gas bubble that will compress the air around it.  Burning will take place at the periphery of the gas bubble, but at a speed of 6km/s, the projectile will have passed through it before there were significant mixing.

Last edited by Calliban (2020-02-27 06:23:27)


Interested in space science, engineering and technology.

Offline

#219 2020-02-27 08:58:32

tahanson43206
Member
Registered: 2018-04-27
Posts: 2,202

Re: Un- conventional ways to LEO

For Calliban re #218 and entire subtopic ...

Thank you for continuing development of this subtopic, and for another substantial contribution.

At the end of this post, i am thinking of proposing moving this subtopic to its own topic, and would ask for your endorsement of the idea, as well as the support of SpaceNut, who can enforce the concept I have in mind.

In the mean time, I agree that the efficiency of the machine we are discussing here should be better than 30%, because the dwell time for the payload inside the launch tube is 1/3 of a second.  The gases themselves will rush out of the tube after the payload, and any mechanical system to try to contain them will take a long time to swing or slide into place. 

If you ever have time (I understand that is unlikely) I think you will (hopefully) enjoy reading Dr. Hunter's report(s) on his development of the SHARP system for the Star Wars program.  In the mean time, I will try here to adapt a concept from Dr. Hunter's design for that working system, to the proposal you have made, to the extent I understand your proposal.  Please correct any errors i inadvertently introduce!

SpaceNut, Calliban has addressed the concern you raised about ignition of the hydrogen gas after the payload has left the muzzle.  Please develop any further concerns you may have, so they can be addressed.  As things stand now, I understand most of the hydrogen used to expel the payload is going to be lost. it will have to be replenished as the cost of doing business.  The hydrogen may provide a visual display as it combines with atmospheric oxygen to make water vapor, and there may even be some interesting sunlight refraction effects if the firing takes place in daylight. 

For Calliban ... Dr. Hunter used a horizontal compression chamber, similar to the one you described, which ** I think ** must be the ones described by [Dayton Engineer] in the email which I posted.  I am intrigued by your idea of making a self-energizing chemical mixture of hydrogen and (some amount of) oxygen.

We have the possibility of someone already in the forum with the appropriate education and experience to develop that idea a bit, to see if it could be realized as a practical launch system.  In addition, it is certainly possible that someone with the appropriate education and experience will take the plunge to join the forum and add clarification to the idea.

For Calliban and SpaceNut ... this subtopic has developed to the point that it could have its own major topic heading under Interplanetary Transportation.

SpaceNut ... would you be willing to support a new topic dedicated to: NewMars Ballistic Launcher

My concept is to develop this new topic as an Open Source Project, with Intellectual Property freely extended to all, so that the human race can benefit from any ideas which show up there.

Financial rewards would flow to those who assume the ** very ** substantial risks of building a launch system, dealing with the regulatory agencies that will inevitably assert themselves, and creating the business organization needed to find customers and meet their needs.

(th)

Last edited by tahanson43206 (2020-02-27 09:02:03)

Offline

#220 2020-02-27 12:57:10

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 351

Re: Un- conventional ways to LEO

Astronautix article on SHARP, developed by Dr Hunter.
http://www.astronautix.com/s/sharp.html

As an aside, the light gas gun may turn out to be a promising route to inertial confinement nuclear fusion.  Consider the following sequence of events:
1. A light gas gun accelerates a deuterium-tritium-lithium projectile at a solid target.
2. Upon impact, the projectile is compressed to many times its original density.
3. A particle accelerator hits the compressed target with a beam of high energy deuterons, leading to a cascade of pions, which subsequently decay into muons inside the target.
4. The muons lead to fusion events within the compressed target, heating it to temperatures at which nuclear fusion takes place.

In this case, the muons serve to initiate rather than sustain fusion, by triggering fusion reactions that create the necessary heating in the compressed fuel.  The process will yield high energy neutrons, which could be used to heat hydrogen propellant flowing around the edges of the reaction chamber, generating thrust.  Alternatively, the neutrons could be used to generate fast-fission in a uranium or thorium shell surrounding the reaction chamber.

If the target itself was made of ice, the neutrons would heat it to plasma, which could then be trapped in a magnetic field and expelled for thrust.

Last edited by Calliban (2020-02-27 13:06:27)


Interested in space science, engineering and technology.

Offline

#221 2020-02-27 13:54:09

tahanson43206
Member
Registered: 2018-04-27
Posts: 2,202

Re: Un- conventional ways to LEO

For Calliban re #220

Thanks for finding and posting that very nice summary of Dr. Hunter's ideas, practical implementation, and hopes for future development.

That's about the best snapshot summary I've seen, and appreciate your making it available to forum readers who may be interested in Hunter's work.

***
Your extrapolation to fusion is impressive as well.

Two activities along those lines come to mind.  You would be aware of both, but new forum readers might be interested to explore them.

One is the laser fusion experiment being carried out by a US Government funded facility in California.  it might even BE Lawrence Laboratories.

The other is a proposal to use (what I recall as) high speed impact of (something) with fusible material in a mechanical flow for a fusion propulsion system.

The second proposal seems a bit closer to your vision, as I remember it, but your analysis of particle creation and interaction is new (to me at least) and I hope other forum contributors will add comments.

Edit#1: Here is a NASA proposal that seems similar to your idea.  This one uses lithium, and employs magnetic manipulation of the moving elements and the target to produce thrust.  The article is dated a year ago.

https://www.nasa.gov/directorates/space … ven_rocket

For Calliban ... we are drifting away from the theme of the topic.  The discussion of fusion seems a better fit for Interplanetary Transportation.  Branches like this are inevitable, because exploration of a given topic reveals application to other topics.

(th)

Last edited by tahanson43206 (2020-02-27 14:33:36)

Offline

#222 2020-02-27 18:30:19

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 18,368

Re: Un- conventional ways to LEO

The launching of the ship within the barrel will require a pressure plate that can tolerate the build up of stress as its fired up the chamber. Its main job would be to protect the engines that will need to work in order to finish the staging of it into orbit.

What will be the sound blast and flash outward from the top of the barrel upon the rockets exit? AS that will be a requirement for use to protect those operating it and the general public that might venture to close as to be harmed if it where fired while they were in that zone.

The ballistics launcher is just a replacement for the first stage of the rocket by what we are configuring for its use.

Online

#223 2020-02-27 19:59:32

tahanson43206
Member
Registered: 2018-04-27
Posts: 2,202

Re: Un- conventional ways to LEO

For SpaceNut re #222

Just a reminder .... we have two different ballistic launchers under discussion here ... Calliban started a discussion of a steam launcher that could be used for a traditional rocket as a first stage.

I've been focusing upon the theme of Dr. John Hunter's hydrogen launcher, which would NOT be used for launching a traditional rocket.  The Hunter style launcher would NOT be located anywhere near people.

It would need to be located near the equator to gain the advantage of the Earth's spin there, and on an island where there are no people, or floating at sea as Dr. Hunter proposed.

In the case of both designs, your observation about replacing the first stage is correct, because (in the case of the Hunter design) a small solid motor rocket is needed to provide horizontal momentum to the payload after it has reached apogee.

(th)

Offline

#224 2020-02-28 07:11:25

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 351

Re: Un- conventional ways to LEO

I think the consensus is that we probably need some type of rocket stage in both cases in order to achieve orbital velocity, which is tangential to the Earth's gravitational gradient.  So a purely ballistic launch is unlikely to be achievable, because of the extreme requirements this would place on muzzle velocity - exceeding 10km/s to reach high Earth orbit, where tangential velocity requirements are small enough to capture the projectile in flight.

So we have a balance between the size, acceleration and muzzle velocity of the gun and the requirements of the upper stage.  A higher acceleration in the gun stage reduces the required delta-V from the upper stage.  But it also places extreme structural requirements on the stage, to withstand high accelerations.  And of course, there are some payloads that are very limited in the acceleration they can withstand.  This places limits on the achievable delta-V provided by the gun stage, as there are practical limits to barrel length that are likely to come into play.  For constant acceleration, muzzle velocity = Squareroot (2x acceleration x barrel length).  You can play with the numbers for each variable, making judgements on the relative practicality of higher accelerations and higher barrel length.  And of course, final velocity is limited by the speed of the propellant gas.

It is difficult to identify minimal requirements for the concept.  Ultimately, we are aiming to reduce the cost of space launch by replacing the lower stage of the rocket with a device that is simpler and more reusable, with lower marginal costs per launch.  To do away with the lower stage entirely, the upper stage would need to demonstrate sufficient payload fraction in orbit, such that the capital and operating cost of the lower stage is no longer justified.  Given that gun launch is presumably cheaper, there would be an optimum gun delta-V at which it reaches breakeven in comparison to a lower stage.  Even if we do still need a lower stage, a boost from the gun would presumably increase total payload capacity.  Initially, I was interested in a device that would accelerate the existing design Starship upper stage without any assumed structural modification to the upper stage, which would hopefully allow the need for the lower stage to be avoided.  This would cut operational costs considerably.  But it is unlikely that a gun launch can replace the delta-V provided by the lower stage within a realistically achievable barrel length.  So there may be payload penalties that will need to be balanced against lower capital and operational costs.

At the high end of gun performance (for robust payload only) the upper stage would have minimum propulsive requirements, say 3km/s orbital velocity, with the gun providing it with enough delta-V to reach GEO altitude and maybe even lunar orbit.  That is quite a tough design exercise.  In addition to engineering a gun with muzzle velocity of 7-12km/s, the shell must include a propulsive rocket stage, electronics and manoeuvring thrusters; which must be rated to survive the extreme acceleration and thermal heating of launch.  The device itself cannot be reusable and must therefore be made cheaply enough to be expendable.  I think it could be done.  The question is more whether it is the cost optimum approach, given the development costs of the gun and projectiles.  If we are operating the gun to deliver bulk elements to high Earth orbit in support of space manufacturing, then the payload is the rocket itself.  We would try to construct it from materials that would be useful and it would be cannibalised in orbit as a source of raw materials.

The low velocity launcher is technically much easier, as muzzle velocities do not exceed 1km/s.  It could be man-rated and it fits in with Musk's existing concepts, so it seems like a good place to start.  Key questions in assessing its usefulness: (1) What is the maximum linear acceleration that the existing design Starship upper stage can safely withstand? (2) What are the practical limits to vertical barrel length and how would capital and operational costs escalate as barrel length increased?

Last edited by Calliban (2020-02-28 07:20:02)


Interested in space science, engineering and technology.

Offline

#225 2020-02-28 18:09:03

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 18,368

Re: Un- conventional ways to LEO

The solid rocket booster would seem prudent for the initial engine to achieve full orbit, followed if we require a liquid engines and thrusters to be able to get the payload to where we need it to be.
Since the G's are greater than a 1st stage would be I agree that its a cargo only function so as to reduce waste and cost...The winged type ships are less likely to be the design which can work though I am sure that a method could be possibly made for one to launch to orbit.

Online

Board footer

Powered by FluxBB