I was disappointed that this link to Quicklaunch Inc. didn't draw even one reply. It is far more interesting that that. It offers a solution to a very troublesome aspect of space exploration. Yes, it is an hour long Google tech talk, but it is a workable idea. Take some time watch it.
http://quicklaunchinc.com/
Affordable LEO Fuel Depot Construction Tech
Re: Affordable LEO Fuel Depot Construction Tech
Co'mon! Give a guy a chance! I just read you other post, and I'm at lunch at work where I can't do a bunch of video viewing and the like!Aero wrote:I was disappointed that this link to Quicklaunch Inc. didn't draw even one reply. It is far more interesting that that. It offers a solution to a very troublesome aspect of space exploration. Yes, it is an hour long Google tech talk, but it is a workable idea. Take some time watch it.
http://quicklaunchinc.com/
OK - I'll cool it.
I would like to know though, how one calculates a figure of merit for this device. Like an equivalent ISP or some such. It launches a third stage rocket plus payload reaching space at mach 6, the payload is 1000 pounds and the mass fraction is 20 to 28 %. The molecular weight of the fuel is 2, and 96 % of the hydrogen fuel is recovered. The speaker claims that for this high launch mass, aerodynamic drag losses are small. I guess an analogy would be meteor impacts. Small ones are slowed by the atmosphere and large ones just punch right through. Same for the launch vehicles proposed by Quicklaunch, Inc. Oh, and note that they have already done higher than mach 6 launches in horizontal tests and they already have part ownership of suitable equipment. They, like a lot of other ideas, just need some funding.
I would like to know though, how one calculates a figure of merit for this device. Like an equivalent ISP or some such. It launches a third stage rocket plus payload reaching space at mach 6, the payload is 1000 pounds and the mass fraction is 20 to 28 %. The molecular weight of the fuel is 2, and 96 % of the hydrogen fuel is recovered. The speaker claims that for this high launch mass, aerodynamic drag losses are small. I guess an analogy would be meteor impacts. Small ones are slowed by the atmosphere and large ones just punch right through. Same for the launch vehicles proposed by Quicklaunch, Inc. Oh, and note that they have already done higher than mach 6 launches in horizontal tests and they already have part ownership of suitable equipment. They, like a lot of other ideas, just need some funding.
Aero
Gerald Bull did a lot of work on this type of thing in the '60s.Aero wrote:I would like to know though, how one calculates a figure of merit for this device. Like an equivalent ISP or some such. It launches a third stage rocket plus payload reaching space at mach 6, the payload is 1000 pounds and the mass fraction is 20 to 28 %. The molecular weight of the fuel is 2, and 96 % of the hydrogen fuel is recovered. The speaker claims that for this high launch mass, aerodynamic drag losses are small. I guess an analogy would be meteor impacts. Small ones are slowed by the atmosphere and large ones just punch right through. Same for the launch vehicles proposed by Quicklaunch, Inc. Oh, and note that they have already done higher than mach 6 launches in horizontal tests and they already have part ownership of suitable equipment. They, like a lot of other ideas, just need some funding.
http://www.astronautix.com/lvfam/gunnched.htm
http://www.islandone.org/LEOBiblio/SPBI1GU.HTM
http://settlement.arc.nasa.gov/Nowicki/SPBI1GU.HTM
Figure the muzzle velocity, figure instantaneous deceleration when the projectile exits the cannon and hits atmo, figure other penalties, figure additional necessary dv to reach orbital velocity (probably solid grain fuel). Isp-equivalent doesn't matter for the cannon, only for the orbital insertion kick-motor.
Vae Victis
I presume this is the same gas cannon in the ocean thing we're knocking around in another group. They said I should watch a 1-hr video too. I have not yet.
Gas guns work as artillery, and I don't doubt you could make one develop this velocity with some work.
My concern is if you attempt to achieve muzzle velocity equal to a normal LEO orbit. This is an approximation of the intent ... you cannot achieve orbit by firing a gun from the surface, so the scheme does launch a rocket stage. The projectile fired at 17,500 mph would lose velocity due to air resistance and the 100-mile climb, so arguably you might want to go for higher muzzle velocity. But it is a number to look at.
Converting to metric flight SI units I get
17500 mile/hour = 7823.2 meter/second
Plugging that airspeed into a spreadsheet I have available that does a "detailed" calculation useful at least at a large fraction of the speed of sound, hopefully still good at high hypersonic speeds, I get the following dynamic pressure at sea level, standard temperature.
37486 kPa (5437 psi)
I don't have hard data on existing spacecraft designs. I would expect this would crush anything NASA presently routinely launches. I expect we could build something that could take it (it would be in the realm of a high-pressure tank). The closest things I know of are nose cones on ballistic missile warheads, intended for re-entry into fairly low and dense atmosphere at somewhat less than orbital velocity. A designer of early ones told me most materials will shatter if they hit so much as a raindrop at that velocity, but they were able to make nitinol work.
I've seen this phenomenon, a tough material that is normally ductile will shatter like glass if the strain rate is high enough. It may be possible to build this projectile, but it is a tough case.
Now, what happens when you integrate the dynamic pressure calculation over all that atmosphere, launching at the fairly shallow angle illustrated in the website I saw? This thing will lose a lot of speed at low altitude, depending on the hypersonic aerodynamics of the projectile. A sea-level launch is the worst-case condition.
Not putting much sonic boom into the water due to impedance mismatch is OK. A huge sonic boom will ensue once in the atmosphere. Mach 17 or so? Again, right at the surface? Hold your ears, seagulls!
I think this is not impossible, but I think it might make rockets look pretty good by comparison. I would personally think it would work better as a fixed installation launching up the side of a very tall mountain into thin air.
Gas guns work as artillery, and I don't doubt you could make one develop this velocity with some work.
My concern is if you attempt to achieve muzzle velocity equal to a normal LEO orbit. This is an approximation of the intent ... you cannot achieve orbit by firing a gun from the surface, so the scheme does launch a rocket stage. The projectile fired at 17,500 mph would lose velocity due to air resistance and the 100-mile climb, so arguably you might want to go for higher muzzle velocity. But it is a number to look at.
Converting to metric flight SI units I get
17500 mile/hour = 7823.2 meter/second
Plugging that airspeed into a spreadsheet I have available that does a "detailed" calculation useful at least at a large fraction of the speed of sound, hopefully still good at high hypersonic speeds, I get the following dynamic pressure at sea level, standard temperature.
37486 kPa (5437 psi)
I don't have hard data on existing spacecraft designs. I would expect this would crush anything NASA presently routinely launches. I expect we could build something that could take it (it would be in the realm of a high-pressure tank). The closest things I know of are nose cones on ballistic missile warheads, intended for re-entry into fairly low and dense atmosphere at somewhat less than orbital velocity. A designer of early ones told me most materials will shatter if they hit so much as a raindrop at that velocity, but they were able to make nitinol work.
I've seen this phenomenon, a tough material that is normally ductile will shatter like glass if the strain rate is high enough. It may be possible to build this projectile, but it is a tough case.
Now, what happens when you integrate the dynamic pressure calculation over all that atmosphere, launching at the fairly shallow angle illustrated in the website I saw? This thing will lose a lot of speed at low altitude, depending on the hypersonic aerodynamics of the projectile. A sea-level launch is the worst-case condition.
Not putting much sonic boom into the water due to impedance mismatch is OK. A huge sonic boom will ensue once in the atmosphere. Mach 17 or so? Again, right at the surface? Hold your ears, seagulls!
I think this is not impossible, but I think it might make rockets look pretty good by comparison. I would personally think it would work better as a fixed installation launching up the side of a very tall mountain into thin air.
Last edited by Tom Ligon on Fri Jan 29, 2010 8:19 pm, edited 2 times in total.
Ok, well then they give the ISP of the orbital insertion kick-motor as about 300-350 seconds, I forget exactly (maybe 340 sec.) but it burns for about 100 seconds. They are using LOX and kerosene and an aerospike design because of the worry about solid fuel detonating in the launch tube from acceleration shock.
Kerosene because of volume restrictions. Liquid hydrogen is to bulky. Aerospike to keep the nozzle from hanging out in the slip stream where it would probably break off.
Thanks for the links. The Youtube speaker is mentioned in one of them. Evidently Quicklaunch, Inc. has discovered something because their numbers are quite a bit better than the numbers from the 60's and in the linked pages.
Kerosene because of volume restrictions. Liquid hydrogen is to bulky. Aerospike to keep the nozzle from hanging out in the slip stream where it would probably break off.
Thanks for the links. The Youtube speaker is mentioned in one of them. Evidently Quicklaunch, Inc. has discovered something because their numbers are quite a bit better than the numbers from the 60's and in the linked pages.
Aero
Tom - Take your groups advice and spend the time to watch the video, you can fast-forward through parts of it. Or at least check out the links that djolds1 posted above. One very good trick to reduce drag by at least one order of magnitude is simply to eject hydrogen gas at the nose into the slip stream. Its been done and it works.
The current altitude record is 180 kilometers for a gun projectile. That's almost high enough, and yes, an orbital insertion kick motor is required. Quicklaunch, Inc. indicated, in the video, that they would launch at a relatively steep angle, exiting the atmosphere quickly at mach 6, then circularize with the kick motor.Do their numbers hold up to scrutiny? I don't know. But what is the delta V, that is orbital velocity minus mach 6 velocity, and can this delta V be achieved using 3000 - 4000 pounds of fuel with an ISP of 340 seconds? (Mass ratio is 20 to 28 %) That's the key because I believe that the gun can get its part of the job done.
The current altitude record is 180 kilometers for a gun projectile. That's almost high enough, and yes, an orbital insertion kick motor is required. Quicklaunch, Inc. indicated, in the video, that they would launch at a relatively steep angle, exiting the atmosphere quickly at mach 6, then circularize with the kick motor.Do their numbers hold up to scrutiny? I don't know. But what is the delta V, that is orbital velocity minus mach 6 velocity, and can this delta V be achieved using 3000 - 4000 pounds of fuel with an ISP of 340 seconds? (Mass ratio is 20 to 28 %) That's the key because I believe that the gun can get its part of the job done.
Aero
I think the original designer of gas guns thought they could launch payloads this way. I've considered this an intriguing possibility for a couple of decades. I just never in my life considered launching at anything approaching orbital velocity from sea level.
Gas guns definitely can work ... Saddam Hussein had one built and aimed at Israel, which we dismantled after we took possession of the place. It was one of his troublesome little toys that makes the world well rid of him.
Saddam's gun was built up the side of a mountain.
If I were developing such a launcher, I would look to possibly put a tampion in the muzzel that could be moved out of the way with some high-speed device, possibly explosive charges. I would then at least partially evacuate the tube, and likely partially back-fill with hydrogen at low pressure. That would reduce the problem of expelling a few miles of dense air from the barrel.
Bleeding some hydrogen from the nose is an interesting twist, but worth avoiding if another trick works better because it robs available payload. Likewise, all the rocket fuel you don't need is payload you can use, and reducing the structural needs of the projectile also increase payload. Those are some of the reasons I always thought you would want the muzzel of such a launcher (gas gun, rail gun, magnetic, whatever) up in as rarified air as you can reach.
Gas guns definitely can work ... Saddam Hussein had one built and aimed at Israel, which we dismantled after we took possession of the place. It was one of his troublesome little toys that makes the world well rid of him.
Saddam's gun was built up the side of a mountain.
If I were developing such a launcher, I would look to possibly put a tampion in the muzzel that could be moved out of the way with some high-speed device, possibly explosive charges. I would then at least partially evacuate the tube, and likely partially back-fill with hydrogen at low pressure. That would reduce the problem of expelling a few miles of dense air from the barrel.
Bleeding some hydrogen from the nose is an interesting twist, but worth avoiding if another trick works better because it robs available payload. Likewise, all the rocket fuel you don't need is payload you can use, and reducing the structural needs of the projectile also increase payload. Those are some of the reasons I always thought you would want the muzzel of such a launcher (gas gun, rail gun, magnetic, whatever) up in as rarified air as you can reach.
I watched the video again and I must apologize for some bad numbers. This time I wrote them down so here are correct ones:
Interestingly, the record muzzle velocity for a hydrogen gas gun is 11.2 km/sec which equals escape velocity.
Quicklaunch expects to fire a 1 km long gun with a nozzle velocity of 9 km/sec, expecting 6 km/sec (not mach 6, my bad) at LEO altitude.
Quicklaunch expects to circularize by using a kick motor to achieve 7.2 km/sec, orbital velocity at LEO. The kick motor will use LOX and RGP, with an ISP ~ 340 sec, burn time about 100 seconds, and so forth.
Will it work? I don't know but the video is pretty convincing.
Interestingly, the record muzzle velocity for a hydrogen gas gun is 11.2 km/sec which equals escape velocity.
Quicklaunch expects to fire a 1 km long gun with a nozzle velocity of 9 km/sec, expecting 6 km/sec (not mach 6, my bad) at LEO altitude.
Quicklaunch expects to circularize by using a kick motor to achieve 7.2 km/sec, orbital velocity at LEO. The kick motor will use LOX and RGP, with an ISP ~ 340 sec, burn time about 100 seconds, and so forth.
Will it work? I don't know but the video is pretty convincing.
Aero
For comparison, my dynamic pressure calculator gives the following pressures at sea level, standard temp.
9000 meters/sec, 49612 kPa, 7196 psi.
11200 m/s, 76832 kPa, 11144 psi.
Sporty. Not totally impossible but this will be one heavy projectile. Presumably only the front of it needs to handle that pressure.
9000 meters/sec, 49612 kPa, 7196 psi.
11200 m/s, 76832 kPa, 11144 psi.
Sporty. Not totally impossible but this will be one heavy projectile. Presumably only the front of it needs to handle that pressure.
Liquid fuels for a (relatively short) cannon launcher?!?!? Such a launcher will be moving cargoes at hundreds to thousands of gees acceleration.Aero wrote:Ok, well then they give the ISP of the orbital insertion kick-motor as about 300-350 seconds, I forget exactly (maybe 340 sec.) but it burns for about 100 seconds. They are using LOX and kerosene and an aerospike design because of the worry about solid fuel detonating in the launch tube from acceleration shock.
http://www.islandone.org/LEOBiblio/SPBI110.HTMTom Ligon wrote:I think the original designer of gas guns thought they could launch payloads this way. I've considered this an intriguing possibility for a couple of decades. I just never in my life considered launching at anything approaching orbital velocity from sea level.
http://settlement.arc.nasa.gov/Nowicki/SPBI110.HTM
Myrabo's Lightcraft used various types of aerospike - plasma, laser, etc.Tom Ligon wrote:Bleeding some hydrogen from the nose is an interesting twist, but worth avoiding if another trick works better because it robs available payload.
Vae Victis
Base bleed is a technique which the shell out gasses behind the base, eliminating the vacuum drag. Used in long range artillery, base bleed increases the shell range by about 30% irrespective of the caliber. Base bleed shells are starting to become more common in units equipped with modern artillery of this type. It requires a small reduction in payload.
The field was largely pioneered by Gerald Bull.
http://en.wikipedia.org/wiki/Base_bleed
The field was largely pioneered by Gerald Bull.
http://en.wikipedia.org/wiki/Base_bleed
Aero
Confirming djolds ...
To achieve the touted 9000 meters/sec at the muzzle, at a modest 3 g acceleration used for manned space flight, you accelerate in 306.1 seconds and the gun need be only 1378 kilometers in length.
A small continent will do.
A thousand gees gets you down to around a 4.13 km gun and a smidge under a second of acceleration. At that acceleration, the pressure over the rest of the projectile due to the liquid payload will be very high, so forget what I said about only the front of the projectile needing to handle thousands of psi.
BTW, I dug into the guts of that dynamic pressure spreadsheet, and it is only valid subsonic, so my pressure values are probably low. I did find a book on-line that specifically handles air data measurements under hypersonic conditions (I do this for a living subsonic). Anyone interested might look up Controlled Hypersonic Flight Air Data System and Flight Instrumentation, by Georg Koppenwallner. This might be a good reference for anyone working on this problem, re-entry, aerobraking, or the behavior of asteroids and comets striking the atmosphere. Any of these have or are likely to come up in this forum.
To achieve the touted 9000 meters/sec at the muzzle, at a modest 3 g acceleration used for manned space flight, you accelerate in 306.1 seconds and the gun need be only 1378 kilometers in length.
A small continent will do.
A thousand gees gets you down to around a 4.13 km gun and a smidge under a second of acceleration. At that acceleration, the pressure over the rest of the projectile due to the liquid payload will be very high, so forget what I said about only the front of the projectile needing to handle thousands of psi.
BTW, I dug into the guts of that dynamic pressure spreadsheet, and it is only valid subsonic, so my pressure values are probably low. I did find a book on-line that specifically handles air data measurements under hypersonic conditions (I do this for a living subsonic). Anyone interested might look up Controlled Hypersonic Flight Air Data System and Flight Instrumentation, by Georg Koppenwallner. This might be a good reference for anyone working on this problem, re-entry, aerobraking, or the behavior of asteroids and comets striking the atmosphere. Any of these have or are likely to come up in this forum.
Just so you don't feel lonely, there is also a discussion of this going on at NASASpaceFlight.com, and SIGMA has one going as well.
http://forum.nasaspaceflight.com/index. ... ic=20098.0
http://forum.nasaspaceflight.com/index. ... ic=20098.0