What kind of launch vehicle for manned Spaceflight?

[damocles]

"hmmm using the laser as a suppliment to a chemical propellant... *makes whistling sound then exploding sound then splattering into the ground in millions of peices gesture.


but seriously the problem remains the craft as it was explain to me is that the craft must spin, obviously carbon and fuel cannot, how then do you feed fuel to the spinning light ring around the craft in such a way that it can be controlled for maximum effifiency.. almost to the point of asking in the ground based laser has to be so powerful is the no way it can be created on board and focused onto the light ring in flight? no. then how to reconcile the spinning and static ring of light and crew modules, and now a fuel payload? would the ring afford enough gyroscopic stabilization couple with the vectored stability an elongated light craft fuselage would impart? that would more than likely involve fins trailing the craft.... what you end up with is a football with a spinning gyroscopic ring acceleracted by magnets most likely but being pushed against by laser... or as some of the models show some of the energy converted from the laser into kinetic energy by the ring is used to spin it. again though the ring must be separate from the main fuselage but still push it upwards. weak chemical jet engines would be used to conteract the spinning of the ring of light to keep the crew module and cargo and fuel payload, most likely one football shaped compartment, form sping at all."

alxian

http://science.howstuffworks.com/light-propulsion1.htm

You get your data and impressions from this crowd who are trying to get a micro-satellite launch system working?(the HARP cannon is more efficient).

The base detonation chamber doesn't have to spin; neither does the spacecraft. There are other means to stabilize the stack(conduit vented RCS ring for example?) The aero spike has the added benefit of having a plasma boundary layer associated with it.(Better than heat tiles for insulation and heat transport.).

There are always ways to stabilize a stack, that do not involve fins or spinning and people have considered those for manned launching.

I do agree that that laser is the engineeing bottleneck to any launcher. It has to be configured to heat and not burn through so a little blooming and divergence is actually a good thing in such a laser.

[alxian]

ok, i concede, i knew little and now know much more


the sad fact is even if building this turns out to be cheaper for surface to orbit transport and could potential help build an american owned and operated space station and space program they still won't go for it.


i think it would put more presure on other nations to play catch up.

i mean simple things like google earth will tell you that NA school kids play with more information than some contries con pay for.

what are they going to do if the US backs out of the global partnership of the ISS to build its own installations. i mean the rumours of starwars went over well enough (joke) what if the US in fact gains easy access to build a limitless number of absurdly powerful micro spy satelites, arm them, in the guise of global policing? more than likely several nations wouldn't be very happy.

i'm not saying that shoe boxing the idea is the answer either but something like this once built can't be unbuilt, once its in use we'll become dependent on it. if we don't share it others will think they have t otae it. should they produce it for themselves whats to stop people from going to war with cheap easily replaced satelites? picking them off and setting up their own offering a cheaper service perhaps than their now impotent competitors?

but as long as people are thinking about the skies again development of near earth space will flourish, won't be long until we're warring on the moon...

bah like i really care anyway, all i wanna know is when the first missions start leaving to mars, once their peeps could mine the asteroid belt to build martian cities. some one would have to entertain those first settlers....

[BlameTheEx]

Originally Posted by damocles

Have you researched why the Army hasn't deployed railguns or coil guns?
1. The magnetic fields generated distort the barrels(Bends them out of alignment).
2. The heat loading distorts the barrels as well.
3. Friction between the projectile and the magnets actually wears away the launcher.
4. The discharge capacitors have a distressing habit of exploding.

Your low acceleration magnetic catapult has to move masses of thee orders of magnitude larger than the masses with which the Army has experimented(1 kilogram versus 1000 kilograms) at two orders of magnitude greater velocity(2 KPS as opposed 8 KPS.).

The Army at every turn runs into the same problem. Its called heat. Their scientists can't unload it from the system fast enough to prevent system failure(See above.). At the moment, the rocket and the cannon remain superior as a means for propelling mass at great velocity.

As for superconductors? We are no closer to a high temperature superconductor now, than we were fifteen years ago when the ytrium barium doped ceramics set our materials scientists on the chase. This is another heat problem. Imagine the refrigeration issues involved for your superconducting magnets along your 250 km accelerator! By the way you do know that you cannot follow the curvature of the Earth with your catapult? It has to be a parallel series of rails or coils. Otherwise kaboom when the projectile hits the barrel.(This applies for your flame thrower below.).



I will keep this one simple.

SCRAMJET

http://www.aircraftenginedesign.com/custom.html4.html

LIQUID FUEL ROCKET MOTOR

http://science.howstuffworks.com/rocket7.htm

In its simplest denomination, the heat regime of the rocket motor is limited to its combustion chamber. The rocket's exhaust actually carriers heat away from the plenum chamber as it flows outward from the venturi. The scramjet has heat loading from friction from intake to exhaust throughout the length of the pipe which becomes too severe for us to currently engineer materials to withstand at velocities above mach 8.

As to what you suggest as to launching a ramjet shell inside a tube filled with hydrogen and oxygen. Ever hear of a Zeppelin called the HINDENBURG? We are speaking of firing a shell down a barrel longer than a hundred kilometers filled with oxygen and HYDROGEN! That is why I call it the worlds largest flame thrower and why a barrel burst would be equivalent to a major industrial disaster.(Oxygen-hydrogen reaction is far more efficient in its brissance than TNT.) In spite of the fact that you are correct that the eventual product of a hydrogen oxygen mix is water vapor and that the ignition point for hydrogen is about 520 degrees Celsius; the FACT remains that simple friction of the projectile inside the barrel will heat the gas mix to ignition ahead of your ramjet and kaboom. The projectile will jam at velocity in the barrel and in the result?

If I wanted to use a cannon as a launcher, I would use a cannon as a launcher and forget about fancy gas mixes or ramjet shells.

http://archives.cbc.ca/IDC-1-71-626-3354/conflict_war/gerald_bull/clip2

The Israelis killed Dr. Gerald Bull when he designed the Baghdad gun for Saddam Hussein. It works and would be a useful micro-satellite launcher into LEO.

Superconductors are feasible for eliminating heating of the projectile. I was never suggesting using superconductors for the barrel - just the missile. Heating of the barrel magnet is no real problem. After all the barrel magnet is 250km long. Long enough to distribute the heat of a launch. Non magnetic friction could be a problem but that is what magnetic support and vacuum filled barrels are for.

Discharge capacitors are feasible - you just have to install circuit breakers for each capacitor and expect a certain level of replacement. Then again you can use inductors or car batteries.

The railguns worked. What you bring up is maintenance issues. All other issues aside the US army was always going to give up with rail guns - the power supplies are just not very portable.

The total force involved in a missile launch to space is indeed several orders of magnitude greater than the army experiments but then so is the length of the launcher. Power per unit of length should be in the same order, and the bulk of launcher rails or magnets per unit of length would be much greater. In short the force and heating on any kilo of launcher would be much less. There is no real problem with the survival of the launcher. The missile is another matter. If it is not superconductive then heating would necessitate loss of some of its mass. Ever heard of ablative shielding?

You can follow the curvature of the earth with a catapult! Presuming the missile reached escape velocity it would follow the same curve, At lower velocity it would follow a greater curve, but at no time would the downwards force be greater than the weight of the missile. Naturally there has to be some corrective counter force. In a traditional cannon that counter force would be provided by scraping against the side. For a catapult this wouldn't be so clever. For a magnetic propulsion this would be (probably active) magnetic correction. For a ramjet it would be some equivalent of air bearings. You could increase the curve of the barrel to eliminate downforce but I question the point. Regardless there is bound to be need for a mechanism to reducing scraping.

Sadly I had no luck with your scramjet link. You can see a diagram of a scramjet here:
http://www.aviation-history.com/engines/ramjet.htm
Just imagine the outer case as part of the tunnel wall.

Your limit of mach 8 is pessimistic. Right now scramjets have reached Mach 9.6.
http://www.nasa.gov/missions/research/x43-main.html

Nasa considers Mach 15 feasible. Friction is the main bugbear, as you rightly point out, but it can be much less inside a tunnel. For starters it is only friction against the oxygen/hydrogen mix inside the tunnel - mostly oxygen. It need be no thicker than necessary. An air fuelled scramjet is fighting against the friction of air which mostly takes no part in combustion. Air is mostly nitrogen. Then again unlike the NASA X-43 the whole diameter of the projectile and a little more is engine. To keep acceleration within reason fuel density (and thus friction) has to be reduced. It takes no great imagination to realise that the oxyen/hyrogen mix in the tunnel would be very thin indeed. Think of all the oxygen and hydrogen inside a rocket but take it out and put it in a container of similar cross section and 250km length. Very thin. Finally the friction is a matter of relative velocity. The fuel need not necessarily be stationary. It could be blasted into the (vacuum filled) pipe at the last moment so that it also has some momentum in the same direction. Does this add up to escape velocity before melt down? I suppose it depends on your optimism. The limits of improvement that can be gained by research and development are not easily determined in advance.

I have indeed heard of the HINDBERG, but this is hardly the same thing. There is no friction ahead of a supersonic missile. It can't build up pressure in front of it because the pressure front travels at the speed of sound, and it travels faster! The flame can't precede the missile because it just can't travel that fast. The missile travels faster than the wavefront of the explosion. As for industrial disasters you are assuming densities of fuel that just won't be.

Canons have been well researched but they have limits. The missile can travel no faster than the velocity of the gas produced by the explosion, and that is sadly less than escape velocity. Worse it is an obscenely (I.E the engineer faced with the task is likely to end up swearing) complicated problem to equalise acceleration down a pipe with explosions as a motive force. Acceleration starts high and then drops sharply. There has been some research with multiple explosions (explosives place in chambers along the pipe), but imagine the complexity! For me the difficulties in front of a scramjet or electromagnetic design seem less.

[damocles]

Superconductors are feasible for eliminating heating of the projectile. I was never suggesting using superconductors for the barrel - just the missile. Heating of the barrel magnet is no real problem. After all the barrel magnet is 250km long. Long enough to distribute the heat of a launch. Non magnetic friction could be a problem but that is what magnetic support and vacuum filled barrels are for.

The heat loading failures were for rail guns of less than a hundred meters length when I commented on the army research. The navy will deploy railguns as they expect to solve the capacitor problem by using recurrent explosive current detonation(vircators) or charge spin armature cvapacitors to replace the charge capacitors that the army tried.
a. Heat loading on the launcher is not a linear progression distributed over length but a peak pulse electrical current loading depending on the magnitude of the mass moved thyrough the laucher. The principle heat generating mechanism is current impedence to move that massive payload(bullet) which is incidentally why you want a high temperature superconductor for the magnetic assembly so that you can eliminate the impedence.(See below)
b. Linear induction or magnetic levitation to mach 8+ velocities has to be accomplished by parallel magnetic rail or coil acceleration. The lateral force vectors applied to the bullet are simply too great to keep the bullet within its guides if you try to follow the curvature of the Earth. That is why we don't use bent barrel guns to shoot around corners.
c. Your assumption that you can send through the 250 kilometers of magnetic array with a travelling electrical pulse to launch a 10 ton bullet to Mach 20+, the equivalent of an electrical current load put out by a MHD generator of about 1.2 x 10^12 joules without it melting bending or shorting something out is laughable. That is far more than the 35 million watt seconds you apply to the electrodes of an 85 ton capacity electric arc steel furnace to reduce scrap steel to its molten state.
d. Since the friction loading of the bullet upon the magnetic barrel requires some slippage to allow reduced friction as well (as current grounding through the bullet if you use railguns, or spacing if you use a coil gun launcher) you would use an open architecture launcher, it would behoove you to study the effects of a travelling hypersonic shockwave upon ytour launcher.(Cannons being a sealed fit between barrel and projectile and relying on the gas expansion of propellant behind the bullet don't have this problem.).

Discharge capacitors are feasible - you just have to install circuit breakers for each capacitor and expect a certain level of replacement. Then again you can use inductors or car batteries.

Car batteries? You are kidding?

The railguns worked. What you bring up is maintenance issues. All other issues aside the US army was always going to give up with rail guns - the power supplies are just not very portable.

Vircators and better solid state charge capacitors or spin charge armature alternators will work, for the small scale application that the navy is seeking.

The total force involved in a missile launch to space is indeed several orders of magnitude greater than the army experiments but then so is the length of the launcher. Power per unit of length should be in the same order, and the bulk of launcher rails or magnets per unit of length would be much greater. In short the force and heating on any kilo of launcher would be much less. There is no real problem with the survival of the launcher. The missile is another matter. If it is not superconductive then heating would necessitate loss of some of its mass. Ever heard of ablative shielding?

Nonsense. As the mass accelerated increases over distance to be accelerated so does the travelling load. That is not a continuous current loading issue: it is a peak current loading issue.

You can follow the curvature of the earth with a catapult! Presuming the missile reached escape velocity it would follow the same curve, At lower velocity it would follow a greater curve, but at no time would the downwards force be greater than the weight of the missile. Naturally there has to be some corrective counter force. In a traditional cannon that counter force would be provided by scraping against the side. For a catapult this wouldn't be so clever. For a magnetic propulsion this would be (probably active) magnetic correction. For a ramjet it would be some equivalent of air bearings. You could increase the curve of the barrel to eliminate downforce but I question the point. Regardless there is bound to be need for a mechanism to reducing scraping.

Recalculate your lateral force vectors again.

Sadly I had no luck with your scramjet link. You can see a diagram of a scramjet here:
http://www.aviation-history.com/engines/ramjet.htm
Just imagine the outer case as part of the tunnel wall.

Scramjets don't work that way! You can't use the tunnel wall as the motor casing! The geometry of the intake ram and the heatplug are roughly semi-conic and the projectile would be unstable in its travel path down the barrel! How do you sustain supersonic COMPRESSION?!?! You need a stable plenum chamber and an intermixer just aft the heatplug to mix oxidizer and fuel for the scramjet to work..

You didn't read the section of my post where I wrote that the heat loading was from intake to exhaust in the engine interior and that we had yet tio design materials that could confine and sustain the temperatures and compression PRESSURES at Mach 8> ? I meant that we have yet to design the equivalent of a brick kiln twice as hot as a Ceramic pottery firing kiln operating in a regime of hot gasses flowing through it at 8600 kph.

Your limit of mach 8 is pessimistic. Right now scramjets have reached Mach 9.6.
http://www.nasa.gov/missions/research/x43-main.html

It was rocket boosted to about 4000 kph before the scramjet ignited. For less than 7 seconds it operated. Your information is incomplete. The motor was slag at the end of the test. and it, the X-43A was nothing more than a paperweight when it fell into the Pacific.

Nasa considers Mach 15 feasible. Friction is the main bugbear, as you rightly point out, but it can be much less inside a tunnel. For starters it is only friction against the oxygen/hydrogen mix inside the tunnel - mostly oxygen. It need be no thicker than necessary. An air fuelled scramjet is fighting against the friction of air which mostly takes no part in combustion. Air is mostly nitrogen. Then again unlike the NASA X-43 the whole diameter of the projectile and a little more is engine. To keep acceleration within reason fuel density (and thus friction) has to be reduced. It takes no great imagination to realise that the oxyen/hyrogen mix in the tunnel would be very thin indeed. Think of all the oxygen and hydrogen inside a rocket but take it out and put it in a container of similar cross section and 250km length. Very thin. Finally the friction is a matter of relative velocity. The fuel need not necessarily be stationary. It could be blasted into the (vacuum filled) pipe at the last moment so that it also has some momentum in the same direction. Does this add up to escape velocity before melt down? I suppose it depends on your optimism. The limits of improvement that can be gained by research and development are not easily determined in advance.

How do you fire a projectile in a near vacuum tube at sea level, pump in an oxygen/hydrogen precursor fuel mix, operate your scramjet(see above on motor materials and compression limitations) have a launch tube muzzle open to space, bend the barrel to follow the curvature of the earth, and avoid predetonation leading to barrel burst when the bullet jams in the barrel?

I have indeed heard of the HINDBERG, but this is hardly the same thing. There is no friction ahead of a supersonic missile. It can't build up pressure in front of it because the pressure front travels at the speed of sound, and it travels faster! The flame can't precede the missile because it just can't travel that fast. The missile travels faster than the wavefront of the explosion. As for industrial disasters you are assuming densities of fuel that just won't be.

If the pressure front travels at the speed of sound, then how does a ramjet compress air at Mach 3 in the SR-71 if it doesn't compress by intake ram effect faster than the speed of sound?? I await your answer.

While you work on that;

Take your scamjet......

You have to boost it up to operating speed to get the fuel/oxidzer mix to compress by intake ram effect so that the heatplug can ignite it as working gas fluid of sufficient mass to impart useful thrust..

[NOTE; THE CASING IS NECESSARY TO HYPERSONICALLY SUSTAIN COMPRESSION EFFECT]


You are writing about filling a launch tube with this gas mix that is about how big? A tube that is about one meter in radius and one hundred thousand meters long for a possible ten ton bullet? That is approximately 314,160 cubic meters of your oxygen/hydrogen gas mix to predetonate. You do realize that you must boost to at least to Mach 3 to get your scramjet to work inside your tube? So you need something(propellant) to boost that scramjet to operating speed? Sounds like a cannon?

There is gas compression present and there is shell heating. If you have studied the actual mechanics of how cannons operate(and you are describing a cannon, no matter how much you keep calling it a launch tube), you would clearly understand that the shells that travel down a cannon barrel(even a brass Napoleon 12 pounder Civil War smoothbore) have the necessary 550 degree celsius ignition temperature to explode your gas mix ahead of the shell. And it is the same thing. Detonation by spark is detonation. It doesn't matter if the spark comes from static electic charge, or from the hot surface of the bullet. Compression of the gas ahead of the projectile is another source of predetonation. Explain to me how the Scramjet inside your cannon is supposed to work again? RAM assisted artillery shells operate after they clear the cannon barrel muzzle; not while the shell is still travelling inside the gun because of the predetonation risk.

Canons have been well researched but they have limits. The missile can travel no faster than the velocity of the gas produced by the explosion, and that is sadly less than escape velocity. Worse it is an obscenely (I.E the engineer faced with the task is likely to end up swearing) complicated problem to equalise acceleration down a pipe with explosions as a motive force. Acceleration starts high and then drops sharply. There has been some research with multiple explosions (explosives place in chambers along the pipe), but imagine the complexity! For me the difficulties in front of a scramjet or electromagnetic design seem less.

Nonsense.

http://www.astronautix.com/articles/abroject.htm

The HARP gun died as a result of politics(Air force versus Army in the United States); I told you that the Baghdad gun would work? The Iraqis test fired a smaller prototype and they were confident that it would operate as Bull advertised.

Now I ask you to reconsider the statements you introduced.

[BlameTheEx]

damocles

a) Heat loading is only geometric if you shove the full current down the full length of the rail. Not exactly an option with a 250km rail. I would expect current to be delivered to local sections by local capacitors or whatever. Only a fraction of the power travels down any particular bit of rail. High currents, but not for long enough to cause overheating.

b) Go back and try to follow what I wrote. Lateral forces are involved but in the opposite direction to what you suppose, and never exceeding the weight of the missile The overriding lateral force is gravity NOT the earths curvature, at least not until the missile exceeds orbital velocity. I need not recalculate because only common sense is involved. At orbital velocity gravity bend the path of a missile into a circle around the earth. At less velocity the curve is tighter than that of the earths surface. To create a path with no lateral velocities the barrel must be more curved than the earth over all but its last section.

c) If the mass of the rails were only 85 tons I would laugh with you but the rails on a 250km railgun would weigh rather more. Nor can you presume that more than a small percentage of the energy involved will end up as heat in the rails.

d) If I was planning to take on the project myself you would be right. But surprise me. Tell me you have done a full feasibility study.

No. I aint kidding about the car batteries. Experiments were conducted with car batteries. Apparently they were the cheapest option at the time.

Oh sod it. I could cover the rest of your points, but life is too short. At least before I started on this I had a life.... I wonder if its still out there somewhere?

[damocles]

Short and sweet:

1. Current loading is not staged through an accelerator. It is a single pulse, through each segment, with the bullet acting as the moving armature through a linear stator.
2. You totally misread what I wrote about the electric arc steel furnace. It was an industrial example of the low end type of electrical current loading and heat production that an industrial application of this magnitude uses. The furnace's capacity of 85 tons of slag steel has nothing to do with the ten ton bullet or the several hundred tons of superconductor built into the launcher. The total heat loading throughput is comparable over time.
3. Your launcher is in effect adding angular momentum to a projectile that is being flung from the surface of a spinning sphere? I understand that quite well. The curvature of the Earth is not a force. How can you say that the lateral OUT^ vector on a bullet that is terminally Mach 26+(7.& mps) within a 250 kilometer acceleration is insignificant when the downward acceleration is only 9.8 mps? That projectile will depart along a ballistic trajectory OUT.(About seven degrees above the plane of launch.)
4. What you wrote about the scramjet in a tube indicates to me that you misunderstand completely how both the scramjet works and why putting just the intake ram and the heatplug elements of the motor inside a tube and expecting that to act as a traveling bobbin or spindle with the hydrogen as a mixed gas with oxygen won't work. That spindle will just sit in the breech and either detonate the gas mix bursting the tube or it will set the gas mix on fire and melt in place. The hydrogen is injected into the intermixer aft of the heatplug. If you design it properly to be a rocket assisted scramjet with a proper motor casing including an intermixer and plenum chamber/plug nozzle; it will set off the gas mix about halfway down the barrel and explode.

Car batteries were/are used with bench table(read garage model) low kilojoule railguns. The army 1 kg/2 kps models were gobbling megajoules.

My life went missing about a month ago. If you find yours, mine should be next to it? Send it along if you do find it, please?

[nkt]

Wow, this is a good thread!

Damocles is right about there being no static thrust from a Ramjet or Scramjet. The whole thing has to be moving pretty fast to get to ignition speeds that actually have a net speed increase from the burn.

However, I'm not sure that you do need an outer casing for the scramjet to work. Do you have a reference for that? I'm fairly sure that if you used a static outside layer you would have some issues, but redesign of the forcing/shock cone might be able to mitigate that.

As for the initial acceleration, why use anything more complex than a buffered black powder or cordite gas expansion? Or even a simple fuel/air burn as found in a car engine? The hot gasses would be channelled through a series of baffles to reduce the initial acceleration, and give a progressive push for the lowest possible cost. Simple nitrate- or oil -based gas generation would keep costs low per launch.

Once up at around the Mach range, further, hotter gases would be used, boosting up to around Mach 1.5, at which point the launch vehicle breaches a thin barrier that lets it pass into a hydrogen rich (3% or so) region. (This could be done at an altitude such that the pressure issues were half that at ground level, but see below.) The fuel is in the tube, and as such the scramjet shaped "missile" starts to generate thrust as it passes through. Obviously there will be problems with staying in front of the shockwave flamefront, since to start with it will move far faster than the missile.

The issues with thrust from the rotation of the earth can be dealt with in two ways:
If you want to impart that force to the craft, have it steer it's thrust slightly to avoid hitting the walls. This is tricky, true enough. Hyper-velocity steering is hard!
If you don't want to, simply bend the launch tube. Have it such that the building/structure is an arc that fits the predicted path at the predicted velocity.

You could, if structure loading allows, pump down the pressure inside the building. However, this would be a big undertaking, but not massive compared to the rest of the endeavour.

I've seen calculated the figures for the rates of acceleration, times of flight, etc. for air-breathing engines for space flight. It turns out that the region and the length of time for which the air-breathing engines are useful are actually not worth the extra mass they imply. This is becuase, once at Mach 7, you only spend a minute or two in a region of the atmosphere that is thick enough to get enough compression and support combustion. Flying longer in the dense air leads to extra heating and more fuel requirement to get into space. This is one reason why HOTOL never got off the drawing board - it is almost impossible to get a good enough design trade off.

The "supergun" type launcher is useless for people. They get turned into mush rapidly. However, for small payload and small satellite lifts, it is ideal. Very cheap, and very easy, unless you want a higher orbit, different arc, to blow up a different city... ;-)

[damocles]

Again, short and quick:

http://en.wikipedia.org/wiki/Scramjet

Quoting from the article:

Like a conventional ramjet, a scramjet consists of a constricted tube through which air is compressed, fuel is combusted, and the exhaust is vented at higher speed than the intake air. Also like a ramjet there are either few or no moving parts. In particular there are no high speed turbines as found in a turbofan or turbojet engine that can be a major point of failure.

The scramjet requires extremely high speed airflow to function and requires acceleration to supersonic speed before it can be started. Recent tests of prototypes have used a booster rocket to obtain the necessary velocity. Theoretically, air breathing engines should have a better specific impulse while within the atmosphere than rocket engines.

And yet again from the article:

All scramjet engines have an inlet, which compresses the incoming air, fuel injectors, a combustion chamber and a thrust nozzle. Typically engines also include a region which acts as a flame holder, although the high stagnation temperatures mean that an area of focussed waves may be used, rather than a discrete engine part as seen in turbine engines. An isolator between the inlet and combustion chamber is often included to improve the homogeneity of the flow in the combustor and to extend the operating range of the engine.

The flame holder may be sculpted as part of the aerodynamic boundary effect within the motor not requiring a shell, but the isolator(intermixer) and the combustion chamber/(plug) thrust nozzle do require a shell of differing internal cross sectional geometries to match the rammed gas fluid flow to moderate aforesaid flow. Note that the fuel(hydrogen) is injected into the air or oxidizer stream aft of the heatplug in the isolator/intermix CHAMBER.

You don't want to operate a rocket or jet motor inside a cannon barrel at the same time as you use a detonated propellant to move the bullet. Gas backflow and the danger of bullet jam in the tube are no joke when you speak of systems that operate in the tens of thousands of megajoules of energy.

Consider that an average tank gun armor piercing dart of about 6 kg fired from an average 12 cmL44 tank gun has a delivered impact kinetic energy of about 10-12 megajoules at roughly 2 kps?

That ten ton bullet at 8 kps delivers 3.2x10^11 joules or 32,000 megajoules of energy at impact. You want THAT to jam in the barrel?

[nkt]

Originally Posted by damocles

http://en.wikipedia.org/wiki/Scramjet

Hasn't changed much since I last read and edited it...

You don't want to operate a rocket or jet motor inside a cannon barrel at the same time as you use a detonated propellant to move the bullet. Gas backflow and the danger of bullet jam in the tube are no joke when you speak of systems that operate in the tens of thousands of megajoules of energy.

Consider that an average tank gun armor piercing dart of about 6 kg fired from an average 12 cmL44 tank gun has a delivered impact kinetic energy of about 10-12 megajoules at roughly 2 kps?

That ten ton bullet at 8 kps delivers 3.2x10^11 joules or 32,000 megajoules of energy at impact. You want THAT to jam in the barrel?

Only if I'm a long way back, and the UK and US presidents are taking the trip... ;-)

Seriously, you don't have to tell me. Which I assume was the point of your response.

Who is using a detonated propellant with a rocket motor? I specifically stated that it was two systems working together - one was a large gas reserve at high pressure, but quite cool, which is buffered through to modulate acceleration. However, either way, there is a barrier between the hydrogen and oxygen/air mix, and the first stage. (Edit: http://en.wikipedia.org/wiki/Scramjet#GASL_projectile will tell you this has been done already)

As I said, I don't know off the top of my head, any more than you do, whether it would be possible to use the side wall of the tunnel as the outer wall of the projectile. It will take a few million dollars of simulation to get the best shape for the given size, as well as an estimate of the thrust per unit mass of fuel mix, specific thrust of the craft, minimum operating speed, exit velocity, etc., etc. "Just" the change in velocity comparing a stationary wall with one doing hypervelocity will have an effect. In fact, skin drag effects on the walls of wind tunnels running at even low speeds have a huge effect, and are still being worked on to this day.

I could have gone and asked the people who did this for a living, but I quit that job before I ever heard of Hypography. Please don't try to teach me to suck eggs.

[damocles]

http://www.spacedaily.com/news/scramjet-01a.html

Notice with interest this quote from the article?

After the titanium projectile was launched, it used its scramjet engine to cover a distance of 260 feet in slightly over 30 milliseconds.

.
The implication is that the scramjet kicked on after it left the muzzle of the low pressure gas gun and that the scramjet itself was built to artillery shell standards. If the scramjet was built like a rocket assisted artillery shell then it was built with a gas sealed base that mechanically unlocked and opened the minute the projectile left the muzzle so that the scramjet had a free flow gas path. That makes sense, if the danger of propellant gas bleed through from the base into the scramjet would interfere with the scramjet's ignition and operation.

By the way, I don't tell anybody how to suck eggs. I have enough trouble juggling them.