What kind of launch vehicle for manned Spaceflight?

[damocles]

Assuming that the support for manned spaceflight continues in the face of the ongoing expense and problems that plague the Space Shuttle;

 

-what kind of launch vehicle would you use in place of the shuttle?

-would you use expendable boosters or try for a totally reuseable system?

-what would you like to see as the ultimate near term goal for manned spaceflight for the replacement vehicle?

 

How would you justify the investment in a new launch vehicle to the average taxpayer?

 

Damocles

[UncleAl]

Before you build a modality you ask what it will be asked to accomplish. Do you want a heavy lifter for colonizing the moon? Ring a Saturn V with eight Space Scuttle solid fuel boosters - use once and toss. That will give you a payload of about 700 tonnes compared to the Space Scuttle's 15 tonnes and be much cheaper per gram boosted. The Space Scuttle costs $30/gram to low Earth orbit. Look up the price of gold. A single Space Scuttle launch coasts $800 million. The payload is never the important part. NASA is buying publicity.

 

http://www.mazepath.com/uncleal/nasa3.htm

 

Do you want to boost smaller payloads? We already have used car lots filled with working possiblities - NASA, ESA, China, Russia... civilian and military. There is no need for a "next generation" booster because we already have every imaginable niche overpopulated with solutions stored as inventory. The needs are to kill off the obscenely expensive and useless Space Scuttle, kill off obscenely expensive and useless International Space Station Freedom FUBAR Space Hole One, and kill off most of obscenely expensive and useless NASA.

 

Before you farm, before you even till the soil, you ask a smple question: What can I plant that will be worth having in large quantities? That will be salable at large profit? The real world answer is inevitably "drugs," and that is the NASA product. Now you proceed onward from there.

 

(The Space Scuttle was originally spec'd at 30 tonnes maximum payload. Added safety hardware upgrades and engineering peformance downgrades have cut that about in half.)

 

The moon is an exceptional platform for physically huge antennas (deep radio to x-ray astronomy) and wonderful launch platform for massive space endeavors (no air resistance and 1/6 gravity, plus its angular mometum of orbit). There isn't much else in local space that is worth visiting for any reason except curiosity - and that is best accomplished with robotics.

[damocles]

Greetings sir.

 

http://hypography.com/forums/showthread.php?p=51387#post51387

 

I love satire!

 

Couple of things;

 

1. Nobody sane trusts a thirty year old rocket.

2. The jigs for building new Saturn boosters don't exist any more.

3. We need to get off this rock and spread out. Too many eggs in one basket.

4. Robotics makes sense, since you can scale from micro- to macro- by using incrementalism. After all, as you said, we don't have the lift in the inventory to put heavy stuff into orbit.

 

The big problem is selling the program to a schmuck(me). I know that the future resource base for humans is space. That the true measure of the standard of living for your average schmuck is the amount of energy he uses per volume over time. The more energy you have the richer you are. I want to get to a place where we can tap energy cheaply. The moon is the first place where a micro-machine step up technology might get us the resources to build a truly massive energy base for exploitation.

 

Consider;

1. Fossil fuel extraction fell below demand last year and will continue to fall as China and India look for more oil to power their new industries.

2. Planet based energy production leads to heat pollution(global warming is just a small part of this problem) and heavy metal poisoning of the aquifer. We need alternatives.

3. Most of the solutions that are in the niche lifter category; are barely beyond V-2 engineering, and are throwaway launchers. They are also ozone destroying;(like the SRBs of the "scuttle" for example) so most of the solutions are really non-starters for the massive numbers of launchings that any true any space program.(even for the X-ray astronomy antennae.). Brute forcing that to the moon requires either a hundred 100 kg loftings of manufactory robots which will build the antennae in about ten years, or a hundred 100,000 kilogram "manned" missions, and then you still have to build the antennae with locally available lunar resources(still takes ten years and you have to build a self sustaining base.). You might as well make, it, the seedling mission go, whole hog and go the whole O'Neill route.

 

Damocles

[nkt]

I'm not sure where you get 100,000 kilos nor 100 launches from. 100 tonnes is more than enough for a bootstrapping colony. Your low estimate of ten tonnes is too low, though.

 

You need electricity, so solar cells and power storage go up first, along with a bit of basic tough gear which transmits a radio locator beacon, a basic 360 view camera, and perhaps some water.

 

Next you take up cutting tools that work without moving parts, such as plasma cutters, and use these to concentrate the power and melt the regolith for a suitable distance around the base to provide for a landing pad that won't raise dust. You also take up some basic shielding materials which can be used to shelter under in the event of a solar flare, etc. which can later be used to line and seal an underground base area. This is started to be excavated at this stage on a small scale. The walls would be glassy regolith at first, then, once the regolith was breached, it would be solid rock. The walls are unlikely to need extra support at 1/6th earth gravity, unless dusty.

 

Next we need something to create oxygen - the oxygen from regolith idea may help a lot with this, but it will still need storage. In the absence of wind, however, a puncture-proof balloon might be useful for this.

 

If enough power can be concentrated, fused rock as concrete, or even metal casting might be available. Another idea might be to have a system similar to the direct metal sintering 3d printers available now, only using regolith instead of metal powders. This would allow almost anything to be made to the right size and shape from native materials.

 

I've got to go out now, so I'll post more latter.

[damocles]

nkt I'm not sure where you get 100,000 kilos nor 100 launches from. 100 tonnes is more than enough for a bootstrapping colony. Your low estimate of ten tonnes is too low, though.

 

You need electricity, so solar cells and power storage go up first, along with a bit of basic tough gear which transmits a radio locator beacon, a basic 360 view camera, and perhaps some water.

 

Next you take up cutting tools that work without moving parts, such as plasma cutters, and use these to concentrate the power and melt the regolith for a suitable distance around the base to provide for a landing pad that won't raise dust. You also take up some basic shielding materials which can be used to shelter under in the event of a solar flare, etc. which can later be used to line and seal an underground base area. This is started to be excavated at this stage on a small scale. The walls would be glassy regolith at first, then, once the regolith was breached, it would be solid rock. The walls are unlikely to need extra support at 1/6th earth gravity, unless dusty.

 

Next we need something to create oxygen - the oxygen from regolith idea may help a lot with this, but it will still need storage. In the absence of wind, however, a puncture-proof balloon might be useful for this.

 

If enough power can be concentrated, fused rock as concrete, or even metal casting might be available. Another idea might be to have a system similar to the direct metal sintering 3d printers available now, only using regolith instead of metal powders. This would allow almost anything to be made to the right size and shape from native materials.

 

I've got to go out now, so I'll post more latter.

 

nkt

 

Hello!

 

I don't think we are starting from the same base assumption.

 

You are thinking of building a manned base through fully functioning teleoperated robots. I, instead, am operating from the assumption that you send simple machines to survey, and then to separate out and harvest raw resources, then build a crude solar power station, then build a crude smelter, then build a first stage fabricator, then climb the materials fabrication technology tree until you can custom design on Earth the device/tool you need and either cast or grow it in a liunar fabricator via teleoperation. Once you can design to demand and fabricate at will in situ, then you can think about sending men. You start building the habitat at that point. The point is that the first teleoperated robots needn't be that big with current technology to seed a site for exploitation.

 

Your estimate that 100 tons is sufficient for a manned bootstrap colony is unrealistic. A human uses at least a kilogram of food, another kilogram of water and at least five kilograms of air. Recycling is not 100% efficient. There will be liquid and gaseous waste that will leak from the containment. Also recycling will be massive per human as it will be biomass based for greatest resilience and least susceptibility to mechanical casualties. I doubt that 100 tons will land more than the basics for a 10 man crew for a month. building an x-ray astronomy antennae(the example) will require closer to 10,000 tons of supplies to sustain a crew of 100 men for the two to five years to try and rush the job to completion.

 

As a side note how many tons of supply does the ISS require to sustain its crew in a year?

 

http://www.comspacewatch.com/news/viewnews.html?id=997

 

Each Progress resupply mission carries abvout 2400 hours(100 days) consumables for the ISS.

 

A Progress rocket carries abou 2 tons(2000 kilograms) of supplies four times a year to the ISS or about 8-10 tons for a crew of three for one year in near earth orbit. A useful lunar base(thirty personnel) would require about 100 tons of supply for sustainment. That does not include subsequent base expansion, the components for brute force building a lunar site based recycling capacity etc. just to dump an Earth launched system of shelters for a five man mission for three months well exceeds the 100 tons postulated.

 

It makes more sense to build the infrastructure first robotically in situ, then send the men.

 

My estimates may be off by one factor, but given that we have never done this before, I am betting my estimates are not pessimistics when it comes to our robotics capabilities and may be wildly optiimistic when it comes to our manned capability!

 

Damocles

[nkt]

Actually, I was working on the assumption that we use a robotic front line to start the building, then move a couple of people up there once things were nearly ready. As the base expands, more people could go up.

 

NASA seems to be very confident that large amounts of breathable air can be obtained from the regolith, so little extra would be needed once a system was in place. Pressure tanks might be heavy and hard to move up there, but they are much lighter if they are almost empty (or full of vacuum, as it were!)

 

It makes more sense to build the infrastructure first robotically in situ, then send the men.

Yes. I just think there will be a lot of things that won't work robotically, so having someone there to do the tricky bits will be essential, even if it is just to operate the robots without a time delay, or go out and plug them into the charger if a battery dies suddenly.

[UncleAl]

I'm not sure where you get 100,000 kilos nor 100 launches from. 100 tonnes is more than enough for a bootstrapping colony. Your low estimate of ten tonnes is too low, though.

We already have lunar bases, complete with pressure hatches in the toilets. They are called "nuclear submarines." Replace the propulsion plant volume with water storage and you have your breathing air through electrolysis. 6-12 months operation between resupplies is perfectly reasonable.

 

Three augmented Saturn V launches is a permanent lunar base :

 

1) Boost a modified NR-1 nuclear sub and miscellaneous supplies into Earth orbit (400 tonnes fully loaded with a crew of 12. That leaves you 300 more tonnes booster capacity for more supplies or for an emergency trip home vehicle).

 

2) Boost a year or more of supplies, consummables, spare parts, and construction equipment. Cover your butt. Doing it over costs more than doing it right the first time.

 

3) Boost the thruster packages for lunar insertion and landing. Assemble and get on with it.

 

4) The whole thing costs less than the Space Scuttle program to date.

 

There is no reason to use a large /_v orbit to ship the hardware. Have it economially arrive. Fast boost human meat through the van Allen radiation belts as with Apollo. Proceed from there. No Space Scuttle. The human meat ships in cheap disposable capsules.

 

If you add solar panels the nuclear reactor only works half time. (Batteries? waste of mass and high on maintenance.) That suggests one or two central power bases and lots of peripheral settlements. Long distance electrical wiring is easy - drop uninsulated conductors onto the surface. Use a berm of local dirt to keep them separated.

 

Cheap, easy, proven, and off-the-shelf. We now have a permanent lunar base staffed with 10-100 folks in 1-10 buried huts. What will we do with it all? (Studies!)

 

Oh yeah... blackwater. Dig a big deep hole at the edge of the base and pump sewage in it when things are cold during the 14-day night. Garbage goes into the same hole. The surface area of the moon is 37.8 million km^2 or Africa plus Australia, or all of North America plus Europe. Lots of room.

[CraigD]

...-what kind of launch vehicle would you use in place of the shuttle?

A leased Shenzhou/Long March.

-would you use expendable boosters or try for a totally reuseable system?

N.A., when you’re buying “commercial off-the-shelf”.

-what would you like to see as the ultimate near term goal for manned spaceflight for the replacement vehicle?

As with any COTS system, whatever the system could do.

How would you justify the investment in a new launch vehicle to the average taxpayer?

I’d use a lot Adam Smith-like buzz phrases about free trade and lowest bidder, and bank on the assumption that the average taxpayer has already been conditioned by the nation-of-origin stickers on the cloths he wears, the TV he watches, and the flag he flies on his front porch to assume that these phrases are synonyms for “buy Chinese”.

 

:rant: That wasn’t really me writing – perhaps it was the channeled spirit of a turn-of-the-90 or 00s, inside-the-beltway economist. Seriously, the average taxpayer may be fine with buying cheap American flags from the PRC, but might have some misgivings about an imported national space program. Not to mention the big and small US aerospace companies, and the US Congress.

 

The real me is a politically and economically oblivious techie who isn’t happy unless I’ve redesigned at least one perfectly adequate system each day before breakfast. That person would like the US’s next manned spaceflight system to embody the most avant-garde engineering available (which can be taken essentially verbatim from the books and essays of he late Robert Forward), something like the following:

• A non-rocket to-orbit system, such as a miniature “space fountain”,
  
• OR an antimatter rocket
  
• 100% reusable
  
• Powered reentry
  

Anything like this would be so fantastically expensive that I couldn’t even begin to estimate its cost to within a couple factors of 2 (I’ve a track record of failing to accurately estimate the costs of projects in the $.5 – 1.5M range, and suspect I’d only do worse with larger ones). It would just have to count on the political and P.R might of the several generations of Star Trek fans, perhaps a vast cabal of them seeded throughout the US government and media. :hyper:

[alxian]

space elevator.

 

direct link to space without explosives.

 

mag-lev all the way to space.

 

the system can be powered from space by solar power, if there is enough excess, that power can be pumped into the local power grid.

[damocles]

Replies to various from Damocles.

 

First, nobody has solved the heat dumping problem for a large fission reactor in space. We use water chiller convection cooling for nuclear reactors on Earth. Despite this I believe a heat radiator system using a circulation fluid could work in space. It is heavy.

 

Second, We CANNOT build Saturn 5's anymore. We would have to build new heavy lift boosters from SSTS components(Space Shuttle engines, SRBs, fuel tanks etc). That would be as expensive, as designing new, so take your pick. Either discreditted 1970's systems or try for something different?

 

Third. has anyone considered what the SIZE of a LINAC launcher powerful enough to put useful payload(10 tons) into LEO would be? The atmospheric shockwave is a tertiary consideration. The heat loading that you have to deal with and the electrical requirements are insane by our current realistic technical capabilities.

 

Fourth, we cannot use atomics to launch(treaty) anything.

 

Fifth, do we have the materials to build a beanstalk?

 

I would suggest that if we had to scrap plans for the SCRAMJET for the moment because we coiuldn't solve the engine cooling problems that we would have problems with 1, 3, and 5. Option 2 is doable if you have the political will. Option 4(ORION) is prohibited, though a ground based MASER induced pulsed detonation rocket might be a treaty dodge?

 

Damocles

[CraigD]

… has anyone considered what the SIZE of a LINAC launcher powerful enough to put useful payload(10 tons) into LEO would be? The atmospheric shockwave is a tertiary consideration. The heat loading that you have to deal with and the electrical requirements are insane by our current realistic technical capabilities.

It’s been pretty extensively considered.

 

The electrical power requirements would be extreme, but reasonable achievable using conventional electrical generation and storage technology.

 

The physical size is another matter. To avoid staggering losses due to friction, and the attending staggering heat, many designs propose some sort of immense, vacuum-filled tube reaching above the dense lower atmosphere - “100 kilometers or so”. IMHO, this is an insurmountable near-term materiel engineering challenge, worse than the problem it solves.

 

The “space fountain,” on of my pet ideas, shares this need, though its more modest power requirements makes the alternative of putting its base on some sort of high-altitude aircraft more feasible.

[alxian]

Fifth, do we have the materials to build a beanstalk?

 

surely

 

but for now we are creating a space station. you have to have somewhere to go before you build roads to it.

 

 

once ISS is built and running the international community can build a beanstalk.

 

before they do they have to think about a politically impartial place to put it. even though technically it would be a satelite it would be owned and operated by one country. none have the resources to build one. least of all the US. no other countries believe in the technique.

 

if the shuttle fails but our faith in space doesn't the US will have to seriously consider jointly building a beanstalk with the help of JA and china, perhaps in california?

 

even so as the russians are fond of saying its easier to get to space than to the states. meaning each country that needs surface to orbit capabilties will have to have their own.

 

canada and the US would have one, europe would have one and china SK and JA would have to share one.

 

we have the tools and the techniques but lack the practice. judging by the US' recent track record they'd leave it up to us to design and build it while they buy it and control it.

[BlameTheEx]

CraigD

 

"100 kilometres or so" elevation is desirable rather than necessary. The air drag it dependent on streamlining. Presumably a missile long enough, streamlined enough and with sufficient extra velocity would punch through. The direction of launch needed is almost horizontal. Launch could be totally horizontal if the missile used the air to turn like a plane does using flaps.

 

Shape the missile just right, fill the pipe with an oxgen/hydrogen mix and most of the boost can be via a ramjet effect. Most of the booster is now just a simple passive pipe lying on the ground. Rather long perhaps but no worse a project than many a motorway.

 

Nor does the contraption have to be quite so immense. It is all about the allowable acceleration. The higher the acceleration the shorter the launcher. Something in the order of 250km (that's about 40G) is necessary for launching humans without collapsing their lungs (presuming they were breathing air and not an oxygenated fluid), but humans are a very small part of the total payload into space. They could still go by rocket.

[damocles]

Again, replies to various by Damocles.

 

About that beanstalk?

 

Its been a while since I looked at it but I remember these considerations.

 

You have to park a countermass in geosynchronous orbit and move it out radially as you extrude a cable(stalk) from it toward the surface of the Earth. The only surface anchor points feasible for "landing" the Earth end of the beanstalk would be in the plane of Earth's rotation(equator).

 

I roughly remember the following details.

-that countermass required a material two times stronger than our best carbon nano-tube fibers which were/are at the moment laboratory curiousities.

-the countermass would probably be in the form of an extruded cable from the geosynchronous midpoint and would easily exceed twenty thousand tons(metric), so double that mass for a tapered stalk at least seventy thousand kilometers in length.

-rotational retardation would put a centripetal force vector on whatever we built so radian length velocity along the length of the stalk would be a serious and deadly engineering problem.(Think of a mouse on a phonograph record travelling at a constant 45 rpm. What? you never put a mouse on a spinning phonograph record?)

 

About the LINAC launcher.

 

The simplest LINAC launcher is a rail-gun. You apply a charge across the two parallel rails through the projectile to produce what in effect is a linear induction motor. Terrific; except that you have some problems. First placing a current through the projectile means you charge both rails with a like charge and that tends to bend the rails apart. Second there is the heat of electrical current impedence. Third there is the severe magnetic distortion effect on the projectile, itself, and finally there is the unknown local effect of such a current discharge, should it by some mischance find an atmospheric ground path(It would make a lightning strike look like a minor spark.).

 

About the rocket tube?

 

Using an oxygen/hydrogen filled tube launcher with a ramjet projectile gives you the world's largest flame thrower/rocket motor until the ramjet-powered projectile becomes a deformed molten blob in the tube at which instant you have a burst tube and a decided disaster at the breached section that would resemble an oil refinery fire at the minimum, until you shut off the oxygen supply.

 

About the beam riding rocket?

 

It sounds to me like that ground based MASER induced pulse detonation rocket, while crazy, is actually a workable scheme. With this scheme, the rocket rides a laser or maser beam into orbit. Its basically an Orion without the fission bombs providing the pulse detonations. That, instead, is provided by the ablation or detonation of the propellant mass against a base plate by the laser/maser; which since it is ground based won't add to the mass of the projectile. It certainly is treaty compliant and is two orders of magnitude simpler from an engineering nightmare point of view than some of the other schemes.

[UncleAl]

once ISS is built and running the international community can build a beanstalk.

That is a bunch of crap. A beanstalk must pin to geosynchrous orbit. A straight line path is not the minimum energy path. A beanstalk must be a dielectric, for an electrical conductor cutting through the Earth's billowing magnetosphere will drive multi-million volt potentials. There is no material known, suspected, or hallucinated that can support its own weight plus tensile stresses in a beanstalk.

 

Assume ten lbs/foot average weight for a beanstalk. That is a very modest girder whether built of Kevlar, Spectra, M5, or diamond fiber. 23,500 miles of it sum to 620,000 tons. Price the manufacture of 600,000 tons of Kevlar (that is not nearly strong enough to do the job) . Eeach Space Scuttle launch costs $800 million, it has a cargo capacity of no more than 20 tons, and it cannot go higher than 300 miles altitude.

 

Now, go build your beanstalk.

[BlameTheEx]

damocles

 

About the LINAC launcher.

 

Why on earth use the simplest launcher if it wont work? - Not that it doesn't. The US military have had technical success with short rail guns. A longer much lower G rail gun suitable for launching payloads into space can only be easier. Speeds are built up over kilometres rather than meters. The force per Kg of payload required is much lower, it just goes on for longer.

Anyway there are alternatives. How about using a magnetic accelerator? If the capsule contained a superconductor magnet then there is no electrical resistance and no heating. Problem solved!

 

About the rocket tube.

 

Why are you convinced that the heat problems would be insurmountable? Scramjets are much the same sort of problem as rocket motors. I'm not sure why you bring in the word "flame-thrower". The missile travels down the pipe. In front is Oxygen/Hyrogen mix. Behind is very hot water vapour. It is no more or less of a flame thrower than a rocket motor. Are you suggesting that the flame will precede a hypersonic missile?

 

If all went wrong you would get an explosion of fuel comparable to that of a rocket disaster - but the good thing is you get that explosion stretched out over, say, 100 kilometres of pipe. No more force on the pipe than a successful launch. In fact rather lower as the front of the explosion would not travel as fast as the missile is meant to. The explosion would actually be more gentle than a successful launch!

[damocles]

damocles

 

About the LINAC launcher.

 

Why on earth use the simplest launcher if it wont work? - Not that it doesn't. The US military have had technical success with short rail guns. A longer much lower G rail gun suitable for launching payloads into space can only be easier. Speeds are built up over kilometres rather than meters. The force per Kg of payload required is much lower, it just goes on for longer.

Anyway there are alternatives. How about using a magnetic accelerator? If the capsule contained a superconductor magnet then there is no electrical resistance and no heating. Problem solved!

 

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.).

 

About the rocket tube.

 

Why are you convinced that the heat problems would be insurmountable? Scramjets are much the same sort of problem as rocket motors. I'm not sure why you bring in the word "flame-thrower". The missile travels down the pipe. In front is Oxygen/Hyrogen mix. Behind is very hot water vapour. It is no more or less of a flame thrower than a rocket motor. Are you suggesting that the flame will precede a hypersonic missile?

 

If all went wrong you would get an explosion of fuel comparable to that of a rocket disaster - but the good thing is you get that explosion stretched out over, say, 100 kilometres of pipe. No more force on the pipe than a successful launch. In fact rather lower as the front of the explosion would not travel as fast as the missile is meant to. The explosion would actually be more gentle than a successful launch!

 

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.