What kind of launch vehicle for manned Spaceflight?

[CraigD]

Originally Posted by damocles

… 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]

Originally Posted by damocles

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.

[alxian]

beanstalks are not going to be built tomorrow. or probably not within the next 50 year. a proper estimate would be 75 years from now. problems of who owns them, who can use them, and who has the money to even build let alone maintain them will keep any such projects from being realized.

i especially appreciated 'materials hallucinated...'

like nanocrystaline diamond polymer cords (woven nanotubes) forming capillary like conduits liquid superconductive materials that also conduct light from microscopic silicon based lasers.. created in orbit from a sooty carbon compound sourced from near earth asteroids and carbon captured from carbon dioxide scrubbers of human inhabited space stations in orbit around earth.

but i wasn't thinking about kevlar per se, i was thinking most important would be a superconductive material, one that can take energy from its interaction with the earth magnetosphere as well as draw it from solar satelite to power ground stations that would then redistribute that power into a global power grid.

today carbon nanotubes are less than 1000$ a gram, or some mind boggling sum (~6.2992E+11x500$, plus or minus eleventibillion) for the ~620K tons of the complete beanstalk and its header station (pretty much a space station from which the beanstalk is grown down from orbit to surface) and footer station, once the beanstalk is complete you travel up and down in a maglev car or even something mechanical but the maglev would put less contact strain on the beastalk.

hopefully it would able to carry a bigger payload than the silly made-in-america shuttle craft or russian soyuz (or whatever they have cooking up if anything at all) or even a french or chinese reusable manned surface to orbit vehicle if they ever cook one up. you'd load up at the either end through the header or footer then launch skyward or plummet in near freefall. on the way back down the vehicle would convert kinetic energy from its interaction with the beanstalk, then use that energy to magnetically slow its decent when nearing the footer. in the case of an emergency the maglev car come-reentry vehicle should be able to detach from the beanstalk and slow its decent by conventional means (laser, chemical rockets, ion wind propulsion... etc).

all of which requires high technology and materials we don't currently have, yet. carbon nanotubes are getting cheaper to manufacture with promises of pennies per gram, making the beanstalk affordable at least for the construction materials, which more than likely would have to be lifted into space by conventional methods and spun earthward [from orbit] (unless the raw materials, mostly carbon, can be sourced off earth). we won't be building one soon but for the most part we have the plans to get it done.

in the meantime i'm partial also to linear magnetic acceleration of a venture star type vehicle, and have less faith in chemically propelled vehicles. the laser lightcraft would require far to much power to push something the size and weight of the space shuttle to escape velocity... if it ever got off the ground (or high launch platform suspended above a pit of high energy laser the kind nike might have used to tag the moon)(not really asking the question of how you could manage to spin such a huge mass [at 10k+rpm] on the outside (and maintain that spin for the duration of acceleration into orbit [while the inside doensn't spin, to keep the humans from becoming a sticky coating on the walls by the time they hit orbit] to gain gyroscopic stability before the laser even hit its thin skin, hurricain force wind? magnetic induction? as for isolating the manned capsule it would have to be either a very low viscocity liquid that can handle the heat from the laser and air spike) and too much could go wrong higher up in the atmosphere shifts in temperature and density of the air could change its refractivity thus shifting the lasers beam perhaps enough to knock the entire craftoff course, what if a bird partially blocks the beam? automatic power modulation would attempt to recover the beams intensity but it would be too easy to fry the passengers if the air spike is destabalized and collapses onto itself, then the laser hitting the wrong part of the hull potentially repturing it... barbecued astronaut fricassee...

[damocles]

"in the meantime i'm partial also to linear magnetic acceleration of a venture star type vehicle, and have less faith in chemically propelled vehicles. the laser lightcraft would require far to much power to push something the size and weight of the space shuttle to escape velocity... if it ever got off the ground (or high launch platform suspended above a pit of high energy laser the kind nike might have used to tag the moon)(not really asking the question of how you could manage to spin such a huge mass [at 10k+rpm] on the outside (and maintain that spin for the duration of acceleration into orbit [while the inside doensn't spin, to keep the humans from becoming a sticky coating on the walls by the time they hit orbit] to gain gyroscopic stability before the laser even hit its thin skin, hurricain force wind? magnetic induction? as for isolating the manned capsule it would have to be either a very low viscocity liquid that can handle the heat from the laser and air spike) and too much could go wrong higher up in the atmosphere shifts in temperature and density of the air could change its refractivity thus shifting the lasers beam perhaps enough to knock the entire craftoff course, what if a bird partially blocks the beam? automatic power modulation would attempt to recover the beams intensity but it would be too easy to fry the passengers if the air spike is destabalized and collapses onto itself, then the laser hitting the wrong part of the hull potentially repturing it... barbecued astronaut fricassee..."

alxian

I wonder that you believe that we cannot launch usable payload(20 tons) using a beam rising rocket?

We wouldn't be using the laser as the pusher.Instead the laser would be used to load heat into a propellant to cause gas expansion(the same thing we do when we mix oxidizer with a combustible). The heated propellant provides the thrust for an otherwise conventional rocket-propelled craft. Why would we have to spin the rocket ballistically like a whirlawhee under these conditions? Haven't we launched rockets for some forty plus years without spinning the vehicles like tops?

You have a better argument when yoiu talk about beam steerage and guidance aiming at the base plate nozzle of a pulse detonation rocket. However, even that is minor when you compare it to the engineering nightmares assoociated with a geosynchronous beanstalk or a mag-lev catapult designed to reach LEO.

An ablative copper base plated propellant package prevents friccasseed astronauts. A high mass propellant with suitable heat loading properties that provides suitable specific impulse when boiled to detonation is what is required for the reaction mass. It also(see rocket citation in previous post) handles the question of heat loading on the vehicle by confining the heat loading to the base of the vehicle-specifically the working fluid(propellant mass squirted out the vehicle base from the propellant package).

Now as to the shock that the crew would feel having a series of pulsed explosions going off under them? Springs and pistons. If our engineers weren't frightened of lofting a thousand ton manned payload into Earth orbit using a few fission bombs under a thick iron plate in the 1960s, why should we be frightened of launching a ten ton payload into Earth orbit using a ground based maser ignited pulse detonation rocket? The diference is that the payload needs a (re-usable) propellant package instead of a throwaway iron baseplate or expensive and twice as heavy(no oxidizer!) solid rocket motors . The propellant package falls into the ocean and is 100% recovered, packed full of new propellant mass and reused, until the copper base plate needs replating. It eventually could be cheaper than the shuttle to launch this way. Every kilogram you save on the pad in propellant wastage cuts the lofting costs by at least $8000.00 per kilogram in lofted payload costs. The real expense is in building the ground based maser. That contraption, all up, could cost a staggering five billion dollars.

Of course that contraption also has other ancillary uses......

[alxian]

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.