h a l f b a k e r yI think this would be a great thing to not do.
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Build two giant airships – lash them together like a tri
marine with a central platform suspended between them
–
build a big catapult & bolt it to the centre platform
Of course when I say ‘catapult’ I’m really thinking of
some kind of faux rail gun powered by stored kinetic
energy, probably
compressed air (so a giant air rifle)
You're using a traditional airship design with a gas
compressor to reduce lift (works a bit like a fishes swim
bladder)
This puppies going to be big so we don’t want it going
hindenburg on us which means we’re probably using
helium
– which means for the same lift it needs to be a whole lot
bigger than the hindenburg, besides which we want a lot
more lift than that anyway as conservatively speaking it
needs to get something as heavy as a half size space
shuttle as high as you can go & then has to have enough
lift to absorb the downward thrust of the catapult
without
losing altitude (causing a loss of upward thrust from the
catapult)
Hmmm – hydrogen will get you higher than helium
anyway
won’t it – maybe we’ll just have to risk it
What was that guy who did the high altitude parachute
jump using in his balloon?
Once you reach maximum altitude you use the catapult
to
launch your shuttle toward space & it ignites its engines
at
the zenith of the arc thus imparted
The airship returns to earth by compressing some of its
gas to lose lift – probably using solar panel powered
electric
motors (the whole point is to cut back the fuel
requirements necessary to achieve escape velocity as
much as possible after all) to pick up a new payload (a
fresh shuttle) & get the catapult reset
Anyone know precisely how close to space you can get
with
hydrogen & helium balloons respectively?
Hopefully we can get high enough to launch small
payloads to escape velocity with a big catapult alone if
we design it with modern materials & engineering
As for re-entry, I’d hope for something with sufficient
wingspan to weight ratio for un-powered gliding once it
reaches adequate air density (of course a wingspan like
that wouldn’t survive traditional re-entry so they
probably need to be retractable) though it might be nice
to have a small onboard atmosphere engine for powered
flight if needed (an electric solar power / alcohol fuel
hybrid engine maybe with a propeller or air turbine
perhaps – we could even have the air turbine reversible
so it generates power from the airflow in the early stage
of decent after it’s re-entered the atmosphere which
can be used to power it when it reaches lower altitudes)
Rockoon 1949...
http://en.wikipedia.org/wiki/Rockoon
[not_morrison_rm, May 31 2014]
Rocket Launch From Balloon
http://www.youtube....watch?v=WfJNNXTt85Q
[Skewed, Jul 06 2014]
NASA Proposal
https://space-acade...sted-launch-system/
[Skewed, Jul 06 2014]
[link]
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Rockoon. Sorry, a lot of this has been covered.... |
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I don't think any amount of lift is going to help resist the thrust of a
catapult. The inertia of the aircraft is all you get, unless you rig a
recoilless of some sort. If you have lift in hand, use it to gain more
altitude. You'll get more altitude with a lighter load and craft, of
course. |
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Firing the rocket at the top of the arc is definitely wrong. It's
complicated, but you want to burn up all the fuel as early in the climb
as possible, so you'll want to fire the rocket as soon as it clears the
balloon. |
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Getting up to altitude is nice, but getting up to orbital velocity is the
trick. If you made this bad-boy balloon work, you'd have saved about
one-tenth of the fuel of a ground launch. |
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As has been said, the Rockoon was done. But it only worked for
sounding rockets, which went straight up, not into orbit. |
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One-tenth, is that all, a disappointingly small return
for the effort. |
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I'm almost inclined to scrap the idea & go back to
NASA's old nuclear bomblets & a recoil plate plan! |
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Sod the fallout & international treaties I want escape
velocity :) |
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Well, if you want escape velocity, you don't need the sideways orbital
business, but you will need about seven miles per second going
straight up. Which is more than orbital velocity. |
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If I was going to build a rockoon launch system, I'd make something
like the early Zeppelins. |
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Make a long launch tube---electric, gas or gunpowder---and use it
as the keel of the airship, with the gasbag around it. Take it up to
altitude, and go nose-up into a vertical climb with the engines racing,
then fire the launcher. |
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(Put the rocket in the middle of the launch tube for the trip up, and
slide it to the back when you want to go vertical.) |
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// If you made this bad-boy balloon work, you'd
have saved about one-tenth of the fuel of a
ground launch.// |
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That's true, except insofar as it isn't. If the rocket
is big, then it's approximately true. |
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But if the rocket is <<big, then a substantial part
of
the fuel is expended in overcoming air resistance.
The rockoon may only get you 1/3rd of the way to
space and 0/3rds of the speed of orbit, but it gets
you past 99% of the atmosphere. |
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As it happens, I'm about to have a drink with the
idiot who founded the N-Prize. I'll ask him about
this stuff. |
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Oh, I didn't see you come in; welcome to the 'bakery,
[Skewed]. |
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//go back to NASA's old nuclear bomblets & a recoil
plate plan// or as it's known at the 1/2 bakery "a
garden-variety Orion.." |
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// escape velocity / is more than orbital velocity. // |
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By definition. Orbit is, after all, a repeated failure to escape. |
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//Orbit is, after all, a repeated failure to escape. |
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Don't say that so loud..all the satellites will feel bad. |
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I did come up with a scheme, of more or less carbon-neutral launching, it was three extremely large hydrogen balloons attached to a triangular frame, with the (hydrogen/oxygen) rocket in the middle. |
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It would go aloft and the rocket would fire, then, bring the balloon platform back for another go. All it would need is electricity to power the h2o cracking and pumping of the gases. I'm sure I'd put it on here, but obviously not. |
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PS you could theoretically use a hydrogen/oxygen cannon to fire the satellite, but if it's recoilless you need to life twice the mass, if not, it's going to break the frame. |
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Didn't mean to pop this back up (I thought only anno's did that), was just adding a couple of links, clearly didn't Google this properly when I first put it up, you can blame [Buoyancy/thrust] & [Max] for making me look at this again. |
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//you'd have saved about one-tenth of the fuel of a ground launch// |
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[brain], the NSA proposal suggests 25%, & they're not using a compressed gas cannon from the balloon. |
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//a compressed gas cannon |
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I did once have this notion for using motorbike bits to make a shotgun-ish thing, using petrol and compressed air, then got told off that it wouldn't work, so maybe take a look at how successful that compressed gas cannon would be. |
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One problem does spring to mind, compressed gases need a heavy tank, which would up the weight. |
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One possible way to do this is Tacitus stylee, have a small tank which is full of compressed air/fuel, explode that in way that will compress the rest of the air/fuel, big piston, or shockwave...must be a way... |
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Further edit, realised I am re-inventing the wheel. A rocket burns some of the fuel to pump the rest of fuel, so get a pump, use one of them (blank) shotgun cartridges to kick start it, then use the pump to compress the rest of the gas/fuel. |
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//compressed gases need a heavy tank// |
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If you've seen (some) modern air rifles you might change your mind (a little) about the weight problem, recently held one of the same power as one I had when 12, considerably lighter than my old one (I know I said low-tech in the title but that's meant to refer to method not material). |
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<later edit> Besides, the heavier the cannon, the bigger the airships. |
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