Half a croissant, on a plate, with a sign in front of it saying '50c'
h a l f b a k e r y
Ceci n'est pas une idée.

idea: add, search, annotate, link, view, overview, recent, by name, random

meta: news, help, about, links, report a problem

account: browse anonymously, or get an account and write.

user:
pass:
register,


                                                                                             

Rockeloonannon

Rockeloon launching a cannon which fires the satelite to orbit
  (+4, -2)
(+4, -2)
  [vote for,
against]

The challenge (see link) is to get a tiny satellite to orbit for cheap. This I break down to several smaller steps: 1. start as close to space as you can using cheap hydrogen filled balloons. 2. Use cheap off the shelf model rocket engines to boost the payload up to 200km altitude and 7km/s. 3. Transmit signal to prove orbit was achieved.

1. Start with multiple surplus weather balloons filled with hydrogen. Even at the optimistic altitude of 52km, the rocket will still have to be launched nearly vertically and slightly east to climb to the 200km LEO we need. 2. The rocket will be a massively staged rocket burning G class model rocket motors (link) in carbon fiber tubing and shedding casing as it goes. Since the rocket starts at an altitude almost devoid of atmosphere it cannot rely on fins for stabilization, so it will have to shift its center of mass to alter its course during thrust. This will not be easy as nearly all of the mass is in the form of engines waiting to burn, so the shift will be accomplished by curving the entire rocket piezoelectronically. The first part of launch will be controlled by a onboard computer that computes position inertially based on an accellerometer and a tiny gyroscope. That will be left behind once the correct altitude and angle are reached for final LEO insertion. Then, just the satellite will be fired into orbit using the last of the rocket tube for a barrel. 3. The satellite will consist of a 20g mylar radar reflector (3 circles on each plane) with a thin tube on the outer edges which has just enough gas to inflate them in vacuum to flatten the reflectors to catch sunlight.

MisterQED, Feb 21 2008

N-Prize Idea N-Prize
[MisterQED, Feb 21 2008]

G Class Engine Supplier http://www.apogeero...aerotech_motors.asp
$20 per 105N/s Impulse [MisterQED, Feb 21 2008]

High Altitude Balloons http://www.aerostar...titude_balloons.htm
[MisterQED, Feb 21 2008]

Into orbit into_20orbit
First incarnation of this concept on the HB. [bungston, Feb 21 2008]

LTA rocket assist. LTA_20_2b_20rocket_20for_20SSTO
Second incarnation. Has the term "Rockoon" in lurch anno. [bungston, Feb 21 2008]

Aerotech G69N engine http://www.rocketry...ntent/view/1758/95/
[MisterQED, Feb 24 2008]

Attacking Space like Everest http://groups.googl...t-a-staged-approach
[MisterQED, Jun 26 2008]

Regulation Discussion Link http://groups.googl...ad/a711f9482ff1f571
[MisterQED, Jun 26 2008]

(?) J. P. Aerospace www.jpaerospace.com
They have a lot of high altitude balloon experience... [mylodon, Sep 14 2008]

NASA kiddie calculations for 90km balloon http://www.lerc.nas...a_high_altitude.htm
How big must a balloon be to nearly make it to space? [mylodon, Sep 14 2008]

Fastest Gun in the 2001 World! http://www.sandia.g...el/NR2001/flyer.htm
Place this on the above balloon, and you are set. [mylodon, Sep 15 2008]

[link]






       Hmmm. Well, the site will be open for registration fairly soon.   

       However, I'm not 101% convinced. I suspect that weather balloons will not cope with the range of pressures involved - might be better with a zero- pressure balloon (essentially an inverted bag filled with gas, which will accommodate enormous expansion).   

       What's the energy available from solid model rockets engines?   

       Finally, by my reckoning, the kinetic energy needed for orbit is much more than the potential energy needed to get to altitude - will you get your satellite up to 7km/s?   

       Incidentally, we only need about 150km, I think - I'm not sure how stable an orbit will be at that altitude, but I think it'll be OK for a number of orbits.   

       Regarding guidance, the body-bending is ingenious but, if you're going to have a gyro, why not use it in a more direct way?   

       I think we need [lurch] here.
MaxwellBuchanan, Feb 21 2008
  

       I agree, all good points. I’m still looking for rocket formulas. I’ll break out my physics books tonight. I did a quick back of the envelope calculation based on Impulse = M * dV taking mass as the rocket as the weight when half the fuel was burned, put in an unrealistically low weight for the casing and got past 4km/s after only six stages! I have to play with pyramid stages, etc. Basically, I wanted to find out if this was possible, or doomed like the cannon launch idea and where the real problems are. The problems are mostly mass. An extra gram or two especially in repeated parts like the motor casings are a killer. I like these motors because they are cheap and they are made for DIY assembly which leaves open the possibility of saving weight on the casings by making the rocket the casing or something. Sadly they don’t ship overseas, so you’ll have to find your own supplier if you like the final plan.   

       I haven’t found a good place to buy balloons. I’ll try Googling zero pressure balloons, that was the idea I was looking for all along. They had the show about the high altitude balloon lifted telescope last night, and that balloon looked too big, but the right design. All the ones I have found are latex which even if I use lots of under inflated ones, will shatter at the temps at altitude.   

       I’m also not sure about the whole cannon shot at the end, but I still think it is more energy efficient than reaction thrust at the end. The explosion would have to be H2/O2 to get the kind of speed to make it worth while. The rockets will actually have less and less contribution as the speeds rise. I included it because it has a nice planes/trains and automobiles feel. First a balloon, then a rocket and then a cannon, then, then, then, a solar sail! I mean this is the Halfbakery.
MisterQED, Feb 21 2008
  

       "Then, just the satellite will be fired into orbit using the last of the rocket tube for a barrel."
Is that under thrust? Otherwise you'll just be kicking back on the cannon, no?
phoenix, Feb 22 2008
  

       Yes, it will kick back on the cannon, but even assuming the lightest of barrel material, the rocket will significantly out weigh the satellite. And for best performance I need to wait until the rockets have given all they can and then fire the satellite. Then the satellite will in effect fire the rocket for reaction mass. This is actually a good thing in that the rocket will not be anywhere near orbital speed and can reenter or burn up and the final mass that needs to be accelerated will be as light as possible.
MisterQED, Feb 22 2008
  

       Another thing you're going to want to look at is a critter called the "boosted dart". Google it, but I'll summarize. A rocket was set up with the "dart" on the nose. The rocket is the thrower, the dart is not powered. The rocket went to 25km altitude; the dart "coasted" up to 70 km. It all has to do with mass and air resistance.   

       It's tempting to think that at some point in space you are above all the air, but in reality, it just gradually gets less and less dense. I think the scenario you're running into would be akin to driving your car (booster stage) up to its max velocity, then hurling a ping-pong ball out of the window in the direction of travel. Obviously that would be an exaggeration, but it does illustrate the point.   

       My thought is that the very last stage should be of the same diameter as your satellite (as small as possible), but once you've boosted the mass, don't throw away the momentum. The extra length can also be a very nice place to mount antennae.
lurch, Feb 23 2008
  

       //A rocket was set up with the "dart" on the nose. The rocket is the thrower, the dart is not powered. //
Sounds like a sabot round.
AbsintheWithoutLeave, Feb 23 2008
  

       //It's tempting to think that at some point in space you are above all the air, but in reality//   

       Quite so. But, at 50km up (the upper limit of a balloon), the atmospheric density is roughly 1/500th of that at ground level.   

       Now, roughly speaking, atmospheric drag is proportional to the density of the fluid and to the square of the velocity. So, for a given amount of power, an object can travel roughly 22 times (square root of 500) faster at 50km than it can at ground level. So, if you wanted to maintain orbital velocity at 50km, you'd need roughly the same amount of power that you'd need to travel at about 1100km/h (700mph) at sea level. Of course, by the time you get up to 100km altitude, the air density is one 250,000th that at sea level, and the power you'd need to maintain orbital velocity is the same as you'd need to maintian 50km/h at ground level. At 150km altitude, the power drops to that needed to maintain a speed of about 2km/h at sea level.   

       Incidentally, at low earth orbit (150km), you pass through as much atmosphere in the course of 1 complete orbit as you would in passing through 30cm of air at ground level. So, in completing 99 orbits, our satellite has to push its way through the equivalent of about 30 metres of "ground level" air, at a speed of 7km/s. It's thin on top.
MaxwellBuchanan, Feb 23 2008
  

       //by the time you get up to 100km altitude, the air density is one 250,000th that at sea level, and the power you'd need to maintain orbital velocity is the same as you'd need to maintian 50km/h at ground level.//   

       True. And yet, at 120 km is where a re-entering spacecraft becomes enveloped in a blazing incandescent sheath of ionized air.
lurch, Feb 23 2008
  

       Indeed they do, but are they not typically travelling at much more than 7km/s?   

       150km is normally given as the lowest fairly-stable orbit. However, lower orbits clearly don't decay instantly. I guess I ought to go and some maths to figure out if you could make 99 orbits at (say) 130km.
MaxwellBuchanan, Feb 23 2008
  

       //boosted dart//, not exactly what I think we need. The boosted dart had the advantage of superior aerodynamics to increase the coasting distance over other final stages.   

       What I am talking about is making the top of the rocket a extremely light weight large caliber rifle that fires the satellite up to orbital speed pushed on the shock wave of a high explosive charge. Like a bullet out of a rifle, except the charge is C4, the bullet is a 20g satellite and the barrel is a tube made from layers of spiral wrapped Dyneema threads in just enough resin to hold it together for one shot.   

       Now we use the balloon to lift our launch platform to 50km, then a launch a multistage rocket that climbs to 200km and a 4km/s and levels off and fires the satellite at 3km/s into a nice stabile orbit. The launcher decelerates and reenters the atmosphere.   

       I think this setup will weigh less than the extra stages needed to accelerate up to orbital velocity. The problem is the satellite must have the strength to survive the ride. THat is why I went with the relatively stupid self inflating mirror.   

       PS [MB] You just said 99 orbits, but your profile says 9 orbits. Which is it?
MisterQED, Feb 23 2008
  

       Well, sounds OK to me as long as everything happens at the right time.   

       Re the 9 vs 99 orbits: the original post was 99 orbits, but I'm reducing it to 9 in the competition (I think).
MaxwellBuchanan, Feb 24 2008
  

       We need a small cheap inertial guidance system and I think I found one in my Wii remote. They contain gyroscopes and accelerometers, so all you have to do is configure an interface between them and a stamp computer. I think it's going to be tough top beat at only $40.
MisterQED, Feb 24 2008
  

       As someone who is unlikely to get a chance to compete, may I suggest that the final acceleration stage is most likely to be achieved with an EFP?   

       -WARNING - watch out searching for the term EFP as a latge % of the use of them is by terrorists, the remainder being "genuine" millitary application -- </W>   

       If you want ~20 grams going a really high speed, look at modifying an EFP to be the final stage in launching your load. An EFP weighing in at maybe 3kg can launch a >1kg mass at over 4km/s relative. That's a hell of a final boost. I'd say you could modify the paylaod of the EFP to have your package at the front, with a small bursting charge for separation once in orbit. Modern EFP's can be within several minute-of-angle accuracy <some testing required>.   

       My guess would be a balloon, with a 1 or 2 stage rocket, with the final payload being an EFP with your package on the tip. making your hardware capable of handling the millions of G's is your problem.   

       --Just my 2c's-- I may move this to the original thread, yet.
Custardguts, Feb 24 2008
  

       One more note on engines: the legal limit (US, though probably other places also) for rocket engines without licenses is 65g of propellant. My new favorite engine is the legal limit engine from Aerotech the "G69N" with 137N/s impulse (link). Again $20 per reload, but you have to have the cartridge to put them in. Basically it produces 20lbs of thrust for 1.5s. There is also a G80T motor of the same thrust in a preassembled format and lighter total weight, but I am assuming that I can make a titanium or Aramid fiber case which is lighter than the phenolic they are using.
MisterQED, Feb 24 2008
  

       I'm reminded of the small-scale mass driver the Princeton students built for Gerard O'neill back in the '70s. Don't know what theirs cost, but if this is for the n-prize you might be able to cover the cost of the mass driver under 'launch facility' rather than launch vehicle.
Moonguy, Jun 26 2008
  

       Any links, Moonguy?
MaxwellBuchanan, Jun 26 2008
  

       I debated using any of the electromagnetic launch systems instead of a cannon, but the electronic energy storage technology doesn't exist yet that can hold a candle to the amount of energy you could do with HE or even standard explosives on a mass comparison basis. I was dreaming of a system that could focus a supersonic explosion to create a hypersonic shockwave to push the satelite up to LEO insertion speed. And the lighter the cannon, the better the decelleration for re-entry.
MisterQED, Jun 26 2008
  

       I am thinking about laws. Could one sidestep all of the rocket motor stuff / air lanes regulations etc by going out into international waters and launching from a boat? It would be nice and dark out there too, for watching via telescope.
bungston, Jun 26 2008
  

       If you go over to N-prize you can see my thoughts on this, which is that the boat solves a lot of issues such as launching a large balloon in windy conditions, just turn the boat down wind to launch in artificial calm. I guess you could do the same with a truck in a salt flat.   

       On the legal side they said that US citizen's are always bound by US federal laws, no matter where they are, so my plan of launching from international waters would just delay the inevitable. They are presently gathering the US teams together to apply for permits for launching.
MisterQED, Jun 26 2008
  

       //look at modifying an EFP to be the final stage in launching your load. An EFP weighing in at maybe 3kg can launch a >1kg mass //
<rubs chin>A multi-stage EFP...hhmm </rc>
AbsintheWithoutLeave, Jun 26 2008
  

       Yes, but that would most likely emulate the rocket, so that's why I thought to go with a smaller more directed charge. Also the cannon drops the G forces down from nearly infinity to something that might be survivable by an electronic device.
MisterQED, Jun 26 2008
  

       //US citizen's are always bound by US federal laws//   

       So, what if someone was born in international waters, in an aircraft over an ocean or in Antarctica?   

       Sorry, i'll say something more serious next time. What i'm getting at is that we're not all American, and some people here might be governed by different laws. Does that apply to us Brits, for example? What about Sealand or another custom-built microstate designed solely for space launches? Maybe near the equator?
nineteenthly, Jun 26 2008
  

       Yes for the Brits, as they seemed to have signed the same treaty, but those were the only two countries that were discussed. I'll put in a link to the discussion.
MisterQED, Jun 26 2008
  

       /Now, roughly speaking, atmospheric drag is proportional to the density of the fluid and to the square of the velocity. So, for a given amount of power, an object can travel roughly 22 times (square root of 500) faster at 50km than it can at ground level.   

       .../   

       As power required is proportional to the cube of velocity (force is proportional to the square), a given amount of power will propel you 8 times faster (cube root of 500) at 50km than at ground level.
Texticle, Jun 26 2008
  

       A thought: instead of one spherical balloon, how about two cylindrical (zepplin-shaped) balloons with a pplatform between them. this would be the mounting for the cannon. You know the rest. . .
Moonguy, Jun 27 2008
  

       This is now being built by Team Prometheus with the slight modification that the cannon part is now a Light Gas Gun. The only problem we are having is finding a satellite that will survive the 1,000,000G launch. We are also looking for more team members. Come join the insanity.
MisterQED, Sep 14 2008
  

       [moonguy] Check out JP Aerospace's plans for tandem ballon, rocket launch platforms.   

       (see link)
mylodon, Sep 14 2008
  

       I have been thinking about toroidal balloons. On the plane (if such a thing existed for the torus), the center of gravity is the co-center of the inner and outer diameters. Another adv. is that shear forces (winds) will act on the entire torus and not the x number of balloons providing lift. This may be of help orienting the launch mechanisms.   

       Another phenomenon I would like to take advantage of ,is that old acorn: "Hubcap overtaking the vehicle" effect.   

       Although, at the end of the day, I would really like to see some form of [Vernon]'s vacuum balloon taking the prize.
4whom, Sep 14 2008
  

       Can anyone think of anything that can survive 1,000,000G? I'm imagining a sphere of, say, steel weighing 20 grams and being accelerated at 1,000,000G by a gas gun (so, I'm assuming the gas pressure will act on one hemisphere of the sphere).   

       In this case, to take a simplistic view, the distal (non-acted-upon-by-the- gun) half of the sphere will act as a sort of dead weight on the proximal half. At a million G's, the distal half of the sphere exerts a force on the proximal half equivalent to 10 million grams, or 10 tons, spread over an area of maybe one square centimetre.   

       Actually, when you think of it like that, it's not totally unreasonable. I guess that local forces will be greatest close to the back of the sphere (I mean, close to the part which is pointing towards the breech of the gas gun), but they're still not *that* outlandish.   

       The secret must be to make the projectile solid, and of as uniform a density as possible.
MaxwellBuchanan, Sep 14 2008
  

       The single sphere is the only workable shape for the balloon as it minimizes the weight of the envelope material. No other shape is really necessary for any orbital attempt as so much easterly speed in needed that angled launches are useful from any decent altitude and any vertical launch would place the seriously fragile balloon too close to the rocket exhaust.
MisterQED, Sep 14 2008
  

       This is probably impractical, but what about fine dust which assembles after being launched? Each speck of dust would be relatively strong, a cloud of them could be squirted out, then they could be electrostatically pulled together into a sphere. Or maybe a liquid projectile that then freezes or dries into a solid object after ejection?
nineteenthly, Sep 14 2008
  

       I don't think a liquid projectile will help you, but no reason (I guess) why a powder couldn't be used, if you can persuade to to aggregate. Problem is, you've still got to detect it, post-aggregation, and I'm not sure how you'd managise that.
MaxwellBuchanan, Sep 14 2008
  

       You need an orbital 3D printer. Fire vaporized rubber and plastic into a collection bell facing earthwards. It then produces superballs, toy ponies, etc, which it then drops all over the world to the delight of children everywhere.   

       It could be called Santallite.
mylodon, Sep 15 2008
  

       Wouldn't they be a bit vapourised?
nineteenthly, Sep 15 2008
  

       Need to do what Santa does, give them each a small ablative re-entry cone and a small parachute.   

       I don't know about powders. The forces are just outside of my rational experience. A million Gs will squeeze a lot of things into a solid. It's like putting something inside a drop forge. Maybe tiny magnetized ball bearings? I'm still hoping to elongate the barrel and drop it down to only several hundred thousand Gs.
MisterQED, Sep 15 2008
  
      
[annotate]
  


 

back: main index

business  computer  culture  fashion  food  halfbakery  home  other  product  public  science  sport  vehicle