h a l f b a k e r yIt's as much a hovercraft as a pancake is a waffle.
add, search, annotate, link, view, overview, recent, by name, random
news, help, about, links, report a problem
browse anonymously,
or get an account
and write.
register,
|
|
|
Rockeloonannon
Rockeloon launching a cannon which fires the satelite to orbit | |
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.
N-Prize Idea
N-Prize
[MisterQED, Feb 22 2008]
G Class Engine Supplier
http://www.apogeero...aerotech_motors.asp
$20 per 105N/s Impulse [MisterQED, Feb 22 2008]
High Altitude Balloons
http://www.aerostar...titude_balloons.htm
[MisterQED, Feb 22 2008]
Into orbit
into_20orbit
First incarnation of this concept on the HB. [bungston, Feb 22 2008]
LTA rocket assist.
LTA_20_2b_20rocket_20for_20SSTO
Second incarnation. Has the term "Rockoon" in lurch anno. [bungston, Feb 22 2008]
Aerotech G69N engine
http://www.rocketry...ntent/view/1758/95/
[MisterQED, Feb 25 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 27 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]
This idea was linked to from a Worldbuilding.SE answer
https://worldbuildi...change.com/a/139906
I'm pretty sure I've read this idea before, but this inbound link is how I got here today. [notexactly, Feb 25 2019]
Inflatable Antenna Experiment Wikipedia article
https://en.wikipedi..._Antenna_Experiment
Mentioned in my anno [notexactly, Feb 25 2019]
Inflatable Antenna Experiment deployment video
https://youtu.be/CyWffZ5QjYw
Mentioned in my anno [notexactly, Feb 25 2019]
Inflatable Antenna Experiment deployment explanation
https://space.stackexchange.com/a/22967
Mentioned in my anno [notexactly, Feb 25 2019]
Project Echo Wikipedia article
http://en.wikipedia.org/wiki/Project_Echo
Mentioned in my anno [notexactly, Feb 25 2019]
Echo 1 & 2 inflation explanation
https://space.stackexchange.com/a/29549
Mentioned in my anno [notexactly, Feb 25 2019]
[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. |
|
| |
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. |
|
| |
"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? |
|
| |
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. |
|
| |
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. |
|
| |
//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. |
|
| |
//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. |
|
| |
//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. |
|
| |
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. |
|
| |
//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? |
|
| |
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). |
|
| |
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. |
|
| |
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. |
|
| |
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. |
|
| |
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. |
|
| |
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. |
|
| |
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. |
|
| |
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. |
|
| |
//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> |
|
| |
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. |
|
| |
//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? |
|
| |
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. |
|
| |
/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. |
|
| |
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. . . |
|
| |
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. |
|
| |
[moonguy] Check out JP Aerospace's plans for tandem ballon, rocket launch platforms. |
|
| |
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. |
|
| |
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. |
|
| |
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. |
|
| |
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? |
|
| |
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. |
|
| |
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. |
|
| |
Wouldn't they be a bit vapourised? |
|
| |
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. |
|
| |
// 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. // |
|
| |
I'm worried about trapped air between the motors. In vacuum, will it push the motors out of the
tube? Maybe put a small hole in the side of the tube between every pair of adjacent motors. |
|
| |
// 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. // |
|
| |
1. Catch sunlight? I was imagining the three discs as being mutually perpendicular and therefore
forming a retroreflector to be observed by Earth-based radar. I'm not sure how three circles
would be arranged to reflect sunlight to Earth in an optimal way. |
|
| |
2. Look at the Inflatable Antenna Experiment [links] to see how inflatable structure deployment
in orbit looks. The IAE wasn't actually supposed to deploy in the way it did, but being a soft
structure with internal pressure allowed it to achieve the desired shape anyway. I expect the
pressure would cause your satellite to rub on the inside of the barrel too much; I suggest some
kind of sabot. |
|
| |
3. "Just enough gas to inflate them in vacuum" is probably more than "the amount of gas left
after it's been folded and all the air is squeezed out". This was learned during Project Echo
[links], where the early satelloons were destroyed by this residual gas. For the successful Echo 1
and Echo 2, they had to deliberately put a bunch of holes in the envelope to enable gas to
escape. Then they put blocks of sublimating solid in as pressurant, which lasted weeks/months.
(Echo 2 was also designed to hold it shape after inflation, so it didn't have a sustainer pressurant
like Echo 1, just an inflator pressurant.) |
|
| |
One of the main goals of Project Echo was to create the
rarest satellite possible, so that it would experience the greatest slowing from aerodynamic
drag, to enable the study of that at orbital altitudes. |
|
| |
// 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. // |
|
| |
I didn't understand any of that. Could you paraphrase it? |
|
| |
Somewhere back there it was explained that the final "-annon"
stage would use explosive combustion and not electricity
because of the energy density. It was also explained that the
explosive release of this dense energy, especially if tightly
directed (as in an explosively formed penetrator) would be very
hard on the poor little satellite. |
|
| |
So I wondered whether there might be any way to release the
energy gradually from an energy-dense material. Having no clue
about either explosives or materials science, I vaguely imagined
the explosive reaction being somehow contained within a maze
of carbon nanotubes, which tubes were so parsimonious in
exposing the next molecule of reagent to the energy from the
last one that they could channel most of the released energy in a
consistent direction and not just be blown to bits and, more
importantly, extend (not to say dilate) the time over which all that
dense energy was released. |
|
| |
... so as not to break the satellite. |
|
| |
I had the though of putting an orifice plate between the
propellant and the projectile (satellite). Apparently this is
how the Russian alternative to the recoilless gun works. But
I thought that might require an excessively long barrel to
avoid the satellite leaving the barrel before getting
accelerated enough, and the satellite might still rub on the
barrel, so I decided a sabot (with a built-in wad or driving
ring) would probably be more practical. |
|
| |
Indeed. I have been up for <checks sleep tracking app> 20
1/3 hours. But I think that error was just due to neglecting
to proofread. |
|
| |
But I'm curious; what is an orifice plate? |
|
| |
Just a rigid plate that blocks the flow, with a specifically
sized hole in it. |
|
| |
// 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. // |
|
| |
// I'm worried about trapped air between the
motors. In vacuum, will it push the motors out of the tube?
Maybe put a small hole in the side of the tube between
every pair of adjacent motors. // |
|
| |
Motors would be hard mounted in the tubes and the thrust
would easily overcome any force caused by expanding air. |
|
| |
// 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. // |
|
| |
// 1. Catch sunlight? I was imagining the three discs
as being mutually perpendicular and therefore forming a
retroreflector to be observed by Earth-based radar. I'm not
sure how three circles would be arranged to reflect sunlight
to Earth in an optimal way. // |
|
| |
You are correct, the idea was three circles, each lying in
orthogonal planes with centers at the origin to create a
standard radar reflector shape, except using flexible
materials stretched flat by the tubes at there outer edges. |
|
| |
// 2. Look at the Inflatable Antenna Experiment
[links] to see how inflatable structure deployment in orbit
looks. The IAE wasn't actually supposed to deploy in the
way it did, but being a soft structure with internal pressure
allowed it to achieve the desired shape anyway. I expect
the pressure would cause your satellite to rub on the inside
of the barrel too much; I suggest some kind of sabot. //
Makes sense. |
|
| |
// 3. "Just enough gas to inflate them in vacuum" is
probably more than "the amount of gas left after it's been
folded and all the air is squeezed out". This was learned
during Project Echo [links], where the early satelloons were
destroyed by this residual gas. For the successful Echo 1
and Echo 2, they had to deliberately put a bunch of holes in
the envelope to enable gas to escape. Then they put blocks
of sublimating solid in as pressurant, which lasted
weeks/months. (Echo 2 was also designed to hold it shape
after inflation, so it didn't have a sustainer pressurant like
Echo 1, just an inflator pressurant.) |
|
| |
One of the main goals of Project Echo was to create
the rarest satellite possible, so that it would experience the
greatest slowing from aerodynamic drag, to enable the
study of that at orbital altitudes. // |
|
| |
Again makes sense, especially now considering solar heating
and cooling that would probably kill any container that
couldn't handle pressure cycling such as this one. |
|
| |
Nice, just get the payload to climb around balloon to sit a top, take in the view before next stage. |
|
| |