Hang-gliding to orbit?

TwinBeam · 2006-04-24 14:59:25

Thinking about the various "jet plane carries rocket to edge of space" schemes - how about using a giant jet-powered hang-glider to get the rocket off the ground?

Big wings are needed to get off the ground - but once you get up to reasonable velocity, a lifting body and small wings should be adequate.

So use an air-filled para-wing to get off the ground. Once you get high and fast enough, drop the parachute-wing. Accelerate under jet power to fly on up to the edge of space - kick on the rocket, dump the jets and small wings and let them parachute down for recovery.

Any winged carrier approach limits the size of the rocket - but it should be a higher limit than for a fixed wing carrier craft.

John Creighton · 2006-04-24 18:52:23

Thinking about the various "jet plane carries rocket to edge of space" schemes - how about using a giant jet-powered hang-glider to get the rocket off the ground?
Big wings are needed to get off the ground - but once you get up to reasonable velocity, a lifting body and small wings should be adequate.
So use an air-filled para-wing to get off the ground. Once you get high and fast enough, drop the parachute-wing. Accelerate under jet power to fly on up to the edge of space - kick on the rocket, dump the jets and small wings and let them parachute down for recovery.
Any winged carrier approach limits the size of the rocket - but it should be a higher limit than for a fixed wing carrier craft.

I think wings would hurt a rocket on ascent more then help it provided the rocket has enough thrust. Wings help you maintain flight for vehicles with less thrust such as air breathing vehicles and they are also helpful for landing. I think for rocket ascent the drag will be worse then any benefit obtained from lift.

TwinBeam · 2006-04-24 23:39:23

I think wings would hurt a rocket on ascent more then help it provided the rocket has enough thrust. Wings help you maintain flight for vehicles with less thrust such as air breathing vehicles and they are also helpful for landing. I think for rocket ascent the drag will be worse then any benefit obtained from lift.

Right - which is why I was writing in the context of air-breathing jets that carry rockets to the edge of space before the rocket kicks in. The para-wing would likely be released a few miles up. It's just for getting off the ground.

GCNRevenger · 2006-04-25 06:32:58

In order to get into orbit and stay in orbit, what you need most is speed, not altitude! If all you want to do is go suborbital, just stick your head above the atmosphere and come back, then launching at a height makes sense, since virtually all the energy required is flying straight up.

Orbital flight is the exact opposit, you need speed much more then altitude. Vehicles stay in orbit because they fly around the Earth as fast as they fall tward it, so they never crash. Since the Earth is kind of big, you need to be going really fast to accomplish this, in the region of Mach twenty five. If you look at the amount of energy needed to reach orbit, getting up to an altitude is only a tiny slice, around 5%.

Infact, if you had enough thrust and fuel, you could launch your rocket horizontally and not lift off upward at all and you could reach orbit, because what you need is speed perpandicular to the ground, not altitude. Actually, the altitude will "take care of itself," since you would keep going straight and level while the curve of the horizon drops out from under you, you would gain altitude by putting your rocket on its side too.

An example of the physics from Wikipedia

This is why the Space Shuttle or rockets tend to roll over and curve away from the launch pad as fast as they safely can, since they need speed much more then altitude, and the faster they can start building up that speed the easier it is to reach orbit.
___________________________________________

So, with this in mind, launching from a slow but high altitude airplane makes sense for suborbital flights, where you could save tens of percent of energy, but doesn't make much sense for orbital flight, where altitude is only ~5% of your energy "bill."

If you are going ot launch from an airplane to orbit, its got to be first a FAST plane, and a high altitude one second. To really see a reduction in the size of your "upper stage" needed, you need the carrier plane to hit some pretty high Mach numbers, I would say Mach-5 or Mach-6 would be minimum.

This would be difficult, but not impractical , to accomplish today. The SR-71 Blackbird, updated with modern technology, could hit Mach-4 perhaps using only jet engines. Boosting these engines with liquid oxygen and perhaps higher energy fuel and you could hit Mach-5 I bet. Another option would be to use jet power to get off the ground, then light up kerosene rockets on the carrier plane to get up to speed.

The upper stage will still have to be pretty light weight, composite structures and Hydrogen fuel would be a must, but it could be done.

Austin Stanley · 2006-04-25 11:46:49

Getting and staying at high-altitude is not really a problem. The U2, for example, was pretty much exactly like what you describe. A big winged, low weight plane, that could reach extreamly high alltitudes and loiter there for long periods.

But to get to space high altitude is not enough. What you need is speed, and big winged aircraft like the U2 are terrible at that. Those big wide wings create incredible amounts of drag, which increases geometricly as you increase in speed. So much so that a plane like the U2, despite having a powerfull jet enigne, cannot even break the sound barrier. So your carrier plane would be rather like a SR-71 rather than a U2.

C M Edwards · 2006-04-25 18:02:06

Actually, it's not a new idea.

Similar concepts have been seriously proposed. At least two got some serious discussion here at New Mars: the Airship to Orbit Thread and the very similar Tom Jolly's Solar Thermal Ground-To-Orbit Concept.

I wrote an article for the New Mars wiki about ATO, which has some useful links on the topic.

And, of course, don't forget the world's fastest winged vehicle. OSC's Pegasus launch vehicle beats out the space shuttle by a technicality.

Reaching the upper atmosphere with a jet-powered parasail. Hmm...

GCNRevenger · 2006-04-25 19:08:32

The solar thermal to orbit idea is just plain batty, it would never work. The sunlight just isn't bright enough, your collector would have to be too big. Does anybody have any idea just how much power is associated with rocket engines?

Airship to orbit is an interesting idea, but I doubt that it would work, the engineering margins are just too slim.

Either we build a spaceplane, a DC-X style rocket, or a space elevator. There isn't much in the way of options otherwise.

C M Edwards · 2006-04-27 13:57:43

The solar thermal to orbit idea is just plain batty, it would never work. The sunlight just isn't bright enough, your collector would have to be too big. Does anybody have any idea just how much power is associated with rocket engines?
Airship to orbit is an interesting idea, but I doubt that it would work, the engineering margins are just too slim.

"Never" is too strong a word for the solar thermal to orbit concept. (Can't argue with batty...) Conceptually, it's very similar to airship to orbit in that it employs a low thrust rocket engine to move a lifting body from aerostatic equilibrium to orbital altitudes. Tom Jolly apparently just never made the conceptual leap necessary to look past the point of minimum vertical force on its trajectory. I didn't either, at the time.

As for how much more power density a rocket engine requires than what sunlight has to give, you're quite right. Any vehicle expecting to use sunlight to power a serious rocket would need a collector area of several hectares. It would need to be as large as, well, Tom Jolly's BalRoc or JPA's Orbital Ascender.

TwinBeam's parasail idea can't provide as great a boost as those other two schemes offer because it it doesn't start from static equilibrium. At no point during its ascent would all of its aerodynamic lift be translated into upward acceleration. But, it could still get a substantial boost.

A parasail vehicle - no more missile than your average ultralight - powered by a more conventional high thrust chemical rocket engine, could be feasible for a suborbital vehicle.

publiusr · 2006-04-28 14:16:34

Thinking about the various "jet plane carries rocket to edge of space" schemes - how about using a giant jet-powered hang-glider to get the rocket off the ground?

How about we just build a bigger rocket? A wider core is mostly empty space. You are only using a bit more metal for a 10 meter core than an 8 meter core. Enough with wings for now.

Austin Stanley · 2006-04-28 16:59:37

"Never" is too strong a word for the solar thermal to orbit concept. (Can't argue with batty...) Conceptually, it's very similar to airship to orbit in that it employs a low thrust rocket engine to move a lifting body from aerostatic equilibrium to orbital altitudes. Tom Jolly apparently just never made the conceptual leap necessary to look past the point of minimum vertical force on its trajectory. I didn't either, at the time.
As for how much more power density a rocket engine requires than what sunlight has to give, you're quite right. Any vehicle expecting to use sunlight to power a serious rocket would need a collector area of several hectares. It would need to be as large as, well, Tom Jolly's BalRoc or JPA's Orbital Ascender.
TwinBeam's parasail idea can't provide as great a boost as those other two schemes offer because it it doesn't start from static equilibrium. At no point during its ascent would all of its aerodynamic lift be translated into upward acceleration. But, it could still get a substantial boost.
A parasail vehicle - no more missile than your average ultralight - powered by a more conventional high thrust chemical rocket engine, could be feasible for a suborbital vehicle.

Suborbital, sure. It might even make sense as some kind of a military vessle. But if you actualy want to get into orbit, that conventional high thrust chemical rocket engine is simply going to mass to much. I could see how the Air-ship to orbit concept could work, but that is because it relies on a super-high impulse ION engine and effectivly mass-free and infinite power solar energy. Replace either one of these, and it's mass simply becomes to much.

TwinBeam · 2006-04-29 22:25:36

By my quick calculations, the benefits of getting above the atmosphere, not needing to directly counter gravity as long, and getting a slight velocity boost from jets, might amount to 10% decrease in fueled rocket mass.

That's not huge - but might make the difference between a SSTO getting payload to orbit or not, if it's close to the edge.

GCNRevenger · 2006-04-30 06:20:31

If you have to launch it from something other then the ground, then its not a SSTO by definition.

If you only reduce the upper stage by ~10%, then its still going to be really huge and too heavy to lift. Easily in the millions of pounds range.

TwinBeam · 2006-04-30 17:04:35

If you have to launch it from something other then the ground, then its not a SSTO by definition.
If you only reduce the upper stage by ~10%, then its still going to be really huge and too heavy to lift. Easily in the millions of pounds range.

I used "SSTO" mainly to specify how I did the rocket calculations. If you want to count jets and parawing as a "stage", feel free. I don't much care how you define it, or whether you use one rocket stage or two, as long as it can make it to orbit.

There's no reason to make the rocket weigh millions of pounds. Project Mercury made it to orbit without millions of pounds - and there are jets that can carry as much weight as the total Mercury mission.

GCNRevenger · 2006-04-30 19:09:30

"There's no reason to make the rocket weigh millions of pounds. Project Mercury made it to orbit without millions of pounds - and there are jets that can carry as much weight as the total Mercury mission."

If you intend to launch anything of useful size into orbit, yes it does. "There is no reason?" Gravity, the low energy density of rocket fuel, and the limits of practical materials (both cost and performance) are all reasons. Its a simple matter of physics, dictated by the Tiokovski rocket equation, and cannot by any present means be avoided.

C M Edwards · 2006-05-01 15:35:50

I don't think a simple airfoil of just any type picked out of a hat is going to get this type of vehicle to orbit.

The point of minimum vertical force is always waiting for anything trying to employ aerodynamic lift. Having a net weight - not floating at equilibrium - only subtracts weight from the available vertical force, causing the minimum to come that much sooner.

If a vehicle dependent on aerodynamic lift to maintain altitude cannot get its net weight under that minimum vertical force, it can never ascend to orbit.

Unfortunately, wings large enough to do the job are large. Heavy too. A simple parasail won't work because there has to be sufficient aerodynamic lift to keep it open at all times, and eventually there won't be. Stiff wing support with compressive strength is required. Gas filled wings would fill the bill, but wings large enough to be useful for this scheme would take several minutes to fill, and wouldn't be something you could just pop out of your rocket. Serious vertical velocity, on the order of at least 3 km/s, would be required for the flight time to even deploy them - there'd be no talk of a checklist.

Having a high altitude rocket plane to maintain it at altitude only gets around these problems until the vehicle is cut loose and has to worry about its own drag.

It would be more practical to just add a rocket stage on the top of that booster instead of a winged vehicle. And, BTW, if you're going to use a gas-filled anything, why not just make it a bouyant airship?

(Yes, GCNR, I'm aware that I'm becoming a vaporware apologist. "Take up your Airship-To-Orbit and follow me", etc., etc.)

No, I don't think this could get you to orbit.

TwinBeam · 2006-05-01 22:03:00

"There's no reason to make the rocket weigh millions of pounds. Project Mercury made it to orbit without millions of pounds - and there are jets that can carry as much weight as the total Mercury mission."
If you intend to launch anything of useful size into orbit, yes it does. "There is no reason?" Gravity, the low energy density of rocket fuel, and the limits of practical materials (both cost and performance) are all reasons. Its a simple matter of physics, dictated by the Tiokovski rocket equation, and cannot by any present means be avoided.

So are you saying physics requires that Project Mercury couldn't get a man into orbit?
Or that getting a man into orbit isn't useful?

My point here is (a) flying to above most of the atmosphere isn't necessarily as useless as you tend to claim; and (b) maybe a para-wing could be useful, as a way to minimize costs and complexity of a separate carrier craft.

And by the way, I used the rocket equation in my calculations - it's not exactly "news".

TwinBeam · 2006-05-01 22:14:18

CM Edwards:

I think you're still getting what I'm saying backwards. I'm not proposing boosting on a rocket and then using a para-wing to fly on up into orbit.

I'm proposing using a para-wing to get off the ground and to an altitude such that when the rocket kicks on, it has far less atmosphere to fly through and a bit less altitude to gain while directly fighting gravity.

The parawing and jets drop off as the rocket kicks on. Or possibly the parawing drops off once the vehicle gets to a velocity such that very small wings can provide adequate lift (with jet power) to carry it on up to very thin atmosphere, and *there* the jets and probably the small wings get dropped.

The whole point is to use the parawing down where it is efficient - not deploying it up where it barely works.

GCNRevenger · 2006-05-02 07:42:48

So are you saying physics requires that Project Mercury couldn't get a man into orbit?
Or that getting a man into orbit isn't useful?
My point here is (a) flying to above most of the atmosphere isn't necessarily as useless as you tend to claim; and (b) maybe a para-wing could be useful, as a way to minimize costs and complexity of a separate carrier craft.
And by the way, I used the rocket equation in my calculations - it's not exactly "news".

Project Mercury's rockets - Redstone and Atlas ICBMs - are both too small to put anything useful into orbit, infact Redstone couldn't even put a man in orbit. Even rockets like the Russian R-7 (Soyuz/Progress) are too small to bother with, only carrying three men or two tonnes respectively.

The Atlas-D rocket used to put Mercury into orbit weighed, fully loaded, just over a quarter of a million pounds. And thats just for a little one-tonne Mercury capsule. The Soyuz R-7 rocket, with its dinky payload, weighs in at just under seven hundred thousand pounds. For a rocket that could lift a useful sized payload, in the >10MT range, modern rockets like Atlas-V weigh one point two million pounds. For a really good payload, in the 20MT range, the light-weight hydrogen burning Delta-IV heavy clocks in at 1.6Mlbs.

Your point that "getting above the atmosphere isn't useless" is simply not true, it is most definatly useless to orbital vehicles of any size. It doesn't matter what altitude your carrier vehicle achieves, it could even go all the way to low orbit before the rocket seperates, but it will still not make any real difference. If your "calculations" indicate otherwise, then you must have done them wrong.

Again, it really is very very simple. Too simple for anyone to have an excuse not to understand. The reason why your math is wrong is beacause it fails this simple logic test:

This is what orbit is all about, horizontal velocity and not altitude. Altitude is almost completly unimportant to orbital vehicles except for getting out of the thicker air, speed is everything. Not altitude.

To get into orbit, you need to be going about 18,000mph: needless to say, this would take alot of energy to go this fast from a standing start, right? And that amount of energy accounts for about 95% of the total energy needed for your average launch, which means that air launch from any slow-moving vehicle will only save you 5-10% of total rocket mass.

So yes, it really is pretty useless

TwinBeam · 2006-05-02 15:00:09

GNC - you can get as insulting as you want, but you can't change the rocket equation. You referenced it, but did you bother trying to apply it?

Losses to atmospheric drag and fighting gravity (i.e. vertical thrust to stay aloft while building up horizontal velocity) seem relatively small - but once you plug the small losses into the the rocket equation as required additional delta-V, they turn out to be not quite so small in terms of payload to orbit.

Suppose you have a rocket that needs 7500m/s net delta-V for orbit (assuming final orbital velocity of ~7900m/s, and a gain of around 400m/s from earth's rotation). But due to atmospheric drag and the need to launch vertically, assume it needs to be built as if it needs 500m/s more delta-V - 8000m/s. Assume average rocket exhaust velocity of ~3600m/s (LOX-hydrogen). The theoretical mass ratio for that is 9.23 : 1.

Then suppose I can shave off just 300m/s by getting above most of the atmosphere and launching more nearly horizontally - call it a net 7700m/s required. That requires a mass ratio of 8.49 : 1.

Hardly looks worth bothering with, doesn't it?

But suppose the original rocket weighs 200000kg fueled and 21670kg dry - 178330kg of fuel, 19670kg rocket, and 2000kg payload. Using the same fuel and rocket, but the 8.49 mass ratio and a bit of algebra, I get 4140kg of payload - well over twice as much!

But I suppose doubling the payload of a rocket is trivial and useless - after all, all you need to do is more than double the mass of the rocket and you can get the same effect.

Sorry, I don't have any cute cartoons to help explain it to you better. :-D

GCNRevenger · 2006-05-02 15:23:46

So you can crunch numbers, but are you even reading what you are writing here? You want to lift a rocket weighing 200,000kg to very high altitudes? Even the massive An-225 plane could hardly lift that, and it can't reach superhigh altitude. And thats for four measly tonnes, even burning hydrogen? You couldn't even launch a dimpy Soyuz capsule on a single stage.

And this is assuming you get your estimated 300mps "boost," which I don't think you will. Your average rocket is well above the majority of the atmosphere quickly, but must curve its path for some time to fight gravity, which simply dropping from a height does not substantially mitigate.

Its not practical, it really is worthless... No method of air launch that doesn't involve several multiples of the "normal" payload is even worth talking about.

cIclops · 2006-05-03 12:58:50

Its not practical, it really is worthless... No method of air launch that doesn't involve several multiples of the "normal" payload is even worth talking about.

t/Space think air launch is worth doing, it's the basis of their CXV proposal to launch 4 crew to ISS

GCNRevenger · 2006-05-03 17:23:28

t/Space? Oh come now, these are the same people that "forgot" that Hydrogen and to lesser extent Oxygen will boil off when they were dreaming up Moon plans.

One of the main reasons they cite for air launch is the improved abort options... there is no way that its worth it to go through the trouble of dropping your rocket from an airplane versus making a groud-launch rocket a little bigger.

Austin Stanley · 2006-05-04 00:03:04

TwinBeam,

I think the issue here is not that giving your rocket a higher and faster start of cannot give you a boost in getting to orbit. It certianly can. The Pegasus launch vehicle relies exactly upon this. The issue here is that as you scale your rocket up, to something bigger then the Pegasus, it rapidly becomes to heavy for most air-launch solutions to lift. For air-launch to work you need to include alot more of that rocket-mass into the lifting craft itself. IE, making it a real first-stage of some-sort. Otherwise, even with the benifit of high-altitude and some moderate velocity your rocket will simply be to heavy.

Though a scaled-up Pegasus type disposable rocket for launching small payloads like satilites might make some sense though. The B-1B Lancer could carry a heavier load than the B-52, and launch it faster (and maybe higher as well). Outfitted with more efficent engines (dare we even hope recoverable?) it might become an ideal method for putting light payloads into orbit.

The problem with the hang-glider type vehicle you propose is that because of it's shape, size, and nature it cannot go fast enough to be an effective first stage for a rocket.

John Creighton · 2006-05-04 19:30:18

Its not practical, it really is worthless... No method of air launch that doesn't involve several multiples of the "normal" payload is even worth talking about.
t/Space think air launch is worth doing, it's the basis of their CXV proposal to launch 4 crew to ISS

I read about that before. I though their separation method was kind of neat. I wonder if it would work at high speeds.

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