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Proposing a new way to Orbit

Posted by: RolandP - Wed Oct 05, 2011 8:34 pm
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Proposing a new way to Orbit 
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Post Proposing a new way to Orbit   Posted on: Wed Oct 05, 2011 8:34 pm
Hello everybody, after having read the goal of many people
here to launch to orbit a microsatellite, I've been asking
myself if another way than the traditional vertically thrown
rocket couldn't be explored ? Please read this text until
you attan the end to follow my idea :
I've been following the project of JPAerospace these three
last years, who, one day, hopes to go to space with huge
airships. These would begin their trip and 4O km altitude,
and then slowly accelerate with an electric thruster (ionic,
plasma, VASIMR engine ?).
This airship would accelerate from zero to orbital speeds, during
many hours and even a few days.
The idea seems seducing to me, but I'm afraid they will need
a more powerful engine, like a traditional rocket's one.
But this makes me imagine another way : Instead of putting
Helium or Hydrogen gas in the airship's envelope, why not put
some pure oxygen gas in it ? Oxygen gas which would be at a few
atmospheres of pressure (and not at the tenuous gas levels of
JPAerospace's projected airships) in an airplane shaped envelope.
Instead of using an electric thruster, a chemical hybrid engine
would be used : A hollowed cylinder of combustible material would
be contained in the long metallic cylinder of this type of motor.
A compressor would inject the gaseous oxygen at a high level
of pressure in the central hollow portion, and the combustible
(same as spaceshipone's) would be ignited and burned in it.
I know that in your domain, hybrid rockets are well known.
Why wouldn't someone build a small toy-like airship, with a small
hybrid motor, and try the idea ?
I'm a computer programmer at the French Ministry of Defense.
Having been interested by the space conquest, and disappointed like
many of you by the failings of the space shuttle and the problems
of traditional rockets, I'm looking for new ideas. Ideas 'out of the
box'.

Your critics regarding this idea interest me, so, you're welcome to come by and write to me.

Let's all make the dream real !


Roland P, France, on the French Riviera


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Post Re: Proposing a new way to Orbit   Posted on: Thu Oct 06, 2011 9:39 am
Well, the thing with an airship is that the gas inside has to be at at least the outside pressure (otherwise the thing collapses), but also has to be lighter than the air it displaces (Archimedes' Law, it doesn't generate any buoyancy otherwise). So, you have to use a light gas (lighter than air balloon), or heat up the gas to keep the volume the same while decreasing the amount (hot air balloon).

Oxygen is heavier than air, because air also contains nitrogen, which has a proton and a neutron less. If you put oxygen into your balloon, and put it in at a high pressure, then unless you're heating your balloon, it's going to be much heavier than the surrounding air, and your airship won't come off of the ground.

So, I don't think it will work. Incidentally, if you don't use the return key at the end of each line in the input box but just let the text wrap, and then use two returns (an empty line) between paragraphs, your posts will be easier to read. The site layout already limits line length, and we can always make our browser windows a bit narrower if needed.

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Post Re: Proposing a new way to Orbit   Posted on: Thu Oct 06, 2011 5:36 pm
JP is working on a thermal-electric engine similar to an arc-jet, not a normal electric engine. So it has a much lower ISP and much higher thrust than an ion engine or equivalent.

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Post Re: Proposing a new way to Orbit   Posted on: Thu Oct 06, 2011 8:33 pm
First of all, thank you, Lourens and TerraMrs, for answering to my post.

I'll follow your double line proposition, Lourens, you're right, that way, my writings will be easier to read.
Concerning my technical proposition, even if I've been talking about the airships of JPAerospace, which will be, effectively, lighter than air, and so use light gas like Helium or Hydrogen (less dangerous in an air one hundred or one thousand more rarefied at 40-60 km altitude than at sea level), my proposition is different :

It would effectively be a heavier than air vehicle; its envelope would be inflated like an airship, with pure gaseous oxygen at, let's say for example, at two atmospheres (or bars). I admit that it could not float, because the total weight of the oxygen would be about two times the weight of the sourrounding air it would displace. Knowing Archimede's Law, only less than half of the weight of the oxygen and its envelope would be submitted to a vertical ascending force.

This kind of airship would have to accelerate like a traditional airplane at an airport, and would get off because of the shape of the inflated envelope, which would have the shape of an airplane, using aerodynamic to make it fly.

But the speed of this strange hybrid (between a plane and an airship, I'm not the first who has been thinking about hybrids like this) necessary to lift of would be really inferior to the speed necessary for a traditional airplane.

And when it would have emptied its envelope of its oxygen, and used all its hybrid engine's combustible, the great GLOW of such a light structure would permit hypersonic speeds at very great altitudes, where the air is very tenuous.

What's your opinion about my idea, now that I've given precisions about it, Lourens ? And your opinion interests me too, TerraMrs.

Thank you for the precision concerning the electric thruster of JPAerospace, TerraMrs. I've read somewhere that they've been working on a device which would accelerate the gas emitted by a classic chemical rocket to improve its ISP. I didn't know it would be an arcjet engine, so, many thanks for this information.

But my recent readings of JPAerospace's blog shows that they've been working on the contrary of the electrically accelerated chemical gas engine I've been talking about : They seem to want to produce electricity by MHD effect. What's your opinion concerning that ?

It's always a pleasure to find other people passionate about the same subject, even beyond the oceans !

I wish you both a nice day.

RolandP


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