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Crazy Idea

Posted by: Texan - Sun Jun 27, 2004 9:28 pm
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Space Walker
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Post Crazy Idea   Posted on: Sun Jun 27, 2004 9:28 pm
Send four suborbital vehicles launched from planes into space.

Three suborbital vehicles carrying a fuel tank.

One Suborbital vehicle carrying an engine.

Combine the fuel tanks and engine at the edge of space.

LAUNCH INTO ORBIT



is anything like the above outlandish sceme possible?


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Post Send four suborbital vehicles launched from planes into spac   Posted on: Sun Jun 27, 2004 11:44 pm
I don't think the "hang time" in suborbital space would be long enough. According to the Scaled site, Mike Melville was only in suborbital space for a few minutes. The building-block approach has however been very successful for constructing the ISS and no doubt will be used in any permanent operations bases on the Moon and Mars. With so much involved in launching just one suborbital vehicle, an operational launch of four at a time and expecting the successful coordination of tank and engine coupleing......well....maybe one day when suborbital launches are as routine as airliner flights. Personally, I can't see it - ever. But, keep that cortex humming. We are going to need lots of out-of-the-box thinking.


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Post    Posted on: Mon Jun 28, 2004 12:26 am
Well.. is this cheaper..? with so manny people needed to fly all those vehicles.. it will add some extra operation costs... + development of multiple vehicles.. and the largest problem is coming back to earth.. going in orbit itself is less difficult (but neither easy of course)..

I think a normal rocket or a spaceshipone style ship with a better rocket engine and more fuel will go into orbit without no problem ;) no need to put them toghetter in subspace... maybe it can split the ship in parts when landing.; so manned part.. and main engine seperated ;)

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Post    Posted on: Mon Jun 28, 2004 12:41 am
the real reason orbit is hard is reentry heating. the real question will be whether or not it's cheaper to do a powered deceleration before reentering, or to use one of the insanely expensive heat-resistant materials currently used to survive reentry. personally i think the former is ultimately the answer, but that's just a guess.

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Post    Posted on: Mon Jun 28, 2004 2:38 am
some people want to leave and never come back.... is it cheaper for us?

:) :D :lol:


Btw what happened to "30 times harder" to get into orbit???

yes I know the "Hang Time" In Sub Orbit is only a few minutes, actually do you ever slow down? you go up and come down, but when stuff is weightless inside the ship, how much is the ship moving?


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Post    Posted on: Mon Jun 28, 2004 2:41 am
[quote="Sigurd"]I think a normal rocket or a spaceshipone style ship with a better rocket engine and more fuel will go into orbit without no problem quote]

Huh?? I thought everyone thought spaceship one was not a good design for getting to orbit...

Not that I see anything wrong with it, but I am not the one who understands these things best.....

When do you see Rutan in orbit?


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Post Crazy ideas & re-entry   Posted on: Mon Jun 28, 2004 2:43 am
First of all, the "crazy idea" would be, no offense intended, a nightmare. On a sub-orbital flight, your "hang time" is an instantaneous moment; otherwise you are going up or down on your ballistic trajectory. Getting your vehicles to reach zero-velocity at the same time *and* in the same place, and *then* trying to mate a whole bunch of stuff together -- that's ridiculous. If you're going to have that many components, better to just do a plain old staged rocket, with re-usable stages.

And about re-entry... these days, everybody is saying that that's the difficult part of going orbital. Even people who should REALLY know better. The only reason they're saying this is because of the Columbia tragedy, and the only reason for the Columbia tragedy is that the Shuttle was an absurd Rube Goldberg device which was much more complicated and fragile than a spacecraft really needs to be. The shuttle shouldn't have had wings, frankly, and were it not for the sharp leading edges of the wings, the expensive and absurdly fragile carbon-carbon wouldn't have been required. And had the Shuttle's airframe been made from a metal with a higher melting point than aluminum (which was a politically-motivated design decision)... et cetera and et cetera. The list of design flaws goes on and on, and *that* is why the shuttle had a hard time with re-entry. In contrast, the Chinese used 3" thick oak planks as thermal protection for their recoverable SKW satellites, which worked just fine (the charring forms a nice heat shield).

That said, orbital *is* a lot more difficult than sub-orbital. But the key words are "mass ratio," not "re-entry".

Sorry for the rant; it was a long time in coming, and someone was going to be on the receiving end of it.


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Post    Posted on: Mon Jun 28, 2004 7:47 am
Don't feel bad fella, don't sit on the fence, you just tell it as it is.

Ha! :-)

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Post Re: Crazy ideas & re-entry   Posted on: Mon Jun 28, 2004 9:21 am
skybum wrote:
First of all, the "crazy idea" would be, no offense intended, a nightmare. On a sub-orbital flight, your "hang time" is an instantaneous moment; otherwise you are going up or down on your ballistic trajectory. Getting your vehicles to reach zero-velocity at the same time *and* in the same place, and *then* trying to mate a whole bunch of stuff together -- that's ridiculous. If you're going to have that many components, better to just do a plain old staged rocket, with re-usable stages.

Yeah, the "crazy idea" is sheer lunacy, but it is stimulating. :)

Dude you really pounded the shuttles there, must have some issues I guess, who knows. Personally I don't hate the shuttles ... never met one. I suppose if I encountered one personally at a party somewhere I might get a chance to form an opinion one way or another (if it spilled my drink or something I suppose could really get pissed, depends on how much of my drink was lost). Until then ... like I said ... who knows.

So this "mass-ratio" thing, tell me more. I am quite interested in how this problem exceeds the "re-entry" problem in more detail. I mean you sort of bring it up, but there is no ... um ... what's the term? Ah yeah, no supporting argument. So if you could just fill in the blanks. I enjoyed your rant, it had a nice touch of directionless fury, thanks for sharing. :wink:

P.S. Your Dad's website is quite nice, he is a very good photographer and there is a lot of useful information there.

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Post    Posted on: Mon Jun 28, 2004 11:39 am
Let me see if I remember this correctly, I think that most people consider re-entry to be the hard part of going orbital, especially SSTO is because whatever re-entry system a design uses throws off the mass ratio and you'd have to give up most of your cargo if you want to come back. That's cargo as anything that didn't actually get you to orbit, including stuff like pilot/life support etc. The way I recall the critics of the DC-X where claiming that the heat shield issues would prevent any DC-X derivitive from making orbit, long before Columbia. Which may have a lot to do with popular opinion that re-entry is the hard part. Basically things get quite a bit easier if you don't plan on coming back.

As for the four ship connection during a sub orbital launch, I would think that driving four cars, one equipped with a jet engine, down a highway at 140 mph, shutting off all four engines and tossing 55 gallon drums of jet fuel from 3 cars to one so the jet engine car could continue and do it all before they all drop below 138 mph would be easier. At the very least I'm sure it'd make an interesting news story.

:oops: jet cars :roll: sometimes some strange and embarrassing things just pop into your head, hahaha.


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Post    Posted on: Mon Jun 28, 2004 12:35 pm
Crazy things popping into head... :lol:

Dr Keith chatting with skybum... are swiss people always so rude? You managed to start a flame war in that other thread....

anyway...

If the heat shields are the hard part why not send like 10(0?) heat shields up together seperately, store them in orbit, and put them on your ship(s) in orbit??

heat shield problem solved :)


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Post    Posted on: Mon Jun 28, 2004 12:35 pm
On the shuttle rant:

Getting to orbit has a number of difficulties, AFAIK:

- Having enough energy and propulsion to slip the surly bonds of Earth (aka. reaching a high enough velocity and altitude to stay in orbit).
- Surviving in space for a length of time (long enough to do what you came to do).
- Getting back down again (i.e. getting rid of all the velocity from before, without burning to bits, and then landing safely somewhere well-defined).

These three problems can be ranked, in my eyes, with the first as the absolutely most difficult (it takes a -lot- of energy!), then the last (getting rid onf energy will be easier, though not by much), and the middle problem as the least difficult one (but still not trivial by far). The more complex your structure is, the more difficult these problems become (notice differences in reentry systems of space shuttle and Apollo capsule). An SSTO design will be a bit complex, by nature.

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Post    Posted on: Mon Jun 28, 2004 1:59 pm
Texan wrote:
Dr Keith chatting with skybum... are swiss people always so rude? You managed to start a flame war in that other thread...

Um, where was I rude? I thought I was being polite. I didn't call him names, I didn't even say he was wrong. What's the bust? Where's the flamewar? Sigurd is pretty quick to jump on me nowadays if I do come across as being overly aggressive ... but ... if you want to see it that way ... aint much I can do about it Tex.

Texan wrote:
If the heat shields are the hard part why not send like 10(0?) heat shields up together seperately, store them in orbit, and put them on your ship(s) in orbit?? heat shield problem solved :)

Excellent joke.

Man, the rules here are tough. Seems like every other poster is a moderator (or wants to be).

Um, I'm not Swiss either ... if you had more experience you might not have jumped to that conclusion, so I'll cut you some slack.

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Post    Posted on: Mon Jun 28, 2004 2:07 pm
perhaps i should explain my reasoning for saying reentry is the hardest part, certainly a debatable opinion. it is relatively easy to both build engines and heat shields, and both need to be done if you go to orbit. the xprize contenders have had to deal with only the engine part of the equation really, heat shielding complicates it. xprize ships could use 3" oak plating for their vehicles, it's cheap, it just weighs a lot, thereby increasing the size of the engine you have to use. they could use highly heat-resistant composites or ceramics, which are relatively cheap compared to carbon-carbon, but still damn expensive, and lighten the vehicle some. basically reentry forces you to choose whether or not you want to spend lots of money on a bigger engine or on getting back to ground, which is why i think powered reentry is a better solution, you can shield the vehicle with the exhaust and decelerate at the same time.

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Post    Posted on: Mon Jun 28, 2004 2:18 pm
Sorry Dr Keith... I knew their was a chance you were not swiss... but I felt like saying swiss. :oops: Where are you from?

Is sending installable heat shields into orbit such a bad idea, just stack them in the cargo bay of one spaceship instead of other cargo, then put them on your other spaceships before re-entry.

That is, if the heat shield is such a big problem.


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