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How did they match NASA so cheaply? Well they haven't...yet

Posted by: jnfranc - Wed Jul 28, 2004 3:52 am
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How did they match NASA so cheaply? Well they haven't...yet 
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Post    Posted on: Wed Oct 06, 2004 2:36 pm
Hello, Alessandro,

SS1 is launched from Wight Knight. So Scaled/Mojave could build a veray larger Wight Knight able to reach the equator to do an air launch there at the used altitude of 15 km.

Launching Wight Knight at the equator would make no difference.

This get's me to the supposition that the equator is providing advantages by using the earth's rotation velocity only to concepts that launch vertical - is that right?



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Post    Posted on: Wed Oct 06, 2004 2:46 pm
Hello there EA, yes, I´m aware of the White Kight and SS1 works, my idea was to save fuel by launching the WK at 2700meter above sealevel and reach a higher altitude than before with the WK and launch the SS1 or similar craft into orbit, using the extra spin from the equator.

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Post    Posted on: Wed Oct 06, 2004 2:50 pm
Alessandro wrote:
Hello there EA, yes, I´m aware of the White Kight and SS1 works, my idea was to save fuel by launching the WK at 2700meter above sealevel and reach a higher altitude than before with the WK and launch the SS1 or similar craft into orbit, using the extra spin from the equator.


The thing is, it's not the first 2700metres that is the problem for White Knight, it zooms up to 30,000 feet (approx 10,000 metres) pretty quickly. It's the last 15,000 feet that is the issue, as the air is thinner (hence the very wide wingspan of WK), and so it takes longer and has to work harder to get up to its final altitude.

The extra spin would work for getting into orbit I believe, but I can't remember why - maybe something about getting you into freefall a bit quicker?

But as Dr_Keith says, the air-launch solution would not be so good for launching a larger craft for orbit. As you are carrying that much extra baggage in terms of fuel anyway, it makes sense to launch from the ground - you are not gaining a lot by air-launching your vehicle.

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Post Air Launch   Posted on: Wed Oct 06, 2004 3:05 pm
Dr_Keith_H wrote:
Alessandro wrote:
Well, wasn´t this thread about going orbit and win the ASP (American Space Prize) pushing down the price of orbital spaceflights?
Surely windfactor could pose a problem on the top of a mountain....

Maybe, but you were talking about SS1 in your post ... so we just felt that there were some things that needed to be pointed out to you. I don't understand your reference to windy mountaintops.

In any case the current thinking is that air-launch to orbit introduces more technical difficulties and not enough advantages to choose that route over ground-launch to orbit.

Although, to be truthful, I'm not convinced either way.

DKH


That's YOUR current thinking, NOT the current thinking of a lot of other people who've actually studied the subject and know that ground launch forces a vehicle to accelerate to supersonic speed in the thickest part of the atmosphere, resulting in the vehicle reaching Max Q by the time it gets to only 30,000 feet. Ground launch adds one minute to the burn time required from the shuttle solid boosters, adding an additional one million pounds of propellant.


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Post Re: Air Launch   Posted on: Wed Oct 06, 2004 3:08 pm
greenmonster wrote:
That's YOUR current thinking, NOT the current thinking of a lot of other people who've actually studied the subject and know that ground launch forces a vehicle to accelerate to supersonic speed in the thickest part of the atmosphere, resulting in the vehicle reaching Max Q by the time it gets to only 30,000 feet. Ground launch adds one minute to the burn time required from the shuttle solid boosters, adding an additional one million pounds of propellant.

Well give us some sort of evidence, a freaking link to something on the web at least ... as opposed to the confusing psychobabble you constantly inflict upon us. :roll:

DKH

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Post Re: Air Launch   Posted on: Wed Oct 06, 2004 3:14 pm
Dr_Keith_H wrote:
greenmonster wrote:
That's YOUR current thinking, NOT the current thinking of a lot of other people who've actually studied the subject and know that ground launch forces a vehicle to accelerate to supersonic speed in the thickest part of the atmosphere, resulting in the vehicle reaching Max Q by the time it gets to only 30,000 feet. Ground launch adds one minute to the burn time required from the shuttle solid boosters, adding an additional one million pounds of propellant.

Well give us some sort of evidence, a freaking link to something on the web at least ... as opposed to the confusing psychobabble you constantly inflict upon us. :roll:

DKH


You GOT the facts. Don't care you refuse to believe anything that shows you don't know what you're talking about.


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Post    Posted on: Wed Oct 06, 2004 3:18 pm
Can you please write something that makes sense?

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Post Air Launch   Posted on: Wed Oct 06, 2004 3:20 pm
http://www.califcity.com/darpa.html


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Post    Posted on: Wed Oct 06, 2004 3:26 pm
You jerk they're talking about 200lbs to orbit using an expendible UNMANNED second stage ... it's a cheaper pegasus system ... just what freaking forum do you think your "contributing" to?

Go away propeller head.

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Post    Posted on: Wed Oct 06, 2004 9:01 pm
Dr_Keith_H wrote:
Go away propeller head.


best. insult. ever. but i think rocket-car head may be more appropriate in this case....

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Post    Posted on: Thu Oct 07, 2004 6:47 am
The equator really gets the spacecraft extra thrust by the rotation of earth. But to me it seams as if the earlier Saturn V did use it at higher altitudes above the clouds only - they launched vertical and later only narrowed the angel to surface to get to the orbit.

This reminds me to The da Vinci Project because they launch at 25 km altitude - high above the clouds. If they go to the equator and fix their ballon at the surface this construction too may get their vehicle the extra thrust by earth's rotation. They only have to provide a bigger balloon and a much stronger engine and spacecraft to be launched not vertical but at a narrower angel to earth's surface.

I may have done mistakes in all this - but might it work in principle?



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Post    Posted on: Sat Oct 09, 2004 9:27 pm
Air launches make a lot of sense for sub-orbital flight, but only dubious sense for orbital flight.

Why is this? Well, firstly for sub-orbital flight, it gets you a significant way towards your target. SS1 cut about 15% of it's total height, which is not insiginicant. Coupled with the fact that breaking the sound barrier in thicker air uses a lot of fuel for SS1, it makes perfect sense for SS1 to have an air launch.

I actually remember a quote from Rutan saying the White Knight meant that SS1 could carry about 50% less fuel than it would need to launch from the ground.

So, how about for orbital flights? Well, Pegasus uses it yes, but the reason for this is primarily convenience, not fuel-savings.

The vast majority of the fuel expended in an orbital flight is spent getting sufficient velocity to get into orbit - 60 times more energy than is needed to break into "space".

While it is true that it wastes fuel trying to break the sound barrier in the thicker atmosphere, in comparison to the total amount of fuel used to go orbital, we're talking about very small differences. At that point, the simple logistical advantages of a ground launch become preferable.

And then there's the one last problem - how to get an air launch.

SpaceShipOne has a wet mass of about 3.5 tonnes (if I remember correctly), around 50% of which is fuel. By comparison, to launch an equal dry weight (basically the flight controls, wings, and passengers) into orbit would require approximately 20 tonnes worth of fuel. You point me to a plane which can easily carry 20 tonnes of highly volatile rocket to a sufficient height to be worthwhile, and I'd be impressed.

The "next day launch" capability of the Pegasus is it's sales point, but it also happens to be the most expensive launch vehicle per lb in the world. There is a good reason for that.

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Post    Posted on: Sun Oct 10, 2004 7:49 am
Hello, Sev,

I myself didn't try to talk of launches to orbit in this thread but comsidered the advantages of the equator for velocity and its use only.

But if the altitude of launches to orbit really could be lifted to the altitude of Brian Feeney's altitude of rocket-ignition? Larger ballons and lighter materials - this not only might cause small amounts of propellant reductions and extra thrust by rotation but also reduce the angel the rocket has to go to be shot into the orbit.

What effect on propellant requirements does this angel have? I remember the first stage of the former Saturn V having been released perhaps below 25 km and the boosters of the Space Shuttle too.

Look s like and advantage -doesn't it?



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Post    Posted on: Sun Oct 10, 2004 3:33 pm
Ekkehard Augustin wrote:
I myself didn't try to talk of launches to orbit in this thread but comsidered the advantages of the equator for velocity and its use only.

But if the altitude of launches to orbit really could be lifted to the altitude of Brian Feeney's altitude of rocket-ignition? Larger ballons and lighter materials - this not only might cause small amounts of propellant reductions and extra thrust by rotation but also reduce the angel the rocket has to go to be shot into the orbit.


Everyone uses the position which is closest to the equator, if it is at all possible. Although, due to the curve of the Earth, it doesn't matter all that much if you are slightly north or south, so long as you aren't way off the equator - anywhere in the tropics is generally fine (as almost all launch sites are).

Yes, using a balloon or something similar to bring it closer to the equation would help, but again, the inconvenience is almost too much to make it cost effective. Remember, money is the prime restraining factor here - and big balloons are expensive.

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What effect on propellant requirements does this angel have? I remember the first stage of the former Saturn V having been released perhaps below 25 km and the boosters of the Space Shuttle too.


Well, provided you are relatively close to the equator, and don't decide to try and launch from Stockholm, the effect won't be that big - 10% max or so. The biggest reason for the multiple-stages on the Space Shuttle and Saturn is to help it gain velocity, although they are fairly unique situations in that launching from Cape Canaveral is actually one of the worst places to launch from on Earth. (As in, it is far enough from the equator to make a difference.)

To be honest, any sensible private launching company would launch from northern South-America, like ArianneSpace does (they launch from French Guyana), or possibly somewhere like north Australia. China and India are also in good positions for launches.

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Post    Posted on: Sun Oct 10, 2004 4:55 pm
In between I recalled that the first stages are used for acceleration in general and from beginning first and only second or third to get altitude before changing the angel of flight.

So I may have been wrong I think.

But may the situation change if something similar to the equipment of an aircraft carrier would be added? At an aircraft carrier the airjet is locked with engines on. A plate is placed directly behind its nozzle and the engine is made running at full thrust - then the airjet is released and gains the required velocity by running a distance much shorter than on a normal runway.

Might it be possible to use such a plate behind the nozzles of a rocket? Or are the temperatures and thrusts too high?

Concerning the required ballons I have still in mind Feeney's ballon and a possible future use of nanocarbontubes - sorry, but I'm fascinated of them because of their reported properties according to scientists. The balloons and the tubes may be providing much more use than we see now at the beginning of their development and the research om them...



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