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Urwumpe

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Current record speed (Friday, 13:00 CET) at the Brocken mountain: 162 km/h gust, 94 km/h average.

---------- Post added at 04:31 PM ---------- Previous post was at 01:31 PM ----------

We should really build a Swimming pool on the moon:

http://what-if.xkcd.com/124/
 

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mikusingularity
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Can't wait for the Lunar Olympics! 1/6 gravity will make sports a lot more interesting.
 
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Urwumpe

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Funnily, the current storm in Germany got the name "Elon" and is much stronger than expected. Is that an omen for the launch tomorrow?
 
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ex-orbinaut

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A6 ugly? From which side it's ugly?

There was one that took pride in the fact...

th


"Ugly, but well hung"

Though it is nowhere near as ugly as its more effective successor. Now that is one ugly aircraft, unless of course beauty really is in the eye of the beholder... ;)


a10_EVG_6581.jpg
 

fsci123

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I thought I would never see the day when gas prices rehit $1.99...

Also does anyone know any scientific papers about the cost of launching cargo into Leo/TLi/TMI and how such cost will be effected by the addition of reusable launch vehicles, SSTO, or propellant depots.
 

fsci123

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Hybrid rocket engines are marvellously "simple" mechanically but a :censored: to even (very) roughly size :beathead:

Don't they have problems like spontaneous explosions?
 

Fabri91

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Well, funny transients can have many causes, but yes, they appear to be a bit of a concern in hybrids during throttling operations.

What I'm more referring to is that hybrids, as opposed to liquid rocket engines or SRMs, don't really operate in a steady condition, as in a constant oxy/fuel ratio, which complicates many things to say the least, since chamber pressure and combustion products are constantly changing so that one doesn't really have a set of steady "design conditions".
 

N_Molson

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I wonder how much petroleum prices can affect the LOX/RP-1 rocket launches prices, if it does ?

That engine only needs oxygen and hydrogen anyways. Pure beauty :

10917422_705146162934537_6589295267694858099_n.jpg


:camera:

So the outer skin of the nozzle stays cold enough for water vapor to condensate immediately into ice ? Impressive.
 

N_Molson

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Well, it is regeneratively cooled, i.e. hydrogen is run through small tubes along the nozzle wall to cool it

Sure, but still, the temperature inside is like 6,000°C :blink:

So in theory, if you can approach the nozzle enough and put a hand on it, it stays sticked to it and the cold probably freezes all your blood in a matter of seconds ; if you move it a few centimeters inwards, it is immediately incinerated. Space environnement is friendly compared to that. :lol:
 
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Urwumpe

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I'm sure that while the outside wall of the nozzle is really cold, the inside one is quite a bit more...toasty. :)

The inside wall is also not at the 6000°C that you have in the center of the combustion chamber. There is a bit of film cooling taking place by injecting hydrogen-rich gas at the sides of the combustion chamber without also injecting oxygen into the stream, also the exhaust cools a bit while expanding in the noozle.

I have some simulation data here, it is not 100% accurate, but gives you a good impression of the conditions at the nozzle heat exchanger:

Variable | Description | Units | 65% RPL | 100% RPL | 104% RPL | 109% RPL
t_4|Fuel temp. inside nozzle HE|R|449.5|465.8|456.4|448.1
t_5|Fuel temp. inside MCC HE|R|509.0|466.0|455.9|443.1
t_9|Preburners fuel supply line temp.|R|295.4|276.4|276.4|276.5
t_op|Oxidizer preburner temperature|R|1,057.0|1,440.3|1,475.8|1,517.6
t_fp|Fuel preburner temperature|R|1,633.5|1,753.9|1,796.1|1,854.8
t_fi|Fuel injector temperature|R|1,392.7|1,560.7|1,593.1|1,636.2
t_c|Main chamber (MCC) temperature|R|6,400.0|6,400.0|6,400.0|6,400.0
tw_15|Hot wall temp. at MCC HE|R|1,228.8|1,214.9|1,203.1|1,187.1
tw_25|Cold wall temp. at MCC HE|R|509.0|466.0|455.9|443.1
tw_14|Hot wall temp. at nozzle HE|R|1,162.5|1,260.3|1,250.4|1,244.5
tw_24|Cold wall temp. at nozzle HE|R|449.5|465.8|456.4|448.1

In case Rankin aren't that easily understood... I can also convert the data into K or °C, the original table was calculated in Rankin
 
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Fabri91

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The inside wall is also not at the 6000°C that you have in the center of the combustion chamber. There is a bit of film cooling taking place by injecting hydrogen-rich gas at the sides of the combustion chamber without also injecting oxygen into the stream, also the exhaust cools a bit while expanding in the noozle.

I have some simulation data here, it is not 100% accurate, but gives you a good impression of the conditions at the nozzle heat exchanger:

table

In case Rankin aren't that easily understood... I can also convert the data into K or °C, the original table was calculated in Rankin

Nice, thank you!:tiphat: Rankine is fine, it's not as unfamiliar a unit as a hogshead or a buttload :)
 

ISProgram

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Hey guys, how big can an add-on documentation be? Working on one, and I kinda wanted to, um, overdo it a bit...

Also, why do people think the A-10 is ugly?
 
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