Author Topic: Basic Rocket Science Q & A  (Read 271014 times)

Offline tnphysics

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Re: Basic Rocket Science Q & A
« Reply #500 on: 05/04/2010 12:05 AM »
I thought more would be B2O3. Does it decompose at some high temperature?

I was thinking 2B2H6+3O2->2B2O3+6H2

Also, is that by mass or by moles?

Offline jongoff

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Re: Basic Rocket Science Q & A
« Reply #501 on: 05/04/2010 03:21 AM »
Why is it so difficult? What are the problems?

Boron trioxide (the stable oxide) is like sand. At O/F 1.73, Pc of 1000psi, I get that 40% of the mass flow is Boron trioxide once you've expanded to atmospheric pressure. For a sea-level nozzle, the B2O3 would be a bunch of entrained liquid particles, they'd be little sand grains in a vacuum engine, which do not accelerate as well in a nozzle, and will bring down your Isp. With 40% of the flow being like that, it sounds like it could bring down your Isp a whole lot. That sound reasonable, Mr. Goff?

Yeah, most boronated fuels are:

1-extremely toxic/nasty
2-their exhausts are extremely toxic/nasty/corrosive/sticky/abrasive
3-the large amount of solids in the exhaust kills the Isp compared to its theoretical potential
4-most of them are pyrophoric, and can produce explosive mixtures with air quite readily.

Both the US and the USSR sunk tons of money into Boronated fuels about 50 years ago.  Both of them abandoned them in disgust after trying to make them work.  Clark has a whole chapter on the topic in "Ignition".

This is one of those areas where while in theory there's no difference between theory and practice, but in practice there is.

~Jon

Offline jongoff

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Re: Basic Rocket Science Q & A
« Reply #502 on: 05/04/2010 03:23 AM »
I thought more would be B2O3. Does it decompose at some high temperature?

I was thinking 2B2H6+3O2->2B2O3+6H2

Also, is that by mass or by moles?

Not to be rude Tnphysics, but it's often important to remember that almost every rocket propellant you can even sanely imagine (and several that you'd have to be insane to imagine) have been tested over the past 60 years.  While there's a large range of workable propellants that haven't made it over the TRL valley of death, almost everything you can imagine has at least been tried in a lab somewhere.

~Jon

Offline jongoff

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Re: Basic Rocket Science Q & A
« Reply #503 on: 05/04/2010 03:24 AM »
Also, what kind of Isp would you get for B2H6/LOX? Use just enough LOX to burn the B (about 1.73 to 1 O/F). Assume 20MPa chamber pressure and altitude compensating nozzle. Engine start @ 40,000 ft.

Boronated fuels have, at least from what I've heard, always been a big disappointment compared to theoretical calculations, and a real pain in the neck.

~Jon
Why is it so difficult? What are the problems?

http://lmgtfy.com/?q=boronated+rocket+fuel  :-)

~Jon
« Last Edit: 05/04/2010 03:25 AM by jongoff »

Offline kevin-rf

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Re: Basic Rocket Science Q & A
« Reply #504 on: 05/04/2010 12:47 PM »

http://lmgtfy.com/?q=boronated+rocket+fuel  :-)

~Jon

Okay, the geek in me says, that was a way cool flame... ISP in the five hundreds?
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Offline jongoff

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Re: Basic Rocket Science Q & A
« Reply #505 on: 05/04/2010 03:48 PM »

http://lmgtfy.com/?q=boronated+rocket+fuel  :-)

~Jon

Okay, the geek in me says, that was a way cool flame... ISP in the five hundreds?

Sorry.  I've been wanting to use that somewhere ever since my coworker got me with it.  :-)

~Jon

Online Robotbeat

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Re: Basic Rocket Science Q & A
« Reply #506 on: 05/04/2010 11:28 PM »
Quadricyclane? Any luck with that? How much does it cost per kilogram? Even if it doesn't make sense for use on a first stage, would it make sense at the tip of the rocket, like for a lander or upper stage?

Also, these higher energy propellants may require exotic high-temperature alloys for the chamber/throat/nozzle.
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Offline tnphysics

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Re: Basic Rocket Science Q & A
« Reply #507 on: 05/05/2010 01:26 AM »
I do not know about quadricyclane. I do know that one does not need exotic allows. Al (!) can be used for even the nozzle throat, provided it is adequately cooled. The latter is not a problem for any sufficiently large engine.

Offline toddbronco2

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Re: Basic Rocket Science Q & A
« Reply #508 on: 05/07/2010 03:53 AM »
Does anybody know where I can find a video of a rocket engine experiencing thrust instability?  Specifically, I'd like to find a video and audio example of a rocket engine that is "chugging."  I've looked around a bit on the web but I haven't had much luck so far

Offline Antares

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Re: Basic Rocket Science Q & A
« Reply #509 on: 05/28/2010 03:21 AM »
Who/when/where was the first to discover the significance of maximum dynamic pressure as a driving environment?

I think this is going to be a hard question.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline dks13827

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Re: Basic Rocket Science Q & A
« Reply #510 on: 05/28/2010 12:44 PM »
Who/when/where was the first to discover the significance of maximum dynamic pressure as a driving environment?

I think this is going to be a hard question.
The NACA guys perhaps ?  Faget comes to mind as
one of the early guys who learned fast !!!

Offline Jim

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Re: Basic Rocket Science Q & A
« Reply #511 on: 05/28/2010 01:33 PM »
Who/when/where was the first to discover the significance of maximum dynamic pressure as a driving environment?

I think this is going to be a hard question.
The NACA guys perhaps ?  Faget comes to mind as
one of the early guys who learned fast !!!

No, because NACA didn't do launch vehicles and Faget only did Mercury and not other earlier spacecraft or launch vehicles.

Maybe one of the NRL White Sands (V-2/Viking) people, Thor designers or Bossart who designed a minimalist vehicle that had to depend on internal pressure to survive this regime.

Offline Antares

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Re: Basic Rocket Science Q & A
« Reply #512 on: 06/14/2010 04:54 AM »
After looking at the Amro ad: what are the pros and cons of orthogrid vs isogrid?
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline DavisSTS

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Re: Basic Rocket Science Q & A
« Reply #513 on: 07/24/2010 10:48 AM »
Why is it that when you re-enter, you have all the heat and friction, but not the same problem when you launch through that same area?

Offline mmeijeri

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Re: Basic Rocket Science Q & A
« Reply #514 on: 07/24/2010 10:50 AM »
Because you reenter at much higher velocities. Airbreathing launch vehicles would have heating problems on ascent too, but those do not exist yet.
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Offline Jim

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Re: Basic Rocket Science Q & A
« Reply #515 on: 07/24/2010 12:05 PM »
There is some heating but during ascent, most of the velocity gain is outside the atmosphere to avoid drag (friction).  During entry, the vehicle reaches the lower parts of the atmosphere at higher velocities.

Offline Ratty_2

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Re: Basic Rocket Science Q & A
« Reply #516 on: 08/07/2010 06:15 PM »
Hi,

I am having a small problem with a launcher design I am doing at the moment and wondered if any one could help. I have designed a 3 stage winged launch vehicle. The first stage uses a liquid engine while the upper two stages uses hybrids. The second stage uses a cluster of hybrids, 4, so the diameter has to be 1.86 m. So the diameter of the first and second stage is 1.86 m, but to save mass, the third stage is 1.28 m. The fairing is released during the second stage burn. Now my problem is, is that I am unsure whether the fairing will collide with the second stage during separation (due to it being a larger diameter)? I cannot find any dynamic information on typical fairing separations, so I am unsure on typical clearance values. Does anyone know the general capabilities of fairing separation mechanisms and have an inclination whether this will be a problem?

At the moment I have three courses of action,

1) it will be ok, so I dont modify,
2) add a flared skirt to increase the fairing diameter closer to the second stage, but I am worried about the aerodynamic consequences,
3) have a hinge point of the fairing via rails down to the top of the second stage, so essentially the fairing is hinged about the larger diameter, but the strength of this rail is the issue.

Any ideas would be greatly appreciated:)

Offline Hoonte

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Re: Basic Rocket Science Q & A
« Reply #517 on: 08/09/2010 02:15 PM »
Hi,
I don't understand a bit about orbital mechanics but I do know that the higher you get, the slower your orbital time will be.

So just for the fun of it. Does anyone knows what the orbital time will be if the earth was a vacuum and the apogeum/perigeum would be around 9 kilometres (so it won't hit the everest).

I gues that this time would be the fastest possible time to travel around earth even with an atmosphere.

Forgive my bizarre mind.

Offline Jim

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Re: Basic Rocket Science Q & A
« Reply #518 on: 08/09/2010 02:25 PM »
http://www.stuegli.com/phyzx/calculators/calc-orbitvel.htm


84.660365294035 minutes at 17673.549882780328 mph

Online ugordan

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Re: Basic Rocket Science Q & A
« Reply #519 on: 08/09/2010 02:29 PM »
That's some fantastic accuracy in those numbers  ;D