Author Topic: Basic Rocket Science Q & A  (Read 271735 times)

Offline Lab Lemming

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Re: Basic Rocket Science Q & A
« Reply #300 on: 07/01/2009 02:26 AM »
And Ares I can't suffer a first stage turbopump failure.

Saying that non-existent technology X is better than well-used technology Y is disingenuous.

Just thinking outside the box here but wouldn't it be *forward looking* if there were a THORIUM (not uranium) nuclear power plant nearby that generated electricity, drew in seawater, and then used some of that electricty to distill and crack the purified water into hydrogen and oxygen gasses? Send the remaining electricity into the grid and send the gasses off to be liquified, maybe even on site at KSC.

Thorium generators (molten salt coolant) can't "melt down" and do not produce any byproducts that can be reprocessed into weapons grade material. And thorium byproduct half lives are extremely short, unlike uranium.

Just musing. Returning you now to your regular programming.

Offline Lab Lemming

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Re: Basic Rocket Science Q & A
« Reply #301 on: 07/01/2009 02:30 AM »
At high temperature and low pressure, CH4 + H2O => CO + 3H2.

Obviously, O2 cannot be present.

The hydrogen comes from steam-reforming natural gas. Actually, after Katrina, we gave most of our hydrogen back to Air Products because Katrina shut down their New Orleans plant for a while at the same time their Canadian plant was down for maintenance, so they didn't have any for their other customers.

Offline whitewatcher

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Re: Basic Rocket Science Q & A
« Reply #302 on: 07/01/2009 09:56 AM »
If so I'd suggest you start with "Fly Me to the Moon" by Edward Belbruno.

This book has a bad amazon comment, but if you recommend it, i'll buy!
Thank you for the recommendation!

Quote
Here's some Pdfs I have found

http://www.agi.com/downloads/support/productSupport/literature/pdfs/whitePapers/0800_wsb.pdf

http://esto.nasa.gov/conferences/nstc2007/papers/Belbruno_Edward_C6P1_NSTC-07-0156.pdf

I've already read the first one, but the second is new to me. Thank you!
« Last Edit: 07/01/2009 09:57 AM by whitewatcher »
"One Percent for Space"

Offline clongton

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Re: Basic Rocket Science Q & A
« Reply #303 on: 07/01/2009 03:09 PM »
And Ares I can't suffer a first stage turbopump failure.
Ares-I 2nd stage can

Quote
Saying that non-existent technology X is better than well-used technology Y is disingenuous.

What's your beef? I was musing about a potential future efficient application of nuclear technology to ground support equipment for launch vehicles. And fyi, the technology DOES exist. There's a ton of information available if you look for it.
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline whitewatcher

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Re: Basic Rocket Science Q & A
« Reply #304 on: 07/01/2009 04:29 PM »
I just had the opportunity to talk to an export. Just in case somebody's interested:

- The departure inclination can be at least between 0 and 51.6°. Higher inclinations are probably possible, but still need analysis. The farther off-plane the ejection is, the more delta-v is required (but in the order of magnitude of 50, maybe 60 m/s).

- The destination inclination can almost be chosen for free.

- WSB transfers from LLO/EML1/EML2 to earth orbit are possible but end up in a high eccentric orbit (apogee 1,4 mio km or so). Perigee can be chosen at almost no additional delta-v, so aerocapture could be an option.

- Transfer between EML1 and EML2 can be done as follows: Go into an unstable manifold which brings you to a random lunar orbit. After 14 days, the EML's have switched and your orbital plane now intersects the destination EML region. Bring the S/C on a stable manifold to your destination EML. That's the trick!
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Offline Archibald

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Re: Basic Rocket Science Q & A
« Reply #305 on: 07/01/2009 05:30 PM »
somewhere in these documents it is said that some WSB trajectories might double your payload to the Moon.
WSB trajectories could be of interest when refueling a EML-1 /EML-2 depot...

Offline whitewatcher

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Re: Basic Rocket Science Q & A
« Reply #306 on: 07/01/2009 08:12 PM »
somewhere in these documents it is said that some WSB trajectories might double your payload to the Moon.
WSB trajectories could be of interest when refueling a EML-1 /EML-2 depot...

Yeah, that's Belbruno. He is known to be somewhat optimistic.

But I think the combination of some new technologies could fly your cargo to the moon (from LEO) with less than 10% of the mass being fuel.

You could use a low thrust trajectory from LEO to EML-1, use an unstable manifold for transfer to a high lunar orbit, transfer to EML-2 on a stable manifold and then use  a lunar space elevator to get things to the surface. Of couse: you need the elevator and you get your cargo delivered to the far side's equator. ;-) You get the idea ....

But for a fuel mass of 50-60 percent you should be able to bring your cargo to any place on the moon. Maybe staging in EML-1 would be a good idea in this case. (Avoids shutteling high thrust engines of a lander between LEO and EML-1.)

I'm currently writing a summary on lunar logistics and it's VERY interesting stuff.
"One Percent for Space"

Offline Bob the Avenger

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Re: Basic Rocket Science Q & A
« Reply #307 on: 07/01/2009 08:23 PM »
I really think this stuff can revolutionise (storable) cargo mission to the moon. Also I think I remember Belbruno writing about using these trajectories to place fuel depots around the moon for return journeys or trips onward. Moving things around the Earth-Moon system for comparitively tiney deltaVs should provide us with lots of opportunities untill a Star Trek type impluse drive can be developed/build but thats going off topic somewhat

Offline Lab Lemming

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Re: Basic Rocket Science Q & A
« Reply #308 on: 07/02/2009 12:52 AM »
My beef is that much Thorium advocacy is based on geological misconceptions:
http://lablemminglounge.blogspot.com/2008/05/thorium-uranium-ratios-and-atomic-power.html

And Ares I can't suffer a first stage turbopump failure.
Ares-I 2nd stage can

Quote
Saying that non-existent technology X is better than well-used technology Y is disingenuous.

What's your beef? I was musing about a potential future efficient application of nuclear technology to ground support equipment for launch vehicles. And fyi, the technology DOES exist. There's a ton of information available if you look for it.

Offline yinzer

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Re: Basic Rocket Science Q & A
« Reply #309 on: 07/02/2009 03:04 AM »
And Ares I can't suffer a first stage turbopump failure.
Ares-I 2nd stage can

Quote
Saying that non-existent technology X is better than well-used technology Y is disingenuous.

What's your beef? I was musing about a potential future efficient application of nuclear technology to ground support equipment for launch vehicles. And fyi, the technology DOES exist. There's a ton of information available if you look for it.

How is it efficient?  Natural gas is used to make electricity and reformed into hydrogen.  The reformation is more thermodynamically efficient than the generation.  If you add a source of nuclear generated electricity, the efficient thing to do would to be the nuclear power to run refrigerators, light bulbs, and air compressors while using the natural gas to make hydrogen.
California 2008 - taking rights from people and giving rights to chickens.

Offline clongton

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Re: Basic Rocket Science Q & A
« Reply #310 on: 07/02/2009 03:38 PM »
And Ares I can't suffer a first stage turbopump failure.
Ares-I 2nd stage can

Quote
Saying that non-existent technology X is better than well-used technology Y is disingenuous.

What's your beef? I was musing about a potential future efficient application of nuclear technology to ground support equipment for launch vehicles. And fyi, the technology DOES exist. There's a ton of information available if you look for it.

How is it efficient?  Natural gas is used to make electricity and reformed into hydrogen.  The reformation is more thermodynamically efficient than the generation.  If you add a source of nuclear generated electricity, the efficient thing to do would to be the nuclear power to run refrigerators, light bulbs, and air compressors while using the natural gas to make hydrogen.

Yes, natural gas can make hydrogen. But I talked about hydrogen and oxygen for launch vehicle propellants. One plant producing all the propellant. Natural gas plants can't do that. Plus there is a *lot* more seawater available, without drilling, than there is natural gas. It can be difficult to find appropriate places to put the natural gas plant, but there are tens of thousands of miles of sea coast that can be accessed much easier. Thorium nuclear energy is also a lot cleaner than the natural gas process. It's non-polluting.
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline Hobbs

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Re: Basic Rocket Science Q & A
« Reply #311 on: 07/22/2009 05:05 PM »
Ok this is a reeeeaaally basic question but just thinking of it now i cant think of a satisfactory answer..

How did the saturn 5 (and for that matter any "inline" rocket) keep upright during launch? , obviously its massively top heavy about where the force is being applied at the bottom which would make it really unstable, it isn't spinning for gyrostabilisation and I cant see the balsa-wood stick, the only way i can think is that the engines were constantly vectored to stay dead on centre of mass but surely if they were just millimetres off then the rocket would tilt.
so how do they manage this?

Offline ugordan

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Re: Basic Rocket Science Q & A
« Reply #312 on: 07/22/2009 05:13 PM »
the only way i can think is that the engines were constantly vectored to stay dead on centre of mass but surely if they were just millimetres off then the rocket would tilt.

Bingo. The engines gimbal keeping not only the thrust vector through the center of mass, but also by nudging the vector slightly they provide pitch/yaw (and if more than one nozzle) roll control. The rocket tends to "fall over", it's not inherently stable in flight (just like trying to keep a pencil upright on your fingertip) so this gimballing is continuous. The angles involved are really small - a couple of degrees in any direction, typically up to 8 degrees, but for the most part it's enough to have good control authority. Also a factor in controlability is how fast the engine can gimbal to a desired position.

If a rocket is really long (e.g. Saturn V), at the other end you can really feel this kicking around - which is what all Apollo astronauts reported.
« Last Edit: 07/22/2009 05:24 PM by ugordan »

Offline cixelsyD

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Re: Basic Rocket Science Q & A
« Reply #313 on: 07/22/2009 05:19 PM »
Maybe a simpler question, how did they support the Saturn V before launch, were there platforms near the base that supported it, or did the arms that retracted before launch hold it?

Offline Jim

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Re: Basic Rocket Science Q & A
« Reply #314 on: 07/22/2009 05:35 PM »
Maybe a simpler question, how did they support the Saturn V before launch, were there platforms near the base that supported it, or did the arms that retracted before launch hold it?

It sat on this

http://www.hq.nasa.gov/pao/History/SP-4204/ch13-4.html

Offline engstudent

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Re: Basic Rocket Science Q & A
« Reply #315 on: 08/13/2009 12:49 PM »
How do you calculate the escape velocity of a rocket and how is it dependent on the density of or choice of propellant?
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Offline Jim

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Re: Basic Rocket Science Q & A
« Reply #316 on: 08/13/2009 01:02 PM »
How do you calculate the escape velocity of a rocket and how is it dependent on the density of or choice of propellant?

Escape velocity or exhaust velocity?

Offline engstudent

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Re: Basic Rocket Science Q & A
« Reply #317 on: 08/13/2009 01:11 PM »
How do you calculate the escape velocity of a rocket and how is it dependent on the density of or choice of propellant?

Escape velocity or exhaust velocity?

Escape velocity - exhaust velocity is C = 9.8*Isp in the basic rocket equation relating deltaV, dry mass and propellant mass.  I'm familiar with this [ dV = C*ln((M+P)/M) ] but not the relationship between the deltaV required of a vehicle depending on its... whats the word density impulse?  How do you lower the dV required when C, exhaust velocity is fixed, or how do you compare the benefits of a propellant choice with slightly different C and grossly different density of P?
« Last Edit: 08/13/2009 01:12 PM by engstudent »
” …All of this. All of this was for nothing – unless we go to the stars.” - Sinclair

Offline Jim

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Re: Basic Rocket Science Q & A
« Reply #318 on: 08/13/2009 01:28 PM »
Escape velocity is dependent on the planetary body that the vehicle is near.

Ve = sqrt(2GM/r)

Offline engstudent

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Re: Basic Rocket Science Q & A
« Reply #319 on: 08/13/2009 01:43 PM »
then this equation may not help me in its current form

Can you assume a vehicle can have a dV equal to the Ve?  So that maybe C*ln( m+P/m ) = sqrt(2GM/r) ?
” …All of this. All of this was for nothing – unless we go to the stars.” - Sinclair