Author Topic: Solids, Q&A  (Read 23709 times)

Offline tu8ca

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Solids, Q&A
« on: 01/03/2011 09:50 pm »
Why aren't solids used more for orbital launches?

I understand the fuel has less energy, so a larger rocket is needed. But why are liquid stages worth all the added complexity, cost and infrastructure?

Offline butters

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Re: Solids, Q&A
« Reply #1 on: 01/04/2011 05:19 am »
Many, many reasons. One understated issue with large solid rockets is that they're very heavy preloaded with propellant and therefore difficult to transport.

Shuttle could not be moved from the VAB to LC-39 without the massive crawler-transporters to distribute the extreme load of the SRBs, which are obviously assembled from segments because of transportation issues.

Ariane 5 faces a similar fixed cost penalty because of its large SRBs, which have to be manufactured on-site at the Guiana Space Center and moved with a special locomotive equipped with a 32-speed transmission.

Add that to the numerous other reasons, including low specific impulse, low mass ratio (because the entire propellant tank is subject to combustion pressure), poor ground crew safety, poor shutdown capability, no restart capability, higher vibrations during flight, hydrochloric acid emissions, etc...

Offline Space Invaders

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Re: Solids, Q&A
« Reply #2 on: 01/04/2011 06:33 am »
Poor ground crew safety? When was the last time a solid rocket killed a ground crew member? SRBs need very high temperatures to ignite, you can't just extinguish your cigarette on one to light it.

Offline cd-slam

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Re: Solids, Q&A
« Reply #3 on: 01/04/2011 08:16 am »
Poor ground crew safety? When was the last time a solid rocket killed a ground crew member? SRBs need very high temperatures to ignite, you can't just extinguish your cigarette on one to light it.

http://en.wikipedia.org/wiki/2003_Alc%C3%A2ntara_VLS_accident

Offline Nomadd

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Re: Solids, Q&A
« Reply #4 on: 01/04/2011 11:31 am »
Poor ground crew safety? When was the last time a solid rocket killed a ground crew member? SRBs need very high temperatures to ignite, you can't just extinguish your cigarette on one to light it.

 How many times have you seen liquid engines cut off right after ignition because something wasn't right? Kinda hard to do with solids. Even harder to offload fuel to pull back into the hangar to fix something.
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Offline Space Invaders

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Re: Solids, Q&A
« Reply #5 on: 01/04/2011 01:33 pm »
http://en.wikipedia.org/wiki/2003_Alc%C3%A2ntara_VLS_accident
Irrelevant of the fuel type. If it had been a liquid rocket that ignited suddenly in the same circumstances, the people standing on the launch pad would have died as well. They were far too close to survive any type of ignition.

How many times have you seen liquid engines cut off right after ignition because something wasn't right? Kinda hard to do with solids. Even harder to offload fuel to pull back into the hangar to fix something.
You don't need to cut solid engines right after ignition because they are much simpler and therefore problems are much less likely. The Challenger disaster was due to a design flaw and redesigned SRBs are safe.

Offline ugordan

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Re: Solids, Q&A
« Reply #6 on: 01/04/2011 01:45 pm »
http://en.wikipedia.org/wiki/2003_Alc%C3%A2ntara_VLS_accident
Irrelevant of the fuel type. If it had been a liquid rocket that ignited suddenly in the same circumstances, the people standing on the launch pad would have died as well. They were far too close to survive any type of ignition.

Not correct. That's kind of why the standard safety procedure is to have very few to no people around the liquid fueled vehicle when it's fueled. In other words, there wouldn't be 20 technicians and engineers just standing around a fully fueled liquid vehicle. Also the fact the propellants are physically separated so you would literally have to blow up the vehicle first before it would provide an major explosion/fire hazard.

Now tell me you can have an unfueled solid vehicle at the pad during checkouts...

Offline ugordan

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Re: Solids, Q&A
« Reply #7 on: 01/04/2011 01:59 pm »
You don't need to cut solid engines right after ignition because they are much simpler and therefore problems are much less likely. The Challenger disaster was due to a design flaw and redesigned SRBs are safe.

Design flaw/production flaw, what difference does it make? A failure is a failure.

Titan 34D, Delta II, Challenger, Titan IV failures were recent solid motor failures. Out of those 4, 3 were explosive failures. How many U.S. explosive liquid engine failures are you aware of in recent history?

Also, cocky statements like "redesigned SRBs are safe" are what gets people killed.

Offline Jim

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Re: Solids, Q&A
« Reply #8 on: 01/04/2011 01:59 pm »

Irrelevant of the fuel type. If it had been a liquid rocket that ignited suddenly in the same circumstances, the people standing on the launch pad would have died as well. They were far too close to survive any type of ignition.

You don't need to cut solid engines right after ignition because they are much simpler and therefore problems are much less likely. The Challenger disaster was due to a design flaw and redesigned SRBs are safe.

That is just plain wrong and shows a complete lack of understanding.

A liquid engine would not have ignited in the first place.  The ignition danger is unique to solids.

Segmented solids are not "simpler".  Solids have a higher failure rate.

Offline Space Invaders

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Re: Solids, Q&A
« Reply #9 on: 01/04/2011 02:15 pm »
Not correct. That's kind of why the standard safety procedure is to have very few to no people around the liquid fueled vehicle when it's fueled. In other words, there wouldn't be 20 technicians and engineers just standing around a fully fueled liquid vehicle. Also the fact the propellants are physically separated so you would literally have to blow up the vehicle first before it would provide an major explosion/fire hazard.

Now tell me you can have an unfueled solid vehicle at the pad during checkouts...
The R-16 of the Nedelin disaster was fueled and surrounded by dozens of people. In other words, there could be 120 technicians and engineers just standing around a fully fueled liquid vehicle. It just depends on how stupid they are.

And you don't need an explosion/fire to happen. If for some reason the liquid rocket fires prematurely and you're around, you die.

That is just plain wrong and shows a complete lack of understanding.

A liquid engine would not have ignited in the first place.  The ignition danger is unique to solids.

Segmented solids are not "simpler".  Solids have a higher failure rate.
Yet again, what about the Nedelin disaster? It was a liquid rocket and it ignited unexpectedly.

Design flaw/production flaw, what difference does it make? A failure is a failure.

Titan 34D, Delta II, Challenger, Titan IV failures were recent solid motor failures. Out of those 4, 3 were explosive failures. How many U.S. explosive liquid engine failures are you aware of in recent history?

Also, cocky statements like "redesigned SRBs are safe" are what gets people killed.
If you develop a liquid rocket with a flawed design, it will eventually explode too. If you develop a microwave oven with a flawed design, it will eventually catch fire or electrocute you too. Anything with a flawed design is dangerous. My point is that a flawed design has nothing to do with rocket type, rather it can affect any sort of rocket.

As for Titaan 34D, if you're talking about the 1985 accident, it happened after solid rocket booster separation.

Hey, it's not like I'm an ATK fan or something, but sometimes it seems solid rockets are the devil incarnate for some users here. Both liquid and solid systems have their roles and there's no point in preaching how wonderful and perfect liquids are and how horrible and flawed solids are.
« Last Edit: 01/04/2011 02:17 pm by Space Invaders »

Offline Jim

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Re: Solids, Q&A
« Reply #10 on: 01/04/2011 02:43 pm »
Yet again, what about the Nedelin disaster? It was a liquid rocket and it ignited unexpectedly.

If you develop a liquid rocket with a flawed design, it will eventually explode too. If you develop a microwave oven with a flawed design, it will eventually catch fire or electrocute you too. Anything with a flawed design is dangerous. My point is that a flawed design has nothing to do with rocket type, rather it can affect any sort of rocket.

As for Titan 34D, if you're talking about the 1985 accident, it happened after solid rocket booster separation.


Wrong again.   The accidents are not the same.  Alcântara happened because of work directly on the rocket.  This can happen anywhere and time with an SRM.  See at EAFB and PSTF incidents.  Nedlin happened because the control center sent commands and would have happen with or without a crew at the pad.

It has nothing to do with flawed design.  SRM are sensitive to process flaws.

Do some research, there were two Titan 34D incidents.

Solid rockets are the devil incarnate for manned missions
« Last Edit: 01/04/2011 02:44 pm by Jim »

Offline ugordan

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Re: Solids, Q&A
« Reply #11 on: 01/04/2011 04:38 pm »
The R-16 of the Nedelin disaster was fueled and surrounded by dozens of people. In other words, there could be 120 technicians and engineers just standing around a fully fueled liquid vehicle. It just depends on how stupid they are.

You're grasping at straws now and are practically admitting it.
Comparing:

a) an event from the very dawn of the space age, employing Soviet military procedures in a government regime which cared little about the value of human life

to

b) a civilian launch vehicle operation at the pad in the 1990's

...is disingenuous. Note I specifically stated it's a "standard safety procedure" to evacuate the pad while tanking/pressurizing tests because you would almost inevitably bring up Nedelin. The fact the Soviets didn't take adequate safety precautions to prevent that from happening does nothing to disprove the fact a solid booster is inherently more dangerous to work with because it is loaded at all times.

And you don't need an explosion/fire to happen. If for some reason the liquid rocket fires prematurely and you're around, you die.

Once again that implies

1) that the vehicle is loaded with propellant
2) that you're stupid enough to be around at the time.

My point is that a flawed design has nothing to do with rocket type, rather it can affect any sort of rocket.

The point about the Challenger because of which you brought up that fact is that there is no health check at ignition because solids don't have that ability. The drop in Challenger SRB booster pressure could have been detected right at liftoff ignition for all we care and it still wouldn't have mattered because once it ignites that's it. Design fault or no design fault. Both booster types are prone to failures happening at some point in flight. Liquids at least have the ability to prevent problems detectable right at ignition from dooming the flight later on. Not to mention that liquid engine failure modes are typically more benign than with solids, even if there are more of them relatively speaking (debatable).
« Last Edit: 01/04/2011 04:43 pm by ugordan »

Offline tu8ca

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Re: Solids, Q&A
« Reply #12 on: 01/04/2011 05:18 pm »
Many, many reasons. One understated issue with large solid rockets is that they're very heavy preloaded with propellant and therefore difficult to transport...
Come to think of it, most all-solid rockets are on the small end.

Does the cost of solid fuel come into play? I understand the cost of lox, h2 and kerosene don't even show on the radar, compared to the rest of the launch cost. Solid fuel seems to be about 100x more expensive per pound (guestimating). Anyone have the numbers on this?
« Last Edit: 01/04/2011 05:19 pm by tu8ca »

Offline kevin-rf

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Re: Solids, Q&A
« Reply #13 on: 01/04/2011 05:35 pm »

I believe that the cost of hypergolic's are also in the stratosphere. Cost does not seem to have kept them from being used. Though to be fair there is a desire to cut back on them from safety/accidental exposure side.

Anyone have a good list of costs?
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Offline tu8ca

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Re: Solids, Q&A
« Reply #14 on: 01/04/2011 05:49 pm »

I believe that the cost of hypergolic's are also in the stratosphere. Cost does not seem to have kept them from being used. Though to be fair there is a desire to cut back on them from safety/accidental exposure side.

Anyone have a good list of costs?

I'm really interested in this. From the cost of rawmaterials, solid fuel seems to be below $5/lb (again, guestimating), but I've read that the SRB's fuel is around $20/lb after manufacturing.

JAXA is using a thermoplastic binder instead of a thermoset. They say it reduces cost because they can manufacture ingots that are easy to store, ship and recycle, then cast the grain as needed from those ingots, thereby greatly reducing the size and cost of their solid fuel manufacturing facilities.

« Last Edit: 01/04/2011 09:42 pm by tu8ca »

Offline Comga

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Re: Solids, Q&A
« Reply #15 on: 01/04/2011 08:14 pm »

I believe that the cost of hypergolic's are also in the stratosphere. Cost does not seem to have kept them from being used. Though to be fair there is a desire to cut back on them from safety/accidental exposure side.

Anyone have a good list of costs?

For everything other than solids, try
http://www.desc.dla.mil/DCM/Files/FY10%20Standard%20Price%20Letter%20%20Price%20Sheet%20Aug%2009_1.pdf

What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Proponent

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Re: Solids, Q&A
« Reply #16 on: 01/11/2011 02:34 am »
Thanks for the price list, Comga.

How does RP-2 differ from RP-1, and where's it used?

Offline jbirdav8r

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Re: Solids, Q&A
« Reply #17 on: 01/11/2011 03:10 am »
RP-2 is similar to RP-1 with a lower sulfur content.  I'm not aware it's being used at all...significantly more expensive to refine for a small benefit.  Neither are solid fuels though...very high-grade kerosene.

Offline Malderi

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Re: Solids, Q&A
« Reply #18 on: 01/18/2011 04:07 pm »
Could someone talk a little bit about the tradeoffs among solid propellants, or point me to a source? Shuttle SRBs use PBAN, I think, but there's HTPB which has been talked about as an alternative. What are the tradeoffs between them (and potentially other solid fuels?)

Offline baldusi

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Re: Solids, Q&A
« Reply #19 on: 01/18/2011 09:47 pm »
Could someone talk a little bit about the tradeoffs among solid propellants, or point me to a source? Shuttle SRBs use PBAN, I think, but there's HTPB which has been talked about as an alternative. What are the tradeoffs between them (and potentially other solid fuels?)
There's also the China Lake Compound 20.

Offline Downix

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Re: Solids, Q&A
« Reply #20 on: 01/18/2011 09:50 pm »
Could someone talk a little bit about the tradeoffs among solid propellants, or point me to a source? Shuttle SRBs use PBAN, I think, but there's HTPB which has been talked about as an alternative. What are the tradeoffs between them (and potentially other solid fuels?)
They're binding agents, the polymers used to hold the fuel in place.  HTPB is the most common, used in over 75% of the solid motors out there.  PBAN has a slower curing time, but gives slightly higher performance. 
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Offline tu8ca

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Re: Solids, Q&A
« Reply #21 on: 01/18/2011 10:36 pm »
Could someone talk a little bit about the tradeoffs among solid propellants, or point me to a source? Shuttle SRBs use PBAN, I think, but there's HTPB which has been talked about as an alternative. What are the tradeoffs between them (and potentially other solid fuels?)
There's also the China Lake Compound 20.

Interesting ... the 1.1 class propellants are supposed to have +4% isp over the standard composites, and the CL-20 a 14% increase over the 1.1 class. So if you had a stage with 280 isp, 1.1 class would bump it up to 291, Cl-20 to 332.


Offline Malderi

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Re: Solids, Q&A
« Reply #22 on: 01/18/2011 11:27 pm »
That's a pretty significant performance boost... There's got to be some major downside to it!

Offline Downix

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Re: Solids, Q&A
« Reply #23 on: 01/18/2011 11:49 pm »
That's a pretty significant performance boost... There's got to be some major downside to it!
More toxic, heavier due to higher density, decomposes more rapidly.  While traditional solids are good for decades, CL-20 decomposes at a faster rate, and needs to be used within 18 months.
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Offline tu8ca

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Re: Solids, Q&A
« Reply #24 on: 01/18/2011 11:59 pm »
That's a pretty significant performance boost... There's got to be some major downside to it!
More toxic, heavier due to higher density, decomposes more rapidly.  While traditional solids are good for decades, CL-20 decomposes at a faster rate, and needs to be used within 18 months.
The 1.1 class propellants are more dangerous. CL-20 is probably a lot more expensive (guessing).

But a doesn't a denser propellant mean a smaller case, thereby saving weight?

Offline Downix

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Re: Solids, Q&A
« Reply #25 on: 01/19/2011 12:05 am »
That's a pretty significant performance boost... There's got to be some major downside to it!
More toxic, heavier due to higher density, decomposes more rapidly.  While traditional solids are good for decades, CL-20 decomposes at a faster rate, and needs to be used within 18 months.
The 1.1 class propellants are more dangerous. CL-20 is probably a lot more expensive (guessing).

But a doesn't a denser propellant mean a smaller case, thereby saving weight?
The casing is lighter, but the fuel itself is heavier.  It's 20% heavier per cubic cm, but only gives 11% more performance.  This means you still have a rocket which is roughly 9% heavier than comparable.  Add to that the cost, then it becomes less appealing.  It is, however, becoming popular for bullets, as it's density is not an issue but the extra kick is welcome.
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Offline alexw

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Re: Solids, Q&A
« Reply #26 on: 01/19/2011 12:11 am »
How many times have you seen liquid engines cut off right after ignition because something wasn't right? Kinda hard to do with solids. Even harder to offload fuel to pull back into the hangar to fix something.
You don't need to cut solid engines right after ignition because they are much simpler and therefore problems are much less likely. The Challenger disaster was due to a design flaw and redesigned SRBs are safe.
     You may well need to cut solid rockets after ignition if there is an abort initiated for any reason -- solids, liquids, guidance, capsule, etc. See the Orion LAS controversy. Gotta unzip that booster case, because the now-lightened solid is going to keep going up like the proverbial bat from the hot place, and its plumage is a bad place for the (manned) payload to be.
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Offline tu8ca

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Re: Solids, Q&A
« Reply #27 on: 01/19/2011 12:20 am »
That's a pretty significant performance boost... There's got to be some major downside to it!
More toxic, heavier due to higher density, decomposes more rapidly.  While traditional solids are good for decades, CL-20 decomposes at a faster rate, and needs to be used within 18 months.
The 1.1 class propellants are more dangerous. CL-20 is probably a lot more expensive (guessing).

But a doesn't a denser propellant mean a smaller case, thereby saving weight?
The casing is lighter, but the fuel itself is heavier.  It's 20% heavier per cubic cm, but only gives 11% more performance.  This means you still have a rocket which is roughly 9% heavier than comparable.

Maybe I'm missing something here ... performance is measured with respect to fuel mass, not density.

So if you have two fuels with identical performance, but one is ten percent denser, they'll still have identical performance if the propellant load is the same mass. But the denser fuel can have a smaller casing. right?


Offline Downix

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Re: Solids, Q&A
« Reply #28 on: 01/19/2011 01:16 am »
That's a pretty significant performance boost... There's got to be some major downside to it!
More toxic, heavier due to higher density, decomposes more rapidly.  While traditional solids are good for decades, CL-20 decomposes at a faster rate, and needs to be used within 18 months.
The 1.1 class propellants are more dangerous. CL-20 is probably a lot more expensive (guessing).

But a doesn't a denser propellant mean a smaller case, thereby saving weight?
The casing is lighter, but the fuel itself is heavier.  It's 20% heavier per cubic cm, but only gives 11% more performance.  This means you still have a rocket which is roughly 9% heavier than comparable.

Maybe I'm missing something here ... performance is measured with respect to fuel mass, not density.

So if you have two fuels with identical performance, but one is ten percent denser, they'll still have identical performance if the propellant load is the same mass. But the denser fuel can have a smaller casing. right?


Semi correct.  You also have to deal with burn rate.  Smaller casings also mean in many cases smaller burning surface, which can then harm performance.  They may overcome this with better chamber designs, but it takes time to develop.  Give it time for them to optimize the design.  Once they have this, then it should indeed give better performance.
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Offline baldusi

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Re: Solids, Q&A
« Reply #29 on: 01/19/2011 02:18 am »
It is, however, becoming popular for bullets, as it's density is not an issue but the extra kick is welcome.
I thought that bullets are limited by chamber pressure, and usually have longer that 18 months of storage requirements. How do they overcome those issues?

Offline Downix

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Re: Solids, Q&A
« Reply #30 on: 01/19/2011 02:32 am »
It is, however, becoming popular for bullets, as it's density is not an issue but the extra kick is welcome.
I thought that bullets are limited by chamber pressure, and usually have longer that 18 months of storage requirements. How do they overcome those issues?
Depends on the bullet. Some anti-tank shells have short lives anyways.
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Offline baldusi

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Re: Solids, Q&A
« Reply #31 on: 01/19/2011 03:40 pm »
Semi correct.  You also have to deal with burn rate.  Smaller casings also mean in many cases smaller burning surface, which can then harm performance.  They may overcome this with better chamber designs, but it takes time to develop.  Give it time for them to optimize the design.  Once they have this, then it should indeed give better performance.
Why don't you simply make a bigger bore and keep the casing (if it supports the extra pressure)?

Offline Downix

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Re: Solids, Q&A
« Reply #32 on: 01/19/2011 05:11 pm »
Semi correct.  You also have to deal with burn rate.  Smaller casings also mean in many cases smaller burning surface, which can then harm performance.  They may overcome this with better chamber designs, but it takes time to develop.  Give it time for them to optimize the design.  Once they have this, then it should indeed give better performance.
Why don't you simply make a bigger bore and keep the casing (if it supports the extra pressure)?
Then you may not have the pressure to get sufficient thrust.  Or your burn-rate could be too fast or too slow.  It's not simple by any measurement.
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Offline baldusi

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Re: Solids, Q&A
« Reply #33 on: 01/19/2011 05:26 pm »
Then you may not have the pressure to get sufficient thrust.  Or your burn-rate could be too fast or too slow.  It's not simple by any measurement.
I was under the impression that a circular central bore gave a (relatively) constant pressure.

Offline tu8ca

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Re: Solids, Q&A
« Reply #34 on: 01/19/2011 05:41 pm »
Semi correct.  You also have to deal with burn rate.  Smaller casings also mean in many cases smaller burning surface, which can then harm performance.  They may overcome this with better chamber designs, but it takes time to develop.  Give it time for them to optimize the design.  Once they have this, then it should indeed give better performance.
Why don't you simply make a bigger bore and keep the casing (if it supports the extra pressure)?
Then you may not have the pressure to get sufficient thrust.  Or your burn-rate could be too fast or too slow.  It's not simple by any measurement.
If you have one fuel denser by 10% over another and go with a smaller case to save weight, there are lots of variables that might avail themselves to tweaking. Grain shape first - lots of ways to add back grain surface area and control thrust profile. Of course this was just an illustrative comparison ... denser solid fuel saves case weight.

« Last Edit: 01/19/2011 05:49 pm by tu8ca »

Offline Downix

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Re: Solids, Q&A
« Reply #35 on: 01/19/2011 08:40 pm »
Semi correct.  You also have to deal with burn rate.  Smaller casings also mean in many cases smaller burning surface, which can then harm performance.  They may overcome this with better chamber designs, but it takes time to develop.  Give it time for them to optimize the design.  Once they have this, then it should indeed give better performance.
Why don't you simply make a bigger bore and keep the casing (if it supports the extra pressure)?
Then you may not have the pressure to get sufficient thrust.  Or your burn-rate could be too fast or too slow.  It's not simple by any measurement.
If you have one fuel denser by 10% over another and go with a smaller case to save weight, there are lots of variables that might avail themselves to tweaking. Grain shape first - lots of ways to add back grain surface area and control thrust profile. Of course this was just an illustrative comparison ... denser solid fuel saves case weight.

Precisely.  This is a new fuel source. They are still working on designs to optimize use of the fuel.  Once they have that done, I expect several systems to use it beyond the particular fast-decay tank shells it's already found in.
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Offline tnphysics

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Re: Solids, Q&A
« Reply #36 on: 01/19/2011 08:47 pm »
That's a pretty significant performance boost... There's got to be some major downside to it!
More toxic, heavier due to higher density, decomposes more rapidly.  While traditional solids are good for decades, CL-20 decomposes at a faster rate, and needs to be used within 18 months.
The 1.1 class propellants are more dangerous. CL-20 is probably a lot more expensive (guessing).

But a doesn't a denser propellant mean a smaller case, thereby saving weight?

The 1.1 props are FAR more dangerous. 1.1 means detonable. Thus, a failure could cause turn the rocket into a bomb of the same size. I suspect that this is an ABSOLUTE no-no for most applications.

Offline Downix

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Re: Solids, Q&A
« Reply #37 on: 01/19/2011 09:54 pm »
That's a pretty significant performance boost... There's got to be some major downside to it!
More toxic, heavier due to higher density, decomposes more rapidly.  While traditional solids are good for decades, CL-20 decomposes at a faster rate, and needs to be used within 18 months.
The 1.1 class propellants are more dangerous. CL-20 is probably a lot more expensive (guessing).

But a doesn't a denser propellant mean a smaller case, thereby saving weight?

The 1.1 props are FAR more dangerous. 1.1 means detonable. Thus, a failure could cause turn the rocket into a bomb of the same size. I suspect that this is an ABSOLUTE no-no for most applications.
I thought CL-20 was a 1.3 class, but I'm not certain.
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Offline tu8ca

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Re: Solids, Q&A
« Reply #38 on: 01/19/2011 09:58 pm »
The 1.1 class propellants are more dangerous. CL-20 is probably a lot more expensive (guessing).

But a doesn't a denser propellant mean a smaller case, thereby saving weight?

The 1.1 props are FAR more dangerous. 1.1 means detonable. Thus, a failure could cause turn the rocket into a bomb of the same size. I suspect that this is an ABSOLUTE no-no for most applications.
I thought CL-20 was a 1.3 class, but I'm not certain.
Yes, I think that's right;
http://www.navair.navy.mil/techTrans/index.cfm?map=local.ccms.view.aB&doc=crada.13

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Re: Solids, Q&A
« Reply #39 on: 02/15/2011 04:21 am »
I apologize if this is the wrong thread, but I'm wondering if anyone can give a link comparing Ares I-X liftoff weight with what Ares I would have had. I heard George Diller say I-X was 200,000 lbs lighter, but can't seem to find the video where he says it. I thought it was during the launch, but apparently not.

Any help would be appreciated. Thanks.
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Offline Nickolai

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Re: Solids, Q&A
« Reply #40 on: 07/29/2011 11:53 pm »
What sort of igniter mechanisms are used, specifically for solid rockets, that work in a vacuum (i.e. the inertial upper stage)? And can any of these be applied to model rockets?
« Last Edit: 07/30/2011 12:18 am by ntrgc89 »

Offline JayP

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Re: Solids, Q&A
« Reply #41 on: 07/30/2011 05:17 pm »
What sort of igniter mechanisms are used, specifically for solid rockets, that work in a vacuum (i.e. the inertial upper stage)? And can any of these be applied to model rockets?

All solid rocket motors, from the smallest estes to the Shuttles SRBs, use the same ignition mechanism, a detonator consisting of some sort of exploding bridge wire is used to ignite a combustible compound and the heat and flame from that ignites the propelant. The only difference is that the bigger motors use multiple stages of ignition to build up a big enough flame. On the shuttles SRBs, There are 3 other combustion steps between the NSI (Nasa standard initiator) and the ingnition of the main propelent. All of the steps happen so fast that they are, for all intents, instantanious. The system works just as well in a vacuum or in freefall as it does on the ground.
« Last Edit: 07/30/2011 05:18 pm by JayP »

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Re: Solids, Q&A
« Reply #42 on: 07/31/2011 03:40 am »
All solid rocket motors, from the smallest estes to the Shuttles SRBs, use the same ignition mechanism, [the] only difference is that the bigger motors use multiple stages of ignition to build up a big enough flame. On the shuttles SRBs, There are 3 other combustion steps between the NSI (Nasa standard initiator) and the ignition of the main propellant.

For Shuttle are there also multiple, independent firing chains for each SRB, making them fault-tolerant?
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Re: Solids, Q&A
« Reply #43 on: 07/31/2011 02:16 pm »
One chain, two NSI's

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Re: Solids, Q&A
« Reply #44 on: 02/14/2015 04:09 pm »
GEM-40/46 question.

I was looking at solid failures today (one actual failure, one separation failure) and was wondering how many GEM-40/46's had flown. It's about 1100 give or take, but was wondering if anyone knew of a good quick to use source for the actual numbers.
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Offline edkyle99

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Re: Solids, Q&A
« Reply #45 on: 02/14/2015 04:18 pm »
GEM-40/46 question.

I was looking at solid failures today (one actual failure, one separation failure) and was wondering how many GEM-40/46's had flown. It's about 1100 give or take, but was wondering if anyone knew of a good quick to use source for the actual numbers.
The best I can offer is a list of every Delta 2 flown.  Only the 7000 series Deltas used GEM-40 and GEM-46 motors.  To these you would need to add 27 GEM-46 motors flown on Delta 3 vehicles.
http://www.spacelaunchreport.com/delta2.html#log
The second digit in the model number tells how many solids were used.

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« Last Edit: 02/14/2015 04:19 pm by edkyle99 »

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Re: Solids, Q&A
« Reply #46 on: 02/14/2015 05:48 pm »
Thanks Ed, took the time to go through it... if I did the math right, it was actually a tad lower than I was estimating. 1071

15 73xx
18 74xx (which surprised me)
103 79xx (including H's)
3 8930

So 1071 have flown with only one solid failure, not too shabby.

btw. I think you have a typo for Dawn, I thought it was a 7925H, not a 7295H

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Offline edkyle99

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Re: Solids, Q&A
« Reply #47 on: 02/15/2015 03:42 am »
Thanks Ed, took the time to go through it... if I did the math right, it was actually a tad lower than I was estimating. 1071

15 73xx
18 74xx (which surprised me)
103 79xx (including H's)
3 8930

So 1071 have flown with only one solid failure, not too shabby.

btw. I think you have a typo for Dawn, I thought it was a 7925H, not a 7295H
Thanks! 

I just noticed that today (February 14, 2015) is the 26th anniversary of the first Delta 2 launch (a 6925).

 - Ed Kyle
« Last Edit: 02/15/2015 03:43 am by edkyle99 »

Offline GClark

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Re: Solids, Q&A
« Reply #48 on: 02/15/2015 06:12 am »
... if I did the math right, it was actually a tad lower than I was estimating. 1071

15 73xx
18 74xx (which surprised me)
103 79xx (including H's)
3 8930

So 1071 have flown with only one solid failure, not too shabby.

There were two GBI-BVs and one BV-Plus using the GEM-40VN, so three more for 1074.  The second BV veered off course after 10 seconds - that's probably a control system failure, not the motor.

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