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
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.
Quote from: cd-slam on 01/04/2011 08:16 amhttp://en.wikipedia.org/wiki/2003_Alc%C3%A2ntara_VLS_accidentIrrelevant 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.
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.
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...
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.
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.
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.
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.
My point is that a flawed design has nothing to do with rocket type, rather it can affect any sort of rocket.
Many, many reasons. One understated issue with large solid rockets is that they're very heavy preloaded with propellant and therefore difficult to transport...
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?
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?)
Quote from: Malderi on 01/18/2011 04:07 pmCould 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.
That's a pretty significant performance boost... There's got to be some major downside to it!
Quote from: Malderi on 01/18/2011 11:27 pmThat'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.
Quote from: Downix on 01/18/2011 11:49 pmQuote from: Malderi on 01/18/2011 11:27 pmThat'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?
Quote from: Nomadd on 01/04/2011 11:31 amHow 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.
Quote from: tu8ca on 01/18/2011 11:59 pmQuote from: Downix on 01/18/2011 11:49 pmQuote from: Malderi on 01/18/2011 11:27 pmThat'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.
Quote from: Downix on 01/19/2011 12:05 amQuote from: tu8ca on 01/18/2011 11:59 pmQuote from: Downix on 01/18/2011 11:49 pmQuote from: Malderi on 01/18/2011 11:27 pmThat'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?
It is, however, becoming popular for bullets, as it's density is not an issue but the extra kick is welcome.
Quote from: Downix on 01/19/2011 12:05 amIt 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?
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.
Quote from: Downix on 01/19/2011 01:16 amSemi 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.
Quote from: baldusi on 01/19/2011 03:40 pmQuote from: Downix on 01/19/2011 01:16 amSemi 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.
Quote from: Downix on 01/19/2011 05:11 pmQuote from: baldusi on 01/19/2011 03:40 pmQuote from: Downix on 01/19/2011 01:16 amSemi 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.
Quote from: tu8ca on 01/18/2011 11:59 pmQuote from: Downix on 01/18/2011 11:49 pmQuote from: Malderi on 01/18/2011 11:27 pmThat'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.
Quote from: tnphysics on 01/19/2011 08:47 pmQuote from: tu8ca on 01/18/2011 11:59 pmThe 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.
Quote from: tu8ca on 01/18/2011 11:59 pmThe 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.
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?
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, [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.
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.
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. 107115 73xx18 74xx (which surprised me)103 79xx (including H's)3 8930So 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
... if I did the math right, it was actually a tad lower than I was estimating. 107115 73xx18 74xx (which surprised me)103 79xx (including H's)3 8930So 1071 have flown with only one solid failure, not too shabby.