We aren't talking about SRB failures really. If the SRB fails while Orion is still on top, all is lost. We are talking about all aborts. The 45th will ALWAYS blow the SRB up for an abort of any type. And this is both of them. Danny Deger
Quote from: Danny Dot on 08/01/2009 12:50 amWe aren't talking about SRB failures really. If the SRB fails while Orion is still on top, all is lost. We are talking about all aborts. The 45th will ALWAYS blow the SRB up for an abort of any type. And this is both of them. Danny DegerRight. I hate to say it but from a range safety point of view the crew is expendable and decreasing the thrust is the most important thing not reducing fragments. However, as I said in a previous post, the one time we blew the linear shape charge during the Challenger accident there was little SRB debris that went very far probably because most of the fuel was already burnt (about 50 seconds left) and pressure was down.
Another thought I hope the committee will consider is that with their Mars approach, which would attempt a "touch and go" test at the moon, there is a logical follow-up there... If you've got one design of lander which can land at Mars, but which has already proven it can also land on the Moon -- WHY NOT USE IT FOR BOTH ??Seems pretty logical that not only have you created your Mars architecture, but you also have a workable -- and proven -- Lunar architecture for free, no?
On blowing the nozzle. This needs lots of work. First the 45th may not agree to this. They may not like the SRB to stay intact.
And blowing the nozzle might result in case fragmentation anyway.
In the long run thrust goes to basically zero, but there is a temporary 10 fold increase in thrust. During the test, this thrust spike had enough impulse to rip the stapon off the bomb and it went something like 2,000 feet. Maybe an SRB with a blown nozzle will do something like this and come after Orion in a big hurry.
What is really bad for the idea the SRB case will stay is a few pieces is the pictures and video of the Titan failure. That is the bases of their report and my model. It is hard to argue the shuttle's SRBs will behave differently. The designs are too similar. Danny Deger
snipThat could be a big problem, depending on how long the thrust transient is. You said milliseconds?
If Direct is designed the same as shuttle then the RSS will only be on the SRB’s and spitting the case is the only option.
I think one of the main differences between Titan IV and Shuttle (and therefore Direct) is that there is no destruct system on the ET to cause an explosion of the Hydrogen and Oxygen tanks.
Quote from: phantomdj on 08/01/2009 02:03 amI think one of the main differences between Titan IV and Shuttle (and therefore Direct) is that there is no destruct system on the ET to cause an explosion of the Hydrogen and Oxygen tanks.That has no bearing on the SRB fragments.
What I was trying to understand was the difference between the Titan IV explosion profile (different SRB’s) that the 45th is using for Direct and Ares analysis
Quote from: kraisee on 07/31/2009 11:27 pmSimple rule: If it's designed to survive the worst case, it can survive the rest.Ross.What is the worst case? MaxQ? Range Safety presses destruct 10 sec, 20 sec late?The reason I ask is this: I test the Range Safety system on the SRB’s. I was there during the Challenger accident and saw the video that stayed with the SRB’s until the Range Safety Officer blew the linear shape charge. He waited at least 24 seconds until after the SRB’s were outside of the flight path. Also, when the LSC blew there was little debris that went very far probably because most of the fuel was already burnt (about 50 seconds left) and pressure was down.It’s just human nature that the RSO will not press the destruct button quickly and it is not automatic. Are there thoughts of making it automatic if the escape rockets are fired? If not, then it’s not reasonable to assume the SRB’s will be destroyed quickly after tank break-up.
Simple rule: If it's designed to survive the worst case, it can survive the rest.Ross.
Quote from: phantomdj on 08/01/2009 02:30 amWhat I was trying to understand was the difference between the Titan IV explosion profile (different SRB’s) that the 45th is using for Direct and Ares analysis The 45th was *NOT* analyzing DIRECT. Their study was strictly limited to Ares-I alone.
Quote from: phantomdj on 08/01/2009 12:04 amQuote from: kraisee on 07/31/2009 11:27 pmSimple rule: If it's designed to survive the worst case, it can survive the rest.Ross.What is the worst case? MaxQ? Range Safety presses destruct 10 sec, 20 sec late?The reason I ask is this: I test the Range Safety system on the SRB’s. I was there during the Challenger accident and saw the video that stayed with the SRB’s until the Range Safety Officer blew the linear shape charge. He waited at least 24 seconds until after the SRB’s were outside of the flight path. Also, when the LSC blew there was little debris that went very far probably because most of the fuel was already burnt (about 50 seconds left) and pressure was down.It’s just human nature that the RSO will not press the destruct button quickly and it is not automatic. Are there thoughts of making it automatic if the escape rockets are fired? If not, then it’s not reasonable to assume the SRB’s will be destroyed quickly after tank break-up.Ares-I is being designed to auto-destruct the SRB and Liquid Stage 3 seconds after Abort Initiation. Each element can handle the receipt of signal, interpretation and destruct commands separately and also thru the vehicle's own internal communications bus as well, so no matter what happens all the elements will blow 3 sec after the Abort happens.We currently plan that Jupiter does exactly the same, although there is a trade going on to see if there are any advantages if the vehicle were to self-destruct 2 seconds or even 1 second after the abort. Those studies are not yet complete.Ross.
Quote from: clongton on 08/01/2009 02:36 amQuote from: phantomdj on 08/01/2009 02:30 amWhat I was trying to understand was the difference between the Titan IV explosion profile (different SRB’s) that the 45th is using for Direct and Ares analysis The 45th was *NOT* analyzing DIRECT. Their study was strictly limited to Ares-I alone.Their analysis was the basis of my modeling of the debris field. So in effect, we are now using their analysis. The report clearly says they think a shuttle SRB will behave like the Titan's did. Ares I and Direct should basically have the same debris field. Danny Deger
Ross, can you post some video of your solution. When we talked you were having problems. It did turn out the -15 angle was bad for the sustainer LAS. Did you fix it with a change to the thrust angle?
What's the difference between the current-design LAS, and the recently tested MLAS? Would the "improved" MLAS make a difference, or would it need to be enhanced as well?
On blowing the nozzle. This needs lots of work. First the 45th may not agree to this. They may not like the SRB to stay intact. And blowing the nozzle might result in case fragmentation anyway. The current method doesn't fragment the case, it opens it up with a line down the side. Last, I worked on the AGM-130 air to ground missile that had a strap on solid. We did a test to terminate thrust by blowing the nozzle. In the long run thrust goes to basically zero, but there is a temporary 10 fold increase in thrust. During the test, this thrust spike had enough impulse to rip the stapon off the bomb and it went something like 2,000 feet. Maybe an SRB with a blown nozzle will do something like this and come after Orion in a big hurry. Anyway, I don't think the 45th is going to like a range package that makes the SRB goes like a bat out of hell before the thrust goes down. Consider an abort fairly close to the ground. The thrust spike might throw the SRB to downtown Coco Beach.
