Yeah I got the impression that the stages may have touched at separation too. Similar to the situation they had with one of the Falcon 1 test flights. Mind you we have to remember that stage 2 was inert so presumably the live stage 2 will have ullage rockets which will aid with stage separation. Maybe a couple of extra retro rockets on stage 1 would help with separation distance. IIRC they had the opposite situation during the Saturn V development when they reduced the number of retro rockets on the S-1C from eight to four which directly translated into extra payload capacity which was utilised during the last three 'J' series missions.
- Status
You can't shut down solid rocket just like that. The propellant burns out, but there will be some residue, which was clearly seen in the video. The residue will provide some intermittent peaks of boost for the first stage making safe separation extremely difficult, if not impossible. Even a very slight amount of residue will do, because the first stage is now ~90% lighter than in the start.
How do you know the motor has completely burned out and not giving any residual boost just when separating the stages?
How do you know the motor has completely burned out and not giving any residual boost just when separating the stages?
Zipi":1zc0a3p4 said:
I remember reading that it was designed to do that to allow some additional clearance between the rocket and the tower. This is why they need to monitor wind gusts from the opposite direction of that motion carefully.
aphh":3w40tjoe said:
Yes, I'm aware of this, but still it seemed pretty close for me. But I guess it was on the design margins of the vehicle...
What comes to the residual thrust issue of SRB, maybe there is some possibilities to went it to some other direction than trajectory? Of course this would add complexity to the SRB structure and the need for the wenting valves, which probably are not so easy to implement thinking of SRB's inside pressure... Probably hitting SRB range safety button just after separation is not very good idea either... :roll:
What I described is clearly visible in this video: http://www.youtube.com/watch?v=4lgaW4piSus (at 02:30).
Just when the staging takes place, there is a burst of residue that makes the 1st stage collide with the 2nd stage. This is no small issue.
The 1st stage is now very light, especially when separated, so only a tiny bit of boost will make it accelerate forward, whereas the 2nd stage is heavy so it won't get out of the way just like that. What a bummer.
Just when the staging takes place, there is a burst of residue that makes the 1st stage collide with the 2nd stage. This is no small issue.
The 1st stage is now very light, especially when separated, so only a tiny bit of boost will make it accelerate forward, whereas the 2nd stage is heavy so it won't get out of the way just like that. What a bummer.
aphh":ioyt78rn said:
Yeah, that was pretty scary, just as they are doing separation.
Is there much/any experience with separation from a solid rocket first stage? I'm only familiar with solid rocket motors as boosters.
radarredux":2sv62of9 said:
I think it's a show stopper. The SRB is still burning after it has done a full rotation around it's center of mass. I can't think of a way to prevent that from happening.
How much would a equally performing kerosene fueled 1st stage weigh? Hopefully Elon gets his rocket working.
Is it possible for stage separation to occur a little bit later, after all residue thrust is gone for good? But I don't think it's possible because after SRB burnout it actually looses all steering capability (or is there some RCS on Ares boosters)?aphh":1uqbk20o said:
aphh":2ty15vjw said:
Very good observation aphh. This is no small issue at all indeed. One possible solution would be to use more powerful "retro-thrusters" (the thrusters that pull the SRB back as stage separation takes place), pwerful enough to counter-balance the residual thrust from the SRB. But of course, this would make it heavier and would reduce the payload mass.
That would start another round of Orion mass vs. booster capability...and another Orion redesign is not what the program needs. As aphh says, a likely show-stopper given the number of holes this dike already has.
I finally got around to watching the full vid and I had the same question. The stage separation does not look particularly graceful. Obviously you do not want your upper stage to separate only to get smacked by the first stage and start spinning about. Was this an expected result of having a dummy upper stage that could not propel itself away from the first stage?
It reminds me of that failed SpaceX Falcon1 flight, where they didn't account for residual post-separation acceleration of the first stage. That was relatively easy for them address given that it was a liquid rocket, but I wonder if the same can be said of a solid booster that they are in less control over? How predictable and consistent is the curve of thrust decline on a solid rocket motor as it nears the end of its fuel supply? Seems like your timing would have to be perfect since you don't want to separate too early as it would result in collision, but you don't want to separate too late because you will have lost directional control upon solid booster flameout. We need a rocket scientist in here, stat!
Edit: According to this graphic, the maneuver was unexpected but not considered a serious performance issue. Ehhhh
Could it have flipped backward because immediately upon separation the lower stage contacted it off-center and caused it to change vector?
It reminds me of that failed SpaceX Falcon1 flight, where they didn't account for residual post-separation acceleration of the first stage. That was relatively easy for them address given that it was a liquid rocket, but I wonder if the same can be said of a solid booster that they are in less control over? How predictable and consistent is the curve of thrust decline on a solid rocket motor as it nears the end of its fuel supply? Seems like your timing would have to be perfect since you don't want to separate too early as it would result in collision, but you don't want to separate too late because you will have lost directional control upon solid booster flameout. We need a rocket scientist in here, stat!
Edit: According to this graphic, the maneuver was unexpected but not considered a serious performance issue. Ehhhh
Could it have flipped backward because immediately upon separation the lower stage contacted it off-center and caused it to change vector?
My opinion is that there weren't enough clearance between the stages to ignite the second stage engine (even if the rocket would have one). First stage collided almost immediately after the separation if you ask me...
radarredux":i5ha0vwg said:
Yup! Everytime you launch a Minuteman or Poseidon/Trident ballistic missile. It has been about 40 years, so my recollections aren't all that clear on details, but IIRC they ignite the upper stage a couple of milliseconds before the sep ring fires. The pressure buildup in the interstage helps insure separation. Same sort of "fire-in-the-hole" was done with the between the 1st and 2nd stages of the Titan liquid boosters. (Note: Titan 34D and IV used SRM's which fired at liftoff (aka "Stage Zero"), but the 1st stage ignited at altitude after boosters separated.)
Since the Ares I is an in-line design, you might be able to use thrust termination ports on the 1st stage. When the propellant grain burns down to a certain point, it uncovers "tunnels" to ports in the side of the forward end of the stage. When the guidance system senses tailoff of thrust, it fires linear shaped charges around round ports in the side of the rocket. Pressure inside the rocket blows the port covers off. The total area of the ports is greater than the area of the nozzle throat. The result is that you get retrograde thrust which helps back the "burned out" stage from the rest of the vehicle. Ports are arranged equally around the sides of the booster, something you can't do with the Shuttle SRB's as the ET and the orbiter wings would be impinged with the port covers and the hot gases of the rocket.
Of course, such things add weight to the vehicle, but that's better than playing bumper-tag with the 1st stage! :roll:
Anybody hear if the chutes deployed properly? Wondering if the alleged contact damaged the frustum and/or the chute packages. If the chutes worked okay, congrats to Pioneer (whatever they are called now...used to be Pioneer Parachute)!
So far as this whole test is concerned, as many of you know from my prior posts, here and elsewhere, I DETEST solid rockets for use with high value (human) payloads! Ya can't turn 'em off! (The last bit of telemetry received from Challenger indicated the Main engines were trying to shut themselves down, having sensed fuel starvation after the ET was destroyed!) Having said that, I am glad the test went off. ANY data you get that either validates or disproves computer modelling or wind tunnel data!
Frankly, I'd rather see the use of EELV's, Falcon 9, or...better yet...Direct or something else, using LIQUID PROPELLANTS!
But, let's not jump NASA for the results of this test...at least, not yet!
Ad LEO! Ad Luna! Ad Ares! Ad Astra!
It certainly is good news about the low vibrations and relative lack of need of to fire the roll control thrusters. But I'm rather surprised they would do a stage separation on the test flight without adequate systems in place to have a successful separation?
I believe stage separation would've been mandatory for the recovery systems on the first stage to operate properly. And they do want that stage back, not only to reuse it but also because of the data stored in the onboard computers.
It is interesting to learn that the tumbling second stage was not intended, and that it may have contacted the first stage. It seems like something which (like the triboelectrification problem) would be easily solved in an operational vehicle. Will be interesting to see what the final analysis of the flight is in a few months. It was certainly successful from a flight operations perspective; the next question is what the engineers will make of the data it obtained. I really want to know about the vibration problem. The all-up five-segment booster test in Utah was promising, but I want to know what the vibrations are like at the top of this thing.
It is interesting to learn that the tumbling second stage was not intended, and that it may have contacted the first stage. It seems like something which (like the triboelectrification problem) would be easily solved in an operational vehicle. Will be interesting to see what the final analysis of the flight is in a few months. It was certainly successful from a flight operations perspective; the next question is what the engineers will make of the data it obtained. I really want to know about the vibration problem. The all-up five-segment booster test in Utah was promising, but I want to know what the vibrations are like at the top of this thing.
So it appears there is a huge dent in the side of the first stage.
How often did this happen when the SRB was used with the Shuttle ?
How many SRBs are there in the Shuttle parts inventory, if NASA needs to re-allocate another booster (or 2 or 3) to the Ares program ?
How often did this happen when the SRB was used with the Shuttle ?
How many SRBs are there in the Shuttle parts inventory, if NASA needs to re-allocate another booster (or 2 or 3) to the Ares program ?
stevekk":1qywm4p5 said:
Here is Spaceflight Now article: http://www.spaceflightnow.com/ares1x/091029dent/
This dent has probably become at stage separation. Dents are not normal operation and I believe shuttle SRBs don't have experienced such things earlier. Of course one possibility is that it landed too hard since some sources are saying that only two chutes from three worked.
The SFN article mentions it was a 4 segment SRB. Am I just remembering wrong that Ares was supposed to be a 5.5 segment SRB or was that a different concept?
Interesting Zipi. There's no visible signs of any scratches that would indicate an impact between the stages. I guess we shall see once the data is all processed.
I would really want to take on a review with the different segments that was being released on the launches.
http://www.space.com/missionlaunches/09 ... -dent.html
"Shuttle officials said Ares I-X engineers will get their first up-close look at the damaged rocket booster Friday once it arrives in Florida.
"The booster comes back in tomorrow," said shuttle integration manager Mike Moses. "So until that point, everything is probably speculation."
"Shuttle officials said Ares I-X engineers will get their first up-close look at the damaged rocket booster Friday once it arrives in Florida.
"The booster comes back in tomorrow," said shuttle integration manager Mike Moses. "So until that point, everything is probably speculation."
Wow- I just watched the footage of the stage separation. Pretty wild. This should be good for a good 1-2 year delay while they study that "behavior." NASA says that they did not expect that to happen (obviously), and this is on an SRB design that has flown roughly 300 times. Wait till they try out their new 5.5 segment design. Hope they haven't put too much work into those plans yet, because they may have to be changed/redesigned. I read once that even with all the SRB's that have been produced, the nature of the grain burn reaction inside an SRB is still not totally understood and cannot be modelled. I would expect the 5.5 segment SRB will need a pretty lengthy experimental testing phase. I would classify the test as a failure, as it doesn't inspire much confidence in the SRB (the crew would have probably been lost in ascent) or NASA's aptitude with parachutes, which if they failed on the Orion, wouldd have caused death in the descent. So in terms of system safety, the crew would have been killed twice. Ironic, NASA's rationale for the Ares design was that in-line SRB placement is safer (inline placement caused the two stages to crash together, which would have killed the crew), and capsule re-entry is safer (parachute malfuntion would have killed the crew). And they still haven't even tested out the real 5.5 SRB, the second stage engine, the crew ejection rocket, the Orion parachutes, Orion separation, Orion life support, Orion re-entry, etc. Does anyone really believe this thing will fly before 2020? In light of that test, I doubt it. Really, when your SRB basically reignites and slams into your second stage hard enough to flip it around at mach 4, I think it may be time to go back to the drawing board and reexamine the decision to use SRB's in the first place.
Calling this a failure is a total joke and people should be ashamed of playing so loosely with the facts. This test was to determine in flight characteristics of the Ares design. It was not a test of stage separation (you can't have an accurate test without a fully loaded and designed second stage which this was not, it was a dummy with no guidance or propulsion) and as far as the parachute end of things, this was not a parachute test either. The parachutes were used on this flight so that the SRB could be recovered for examination post flight. I wish people would stop playing so loosely with the facts, from an in flight perspective this test flight was a success.
mr_mark":300r00h1 said:
Probably true. If the upper stage was actually designed to continue it would have separated and kept going no matter what residual thrust the solid continued to produce. This seems to be a non-issue, at this point. That it separated as it did seems to be more a matter of not knowing what effect the atmosphere at that altitude would have or figuring it didn't really matter as the priorities of the mission had been met.
The dent issue probably relates to impact and the failed chute, as pointed out a collision with the fake upper stage would have left evidence and an angled impact with the water would make more sense. Realistically the areas being tested ended at the time the upper stage departed and met all expectations.
That it can't compete with Delta, Atlas and Falcon is the real consideration.
- Status
Similar threads
TRENDING THREADS
-
Basic Error: The accelerating Universe conclusion - reason- Started by Gibsense
- Replies: 191
-
-
David Lynch's 'Dune' at 40: David Lynch's 1984 adaptation is a true spice oddity
- Started by Admin
- Replies: 1
Facebook
Twitter
Instagram