That's great news... Time to move on to the next launch and hope SpaceX can fix the restart problem.
Presumably the various CubeSATS are near the upper stage orbital altitude, but there are probably another dozen objects that are not accounted for, and which are randomly scattered. Since some of these are lower than the upper stage, I would have to guess that it is because their drag coefficient is greater than an upper stage, meaning that they could be empty small objects, or flat objects like panels that are not flying edge on.
I guess the flat objects are pieces of foam insulation from the upper stage dome. Due to their high drag coefficient, they are already in a lower orbit than the upper stage. Over the next few days, we should see greater dispersions and lower perigees from these objects.
I guess the flat objects are pieces of foam insulation from the upper stage dome.
If that turns out to be the case then are they the cause (prop temp not within limits?), the effect or unrelated to the engine relight anomaly?
I guess the flat objects are pieces of foam insulation from the upper stage dome.
If that turns out to be the case then are they the cause (prop temp not within limits?), the effect or unrelated to the engine relight anomaly?
http://www.nbcnews.com/science/spacex-knocks-down-claim-falcon-9-rocket-exploded-orbit-8C11310947Musk offered a similar explanation in an email to Jay Barbree, NBC News' Cape Canaveral correspondent: "During venting to safe the stage, some foil insulation on the engine came loose. This is very lightweight, so will quickly re-enter and burn up, but it is reflective on radar."
This contradicts the dome foam theory, but in each case (as I understand it) the liberation is thought to have happened during stage safing so
after the engine restart attempt.
I've been contemplating why they were able to successfully relight 3 first stage engines, and then relight the first stage center engine yet again during the "water landing" test, but did not succeed in relighting the second stage.
As far as I can tell it boils down to
1. A difference in the environment such as gravity settling or the lack there off, ambient temp or pressure etc.
2. A difference in the engine between the booster and vacuum versions of the Merlin-1D such as the nozzle shape or control software etc.
3. A random failure that could have happened on any of the restarts and the luck of the draw was the upper stage
It sounds like #1 has the inside track. Anyone have any informed speculation about specific parameters though?
On a related track, thinking about the reflective foil that apparently got knocked loose when safeing the stage after the restart didn't happen, how is that done, just open the valves and let oxidizer spew out under tank pressure? Anyone have any thoughts about why that would knock stuff loose that stayed put under some pretty severe vibration during launch? Seems odd if it exits via the nozzle, just not burning.
I've been contemplating why they were able to successfully relight 3 first stage engines, and then relight the first stage center engine yet again during the "water landing" test, but did not succeed in relighting the second stage.
As far as I can tell it boils down to
1. A difference in the environment such as gravity settling or the lack there off, ambient temp or pressure etc.
2. A difference in the engine between the booster and vacuum versions of the Merlin-1D such as the nozzle shape or control software etc.
3. A random failure that could have happened on any of the restarts and the luck of the draw was the upper stage
It sounds like #1 has the inside track. Anyone have any informed speculation about specific parameters though?
On a related track, thinking about the reflective foil that apparently got knocked loose when safeing the stage after the restart didn't happen, how is that done, just open the valves and let oxidizer spew out under tank pressure? Anyone have any thoughts about why that would knock stuff loose that stayed put under some pretty severe vibration during launch? Seems odd if it exits via the nozzle, just not burning.
Good post, I had some thinking about those lines.
1) My take, expanding later.
2) Not my guess.
3) Not my guess.
One of the main valves, positioned before turbopump (probably LOX) got stuck. This was caused by cooling and space environment (something similar happened in F9 f1, with freezing of roll control actuator on 2nd stage). The fault resulted in quite strong venting after SECO, with two effects:
a) insulation of the bottom dome got loose;
b) loss of pressurization in the tank.
Effect b) makes restart impossible.
This scenario copes well with Elon's mood about the reason of the fault; a stuck main valve is easily detectable, and avoiding the problem should not be a difficult task.
Usual disclaimer: only my opinion.
b) loss of pressurization in the tank.
Effect b) makes restart impossible.
In fact, it would probably preclude even
attempting to restart the engine. Loss of inlet pressure is one of those engine start box things. Yet it was reported that the engine got to 400 psi before aborting, suggesting it was within the start box as it attempted ignition. Elon speculated something about an extended spin-start, but said they really need to look into the data first.
Just for reference, MVac 1C was known to vent heavily as well - granted, this was
before ignition, not after: www
.youtube.com/watch?v=BqCELhkXtsY#t=206s at 3:26 into the video, view from inside the interstage.
Here the LOX path on Merlin 1C (not Vac, but must be similar).
Green is inlet and turbopump, red pressure duct and main valve of engine.
The failed valve in my scenario is before the engine, between tank and inlet; there must be also a venting valve, emptying the turbopump assembly after shutdown (honestly this is only a supposition).
The LOX leak would justify also the infrared pic at the end of the coverage of the launch; oxigen reacting with soot would cause heating.
But this is highly speculative.
b) loss of pressurization in the tank.
Effect b) makes restart impossible.
In fact, it would probably preclude even attempting to restart the engine. Loss of inlet pressure is one of those engine start box things. Yet it was reported that the engine got to 400 psi before aborting, suggesting it was within the start box as it attempted ignition. Elon speculated something about an extended spin-start, but said they really need to look into the data first.
Just for reference, MVac 1C was known to vent heavily as well - granted, this was before ignition, not after: www.youtube.com/watch?v=BqCELhkXtsY#t=206s at 3:26 into the video, view from inside the interstage.
Effect b) doesn't make restart impossible or make an attempt impossible. It all depends on how much margin there is to the defined operating parameters (sometimes you don't test to find all of the "cliffs") and how much the pressure actually dropped. I've seen engines start and continue to run at operating conditions that were way outside the boxes.
The camera view on that youtube video was from a different angle, and does appear to show a vent path that was flowing during engine operation. 1D could certainly be different.
Attached video is a cutout of the coverage and show the leak after SECO.
A leak from LOX tank would be repressurized by LOX evaporation, but the decrease of temperature would make impossible feeding the engine after restart.
- I think we all expected more v1.0 flights before the block-II/v1.1 was introduced
I should not that we really didn't know that V 1.0-powered ISS re-supply flights could not carry enough cargo to meet CRS requirements. SpaceX was not clear that the original Falcon 9 could not fly a completely loaded Dragon to ISS.
If we had known that, then we would all have predicted that the 1.1 first launch would come early in CRS.
You're missing something, here. I think just about everyone who knew what they were talking about knew that the very first "Block I" version of Falcon 9 was only going to be used on a handful of flights. After all, the user's guide was written for Block II and presumably they sold just Block IIs to their customers (since that is what was advertised) except for COTS and the initial CRS, since they didn't require anything better. So we assumed some sort of upgrade for the majority of the CRS flights, just not as big.
The big thing is that they skipped Block II and went straight to a much, much improved vehicle (v1.1), not just an incremental improvement to Block II.
You are revising history.
Attached is the official F9 data sheet from 2007 (post COTS award) showing performance from the standard F9 as 10,000+ kg.
There is no mention of a Block II or 1.1 or anything other than a single F9 variant (plus the Heavy).
The emergence of an "evolved" F9 is relatively recent. I started up a thread way back when complaining that the payload numbers of the F9 as published did not make sense, and the vast majority of the responses from the SpaceX amazing people was that I was simply wrong. It took a couple of years for the SpaceX crowd to understand that the plan was to meet the numbers via an evolved F9, and then the official story became that it was Block II/Falcon 9 1.1 that was going to be the standard CRS launcher.
Looking through my files, I see a mention of Block II becoming the standard variant in the 2009 Falcon 9 User Guide. Does anyone have anything published by SpaceX mentioning a Block II or 1.1 earlier than 2009?
Wasn't M1Cb1 95klb @ SL?
9x95 = 855klb (ignoring plume infringement).
• First stage powered by 9 SpaceX Merlin engines
o 101,900 lbs-f sea level thrust per engine
o Total thrust on liftoff of just under 1 Million lbs-f
cheers, Martin
Some insider info:
The attitude control system was railed, wanted more thrust, but engines couldn't provide anymore. Doubts that they would solve it by stockpiling more RCS fuel.
Me:
Apparently there was so much aero roll that the RCS couldn't dampen it away. They probably just need to make some changes to the outside aero surface to fix things. I doubt they'll add pop out fins though.
Me:
What about if they put RCS thrusters at the end of the legs. Wouldn't that provide a lot more roll control authority for the same amount of prop?
cheers, Martin
By my count, 4 of the 5 attempted relights on this flight were successful. Who wants to speculate, with the limited information we have, what the difference is with the the M1Dvac that may have caused the issue?
Stage 1 relights were with small amount of atmospheric drag, while Stage 2 relights were in microgravity. (But remembering that initial light of S2 would be pretty much in free fall [I believe].)
Also, suspect S2 relight was a longer delay after SECO1 than S1 after MECO2 or MECO3.
cheers, Martin
