4 ms·

Why did the booster explode? No thrust causing it to lose direction?

by vsareto 7y ago

shkkmo 7y ago
It lost it's areodynamic nose cone and so started to tumble.
deleted 7y ago
[deleted]
hoorayimhelping 7y ago
The pointed nosecone on the top of the rocket came off and it lost aerodynamic stability, and started to tumble. The tumbling caused the fuel and oxydizer to slosh around the very thin (and lightweight) tanks that are not designed with withstand that kind of force. The sloshing accelerated the tumbling. The thin tanks rupture causing the fuel and oxidizer to mix in the vicinity of a lit rocket engine. BOOM.
code4tee 7y ago
Given the velocity it was going the capsule popping off the top basically turned the rest of the rocket into a supersonic flying brick. The amount of drag would be enormous and the rest of the ship basically just tore itself apart. As soon as the oxidizer and fuel combined in the crumbing mess you get a big explosion. That was all expected to happen and why they launch these things out over the ocean. These rockets also usually have a self-destruct mechanism that a range safety officer can trigger if the rocket starts coming back towards land.
- rtsil 7y ago
  Falcon 9's self-destruct is automatic since a couple of years now.
  - goshx 7y ago
    They mention in the stream that it was not going to be used today.
    - 0xTJ 7y ago
      Based on what they said, I'm assuming that it would have been triggered at some point before it started coming down, but they were expecting that it would be destroyed before that happened.
      - JshWright 7y ago
        The upper stage hit the ocean intact. That suggests the FTS was not triggered (or it was triggered and failed to destroy the stage, which would be more concerning)
    - twexler 7y ago
      Pretty sure there was a call out late in the countdown regarding arming the FTS.
      - vibrolax 7y ago
        They armed the FTS, as they would need that if the range safety officer needed to do that. But it was not needed or used by the RSO.
        JshWright 7y ago
        Falcon 9 doesn't use an FTS manually triggered by an RSO. It uses an AFTS, which is controlled by the rocket itself. My guess is it was armed for the early stages of the flight (when there was still a risk something could go seriously wrong and the rocket could start heading towards Orlandit), but it was disarmed (or just given very generous parameters) once the rocket was downrange a ways.
    - bonestamp2 7y ago
      I suspect they'll still log when it would have happened so they can confirm it was working properly. That would be interesting to hear about.
  - xenospn 7y ago
    Do they actually go around collecting all of the various parts that fall back into the ocean? I imagine that's a huge amount of debris.
- usrusr 7y ago
  At some point there must have been a mission design meeting for this test where they decided on fuel levels in the booster. Just as much as needed to get to max Q? Just like a real launch that would put the capsule into orbit and land the booster? Something in between that creates a nice fireball but not too wasteful? (and on an entirely unrelated note, I really hate watching those parachutes bounce off each other. I know it must be perfectly safe or else it wouldn't have been the unquestioned method off choice for at least half a century, but it looks so uncontrolled it gives me nausea)
  - greglindahl 7y ago
    Well, the decision was to fully fuel everything, including the second stage. Which had no engine.
    - Klathmon 7y ago
      And even thought it had no engine, it had a "mass simulator" to replace it.
  - joshvm 7y ago
    You want to test this stuff as realistically as possible. Changing the amount of fuel means changing launch weight which means (presumably) changes in throttle profile etc. The control systems are also probably designed with a certain weight to reach orbit so it's possible that an unusually light rocket would be unstable. I'm not sure whether this would actually make a difference, but if you know it works at nominal fuel weight then you have some confidence it would work during a real launch.
CarVac 7y ago
The automated flight termination system may have detonated it due to it deviating from the "planned" flight path. It looked too instantaneous and clean of an explosion to have broken up naturally.
- olex 7y ago
  There are pictures of the second stage coming down in one piece and exploding upon hitting the water (at a safe distance away from the capsule and recovery crews). So it certainly doesn't look like the flight termination system was engaged.
  - bob1029 7y ago
    The SpaceX FTS should be fully-automated per this test. It is one criteria that still needs to be certified for the commercial crew program. That entire sequence should have been performed automatically by a computer (throttle back->fire abort rockets->terminate stage 1 booster). I suspect the FTS was appropriately triggered and that the 2nd stage simply survived the initial carnage via happenstance or potentially unintentionally due to changes in the structure regarding the missing front piece.
    - JshWright 7y ago
      The webcast hosts explicitly said the FTS wouldn't be triggered.
- _Microft 7y ago
  Yes, it definitely looked different from the CRS-7 launch anomaly.
  - lutorm 7y ago
    I agree, although CRS-7 was higher altitude so the atmospheric pressure and aerodynamic forces were smaller, so that may not be unexpected.
  - JshWright 7y ago
fit2rule 7y ago
It was intended to be disposed of this way. I too wonder whether it was demolished by way of explosion, or if SpaceX instead used this opportunity to see what a non-optimal flight pattern would do to the structure ..
- deleted 7y ago
  [deleted]
HALtheWise 7y ago
In addition to the loss of the aerodynamic nose, it also started tumbling simply because the engines were powered off. Modern rockets, falcon 9 included, are not actually aerodynamically stable during flight, and rely on active controls from gimballing the engines to keep pointed in the right direction. Once the engines power down, the rocket has little chance of surviving.

Why did the booster explode? No thrust causing it to lose direction?

shkkmo 7y ago

It lost it's areodynamic nose cone and so started to tumble.

deleted 7y ago

[deleted]

hoorayimhelping 7y ago

The pointed nosecone on the top of the rocket came off and it lost aerodynamic stability, and started to tumble. The tumbling caused the fuel and oxydizer to slosh around the very thin (and lightweight) tanks that are not designed with withstand that kind of force. The sloshing accelerated the tumbling. The thin tanks rupture causing the fuel and oxidizer to mix in the vicinity of a lit rocket engine. BOOM.

code4tee 7y ago

Given the velocity it was going the capsule popping off the top basically turned the rest of the rocket into a supersonic flying brick. The amount of drag would be enormous and the rest of the ship basically just tore itself apart. As soon as the oxidizer and fuel combined in the crumbing mess you get a big explosion. That was all expected to happen and why they launch these things out over the ocean. These rockets also usually have a self-destruct mechanism that a range safety officer can trigger if the rocket starts coming back towards land.

rtsil 7y ago
Falcon 9's self-destruct is automatic since a couple of years now.
- goshx 7y ago
  They mention in the stream that it was not going to be used today.
  - 0xTJ 7y ago
    Based on what they said, I'm assuming that it would have been triggered at some point before it started coming down, but they were expecting that it would be destroyed before that happened.
    - JshWright 7y ago
      The upper stage hit the ocean intact. That suggests the FTS was not triggered (or it was triggered and failed to destroy the stage, which would be more concerning)
  - twexler 7y ago
    Pretty sure there was a call out late in the countdown regarding arming the FTS.
    - vibrolax 7y ago
      They armed the FTS, as they would need that if the range safety officer needed to do that. But it was not needed or used by the RSO.
      - JshWright 7y ago
        Falcon 9 doesn't use an FTS manually triggered by an RSO. It uses an AFTS, which is controlled by the rocket itself. My guess is it was armed for the early stages of the flight (when there was still a risk something could go seriously wrong and the rocket could start heading towards Orlandit), but it was disarmed (or just given very generous parameters) once the rocket was downrange a ways.
  - bonestamp2 7y ago
    I suspect they'll still log when it would have happened so they can confirm it was working properly. That would be interesting to hear about.
- xenospn 7y ago
  Do they actually go around collecting all of the various parts that fall back into the ocean? I imagine that's a huge amount of debris.
usrusr 7y ago
At some point there must have been a mission design meeting for this test where they decided on fuel levels in the booster. Just as much as needed to get to max Q? Just like a real launch that would put the capsule into orbit and land the booster? Something in between that creates a nice fireball but not too wasteful? (and on an entirely unrelated note, I really hate watching those parachutes bounce off each other. I know it must be perfectly safe or else it wouldn't have been the unquestioned method off choice for at least half a century, but it looks so uncontrolled it gives me nausea)
- greglindahl 7y ago
  Well, the decision was to fully fuel everything, including the second stage. Which had no engine.
  - Klathmon 7y ago
    And even thought it had no engine, it had a "mass simulator" to replace it.
- joshvm 7y ago
  You want to test this stuff as realistically as possible. Changing the amount of fuel means changing launch weight which means (presumably) changes in throttle profile etc. The control systems are also probably designed with a certain weight to reach orbit so it's possible that an unusually light rocket would be unstable. I'm not sure whether this would actually make a difference, but if you know it works at nominal fuel weight then you have some confidence it would work during a real launch.

CarVac 7y ago

The automated flight termination system may have detonated it due to it deviating from the "planned" flight path. It looked too instantaneous and clean of an explosion to have broken up naturally.

olex 7y ago
There are pictures of the second stage coming down in one piece and exploding upon hitting the water (at a safe distance away from the capsule and recovery crews). So it certainly doesn't look like the flight termination system was engaged.
- bob1029 7y ago
  The SpaceX FTS should be fully-automated per this test. It is one criteria that still needs to be certified for the commercial crew program. That entire sequence should have been performed automatically by a computer (throttle back->fire abort rockets->terminate stage 1 booster). I suspect the FTS was appropriately triggered and that the 2nd stage simply survived the initial carnage via happenstance or potentially unintentionally due to changes in the structure regarding the missing front piece.
  - JshWright 7y ago
    The webcast hosts explicitly said the FTS wouldn't be triggered.
_Microft 7y ago
Yes, it definitely looked different from the CRS-7 launch anomaly.
- lutorm 7y ago
  I agree, although CRS-7 was higher altitude so the atmospheric pressure and aerodynamic forces were smaller, so that may not be unexpected.
- JshWright 7y ago

fit2rule 7y ago

It was intended to be disposed of this way. I too wonder whether it was demolished by way of explosion, or if SpaceX instead used this opportunity to see what a non-optimal flight pattern would do to the structure ..

deleted 7y ago
[deleted]

HALtheWise 7y ago

In addition to the loss of the aerodynamic nose, it also started tumbling simply because the engines were powered off. Modern rockets, falcon 9 included, are not actually aerodynamically stable during flight, and rely on active controls from gimballing the engines to keep pointed in the right direction. Once the engines power down, the rocket has little chance of surviving.