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This is far from the closest to launch SpaceX has called an abort. Many may not remember 3 years ago when they called the abort at T-1 after main engine ignitio

This is far from the closest to launch SpaceX has called an abort. Many may not remember 3 years ago when they called the abort at T-1 after main engine ignition: https://www.youtube.com/watch?v=5v0k_0PTLnI https://www.youtube.com/watch?v=5v0k_0PTLnI To be honest, though, neither case is really abnormal. There's a whole reason it's "T-minus" and "T-plus". T-zero is the point of no return (on the STS, this was when the solid boosters were fired). An abort at any point before then is still considered normal. Aborts after T-zero are anomalies. (FWIW, even the STS has aborted take-off post-main-engine ignition: https://www.youtube.com/watch?v=8bkYP3pU76I https://www.youtube.com/watch?v=8bkYP3pU76I . The main difference between the SpaceX Falcon and the STS is that the Falcon is capable of re-igniting its engines almost immediately, making a same-day re-attempt of a post-engine-ignition abort possible. The STS main engines require a manual reset, making abort post-engine-ignition more costly.)

bisby 10y ago
I had found it odd, knowing that SpaceX ignites engines at T-2 (and releases clamps at T-0), watching the Arianespace launch earlier in the week. They ignited the main engine at roughly T-1, then revved it up until T+7, and then fired the solid boosters and released at T+8 or so. https://youtu.be/pgj0kSXEtdQ?t=890 https://youtu.be/pgj0kSXEtdQ?t=890 The STS fired the solids at T-0, thus being the "point of no return", why is it that Arianespace waits until +8 to fire solids? Do they just consider igniting the liquid main stage as "no return" ? Also, SpaceX had a T-1 abort after main engine ignition later too. (the one you showed doesnt even have landing legs!). The later one was SES-9 in Feb 2016 - https://www.youtube.com/watch?v=LuS5mehCAMI https://www.youtube.com/watch?v=LuS5mehCAMI A boat was down-range and the cryo propellants had warmed up and started getting bubbles in it... the engines fire at T-2, run diagnostics, determine if they are running properly, THEN release clamps for lift off, but in this case, the bubbles caused lower than expected thrust, so it turned itself off.
- sitharus 10y ago
  The Arianespace count is just a difference of opinion. The US space industry use T-0 as the moment of departure from the launch pad, whereas the European program uses T-0 as the moment of main engine ignition. Ariane 5 has aborted after T-0 but prior to igniting the boosters, video here: http://www.space.com/11266-ariane-5-launch-aborted-engine-ignition.html http://www.space.com/11266-ariane-5-launch-aborted-engine-ig...
JshWright 10y ago
An abort after T-00:02 was iffy for STS. If an abort was called after T-00:02, the RS-25s kept running until T-00:00 just in case the SRBs lit anyway.
- jballanc 10y ago
  Makes you wonder why anyone ever thought it was a good idea to put solid boosters on a man-rated rocket...and yet NASA is repeating that "mistake" with the SLS.
  - greglindahl 10y ago
    Didn't Congress order NASA to do that, this time around?
  - wolf550e 10y ago
    It's a way to use NASA budget to prop up military contractor ATK.
  - sand500 10y ago
    Not a problem this time because the capsule has a launch escape system
    - JshWright 10y ago
      A launch escape system which uses parachutes, which will not react well to descending through a cloud of burning solid rocket fuel...
- robryk 10y ago
  I can't quite imagine what failure modes were they thinking about. Those failure modes must have had a nonnegligible chance of lighting off _both_ SRBs, but a very small one of lighting off a single SRB.
  - jballanc 10y ago
    IIRC, the SRBs generated enough thrust to break the hold-down bolts even in the event the frangible nuts don't fire. I'd guess the thinking is that, if both fire you might as well have the main engines running than not (since, as I noted before, the SSMEs couldn't be re-ignited in flight). True, if only one SRB fires, you're pretty much toast no matter what, but NASA loves their contingencies of contingencies of contingencies. For example, I've read that there were serious doubts that a Return-to-Launch-Site (RTLS) abort would actually, you know, be survivable, and yet it remained one of the official abort modes throughout the shuttle program.
hcrisp 10y ago
It wasn't an abort, but the Mercury-Redstone 1 had a "T-plus" stop time [0]. It attempted to launch and the engine shut down immediately after lift off. It didn't explode, the escape rocket jettisoned, the capsule deployed its drogue, and the the rocket settled back on the pad untethered [1]. It came to be referred to as the "four-inch flight". After considering some risky ways to deal with the fully-fueled rocket, flight control ultimately decided to wait until the LOX boiled off. Chris Kraft declared, "That is the first rule of flight control. If you don't know what to do, don't do anything." [0] https://en.wikipedia.org/wiki/Mercury-Redstone_1 https://en.wikipedia.org/wiki/Mercury-Redstone_1 [1] https://www.youtube.com/watch?v=7O4V7JfeTSU https://www.youtube.com/watch?v=7O4V7JfeTSU
- teleclimber 10y ago
  And if you like stories like that, "Failure is not an option" by Gene Kranz is a must-read/listen. It seems every single flight of the early American Space Program was a nail-biter.
  - cbanek 10y ago
    When you're responsible for it, or even a part of it, every moment is a nail-biter. You know exactly what can go wrong and how bad it could be.
- deleted 10y ago
  [deleted]
_delirium 10y ago
> FWIW, even the STS has aborted take-off post-main-engine ignition This happened five times, in fact, all computer-initiated: https://en.wikipedia.org/wiki/Space_Shuttle_abort_modes#Redundant_set_launch_sequencer_.28RSLS.29_abort https://en.wikipedia.org/wiki/Space_Shuttle_abort_modes#Redu...

bisby 10y ago

I had found it odd, knowing that SpaceX ignites engines at T-2 (and releases clamps at T-0), watching the Arianespace launch earlier in the week. They ignited the main engine at roughly T-1, then revved it up until T+7, and then fired the solid boosters and released at T+8 or so. https://youtu.be/pgj0kSXEtdQ?t=890 https://youtu.be/pgj0kSXEtdQ?t=890 The STS fired the solids at T-0, thus being the "point of no return", why is it that Arianespace waits until +8 to fire solids? Do they just consider igniting the liquid main stage as "no return" ? Also, SpaceX had a T-1 abort after main engine ignition later too. (the one you showed doesnt even have landing legs!). The later one was SES-9 in Feb 2016 - https://www.youtube.com/watch?v=LuS5mehCAMI https://www.youtube.com/watch?v=LuS5mehCAMI A boat was down-range and the cryo propellants had warmed up and started getting bubbles in it... the engines fire at T-2, run diagnostics, determine if they are running properly, THEN release clamps for lift off, but in this case, the bubbles caused lower than expected thrust, so it turned itself off.

sitharus 10y ago
The Arianespace count is just a difference of opinion. The US space industry use T-0 as the moment of departure from the launch pad, whereas the European program uses T-0 as the moment of main engine ignition. Ariane 5 has aborted after T-0 but prior to igniting the boosters, video here: http://www.space.com/11266-ariane-5-launch-aborted-engine-ignition.html http://www.space.com/11266-ariane-5-launch-aborted-engine-ig...

JshWright 10y ago

An abort after T-00:02 was iffy for STS. If an abort was called after T-00:02, the RS-25s kept running until T-00:00 just in case the SRBs lit anyway.

jballanc 10y ago
Makes you wonder why anyone ever thought it was a good idea to put solid boosters on a man-rated rocket...and yet NASA is repeating that "mistake" with the SLS.
- greglindahl 10y ago
  Didn't Congress order NASA to do that, this time around?
- wolf550e 10y ago
  It's a way to use NASA budget to prop up military contractor ATK.
- sand500 10y ago
  Not a problem this time because the capsule has a launch escape system
  - JshWright 10y ago
    A launch escape system which uses parachutes, which will not react well to descending through a cloud of burning solid rocket fuel...
robryk 10y ago
I can't quite imagine what failure modes were they thinking about. Those failure modes must have had a nonnegligible chance of lighting off _both_ SRBs, but a very small one of lighting off a single SRB.
- jballanc 10y ago
  IIRC, the SRBs generated enough thrust to break the hold-down bolts even in the event the frangible nuts don't fire. I'd guess the thinking is that, if both fire you might as well have the main engines running than not (since, as I noted before, the SSMEs couldn't be re-ignited in flight). True, if only one SRB fires, you're pretty much toast no matter what, but NASA loves their contingencies of contingencies of contingencies. For example, I've read that there were serious doubts that a Return-to-Launch-Site (RTLS) abort would actually, you know, be survivable, and yet it remained one of the official abort modes throughout the shuttle program.

hcrisp 10y ago

It wasn't an abort, but the Mercury-Redstone 1 had a "T-plus" stop time [0]. It attempted to launch and the engine shut down immediately after lift off. It didn't explode, the escape rocket jettisoned, the capsule deployed its drogue, and the the rocket settled back on the pad untethered [1]. It came to be referred to as the "four-inch flight". After considering some risky ways to deal with the fully-fueled rocket, flight control ultimately decided to wait until the LOX boiled off. Chris Kraft declared, "That is the first rule of flight control. If you don't know what to do, don't do anything." [0] https://en.wikipedia.org/wiki/Mercury-Redstone_1 https://en.wikipedia.org/wiki/Mercury-Redstone_1 [1] https://www.youtube.com/watch?v=7O4V7JfeTSU https://www.youtube.com/watch?v=7O4V7JfeTSU

teleclimber 10y ago
And if you like stories like that, "Failure is not an option" by Gene Kranz is a must-read/listen. It seems every single flight of the early American Space Program was a nail-biter.
- cbanek 10y ago
  When you're responsible for it, or even a part of it, every moment is a nail-biter. You know exactly what can go wrong and how bad it could be.
deleted 10y ago
[deleted]

_delirium 10y ago

> FWIW, even the STS has aborted take-off post-main-engine ignition This happened five times, in fact, all computer-initiated: https://en.wikipedia.org/wiki/Space_Shuttle_abort_modes#Redundant_set_launch_sequencer_.28RSLS.29_abort https://en.wikipedia.org/wiki/Space_Shuttle_abort_modes#Redu...