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SpaceX's Falcon Heavy center booster lacked ignition fluid to re-light engines

latimes.com

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Re: SpaceX's Falcon Heavy center booster lacked ignition fluid to re-light engines

#151

Post by rory096 »

nickparker wrote: post #120
Footkerchief wrote: post #53

Earlier quoted context omitted.

> Musk said Monday that there wasn't enough ignition fluid to light the outer two engines of the booster "after several three engine relights." I don't see a mention of whether the previous relights succeeded or not. I'm guessing they did succeed, but the center booster had to perform a higher number of relights than a Falcon 9 booster due to its higher speed.

By my reading, the center core was using three engine burns for more efficient boost-back and re-entry burns. The side cores and typical F9 boosters (afaik) always use single engines for those and occasionally three-engine burns at landing, so three engine-ing all three burns would be 4 more relights than any previous core. So, an equal number of "relights" of the entire rocket but more engine relights, and engine re…

Boostback and reentry burns are always 3 engines. Landing burns are often 2 engine and often 1-3-1, usually on the drone ship.

The unique part of the GovSat "failed to expend" mission a few weeks ago was not cutting off the outer two engines some time before hitting the surface, not that it used three engines at all.

Re: SpaceX's Falcon Heavy center booster lacked ignition fluid to re-light engines

#152

Post by JshWright »

nickparker wrote: post #120
Footkerchief wrote: post #53

Earlier quoted context omitted.

> Musk said Monday that there wasn't enough ignition fluid to light the outer two engines of the booster "after several three engine relights." I don't see a mention of whether the previous relights succeeded or not. I'm guessing they did succeed, but the center booster had to perform a higher number of relights than a Falcon 9 booster due to its higher speed.

By my reading, the center core was using three engine burns for more efficient boost-back and re-entry burns. The side cores and typical F9 boosters (afaik) always use single engines for those and occasionally three-engine burns at landing, so three engine-ing all three burns would be 4 more relights than any previous core. So, an equal number of "relights" of the entire rocket but more engine relights, and engine re…

No, three engine burns are typical for boostback/re-entry. In many of the webcasts you can see the initial round plume turn into a rectangle as the two outboard engines ignite.

Re: SpaceX's Falcon Heavy center booster lacked ignition fluid to re-light engines

#153

Post by twostorytower »

Waterluvian wrote: post #23
std_throwaway wrote: post #19

I bet it didn't randomly lack fluid due to some stupid miscalculation. It's probably more like: "Due to unforeseen circumstances it needed more fluid than expected. But we adjust our numbers and next time we expect more (in the hopes that it will be enough, which it will probably be)."

Yeah. I guess in space flight you can't just double the calculated requirement. That would be expensive.

Probably not as expensive as losing the entire booster, though.

Re: SpaceX's Falcon Heavy center booster lacked ignition fluid to re-light engines

#154

Post by philipwhiuk »

aerophilic wrote: post #116
jccooper wrote: post #43

Earlier quoted context omitted.

They probably used a simple model (and experience) to determine the needed amount. But the model was wrong because, well, it encountered the real world. So they'll adjust in the future. Probably they could have analyzed the heck out of it for years, and gotten it right, but then that would take years and cost buckets.

This reminds me of a phrase: “All models are wrong; Some models are useful”. https://en.m.wikipedia.org/wiki/All_models_are_wrong

Or to quote a Prussian general:

"No plan of operations extends with any certainty beyond the first contact with the main hostile force."

Re: SpaceX's Falcon Heavy center booster lacked ignition fluid to re-light engines

#155

Post by philipwhiuk »

jacquesm wrote: post #138
cycrutchfield wrote: post #131

Earlier quoted context omitted.

Did the N-1 rocket really "fly"?

It flew all the way to the scene of the crash.

Ah, the Chuck Yeager school of flying:

"If you can walk away from a landing, it's a good landing. If you use the airplane the next day, it's an outstanding landing"

Re: SpaceX's Falcon Heavy center booster lacked ignition fluid to re-light engines

#156

Post by walrus01 »

olympus wrote: post #42
ZeroGravitas wrote: post #18

He also announced the 3rd drone ship's name on twitter as "A Shortfall of Gravitas".

Going all in on the Culture ship names. I'd be happy if he just made 100(ish) more just to name them after every ship that Iain M. Banks named. They don't need to catch rockets, they can just link up and make a floating utopia.

Mistake Not My Current State Of Joshing Gentle Peevishness For The Awesome And Terrible Majesty Of The Towering Seas Of Ire That Are Themselves The Mere Milquetoast Shallows Fringing My Vast Oceans Of Wrath

Re: SpaceX's Falcon Heavy center booster lacked ignition fluid to re-light engines

#157

Post by ReverseCold »

jessriedel wrote: post #124
ReverseCold wrote: post #119

Earlier quoted context omitted.

I think it's not exactly 328 feet, so it's about 328 feet.

Equally well could have said "about 328.084 feet".

Hm, I don't know of a rule that specifies how to use the word "about".

To me at least, "about 328 feet" seems okay. It gives you more precision than "about 300 feet" while still letting you know that it's not exactly 328 feet.

Re: SpaceX's Falcon Heavy center booster lacked ignition fluid to re-light engines

#158

Post by williamscales »

ReverseCold wrote: post #157
jessriedel wrote: post #124

Earlier quoted context omitted.

Equally well could have said "about 328.084 feet".

Hm, I don't know of a rule that specifies how to use the word "about". To me at least, "about 328 feet" seems okay. It gives you more precision than "about 300 feet" while still letting you know that it's not exactly 328 feet.

The point is that extra precision is unwarranted. We only know that it missed by somewhere between 50 and 149 meters, so it's not appropriate to imply that we know it more precisely.

Re: SpaceX's Falcon Heavy center booster lacked ignition fluid to re-light engines

#159

Post by 0xTJ »

ReverseCold wrote: post #157
jessriedel wrote: post #124

Earlier quoted context omitted.

Equally well could have said "about 328.084 feet".

Hm, I don't know of a rule that specifies how to use the word "about". To me at least, "about 328 feet" seems okay. It gives you more precision than "about 300 feet" while still letting you know that it's not exactly 328 feet.

328 feet is a unit conversion after already rounding to one significant figure

Re: SpaceX's Falcon Heavy center booster lacked ignition fluid to re-light engines

#160

Post by 0xTJ »

evanlivingston wrote: post #101

I'm someone who doesn't follow a lot about current aerospace capabilities and technologies. Can someone explain why the work SpaceX is doing is so much more exciting than that of United Launch Alliance or Khrunichev or similar systems?

All my other "real" points have been covered by other users, but one other thing that SpaceX is doing is making space cool again. I've always found it interesting, and the launch vehicles technically incredible, but (as a university student) it's the first time in my life that current space-related events have been at the front of my mind. Various news outlets called the Falcon Heavy launch the most anticipated launch of the last decade, and I'd agree. In the lecture I was in during the launch, everyone was either watching it on their laptop, or looking over the shoulder of the person in front of them. People were shaking from excitement, and nearly tearing up as the FH lifted off.
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