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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

#161

Post by 0xTJ »

fma wrote: post #96
delecti wrote: post #81

Earlier quoted context omitted.

One big flaw in your argument is that the payload was delivered safely and successfully. They're making great strides towards making components reusable when they never really were before. That they're not perfect right out of the gate isn't reason to give up hope it ever could be.

Actually...the payload was put on the wrong trajectory, so OP's argument still stands. "Elon Musk’s cherry red Tesla sports car and its dummy test pilot Starman were on a new course hurtling towards the asteroid belt on Wednesday after overshooting their planned trajectory." https://www.theguardian.com/science/2018/feb/07/elon-musk-sp...

That's not at all a mistake. Any sort of overshoot is extremely unlikely to occur with these situations. The public plan was to put it into an orbit around the sun with the perihelion near Earth's orbit and its aphelion near Mars's. Using the additional remaining fuel, they decided to burn until the aphelion reached well past mars towards the asteroid belt.

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

#162

Post by 0xTJ »

dingo_bat wrote: post #143
jacquesm wrote: post #130

Earlier quoted context omitted.

In this case they ran out because they were relighting three times as many engines.

But didn't put in 3 times as much fuel? Seems like a simple oversight.

It's not quite that simple. So many factors, as well as random chance, affect the quantity of TEA/TEB used that it's virtually impossible to create an accurate prediction. Other comments in this thread mention that they could probably have modeled and tested on the ground until they had a better idea, but that takes a long time and is expensive. Actually launching the thing and learning from that is a much more effective usage of time and money. As someone else ITT quoted George Box "all models are wrong, but some are useful.".

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

#163

Post by 0xTJ »

Stratoscope wrote: post #118
quadyeast wrote: post #39

Is that also why the video feed was not working? SpaceX commentators said it was possibly due to vibration.

The video feed didn't stop working, or if it did, it was only for a brief moment. If you watch this part of the YouTube stream, after it cuts back to the two hosts there is a monitor at the far right center of the video that shows the continuing camera feed of the drone ship landing pad. Only part of the monitor is visible, but after the smoke clears over the next few minutes you can see the empty pad: https://www.yo…

Although I understand why they would have done that for click-bait news outlets, it did really bother me that they were so slow in revealing what happened. What I like about SpaceX is that they're always been very open about their failures, even compiling that great video of their failures. Being able to seeing the full result would have been nice, and I spent a fair bit of time for the following hours refreshing Twitter.

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

#164

Post by Dylan16807 »

vkou wrote: post #129
mulmen wrote: post #91

Earlier quoted context omitted.

An airliner is on a building scale and carries a slightly less refined petroleum fuel. RP-1 and Jet Fuel are both refined petroleum fuels. Rockets only carry LOX because they go into space where there is no atmospheric oxygen to burn the fuel. Airliners are fully capable of turning themselves into fireballs. It doesn't happen often because we have a lot of experience operating them. The same safety levels are possibl…

> An airliner is on a building scale and carries a slightly less refined petroleum fuel. RP-1 and Jet Fuel are both refined petroleum fuels. Rockets only carry LOX because they go into space where there is no atmospheric oxygen to burn the fuel. That's true, but a 747 does not burn its weight in fuel in 397 seconds. A Falcon 9 does. It's the difference between igniting a gas barbecue in your back yard, and igniting t…

> the tyrrany of the rocket equation

It's actually not that bad for suborbital flights. You can overbuild by a lot.

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

#165

Post by chii »

everdev wrote: post #5

This is why we compare hard problems to rocket science. It's so hard to recover from failure of even the smallest sources.

but the hip programming tips these days are to move fast and break things!

a rocket certainly moves fast...

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

#166

Post by prewett »

chii wrote: post #165
everdev wrote: post #5

This is why we compare hard problems to rocket science. It's so hard to recover from failure of even the smallest sources.

but the hip programming tips these days are to move fast and break things! a rocket certainly moves fast...

It would have broken a bunch of things if it weren't "about 328 feet" off target, too.

When they said they lost the core, I've been envisioning a barge with a big, round hole in the center...

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

#167

Post by ncallaway »

chii wrote: post #165
everdev wrote: post #5

This is why we compare hard problems to rocket science. It's so hard to recover from failure of even the smallest sources.

but the hip programming tips these days are to move fast and break things! a rocket certainly moves fast...

It's not like SpaceX didn't break things either: https://www.youtube.com/watch?v=bvim4rsNHkQ.

The real trick is knowing when it's OK to break things in experimentation and the acquisition of knowledge, and when everything needs to run smoothly.

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

#168

Post by ncallaway »

prewett wrote: post #166
chii wrote: post #165

Earlier quoted context omitted.

but the hip programming tips these days are to move fast and break things! a rocket certainly moves fast...

It would have broken a bunch of things if it weren't "about 328 feet" off target, too. When they said they lost the core, I've been envisioning a barge with a big, round hole in the center...

They intentionally aim off-target, and have the final engine burn steer them back into the landing.

If an engine relight doesn't happen, they won't hit the barge.

I think the biggest danger to the barge is a final engine relight without enough fuel, or with a guidance and nav systems failure or error.

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

#169

Post by lb1lf »

ncallaway wrote: post #168
prewett wrote: post #166

Earlier quoted context omitted.

It would have broken a bunch of things if it weren't "about 328 feet" off target, too. When they said they lost the core, I've been envisioning a barge with a big, round hole in the center...

They intentionally aim off-target, and have the final engine burn steer them back into the landing. If an engine relight doesn't happen, they won't hit the barge. I think the biggest danger to the barge is a final engine relight without enough fuel, or with a guidance and nav systems failure or error.

-OT, but related - for the same reason, offshore vessels set their autopilot targets say, half a mile off the oil rig/whatever they are headed for - just in case someone doesn't pay attention as they approach.

I once saw a nice enamelled sign on a bridge stating 'Whoever programs a target on target will be promoted to figurehead prior to arrival at said target.'

(And, in that position, being the first to regret their sloppiness. Plus, they will somewhat soften the impact. Cough.)

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

#170

Post by taneq »

toufka wrote: post #44
ZeroGravitas wrote: post #18

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

That's a great name to add to the stable of Autonomous Spaceport Drone Ships: - Of Course I Still Love You - Just Read the Instructions - A Shortfall of Gravitas (and doubly great for you, u/ZeroGravitas)

If they ever start doing regular military missions (or we end up fighting bug-eyed aliens) I hope they add Falling Outside The Normal Moral Constraints. (Edit: Falling, not Operating.)
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