Cracks in SpaceX’s Falcon 9 Fuel Pumps Could Pose Threat to Astronauts

Megalith

Megalith

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In what sounds like another substantial setback for SpaceX, investigators have reportedly found that an integral component of the Falcon 9 vehicle may be prone to cracking. While I will not take credit for this thought, it is possible that this issue existed since the craft’s inception but only came to light after SpaceX finally managed to land one successfully back in January.

…the Wall Street Journal reports that a problem in the Falcon 9's engine could jeopardize SpaceX's goal of becoming the first private company to deliver astronauts to the International Space Station in 2018. The WSJ article (which is behind a paywall) reports that the Government Accountability Office found the turbine blades that pump fuel into the Falcon 9's engines liable to crack. A GAO report later this month is expected to detail the leaked findings. Popular Science reached out to GAO to check the facts, but the public affairs office isn't allowed to discuss the report's findings until it comes out in a few weeks. WSJ reports the turbopump cracks could "pose an unacceptable risk for manned flights." Which is not great news, given the fact that SpaceX hopes to launch its first astronauts in 2018—a milestone that has already been delayed several times.
 
It's one advantage of having reuseable rockets, the post launch inspection.

Otherwise, this problem likely wouldn't have been found until a post-disaster investigation.
 
Long term testing like this is advisable before us actual critters go for rides.
 
Ground test exist for a reason. A reusable rocket doesn't necessarily help. This should have been caught before the engine ever flew. But this report is extremely vague: cracks after two flight cycles or after 10?

The Space Shuttle has reusable engines. Off the top of my head, I can't remember if they even tore them down after every flight to check for damage... the turbo pumps, at least... They're easily the most complex part of rocket engines.
 
umeng2002 said:
Ground test exist for a reason. A reusable rocket doesn't necessarily help. This should have been caught before the engine ever flew. But this report is extremely vague: cracks after two flight cycles or after 10?

The Space Shuttle has reusable engines. Off the top of my head, I can't remember if they even tore them down after every flight to check for damage... the turbo pumps, at least... They're easily the most complex part of rocket engines.
Click to expand...
Although intended to be used for more than 1 flight in between refurbs, the RS-25 (aka SSME) was overhauled after every flight.
But I agree with everything in your first 3 sentences.
 
This vague report leak brought to you by your friends at ULA.
 
Pictures of rocket motors make me feel funny...

...Down there...

Warning: Pornography Follows

Moteur-Vulcain.jpg
 
umeng2002 said:
Ground test exist for a reason. A reusable rocket doesn't necessarily help. This should have been caught before the engine ever flew. But this report is extremely vague: cracks after two flight cycles or after 10?

The Space Shuttle has reusable engines. Off the top of my head, I can't remember if they even tore them down after every flight to check for damage... the turbo pumps, at least... They're easily the most complex part of rocket engines.
Click to expand...


the space shuttle was meant to re-use engine assemblies and boosters but never did. the only thing re-used from the solid boosters was the shell, everything else was replaced internally. it's why the shuttle never really became the low cost way to send humans and satellites to space that was originally promised.

as far as spaceX goes i believe they've only re-used one first stage so far.. otherwise every other launch has used a brand new first stage. but i also don't expect them to re-use the first stage on human flights at least for the first few years even though they could potentially do it. cost savings isn't worth the risk until they can definitively show that they can be re-used successfully.
 
umeng2002 said:
Ground test exist for a reason. A reusable rocket doesn't necessarily help. This should have been caught before the engine ever flew. But this report is extremely vague: cracks after two flight cycles or after 10?

The Space Shuttle has reusable engines. Off the top of my head, I can't remember if they even tore them down after every flight to check for damage... the turbo pumps, at least... They're easily the most complex part of rocket engines.
Click to expand...
They have been testing the engine for well over a decade and it's not been an issue until now apparently. We'll see what the actual GAO report was and where their data came from soon enough. I've seen my share of garbage GAO reports in the past few years.

Either way, this is a problem that can be fixed.
 
The issue with rocket engines and turbo fuel pumps is the pogo effect due to oscillations in fuel flow, high pressure liquids bounce forwards and backwards in the high pressure pipework smashing things to pieces. I believe it was an issue in the RS25 engines fitted to the shuttle that took time to solve, but it was a real issue in the engines that powered the Saturn craft and others before the shuttle.
 
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Spidey329 said:
It's one advantage of having reuseable rockets, the post launch inspection.

Otherwise, this problem likely wouldn't have been found until a post-disaster investigation.
Click to expand...
On a disposable rocket it would've been caught in testing. The one (big) advantage of resusable rockets is cost of rocket production can be spread out over multiple launches.
 
Couple of things ... Andy Pasztor (at WSJ) has written several critical articles about SpaceX. His article cited here is misleading with regards to the fuel pumps posing a threat to astronauts. Both him and Loren Thompson (at Forbes) need to be taken with a grain of salt ... more worrisome is how he got a hold of a leaked draft copy and made a pretzel of its context. For clarification purposes:

Right off the bat you have to realize that these Merlin engines aren't manned rated. These micro-cracks are not new with SpaceX and they have qualified the engines to be robust to turbine wheel cracks. For Block 5, they are working with NASA in modifying the pumps to avoid micro-cracks all together for manned flights. Once again, Block 5 will have manned rated Merlin's and only new cores will be manned flights (reused cores will be used for cargo).

Should also be noted that 300+ Merlin's have flown with zero pump failures. During the qualifications test the Merlin's had steel nuts thrown into the pumps and they didn't fail. These engines are stout.

How about this ... the JCSat14 Merlin's (the F9 which launched last May): No refurbishments between the following: Individual engine qual, F9 pre-flight stage burn, static fire, launch/recovery and 8 more mission burns at McGregor.

Now, I'm not saying that this shouldn't be ignored ... but it isn't. SpaceX/NASA are well aware of the micro-cracks and have been working on the final modifications for the manned-rated Merlin's.


Side note: Saw someone mention the SSME's. The RS-25's had the same problems, same reports and never had one fail. 42 engines covered all 135 launches with 6 engines lost due to no fault of their own (Challenger engines 2021, 2020, 2023) and Columbia (engines 2055, 2053, 2049). In fact, engine 2055 was brand new and was only one of two engines to be only flown once (the other being engine 2051 on STS-130)
 
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musk keeps trying to work with systems that someone else built and force them to do more than they are designed to instead of dreaming bigger because getting funding for building what makes sense instead of what you can sell as an idea to a money market fund broker is very hard. The fuel densities are way too low for most of the systems. The materials are way too thin because they keep thinking lighter is better since they don't have enough newtons to get off the ground with structural sound ideas. I happy because it gives the military enough time to build an interceptor to be able to make them veer off if they are on a ballistic course for a populated city. That an the air frame the united states military told me back in 1997 that we would never need now has to be built by someone. snicker... I still owe the base commander of Sheppard Air Force base in Witcha Falls Texas one. He told me if I ever got a finished design he would buy one. I have no idea what company is going to build it but it would not surprise me to see ford and chevy get into the game trying to build an interceptor, based on this... http://vasdrakken.com/writing/Banshee_Model_One.html thankfully that concept has to go through the Senate Armed Forces Committee before anyone can simply start building one for the military.

oh one other thing so a suborbital is going four times the speed of the concord if it flies by a building it does four times the damage of concord which can blow out windows at a mile away due to the sonic boom. The odds of aerofoil interceptor being a civilian craft any time are very slim due to systems being the fastest thing possible as the newtons force exceed most material science. It does not need weapons to know other craft off course the sonic boom due to the shape and the ability to reach speeds in excess of mach forty means that a craft on a terminal balistic flight path to a city that can not divert can be knocked aside by a YF-37A simply by flying across the terminal flight path. But then again congress may not care I am not congress. grin.
 
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