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SpaceX discloses cause of Starship anomalies as it clears an FAA hurdle

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Re: SpaceX discloses cause of Starship anomalies as it clears an FAA hurdle

#41

Post by CarVac »

foobarian wrote: post #35
Sebb767 wrote: post #9

Earlier quoted context omitted.

Why do those rockets have a fuel filter at all? I get why we have them in cars; we refuel quite often, in dirty environments and with possibly low quality fuel. For space rockets, it seems that it would be (comparatively) easy to ensure that the tanks are clean and the fuel is of high quality. On the other hand, if there wasn't any dirt, the filters would not have clogged, so I guess it does make sense after all.

In my mind a rocket engine would be much more tolerant of debris since you just pipe the fuel into a giant fireball (yes I can practically see the eyes rolling, sorry! :-). For ICEs I can understand clogging tiny injectors or carbs would be a problem, do rocket engines also have injectors or other narrow parts susceptible to clogs?

Yes, rocket engines have many small orifices to atomize and mix the propellant.

It's like a showerhead, except if the fuel side clogs, the oxidizer might eat your chamber wall.

Re: SpaceX discloses cause of Starship anomalies as it clears an FAA hurdle

#42

Post by bryanlarsen »

sebzim4500 wrote: post #30
rbanffy wrote: post #5

Earlier quoted context omitted.

I love that Superheavy/Starship can be profitable even if they are expendable.

Expending the second stage would almost certainly be cheaper per kg than Falcon 9, but I doubt this is still true if you have to expend the booster. Keep in mind we would have to compare it to the ~20M marginal cost of a F9 launch, not the $70M sticker price that a customer would pay.

It might actually be cheaper even if the booster is expended.

Falcon9 is estimated to cost about $30M/launch. $20M to build the upper stage, and $10M to launch. Starship is estimated to cost about $100M to build both the booster and the second stage. Add $10M to launch.

So 17t/$30M vs 150t/$110M.

Re: SpaceX discloses cause of Starship anomalies as it clears an FAA hurdle

#43

Post by Ajedi32 »

foobarian wrote: post #35
Sebb767 wrote: post #9

Earlier quoted context omitted.

Why do those rockets have a fuel filter at all? I get why we have them in cars; we refuel quite often, in dirty environments and with possibly low quality fuel. For space rockets, it seems that it would be (comparatively) easy to ensure that the tanks are clean and the fuel is of high quality. On the other hand, if there wasn't any dirt, the filters would not have clogged, so I guess it does make sense after all.

In my mind a rocket engine would be much more tolerant of debris since you just pipe the fuel into a giant fireball (yes I can practically see the eyes rolling, sorry! :-). For ICEs I can understand clogging tiny injectors or carbs would be a problem, do rocket engines also have injectors or other narrow parts susceptible to clogs?

> do rocket engines also have injectors

Yes[1]. You want the fuel and oxidizer mixed as well as possible to achieve efficient combustion.

There are also other small channels fuel has to flow through, like the ones used for regenerative cooling[2].

And not sure how well most turbopumps[3] would tolerate debris either, though that probably depends on the exact design.

There are some really simple rocket designs out there that I could imagine tolerating debris (like solid motors[4] or pressure fed hyperbolic engines[5]) but Raptor definitely doesn't fall into those categories.

[1]: https://en.wikipedia.org/wiki/Liquid-propellant_rocket#Injec...

[2]: https://en.wikipedia.org/wiki/Regenerative_cooling_(rocketry...

[3]: https://en.wikipedia.org/wiki/Turbopump

[4]: https://en.wikipedia.org/wiki/Solid-propellant_rocket

[5]: https://en.wikipedia.org/wiki/Hypergolic_propellant#Characte...

Re: SpaceX discloses cause of Starship anomalies as it clears an FAA hurdle

#44

Post by misiti3780 »

somenameforme wrote: post #33
baq wrote: post #14

Earlier quoted context omitted.

There are customers from three letter agencies who could find a use for this payload capacity, for sure. OTOH imagine if a reusable launch of this costs approximately the same as an expendable Atlas 5 in it's most performant configuration and reliability is proven - NASA could launch a Pluto probe like New Horizons, except it'd be able actually make orbit over there.

Atlas 5 is already completely obsoleted by the Falcon Heavy which costs about half as much, for a reusable launch, and carries about 3x as much. But for Starship, most people don't seem to realize what a potential game changer this is. The goal for Starship is to get costs down to about 15x less than Falcon Heavy. When you can start sending stuff to space for a few dollars per pound, we're not talking about just prob…

Also, wont it theoretically speed up and decrease international shipping + travel. We should be able to go from the US to Japan in an hour or two in the future.

Re: SpaceX discloses cause of Starship anomalies as it clears an FAA hurdle

#45

Post by db48x »

foobarian wrote: post #35
Sebb767 wrote: post #9

Earlier quoted context omitted.

Why do those rockets have a fuel filter at all? I get why we have them in cars; we refuel quite often, in dirty environments and with possibly low quality fuel. For space rockets, it seems that it would be (comparatively) easy to ensure that the tanks are clean and the fuel is of high quality. On the other hand, if there wasn't any dirt, the filters would not have clogged, so I guess it does make sense after all.

In my mind a rocket engine would be much more tolerant of debris since you just pipe the fuel into a giant fireball (yes I can practically see the eyes rolling, sorry! :-). For ICEs I can understand clogging tiny injectors or carbs would be a problem, do rocket engines also have injectors or other narrow parts susceptible to clogs?

Yes, they do. All of the fuel and oxidizer goes through injectors to atomize it as it is sprayed into the combustion chamber. For a Merlin 1D, that’s about 340 pounds of propellant going through the injector plate every second.

Rocket Fuel Injectors - Things Kerbal Space Program Doesn't Teach https://www.youtube.com/watch?v=aa4ATJGRqA0

Re: SpaceX discloses cause of Starship anomalies as it clears an FAA hurdle

#46

Post by rob74 »

cduzz wrote: post #16
Tuna-Fish wrote: post #11

Earlier quoted context omitted.

Most rockets don't have fuel filters, but this requires their tanks to be kept in a much more strict state of cleanliness, and any failure to do so would result in mission failures. SpaceX has long had a very different idea about FOD than most other rocket companies, famously Merlin engine qualification testing contains ingesting stainless steel nuts.

That's bonkers. What size nuts do they pass through their engine? Every engine before it goes to space has to have a nut passed through the system? Like a 12mm "go into space" grade nut or a little itty bitty nut like I might find holding down a heat sink assembly in a 1998 vintage motherboard? I'm off to the googles to find videos...

Actually I'd rather have such "bonkers" tests than the other extreme, like NASA not thinking about what could happen if pieces of foam from the external fuel tank impacted the Space Shuttle on launch until it was too late (https://en.wikipedia.org/wiki/Space_Shuttle_Columbia_disaste...).

Re: SpaceX discloses cause of Starship anomalies as it clears an FAA hurdle

#47

Post by s1artibartfast »

Sebb767 wrote: post #9
tromp wrote: post #3

> "The most likely root cause for the booster RUD (rapid unscheduled disassembly) was determined to be filter blockage where liquid oxygen is supplied to the engines, leading to a loss of inlet pressure in engine oxidizer turbopumps that eventually resulted in one engine failing in a way that resulted in loss of the vehicle," the company stated. "SpaceX has since implemented hardware changes inside future booster oxi…

Why do those rockets have a fuel filter at all? I get why we have them in cars; we refuel quite often, in dirty environments and with possibly low quality fuel. For space rockets, it seems that it would be (comparatively) easy to ensure that the tanks are clean and the fuel is of high quality. On the other hand, if there wasn't any dirt, the filters would not have clogged, so I guess it does make sense after all.

Rockets and cars have fuel filters for different reasons.

You car has a fuel filter because dirt causes wear and tear on the engine over time.

In a rocket, a stray particulate is a potentially explosive event. the Fuel pumps are approximately 100,000 horsepower and particles in flow can have enough kinetic energy to trigger combustion with the walls of the system the fuel is flowing through. Most metals will burn as fuel in a high oxygen environment, even at standard pressures, let alone pressures 100x higher.

Re: SpaceX discloses cause of Starship anomalies as it clears an FAA hurdle

#48

Post by jwells89 »

martythemaniak wrote: post #2

This is good. Flight 1 had 63 corrective actions and it took 5 months to complete the report. This one took 3 months and had 17 corrective actions. They'll get to orbit this year for sure

It’s so exciting to keep track of. Feels like everything I hoped to see happening in spaceflight back in the 90s and 00s is finally (maybe) becoming reality and absolutely shattering the stagnancy that had overcome the field, hopefully this time for good.

If this pace can continue unabated, maybe it’s not too unrealistic to hope that my grandkids’ generation in a few decades has astronaut as one of their most aspired careers much as was the case for the kids of the 70s, 80s, and 90s… except this time it’d be much more practically achievable since there’d be greatly increased demand for people with that skillset.

Re: SpaceX discloses cause of Starship anomalies as it clears an FAA hurdle

#49

Post by cduzz »

toss1 wrote: post #40
cduzz wrote: post #16

Earlier quoted context omitted.

That's bonkers. What size nuts do they pass through their engine? Every engine before it goes to space has to have a nut passed through the system? Like a 12mm "go into space" grade nut or a little itty bitty nut like I might find holding down a heat sink assembly in a 1998 vintage motherboard? I'm off to the googles to find videos...

Let us know what you find. I find it not 'bonkers' but a great idea, and hope they are qualifying with the largest nuts found upstream, in 'go to space' grades. Robustness and anti-fragility may not be so critical for an expendable vehicle that operates once for something like 12 minutes, but seems a key attribute for a refuel-able and reusable spacecraft?

Oh I agree it's not bonkers from the perspective of "wait you want to put people on that bomb and then explode it?"

You can make all sorts of rules about what's not allowed to happen, but often those things happen.

I'm just ... astonished if they've got a little practice room somewhere in their factory where they give each of their new rockets a nut to process... "Okay kid here's your graduation test!". A "we need screens to cope with big things and filters to deal with small things" is probably smart for any anything that's going to be reused.

A nut's probably in some ways easier to deal with than a blob of wd40 (in your lox tank).

Re: SpaceX discloses cause of Starship anomalies as it clears an FAA hurdle

#50

Post by Sanzig »

misiti3780 wrote: post #44
somenameforme wrote: post #33

Earlier quoted context omitted.

Atlas 5 is already completely obsoleted by the Falcon Heavy which costs about half as much, for a reusable launch, and carries about 3x as much. But for Starship, most people don't seem to realize what a potential game changer this is. The goal for Starship is to get costs down to about 15x less than Falcon Heavy. When you can start sending stuff to space for a few dollars per pound, we're not talking about just prob…

Also, wont it theoretically speed up and decrease international shipping + travel. We should be able to go from the US to Japan in an hour or two in the future.

I am pretty skeptical of Starship ever getting used for suborbital transportation, other than maybe for ultra-elite VIP transport or something like a rapid deployment system for military special forces. It seems highly unlikely they will ever get the price down to where it can compete with commercial airliners, and Concorde's commercial failure showed us that people will happily choose cheap subsonic flight over fast supersonic flight. You can get almost anywhere on Earth in 36 hours' notice with conventional jet travel relatively cheaply on 1-2 weeks of US median income for a return ticket - that sweet spot of speed and cost is hard to beat.
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