Author Topic: Raptor Utilization  (Read 13540 times)

Offline Bananas_on_Mars

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Re: Raptor Utilization
« Reply #60 on: 08/04/2018 08:22 PM »
People talk about shutting down falcon first stage production and 'betting the farm' on the BF's.
Can the mechanical engineers who post here please explain if the contemporary management of production engineering makes it any easier to shut down a production line and restart it later, and do they think SpaceX need to gain that experience?
Presumably Boeing has to do something similar when there are radical variations in demand in the highly cyclical airline business? Can falcon first stage production be compared to airliner production in this way or is there even more tacit knowledge retained by rocket 'plumbers' than is the case for airliner production engineers?
The relevance of this is to try to understand if they really are betting the business on the new rocket.
EDIT: ...and that might make it less urgent to deliver a raptor powered vehicle.
SpaceX as a company has shown to be kind of hoarders, so they might keep everything in storage.

IMO they're not betting the farm, they're aiming high, even though they currently have the most economic rocket available.
They are driven by a vision and their leader, not by their competitors.
Good enough in their opinion means "good enough for the next 5 years" while they built the next generation, not "good enough" until their competitors catch up.

Offline Doesitfloat

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Re: Raptor Utilization
« Reply #61 on: 08/06/2018 02:18 PM »
People talk about shutting down falcon first stage production and 'betting the farm' on the BF's.
Can the mechanical engineers who post here please explain if the contemporary management of production engineering makes it any easier to shut down a production line and restart it later, and do they think SpaceX need to gain that experience?
Presumably Boeing has to do something similar when there are radical variations in demand in the highly cyclical airline business? Can falcon first stage production be compared to airliner production in this way or is there even more tacit knowledge retained by rocket 'plumbers' than is the case for airliner production engineers?
The relevance of this is to try to understand if they really are betting the business on the new rocket.
EDIT: ...and that might make it less urgent to deliver a raptor powered vehicle.
SpaceX as a company has shown to be kind of hoarders, so they might keep everything in storage.

IMO they're not betting the farm, they're aiming high, even though they currently have the most economic rocket available.
They are driven by a vision and their leader, not by their competitors.
Good enough in their opinion means "good enough for the next 5 years" while they built the next generation, not "good enough" until their competitors catch up.
Spacex has stated that Raptor uses the same build process as Merlin, add to that they are currently producing both Merlin and Raptor engines.  So the output of the engine shop today could be Merlin Merlin Merlin Raptor Merlin Merlin.  In the future they can shift to Raptor Raptor Merlin Merlin Raptor Raptor.
Spacex has stated they made their engine production modeled after an automotive production line.  Elon hired production engineers and managers from the auto industry years ago; and he has that car company. 
On a modern production line ( Take the Rouge Tour (Dearborn MI Ford F150) or (Bowling Green KY Tour GM Corvette)) you will see the most extravagant and expensive Verizon followed by the basic cheapest version following each other down the line.  The expensive version may have twice the number of parts than the base model but the production is planned to accommodate both.
I doubt any other racket engine manufacturer would set up this type of production;  because no other manufacturer is as focused on the cost of their engines.  The others set up a dedicated process and the cost is the cost.

Offline Bananas_on_Mars

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Re: Raptor Utilization
« Reply #62 on: 08/06/2018 02:43 PM »
People talk about shutting down falcon first stage production and 'betting the farm' on the BF's.
Can the mechanical engineers who post here please explain if the contemporary management of production engineering makes it any easier to shut down a production line and restart it later, and do they think SpaceX need to gain that experience?
Presumably Boeing has to do something similar when there are radical variations in demand in the highly cyclical airline business? Can falcon first stage production be compared to airliner production in this way or is there even more tacit knowledge retained by rocket 'plumbers' than is the case for airliner production engineers?
The relevance of this is to try to understand if they really are betting the business on the new rocket.
EDIT: ...and that might make it less urgent to deliver a raptor powered vehicle.
SpaceX as a company has shown to be kind of hoarders, so they might keep everything in storage.

IMO they're not betting the farm, they're aiming high, even though they currently have the most economic rocket available.
They are driven by a vision and their leader, not by their competitors.
Good enough in their opinion means "good enough for the next 5 years" while they built the next generation, not "good enough" until their competitors catch up.
Spacex has stated that Raptor uses the same build process as Merlin, add to that they are currently producing both Merlin and Raptor engines.  So the output of the engine shop today could be Merlin Merlin Merlin Raptor Merlin Merlin.  In the future they can shift to Raptor Raptor Merlin Merlin Raptor Raptor.
Spacex has stated they made their engine production modeled after an automotive production line.  Elon hired production engineers and managers from the auto industry years ago; and he has that car company. 
On a modern production line ( Take the Rouge Tour (Dearborn MI Ford F150) or (Bowling Green KY Tour GM Corvette)) you will see the most extravagant and expensive Verizon followed by the basic cheapest version following each other down the line.  The expensive version may have twice the number of parts than the base model but the production is planned to accommodate both.
I doubt any other racket engine manufacturer would set up this type of production;  because no other manufacturer is as focused on the cost of their engines.  The others set up a dedicated process and the cost is the cost.
The difference in output between Elon's car company (Model 3) and the SpaceX engine  section is exactly 3 orders of magnitude.

I'm willing to bet the SpaceX engine assembly does NOT look like a typical car assembly line built around a central conveyor, because the speed of that conveyor would be one workstation per day...

There's a lot to be learned from car manufacturers when you're into built reliability, things that might not have yet carried over for other aerospace companies. Automated documentation, Traceability etc. for a lot of steps should be quite helpful for engine assembly and are a huge part of automotive manufacturing.

Offline cheesybagel

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Re: Raptor Utilization
« Reply #63 on: 08/06/2018 06:22 PM »
Intel, which is one of the examples of a company which has been successful for decades in the high tech sector, basically has a rule where they don't change the process materials and the chip design at the same time. First they change the process materials with an existing and well understood design, and sell that, in the next iteration now that they understand the process materials, they come up with a new chip design.

Seymour Cray, one of the electronics industry's main innovators, also had a maxim: you should only apply one new technology per product iteration, two new technologies was to risk a major disaster, and three new technologies was a complete disaster.

So you basically want to do small changes per vehicle but have a rapid product iteration cycle. Much like what SpaceX did with Falcon 9. Compare the specs of the initial Falcon 9 with the Block 5 and you'll see what I mean. It would have been trivial for SpaceX to manufacture a LOX/Methane rocket with their existing Al/Li tools, a technology they dominate, without requiring an investment into composites. Remember the accident that happened with the small composite tank in the second stage of the Falcon 9. Composite materials are really hard to ensure consistent quality and this is a particular problem with either LOX or deep cryogenic environments. It's one thing to use the composites in the outer shell of the vehicle and quite another to use them for cryogenic fuel tanks that are supposed to be reused multiple times. Even the aeronautics sector, with a much more benign operating environment, finds that for most structures in theory composites are supposed to be lighter, but when you take into consideration the failure modes of composites, and apply them to an actual design, you end up having to use thicker panels than originally expected which ends up being heavier than Al-Li in many cases.
It also makes reparations much harder. Instead of welding a crack, you basically have to glue a crack, and typically because of the multi-layer nature of composites instead of the crystalline nature of metals this ends up being less reliable.

So in short I think they shouldn't try to use composites as much on their next generation vehicle. AFAIK their large composite main tank test, which they heralded as a "success", failed the water pressure burst test, it basically came out at the seams. Imagine that was cryogenic LOX instead of water and that you had to do multiple flights with it. It's a whole different ball of wax. This was indeed one of the causes of the failure of the X-33 except in that case they had to handle not only LOX like temperatures, but they had to handle LH2 as well which is MUCH worse.

IMHO they should just use Raptor in an Al-Li vehicle with limited use of composites. Also the vehicle should prove technologies for their BFR but it should be able to launch useful payloads to space by itself to pay for its own design. Not just conduct hops. Even it it requires an expendable second stage to do that.
« Last Edit: 08/06/2018 06:34 PM by cheesybagel »

Offline CuddlyRocket

Re: Raptor Utilization
« Reply #64 on: 08/07/2018 02:31 PM »
AFAIK their large composite main tank test, which they heralded as a "success", failed the water pressure burst test, it basically came out at the seams.

My understanding is that they tested it to destruction.

Online matthewkantar

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Re: Raptor Utilization
« Reply #65 on: 08/07/2018 03:01 PM »
The X33 was two decades ago, had cryogenic hydrogen for fuel, and had a very complicated shape for the hydrogen tank. This a different era, a different fuel, and a simpler design closer to an ideal tank shape. SpaceX is doing the work to make Al rockets a thing of the past.

Matthew
« Last Edit: 08/07/2018 03:01 PM by matthewkantar »

Online Slarty1080

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Re: Raptor Utilization
« Reply #66 on: 08/08/2018 09:28 PM »
AFAIK their large composite main tank test, which they heralded as a "success", failed the water pressure burst test, it basically came out at the seams.

My understanding is that they tested it to destruction.

If you look at Elon Musk's 2017 presentation he shows a video of a BFR LOX tank pressure test. From memory I think its design max pressure was 2 atmospheres, they tested it to destruction and it failed at 2.2 atmospheres.
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Online Coastal Ron

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Re: Raptor Utilization
« Reply #67 on: 08/08/2018 10:02 PM »
Intel, which is one of the examples of a company which has been successful for decades in the high tech sector...

And now is looked at as a laggard in the field of low-power processors. Apple is rumored to be moving away from Intel by making their own processors that are based on the ARM platform. Best not to use old examples to argue for current day issues...  ;)

Quote
Seymour Cray, one of the electronics industry's main innovators, also had a maxim: you should only apply one new technology per product iteration, two new technologies was to risk a major disaster, and three new technologies was a complete disaster.

Cray did innovative stuff wrt supercomputers, but he was in a completely different market space than SpaceX is in, and different goals. Elon Musk wants to get to Mars as quickly as SpaceX can do it.

Quote
So you basically want to do small changes per vehicle but have a rapid product iteration cycle. Much like what SpaceX did with Falcon 9.

SpaceX rolled out lots of BIG changes too, so don't be thinking that SpaceX only did small incremental changes - they were OK with crashing rockets to learn information that could only be learned by flying real hardware. And they seem like they will use the same approach with the BFS and BFR.

Quote
Compare the specs of the initial Falcon 9 with the Block 5 and you'll see what I mean. It would have been trivial for SpaceX to manufacture a LOX/Methane rocket with their existing Al/Li tools, a technology they dominate, without requiring an investment into composites.

They don't "dominate" in the field of Al/Li tools. They use standard friction stir welding, which was not invented by SpaceX. Maybe I'm missing something here, but why do you think the "dominate" with their tooling?

Quote
Remember the accident that happened with the small composite tank in the second stage of the Falcon 9. Composite materials are really hard to ensure consistent quality and this is a particular problem with either LOX or deep cryogenic environments.

The BFS won't use COPV tanks. They plan to rely on autogenous pressurization, which is the heating of the propellant (i.e. methane & LOX) to pressurize each tank. The only embedded tanks are for propellant dedicated for landing purposes, which are positioned to ensure that landing propellant is not allowed to boil off.

Quote
IMHO they should just use Raptor in an Al-Li vehicle with limited use of composites.

Hey, go for it if you think you are right. Raise some funds and show how your approach works better. But SpaceX, which has thousands of engineers highly invested in the success of the BFS, plans to go with composites...  ;)
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Offline oiorionsbelt

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Re: Raptor Utilization
« Reply #68 on: 08/08/2018 10:48 PM »
AFAIK their large composite main tank test, which they heralded as a "success", failed the water pressure burst test, it basically came out at the seams.

My understanding is that they tested it to destruction.

If you look at Elon Musk's 2017 presentation he shows a video of a BFR LOX tank pressure test. From memory I think its design max pressure was 2 atmospheres, they tested it to destruction and it failed at 2.2 atmospheres.
What's the source for, design was 2 atmospheres and 2.2 atmospheres failure point?

Offline su27k

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Re: Raptor Utilization
« Reply #69 on: 08/09/2018 01:45 AM »
So in short I think they shouldn't try to use composites as much on their next generation vehicle. AFAIK their large composite main tank test, which they heralded as a "success", failed the water pressure burst test, it basically came out at the seams. Imagine that was cryogenic LOX instead of water and that you had to do multiple flights with it. It's a whole different ball of wax. This was indeed one of the causes of the failure of the X-33 except in that case they had to handle not only LOX like temperatures, but they had to handle LH2 as well which is MUCH worse.

SpaceX already has a lot of experience with composites: COPV, fairing, interstage, legs, probably more smaller pieces we don't know about (for example we just recently learned composites were used in octaweb for Block 4 and older). So moving to composite tank is not a super big jump in terms of technology, it's more a natural evolution.

Also I'm fairly sure that the test tank failed in a cryogenic test, not a water test, you can see it in the video.
« Last Edit: 08/09/2018 01:51 AM by su27k »

Online docmordrid

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Re: Raptor Utilization
« Reply #70 on: 08/09/2018 02:54 AM »
>
If you look at Elon Musk's 2017 presentation he shows a video of a BFR LOX tank pressure test. From memory I think its design max pressure was 2 atmospheres, they tested it to destruction and it failed at 2.2 atmospheres.

What's the source for, design was 2 atmospheres and 2.2 atmospheres failure point?

Can't find a source for the 2 atm design pressure, but it was tested to 2.3 atm.
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Online Slarty1080

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Re: Raptor Utilization
« Reply #71 on: 08/10/2018 12:08 PM »
The source was in the presentation
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Offline Negan

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Re: Raptor Utilization
« Reply #72 on: 09/18/2018 09:24 PM »
Major BFS design change to speed up Raptor utilization. Not surprised.

Online Lemurion

Re: Raptor Utilization
« Reply #73 on: 09/18/2018 10:59 PM »
Major BFS design change to speed up Raptor utilization. Not surprised.

I don't know if I'd really call it "speeding up." They're still scheduling 2019 for the first tests of the SL Raptor. The only real difference WRT Raptor is that they're pushing the RVac off to a later iteration BFS, which is not exactly a new idea. I've seen quite a few mentions of the possibility of putting all SL engines on the initial BFS; this is just leaving more headroom in the initial design.

Online docmordrid

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Re: Raptor Utilization
« Reply #74 on: 09/18/2018 11:14 PM »
The second USAF upper stage engine contract had a delivery date of 30 April 2018. It'd be nice to see how that tuned out WRT RVac.
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Offline wannamoonbase

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Re: Raptor Utilization
« Reply #75 on: 09/18/2018 11:39 PM »
The source was in the presentation
Major BFS design change to speed up Raptor utilization. Not surprised.

I don't know if I'd really call it "speeding up." They're still scheduling 2019 for the first tests of the SL Raptor. The only real difference WRT Raptor is that they're pushing the RVac off to a later iteration BFS, which is not exactly a new idea. I've seen quite a few mentions of the possibility of putting all SL engines on the initial BFS; this is just leaving more headroom in the initial design.

They donít need the full RVac performance to accomplish the currently planned missions.  May as well make sure the Raptor is mature before developing the RVac. After the number of MVac variants developed maybe they want to save the time and money and fly.
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« Last Edit: 09/18/2018 11:53 PM by wannamoonbase »
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Offline niwax

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Re: Raptor Utilization
« Reply #76 on: 09/18/2018 11:40 PM »
The second USAF upper stage engine contract had a delivery date of 30 April 2018. It'd be nice to see how that tuned out WRT RVac.

Would that necessarily need a vacuum version? ISP is not massively different from MVac either way since they claim 348s already. I would have thought most of the additional performance would come from doubling thrust and carried fuel.

Online Robotbeat

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Re: Raptor Utilization
« Reply #77 on: 09/19/2018 02:56 AM »
By using the sea level Raptor as the BFS engine, they've made it into an upper stage engine, thus probably helping to fulfill the contract...
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