Author Topic: F9 Block 5 Updates and Discussion  (Read 309087 times)

Offline wannamoonbase

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Re: F9 Block 5 Updates and Discussion
« Reply #320 on: 11/18/2017 02:38 PM »
If Block 4 is the thrust upgrade then the performance of Block 5 shouldn't be much better than Block 4.

If the heat shielding is improved, smaller re-entry burn can be used, saving more fuel to the ascent phase, increasing reusable payload.

Payload without reuse would not be increased.


But I thought block 4 was mostly the titanium grid fins and has already flown? And the recently-test-exploded engine was the more powerful engine for block 5?

I maybe mistaken, but I thought Block 4 was the bolted Octoweb and a partial thrust increase and not much else.

Not certain but I thought the titanium grid fins were Block 5 only.
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Re: F9 Block 5 Updates and Discussion
« Reply #321 on: 11/18/2017 02:51 PM »
I maybe mistaken, but I thought Block 4 was the bolted Octoweb and a partial thrust increase and not much else.

Not certain but I thought the titanium grid fins were Block 5 only.

My understanding is that Block 5 is a collection of a number of improvements, but that some of those improvements are being tested or used on Block 3 & 4 too. But Block 5 will bring them all together, probably add some things that could not be tested or used on Blocks 3 or 4, plus add crew certification for the entire system.
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Offline old_sellsword

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Re: F9 Block 5 Updates and Discussion
« Reply #322 on: 11/18/2017 02:53 PM »
But I thought block 4 was mostly the titanium grid fins and has already flown?

The Titanium grid fins have only flown once, and they flew on the last Block 3 first stage. So they’re not a Block 4 upgrade.

Offline john smith 19

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Re: F9 Block 5 Updates and Discussion
« Reply #323 on: 11/19/2017 07:43 PM »
But I thought block 4 was mostly the titanium grid fins and has already flown?

The Titanium grid fins have only flown once, and they flew on the last Block 3 first stage. So they’re not a Block 4 upgrade.
Although Titanium has come down in price a lot it's still much more expensive than Aluminum. You'd use if it you expect to run hot (IE a lot of the ablative protection is worn off on every flight) or you want to radically lower maintenance between flights.  However to make that worthwhile you need the design to survive for enough reuses, and that's not happening at present.
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Online Coastal Ron

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Re: F9 Block 5 Updates and Discussion
« Reply #324 on: 11/19/2017 08:15 PM »
You'd use if it you expect to run hot (IE a lot of the ablative protection is worn off on every flight) or you want to radically lower maintenance between flights.

Which describes the reuse goals of the Block 5 - to radically lower the maintenance between flights compared to Block 3/4.

Quote
However to make that worthwhile you need the design to survive for enough reuses, and that's not happening at present.

For the aluminum version sure, but the one use of the titanium fins looked successful.
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Offline john smith 19

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Re: F9 Block 5 Updates and Discussion
« Reply #325 on: 11/19/2017 08:54 PM »
Block 5 will have reusable TPS (my guess: carbon-carbon at least for parts of it) and legs that can fold back (i.e. without needing to be removed).

For those that haven't seen it, this is from Tom Mueller's recent talk.
Interesting find. Stuff like
RP-1 is now down from $8/gal to more like $2/gal for SX
Block5 is going with metallic TPS
Legs will fold/unfold rather than be removed.
Still keen on F9 sized US reuse but definitely not for all missions
500Kw of energy to make all the propellant on Mars to get home (I think that's generating capacity, not total energy needed IOW 2.5x bigger than the ISS PV array, without allowing for the greater distance from the Sun).
NTR can "Double performance" to Mars. Not sure what that means? Isp should be a bit more than double. Payload?
If BFS can put 100 tonnes on Mars it could put 20 tonnes to Jupiter, without years long gravity assists.

Merlin uses "face shutoff" valves to with fuel valve opening slaved to pressure rise from LOX flow. Fuel valve can't open before LOX and (presumably) can't shut before LOX flow dies, stopping the thrust cold.  BTW face shutoff should be quite a lot easier on a Pintle injector because you can have fluid flow right up to the face. Normal design have lots of injectors where you can cut off flow to them as a group, but there's still a bunch of cavities behind the injectors (the propellant "galleries") with vaporizing LOX and RP-1, potentially ready to form a cloud of explosive vapor for a hard start. The joker with other designs is the unpredictable LOX valve behavior, dependent on hardware temperature, humidity etc.   

SX are working with NASA on Kilopower nuclear electric reactor. They'd like a 1MW unit, but they'll take what they can get.
Long term he thinks fisson is the way to go for Mars power needs.

Basically Musk looks at problems from first principles. The simple question he asks is "If this is the physics limit, and this is what we are doing now, what stops us from getting X times closer to the physics limit?"


Incidentally metallic TPS is has always been viewed as a bit of a mixed bag. The "Metal is more robust" meme sounds good but superalloys are heavy (AFAIK only Beryllium is  both less dense than Aluminum and has a much higher melting temperature), so designers have used it "foils," where it's no longer a thick rugged section but in material not much thicker than baking foil, which is not very impact resistant.
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Offline john smith 19

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Re: F9 Block 5 Updates and Discussion
« Reply #326 on: 11/19/2017 09:08 PM »
You'd use if it you expect to run hot (IE a lot of the ablative protection is worn off on every flight) or you want to radically lower maintenance between flights.

Which describes the reuse goals of the Block 5 - to radically lower the maintenance between flights compared to Block 3/4.

Quote
However to make that worthwhile you need the design to survive for enough reuses, and that's not happening at present.

For the aluminum version sure, but the one use of the titanium fins looked successful.
I was unclear. By "enough reuses" I meant of the stage

If the statement that Ti fins have only been used once is correct, and SX are at present staying with Al grids and ablative covering that suggests (in usual SX SOP) that that combo is (mostly) good enough to get the job done for now. IOW barring a really hard mission (high mass, GTO trajectory) they (or rather their ablative coating) will survive the life of the stage.

Obviously if you want to hit that 24 hour refurb time you want something much more low maintenance, unless you're happy to have 2 sets of fins, which you swap over and refurb off line. However that doesn't eliminate the problem that you are still refurbing them in the first place, so still have staff involved.

Likewise if block 5 delivers the sort of reuse numbers people are hoping for the the extra cost of mfg in Titanium (because AFAIK all Ti mfg routes are more difficult than Aluminum due to Ti's properties) is cancelled out by the more or less zero maintenance ruggedness of the material for anything less than a worst case payload mass and trajectory.

I expect Ti fins will be SOP for Block 5 and beyond.
« Last Edit: 11/20/2017 08:09 AM by john smith 19 »
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline biosehnsucht

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Re: F9 Block 5 Updates and Discussion
« Reply #327 on: 11/21/2017 02:57 AM »
I suspect the simplest answer is simply they have a stack of Aluminum fins and they work, so they're going to use them until they're used up.

Offline john smith 19

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Re: F9 Block 5 Updates and Discussion
« Reply #328 on: 11/21/2017 07:21 AM »
I suspect the simplest answer is simply they have a stack of Aluminum fins and they work, so they're going to use them until they're used up.
Partly that, but also the life of the current generation booster stage is not long enough to justify Ti as well.

I expect once Block 5 arrives Aluminum grid fins will be obsolete, not because they can't do the job, but because of the work needed to check/fix if they are OK for the next flight.

The goal is "Management by exception." IOW the fin tells the refurb crew "I am marginal/failed," and they decide wheather to scrap it or retain for maybe low stress launches. This is a very radical departure from the classic "Check absolutely everything, then check it again" philosophy that is SOP for most LV's.
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Online jpo234

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Re: F9 Block 5 Updates and Discussion
« Reply #329 on: 11/21/2017 07:51 AM »
Partly that, but also the life of the current generation booster stage is not long enough to justify Ti as well.

Why would there be a correlation between the life of the booster and Ti grid fins? If they scrap the booster, they don't have to throw away the fins...
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Re: F9 Block 5 Updates and Discussion
« Reply #330 on: 11/21/2017 01:19 PM »
Partly that, but also the life of the current generation booster stage is not long enough to justify Ti as well.

Why would there be a correlation between the life of the booster and Ti grid fins? If they scrap the booster, they don't have to throw away the fins...
They may be dealing with the risk of losing a booster during landing; don't want to lose your only set of Ti fins just because a Block 3 booster was lost. At least that's been my explanation thus far. If they keep using aluminum fins into 2018, then I won't know what to think.

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Re: F9 Block 5 Updates and Discussion
« Reply #331 on: 11/21/2017 03:38 PM »
Maybe Al fins are good enough for low energy returns where the stage can be reused and for high energy returns the block 3 stage gets too toasted anyway. So perhaps see Ti fins on block 5 high energy returns first.

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Re: F9 Block 5 Updates and Discussion
« Reply #332 on: 11/21/2017 04:11 PM »
I'm posting this here: SpaceX aims to follow a banner year with an even faster 2018 launch cadence

Lot's of interesting information about Block 5, but also BFR and Raptor. There should be a general SpaceX thread for broad interviews like this one.

Edit: Already posted in the Manifest Updates and Discussion Thread
« Last Edit: 11/21/2017 04:15 PM by jpo234 »
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Re: F9 Block 5 Updates and Discussion
« Reply #333 on: 11/21/2017 05:09 PM »
There should be a general SpaceX thread for broad interviews like this one.

You mean something like General Falcon and Dragon discussion (Thread 14)?

Online jpo234

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Re: F9 Block 5 Updates and Discussion
« Reply #334 on: 11/21/2017 05:30 PM »
There should be a general SpaceX thread for broad interviews like this one.

You mean something like General Falcon and Dragon discussion (Thread 14)?
I considered that one. But Raptor and BFR does not fit there either.
You want to be inspired by things. You want to wake up in the morning and think the future is going to be great. That's what being a spacefaring civilization is all about. It's about believing in the future and believing the future will be better than the past. And I can't think of anything more exciting than being out there among the stars.

Offline john smith 19

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Re: F9 Block 5 Updates and Discussion
« Reply #335 on: 11/21/2017 07:08 PM »
Partly that, but also the life of the current generation booster stage is not long enough to justify Ti as well.

Why would there be a correlation between the life of the booster and Ti grid fins? If they scrap the booster, they don't have to throw away the fins...
Why waste money on a sub system that can outlast the vehicle it's mounted on?

F9 Block 4 seems to be good for a life of 3 launches.  Shotwell is saying Blk 5 will be good for 10. Titanium is much harder (and more costly) to machine. The vehicle has to last longer to justify that. Likewise eliminating inspection and/or maintenance also shifts the balance to Titanium.

Regarding Shotwells interview I think the most interesting things were the that Raptor on F9 is not going to happen and F9 US recovery will not really be recovery but more to try and examine what damage is done to better inform the design of the BFS/BFR
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Online Coastal Ron

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Re: F9 Block 5 Updates and Discussion
« Reply #336 on: 11/21/2017 07:47 PM »
Why waste money on a sub system that can outlast the vehicle it's mounted on?

Every component has a different lifetime, so it doesn't matter if the titanium grid fins last beyond the life of the first booster they are attached to because there will be plenty more components (Merlin engines as more expensive items) that will also be transferred from the booster body after it has reached the end of it's useful life.

Quote
F9 Block 4 seems to be good for a life of 3 launches.  Shotwell is saying Blk 5 will be good for 10. Titanium is much harder (and more costly) to machine.

Actually the titanium grid fins are forgings, not machined. Both are expensive and hard, but just wanted to point that out.

Quote
The vehicle has to last longer to justify that. Likewise eliminating inspection and/or maintenance also shifts the balance to Titanium.

I was just reading about the first A380 that was going to be put into flyable storage, and they were talking about how most of the value of the aircraft was in it's engines, since they can be pulled and used on another aircraft. So using commercial aircraft as analogies, there will be lots of parts that will move around onto new and used boosters. Titanium grid fins are just one of the parts.

Something else to keep in mind is that it probably matters to the Falcon 9 control software whether the aluminum grid fins are used or the titanium ones, and history is littered (literally) with hardware that failed because updates were not done properly. So standardizing on one type of control surface likely makes a lot of sense, and not having to replace them all the time would likely be the least expensive option too.
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Online Prettz

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Re: F9 Block 5 Updates and Discussion
« Reply #337 on: 11/21/2017 08:07 PM »
Why waste money on a sub system that can outlast the vehicle it's mounted on?
The aluminum fins last for one (1) mission before needing refurbishment. The titanium fins never need any; they'll outlast every booster they're ever attached to. That math doesn't work out, so there must be other considerations.

Regarding Shotwells interview I think the most interesting things were the that Raptor on F9 is not going to happen and F9 US recovery will not really be recovery but more to try and examine what damage is done to better inform the design of the BFS/BFR
We already knew there wasn't going to be a Raptor upper stage, though. What I thought was interesting is that this first FH mission will be the only one to use non-Block 5 boosters. These side boosters definitely will not be going on another flight. Also the first block 5 flight pushed further back, now the end of Q1.

Offline Robotbeat

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Re: F9 Block 5 Updates and Discussion
« Reply #338 on: 11/21/2017 11:37 PM »
Partly that, but also the life of the current generation booster stage is not long enough to justify Ti as well.

Why would there be a correlation between the life of the booster and Ti grid fins? If they scrap the booster, they don't have to throw away the fins...
Why waste money on a sub system that can outlast the vehicle it's mounted on?...
You're begging the question. It's not a waste of money.
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Re: F9 Block 5 Updates and Discussion
« Reply #339 on: 11/21/2017 11:46 PM »
You'd use if it you expect to run hot (IE a lot of the ablative protection is worn off on every flight) or you want to radically lower maintenance between flights.

Which describes the reuse goals of the Block 5 - to radically lower the maintenance between flights compared to Block 3/4.

We have no real insight into the costs.

It doesn't need to get very expensive for the labour of a guy spending a week sandblasting/recoating the fins to be cheaper than the cost of shiny new titanium fins.
If the labour costs $5K, and the forged Ti finset 250K, ...

It wouldn't even slow down the flow perhaps as the fins don't have to go back on a reflight.

For the case of one or two reuses per stage, especially as they have quite a lot of nonreflown stages to pull parts off if they choose, light repairs could be significantly cheaper.

Or perhaps they've just found something more productive in the future for their Ti forging of large billets capabilities to do, and they'd rather have the few guys experienced in that area do that, rather than 'fix' what they now realise is a problem that now doesn't seem as bad once they've got experience.

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