totm nov 2023 SpaceX Discussion Thread

[magnemoe]

31 minutes ago, sevenperforce said:

One thing to consider in looking at the economics of reuse is that the initial version of Falcon 9, v1.0, had a lower payload flying expendable than Falcon 9 FT has flying reusable. Granted, Falcon 9 v1.0 didn't have the extensive development investment that F9FT has behind it. But since SpaceX can almost certainly refurbish F9FT for MUCH cheaper than the cost of a new Falcon 9 v1.0 (or something like Falcon 5), I think the argument closes rather well.

Yes refurbish costs will come down a lot with more experience with it, currently they are very careful and use a lot of time. 
Anyway far cheaper than building an new rocket. 
The other fixed costs are mostly launch costs and administrative ones who is the same if rocket is new or reused. 
 

[KSK]

49 minutes ago, sevenperforce said:

One thing to consider in looking at the economics of reuse is that the initial version of Falcon 9, v1.0, had a lower payload flying expendable than Falcon 9 FT has flying reusable. Granted, Falcon 9 v1.0 didn't have the extensive development investment that F9FT has behind it. But since SpaceX can almost certainly refurbish F9FT for MUCH cheaper than the cost of a new Falcon 9 v1.0 (or something like Falcon 5), I think the argument closes rather well.

I guess the question is whether the refurbishment cost range that SpaceX have quoted ends up being consistent and how accurate their expectations are around the number of re-uses they can get out of each booster.

It may well be that every booster they've recovered so far is showing a consistent level of wear and requires a correspondingly consistent amount of refurbishment. Or they may have cherry picked a not-too-badly-dented booster for their one refurbishment and re-flight. We simply don't know yet. Or if we do and somebody has a source - please share!

With all that said, even assuming a fairly pessimistic scenario where each recovered booster is only fit for one additional flight, provided that the refurbishment costs are reasonably consistent, that's still a big step forward to my mind. It may not be gas-and-go spaceflight yet but it's still effectively 'buy one first stage booster, get a second for half price.' Which, naively, sounds to me like reuse is still worth it.

The space cadet in me is naturally hoping for a rather more optimistic outcome.  

[CatastrophicFailure]

It's worth noting that SpaceX's current experiences are really only prototypes, at least as far as reusability is concerned. They're figuring everything out as they go along, while still running a successful and (presumably) profitable company (even if those profits go right back intio R&D). It may turn out that the Falcon just isn't cut out for rapid reusability. The second (third?) generation reusable rockets, tho...

[Soda Popinski]

3 hours ago, CatastrophicFailure said:

It's worth noting that SpaceX's current experiences are really only prototypes, at least as far as reusability is concerned. They're figuring everything out as they go along, while still running a successful and (presumably) profitable company (even if those profits go right back intio R&D). It may turn out that the Falcon just isn't cut out for rapid reusability. The second (third?) generation reusable rockets, tho...

That's a good point.  They're learning a lot about how to build reusable rockets right now.  One thing I recall reading was the planned switch on the grid fins from aluminum to titanium.  The increased up front cost leads to long terms savings, as they won't need to replace them as often.

I'm guessing we'll see these changes, along with many others, in the Rocket Formerly Known as Block 5, the final version of Falcon 9,

Edited May 2, 2017 by Soda Popinski

[tater]

Cost savings via reuse certainly seems very plausible. We'll have to see if it pans out.

[KSK]

48 minutes ago, CatastrophicFailure said:

It's worth noting that SpaceX's current experiences are really only prototypes, at least as far as reusability is concerned. They're figuring everything out as they go along, while still running a successful and (presumably) profitable company (even if those profits go right back intio R&D). It may turn out that the Falcon just isn't cut out for rapid reusability. The second (third?) generation reusable rockets, tho...

And going back to @Ten Key's point about disruption - they've proved that it's possible! You can put together a two stage to orbit rocket, reserve enough fuel in the first stage for a powered landing whilst keeping the overall mass fraction acceptable (if that's the correct terminology) and then successfully execute that landing.

It's a lot easier to work on a problem if you know it's solvable before you start. I hope SpaceX go on to achieve even greater things but if they don't, they've still made a priceless contribution to spaceflight.

[tater]

They've also given NASA a large amount of data on supersonic retropropulsion. They've really moved the needle in that area.

[WinkAllKerb'']

hum, transport and maintenance thingies, what i m curious now is the relative/absolute "atom loss"(fuel mostly it seem) with supersonic retropuplsion ratio between 70 and 150km and in comparison with some of the previous first stage tek, but i guess part of it have a reentry trajetory as well at there own scale ?

Edited May 2, 2017 by WinkAllKerb''
every single earth atom is priceless for the day to come

[CatastrophicFailure]

I think the most telling thing here is that, just a few years ago, "everyone" was laughing at the idea of reusability... and now "everyone" (ULA, Arianespace, etc) is at least giving it lip service. 

[VaPaL]

More on the first stage telemetry:

http://spaceflight101.com/falcon-9-nrol-76-flight-data/

[StupidAndy]

whats the difference between the technical broadcast and the other one that has a switching name? and does the NROL one not have one because of classification?

[Mad Rocket Scientist]

8 minutes ago, StupidAndy said:

whats the difference between the technical broadcast and the other one that has a switching name? and does the NROL one not have one because of classification?

Technical webcast has mostly rocket views and launch net audio, while hosted has people describing what's happening. The technical webcast also has speed in m/s instead of km/h.

The NROL-76 one probably didn't because they can't say much about anything.

[CSE]

On 01/05/2017 at 9:56 PM, Crimeo said:

Hi, I've always been suspicious of the SpaceX reusability strategy, because you get the most efficiency out of the last drops of fuel in a tank, so leaving that unused for landing is setting aside a lot of delta v, isn't it? Thus, they have to build a much larger rocket than they could have built otherwise, introducing a question of cost vs. benefit. Is there anywhere that I can go to see where people have done the actual math to prove that making a larger rocket in the first place (in order to have enough fuel to land the first stage) does not end up costing more money overall than ditching the first stage would cost?

No; I wouldn't expect there to be a definitive calculation with actual concrete numbers known in advance, because I expect that it depends in part on the payloads that customers bring. A commercial launcher serves a range of payload masses and orbits, with the most massive payloads to the hardest orbits needing to use the fully-expendable flight plan. Thus when a customer wants to put a light payload into an easy orbit, you can add dV to the launcher for just the cost of the extra fuelling. The economics becomes a question of how wide a range of payloads you get offered over the life of the launcher family.

What will be really interesting is whether an F9 expendable or an FH reusable is chosen once both are flying, and if and when there's a payload of the relevant size. I do wonder whether the delay in the FH is due in part to the success of the F9 upgrades to date: the next F9 launch, later this month, was apparently originally intending to use the heavy.

[Crimeo]

Does it really take any significantly greater R&D or scaling costs though to simply make the exact same tube but shorter to take advantage of a lighter payload (as the alternative to taking advantage of the lighter payload with reusability)?

Regardless of the answer, it seems like something you could indeed do some math on. Even if it's a continuum graph not a single answer.

[IncongruousGoat]

17 minutes ago, Crimeo said:

Does it really take any significantly greater R&D or scaling costs though to simply make the exact same tube but shorter to take advantage of a lighter payload (as the alternative to taking advantage of the lighter payload with reusability)?

If only it were that easy. You can't actually just stretch or shrink a rocket like that, since changing the tank volume will change a whole bunch of other things, like the structural and aerodynamic load on the entire vehicle, the propellant distribution, the center of mass (and therefore your avionics programming), the amount of backfill helium needed, and probably some other stuff I'm not thinking of right now. Plus, you have to change your assembly line around, which is a lot of effort. It's simply easier to build a standard size rocket, and just not use all of its capacity for some (or, more realistically, most) launches.

[Crimeo]

The structural and aerodynamic load, avionics, center of mass, etc.ALSO change if you're only burning 90% of your fuel, similarly to changing that 10% by stretching or shrinking, and then having the shell fly on a completely different trajectory and do a completely different thing (land on boat, land on pad, splash down, etc.). So those really don't seem very convincing arguments to me. You're going to have to recalibrate all that stuff, and I'm sure it's difficult and expensive and all, but you have to do it with BOTH strategies anyway.

I.e. a tank decoupling with fuel still left in it will fly differently and require all that different engineering regardless than a tank decoupling empty. If one system is able to adapt fluidly to those different situations on the fly for mission profiles with the one tank, then it should have been able to with slightly different sized tanks too.

Edited May 3, 2017 by Crimeo

[IncongruousGoat]

Just now, Crimeo said:

The structural and aerodynamic load, avionics, center of mass, etc.ALSO change if you're only burning 90% of your fuel, similarly to changing that 10% by stretching or shrinking, and then having the shell fly on a completely different trajectory and do a completely different thing (land on boat, land on pad, splash down, etc.). So those really don't seem very convincing arguments to me. You're going to have to recalibrate all that stuff, and I'm sure it's difficult and expensive and all, but you have to do it with BOTH strategies anyway.

I.e. a tank decoupling with fuel still left in it will fly differently and require all that different engineering regardless than a tank decoupling empty.

I was more concerned with the way a shorter tank would affect the center of mass, given that changing the first stage length necessarily moves the second stage up or down, which is going to change the CoM, especially when the first stage is nearly empty.

But, regardless of that, the real problem here is that you would have to re-build the assembly line in order to change the tank size. The manufacturing that goes into something like a rocket fuel/oxidizer tank turns out to be non-trivial to change. Making significant changes to the assembly line for every launch would be prohibitively expensive.

[Crimeo]

Yeah, but why would you expect the center of mass to change particularly more meaningfully due to a 10% longer stage versus the amount it changes with 10% more mass of fuel still left in it? One is a small change to drag/gimbaling, one is a small change to mass, they should both have probably roughly similarly difficult to correct for impacts on the avionics. As in, every launch is different if the stage is always a different length OR if the stage has different amounts of fuel left at different points in the launch. Either way changes everything.

Manufacturing: Mayyybe... I'm not at all just a priori convinced that the manufacturing cost of having, say, 4 different tank lengths is "obviously" less than the manufacturing cost of adding grid fins, legs, and building a fleet of autonomous robot boats that also require manufacturing... Maybe, but that brings us back to a "where's the math, if anywhere?" question, not just an "obvious" answer.

[IncongruousGoat]

9 minutes ago, Crimeo said:

Manufacturing: Mayyybe... I'm not at all just a priori convinced that the manufacturing cost of having, say, 4 different tank lengths is "obviously" less than the manufacturing cost of adding grid fins, legs, and building a fleet of autonomous robot boats that also require manufacturing...

It's not a question of doing the things themselves. Grid fins, landing legs, etc. are more economically efficient simply because you're only producing one launch vehicle. Running one rocket assembly line is hard enough. Running, say, 4 would be a nightmare. It would, to an extent, defeat the point of assembly line construction. And seeing as having a really good vertically integrated rocket assembly line is one of the things that makes SpaceX so price competitive, moving away from that model would be crippling.

It's all about standardization. It's much easier to do one thing really well than 4 things really well.

[Crimeo]

They're just on sleds on tracks, dude. I don't see why adding 3 meters to any of those fundamentally changes the concept of the assembly line, that's a pretty out-there statement. Assembly lines have parameters that can change allllll the time. The same machine makes 15 kinds of chain with slightly different settings, turning a few screws, etc. And this one is similarly pretty clearly from the photo already modular, you can see the same sleds being used for completely different parts on the lower left, in the same room, on the same rails. Let alone different sized parts. Though you can also already see tube sections of completely different lengths on the same sleds on the same rails in the same room (bottom vs. top half of image).

It seems very very unlikely that this room here cannot accomodate a tube of the same sort but 3 meters longer or shorter. Or if it can't, it could have been made to without being much different than it is now.

And just like high end sports cars, these sort of assembly lines are by nature a bit "boutique" anyway, with hands-on manual labor used to double check things, etc. Not the same as a toothpick assembly line. See all the ladders and stuff next to the parts, for example.

Edited May 3, 2017 by Crimeo

[IncongruousGoat]

4 minutes ago, Crimeo said:

It seems very very unlikely that this room here cannot accomodate a tube of the same sort but 3 meters longer or shorter. Or if it can't, it could have been made to without being much different than it is now.

I'm not concerned about accommodating a longer tube. I'm concerned about making a longer tube. Fuel tanks aren't trivial to make, and they certainly aren't off-the-shelf.

[Crimeo]

I'd wager quite a lot that the manufacturing complexity of producing  [30m long tanks + 35 meter long tanks + 40m long tanks] is a hell of a lot simpler than the manufacturing complexity of producing  [30m long tanks + autonomous robot boats + landing legs + fins + a redundant set of avionics probably not of the same type as in the upper stage]... could be wrong, but would never believe this off-the-cuff without math to back it up.

Edited May 3, 2017 by Crimeo

[DVDRW]

So when and why F9 gets sooty? In video looks like sootyness comes right after separation.

[Thor Wotansen]

When you change the volume of a tank, you also change the structural requirements to support the mass the tank holds.  Shortening a rocket by even 5 meters requires an entire redesign of the tank structure, unless you go the big dumb booster route, in which case your point is void.  It's far cheaper to have slightly more performance than you need, then to have several sub-designs optimized for different payloads.

[Scotius]

4 hours ago, Crimeo said:

I'd wager quite a lot that the manufacturing complexity of producing  [30m long tanks + 35 meter long tanks + 40m long tanks] is a hell of a lot simpler than the manufacturing complexity of producing  [30m long tanks + autonomous robot boats + landing legs + fins + a redundant set of avionics probably not of the same type as in the upper stage]... could be wrong, but would never believe this off-the-cuff without math to back it up.

And yet Delta IV Heavy is three Delta IV boosters tied together. Same goes for Falcon Heavy. Apparently it's easier and cheaper to combine three identical rockets and call it a day, than to build another rocket with higher individual capabilities.