Author Topic: Mini-Super Heavy (BFR) ship F9 Second Stage  (Read 89801 times)

Offline Vultur

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #480 on: 09/26/2022 05:00 pm »
Isn't Crew Dragon effectively contracted out to 2030 (or maybe 29 if NASA puts 2 or 3 Starliner missions in a row at the end) with the six new missions?

Offline spacenut

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #481 on: 09/26/2022 05:10 pm »
A mini Starship would have to have a new engine for the second stage/mini-Starship.  It could possibly be about 5-6m wide.  It could use a plug nozzle engine for atmosphere reentry and use the same engine(s) for landing.  This would possibly be heavier and only allow 20-25 tons to LEO at most.  The plug nozzle would be circular and have at least 4 engine sections using 4 sets of turbo-pumps.  All 4 firing to get to orbit with only say two firing to land. 

Advantages, no worry with TPS with tiles breaking off.  No flip maneuver needed, just land like a capsule except with control.  Any size payload can be on the nose, as fairing could be longer or wider as needed. 

Disadvantages would be increased mass, thus lower payloads capability for FH.  It could not fit F9 due to mass. 

I've always been an advocate of the circular plug nozzle.  It can serve as both engine and heat shield for a SSTO or a TSTO vehicle.  I'm kind of surprised Musk did us a circular plug nozzle on the Starship.  Nice robust landing legs could be put on the sides with almost any type of payload as the fairing wouldn't be needed for atmospheric reentry. 

See Rombus and Pegasus ideas from the 1960's. 

Online DanClemmensen

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #482 on: 09/26/2022 05:26 pm »
Again, not sure why otherwise-intelligent people have a hard time grasping this, but it's pretty straightforward.
It's even more straight forward than that.  All you need to shutdown F9 is that the Starship infrastructure exists and that marginal costs are lower.
Only if the reasons for operating Falcon 9 are purely economic.

For example: Falcon 9 is the launch vehicle for Dragon 2, and Dragon 2 is currently SpaceX's only human carrying vehicle. Not only is it already contracted for flight out to 2026, continuing to operate Dragon gains SpaceX valuable experience with human spaceflight. Letting that practical operational experience lapse would not be conducive to Starship development, as the ECLSS problem is even harder than Dragon's, so SpaceX would want all the experience they can get.
In your opinion, when will SpaceX have an operational crewed EDL-capable Starship?

I agree that they will operate F9/Dragon up until that time and a little beyond. However, if Dragon is the only remaining F9 customer, then F9 will not be profitable at the currently-negotiated fixed CRS and CCP prices. Crewed Starship is flying by (say) 2027, then it will be cost-effective for SpaceX to develop a way to provide these services without using F9, and retire F9.

Offline Vultur

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #483 on: 09/26/2022 05:35 pm »
Probably a significant gap between "flying" and "NASA willing to put NASA astronauts on it" though. Polaris 3 and Dear Moon (is that still on?) are one thing, replacing Dragon in Commercial Crew contracts another.

Offline edzieba

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #484 on: 09/26/2022 05:41 pm »
Again, not sure why otherwise-intelligent people have a hard time grasping this, but it's pretty straightforward.
It's even more straight forward than that.  All you need to shutdown F9 is that the Starship infrastructure exists and that marginal costs are lower.
Only if the reasons for operating Falcon 9 are purely economic.

For example: Falcon 9 is the launch vehicle for Dragon 2, and Dragon 2 is currently SpaceX's only human carrying vehicle. Not only is it already contracted for flight out to 2026, continuing to operate Dragon gains SpaceX valuable experience with human spaceflight. Letting that practical operational experience lapse would not be conducive to Starship development, as the ECLSS problem is even harder than Dragon's, so SpaceX would want all the experience they can get.
In your opinion, when will SpaceX have an operational crewed EDL-capable Starship?
For private spaceflight: as soon as somebody is willing to pay for a flight whilst also willing to take the risks for early flights. If somebody has a very high risk tolerance that could be fairly quick after the first few successful recoveries, using basic open-loop life support for a short flight.

For NASA astronauts, probably not for quite some time: demonstrating the ability to meet the LOC requirements without a dedicated launch escape system for every phase of ascent is going to be uphill slog doing so purely based on modelling and simulation and component testing, so faster to keep flying operationally and demonstrate it practically.

For general private spaceflight with a risk appetite similar to current private spaceflight: likely closer to when NASA is willing to unless an early daredevil flight is successful. Without anyone willing to shoulder the risk, most will likely prefer to wait until NASA has dotted 'i's and crossed 't's to their satisfaction, in lieu of performing their own assessment of readiness.

Online DanClemmensen

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #485 on: 09/26/2022 06:34 pm »
I was hoping for actual date guesstimates: timing is everything. If there are only one or two Crew Dragon flights left after Starship is certified, then SpaceX will eat the loss and fly Crew dragon at a loss once or twice, and maybe keep flying Cargo Dragon for CRS. If there are (say) four more CCP flights after Starship is certified, they might get creative and come up with a way to use Starship.

Offline Vultur

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #486 on: 09/26/2022 07:44 pm »
I'd say that *if* no major problems arise (need a radical change to TPS plan, accident massively damages ground facilities or gets a FAA pause on launches) Starship could be ready for a Polaris 3 type mission by 2025. They might manage 1 flight this year, and by 2024 they should be able to launch from Florida so no longer limited to 5/year.

But I don't see NASA astronauts flying on it from Earth until much later.

Offline john smith 19

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #487 on: 09/27/2022 07:26 am »
We are years, maybe decades, away from Starship marginal costs being $1.5M

Elon can keep saying that is the cost of fuel, but they have billions of development costs for the vehicle and infrastructure and then operational costs. 

Once Starship is capable of the required flight rate SpaceX will put everything possible onto it to help bring those costs down.

I look forward to see it, but they are not going to give away super cheap launches with their development costs and no real competition.  Except for Starlink, that will get the company discount.
Yup. No effective competiton being the big thing.
Again, not sure why otherwise-intelligent people have a hard time grasping this, but it's pretty straightforward.
No effective priced competition --> no effective price reduction.

I think that's a pretty simple idea to grasp as well.  :(
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Offline edzieba

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #488 on: 09/27/2022 01:44 pm »
I was hoping for actual date guesstimates: timing is everything. If there are only one or two Crew Dragon flights left after Starship is certified, then SpaceX will eat the loss and fly Crew dragon at a loss once or twice, and maybe keep flying Cargo Dragon for CRS. If there are (say) four more CCP flights after Starship is certified, they might get creative and come up with a way to use Starship.
Even with many remaining Dragon flights, SpaceX would need to trade off purely operational (development is done, certification is done, the Dragon capsules are already built, the ground infrastructure is already built, the first stages are mostly already built) costs of continuing Dragon operations, vs. the costs of developing and certifying Starship to meet existing Commercial Crew standards (and adding any additional hardware and infrastructure needed), plus operational costs.

Offline Barley

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #489 on: 09/27/2022 02:09 pm »
Again, not sure why otherwise-intelligent people have a hard time grasping this, but it's pretty straightforward.
It's even more straight forward than that.  All you need to shutdown F9 is that the Starship infrastructure exists and that marginal costs are lower.  So you can simplify some of your premises and calculations to:

The marginal cost for Falcon 9 are $15 million per launch. And say the marginal cost for Starship is $1.5 million.

Let's say there's demand for 1 Starship launch per year.

We are years, maybe decades, away from Starship marginal costs being $1.5M

Elon can keep saying that is the cost of fuel, but they have billions of development costs for the vehicle and infrastructure and then operational costs. 

Once Starship is capable of the required flight rate SpaceX will put everything possible onto it to help bring those costs down.

I look forward to see it, but they are not going to give away super cheap launches with their development costs and no real competition.  Except for Starlink, that will get the company discount.
They have billions of development costs for Starship whether or not they transfer future launches from F9 to SS.

They don't have to get the marginal cost down to $1.5M, anything below F9's costs is enough.

It doesn't matter if there is competition or not.  The market price for launching a payload will not change with the vehicle (modulo things like insurance, if one vehicle is viewed as more risky, but that can be subsumed into the marginal cost).  If SpaceX choses to bid the cheaper vehicle they get more profit.

A specific contract that requires F9 might be a reason to keep F9 active, but it is not a reason to launch any other payload on F9.  It is also a good reason the take a look at the cancellation clauses in the contract and/or negotiate a contract modification.  Once SS has 50 launches (possibly by 2027) they may be able to make an attractive offer, they can also point out that the "safer" F9 is only being launched 4 times a year from obsolescent facilities by the B team sitting out retirement, so things are getting sketchy.

Offline Robotbeat

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #490 on: 09/27/2022 02:24 pm »
Cost of the 4600tonnes of propellant is closer to $750,000, BTW, at least if they have on-site liquefaction.

If they increase the mix ratio from 3.5 to 3.8 or higher, the cost gets even lower.
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Online wannamoonbase

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #491 on: 09/27/2022 02:30 pm »
Cost of the 4600tonnes of propellant is closer to $750,000, BTW, at least if they have on-site liquefaction.

If they increase the mix ratio from 3.5 to 3.8 or higher, the cost gets even lower.

What is missed with all the propellant costs, is the value add of subcooling.

Also any expenses for the lost boil off or recondenser expenses to prevent boil off.

Also lots of LN2 required to support each flight. 

It's still a small percentage of legacy launch vehicles, but it's not simply the cost of the commodity to fill the vehicle.
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Offline Robotbeat

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #492 on: 09/27/2022 02:31 pm »
I was hoping for actual date guesstimates: timing is everything. If there are only one or two Crew Dragon flights left after Starship is certified, then SpaceX will eat the loss and fly Crew dragon at a loss once or twice, and maybe keep flying Cargo Dragon for CRS. If there are (say) four more CCP flights after Starship is certified, they might get creative and come up with a way to use Starship.
Even with many remaining Dragon flights, SpaceX would need to trade off purely operational (development is done, certification is done, the Dragon capsules are already built, the ground infrastructure is already built, the first stages are mostly already built) costs of continuing Dragon operations, vs. the costs of developing and certifying Starship to meet existing Commercial Crew standards (and adding any additional hardware and infrastructure needed), plus operational costs.
Considering Starship will need crew certification anyway, seems pretty obvious which direction SpaceX will go long-term.
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Offline edzieba

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #493 on: 09/27/2022 02:39 pm »
I was hoping for actual date guesstimates: timing is everything. If there are only one or two Crew Dragon flights left after Starship is certified, then SpaceX will eat the loss and fly Crew dragon at a loss once or twice, and maybe keep flying Cargo Dragon for CRS. If there are (say) four more CCP flights after Starship is certified, they might get creative and come up with a way to use Starship.
Even with many remaining Dragon flights, SpaceX would need to trade off purely operational (development is done, certification is done, the Dragon capsules are already built, the ground infrastructure is already built, the first stages are mostly already built) costs of continuing Dragon operations, vs. the costs of developing and certifying Starship to meet existing Commercial Crew standards (and adding any additional hardware and infrastructure needed), plus operational costs.
Considering Starship will need crew certification anyway
Only if they intend to bid it for NASA astronaut surface-to-orbit tasks (e.g. Commercial Crew for Commercial Destinations). All other crew surface-to-orbit does not require certification (as no such certification exists), and NASA have already demonstrated willingness to fly on Starship as long as crew transfer to it in orbit (skipping the abort issue entirely). For all private spaceflight, NASA certification is not a requirement.
Now, how many NASA astronaut missions will there be to justify the costs of certification (including any demanded modifications to meet abort requirements) vs. SpaceX either keeping Dragon around for that handful of missions, or just hiring one of the other commercial Crew providers for the handful of NASA missions?

tl;dr is the assumption that SpaceX will want to bid Starship for Commercial Crew a valid one?

Online DanClemmensen

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #494 on: 09/27/2022 03:02 pm »
I was hoping for actual date guesstimates: timing is everything. If there are only one or two Crew Dragon flights left after Starship is certified, then SpaceX will eat the loss and fly Crew dragon at a loss once or twice, and maybe keep flying Cargo Dragon for CRS. If there are (say) four more CCP flights after Starship is certified, they might get creative and come up with a way to use Starship.
Even with many remaining Dragon flights, SpaceX would need to trade off purely operational (development is done, certification is done, the Dragon capsules are already built, the ground infrastructure is already built, the first stages are mostly already built) costs of continuing Dragon operations, vs. the costs of developing and certifying Starship to meet existing Commercial Crew standards (and adding any additional hardware and infrastructure needed), plus operational costs.
It's all about incremental marginal costs and incremental development costs. You correctly point out that the dev costs and capital costs have already been incurred and therefore don't count for Dragon and F9, so only the fixed running costs and per-launch costs remain. However, In the replacement scenario the dev costs for crewed Starship also do not count, because SpaceX is going to build it anyway, so only the incremental development costs for CCP and CRS operations and certification, plus per-launch costs count against Starship. Fixed Starhip ops costs don't count because they are shared with all other Starship flights and must be incurred anyway. Fixed operational costs for Dragon/F9 do count in this scenario, because they will no longer be paid when Dragon/F9 retires.

So for a totally made-up example schedule, we get a generic non-certified crewed EDL Starship in 2025. SpaceX can choose to dev, build, and certify something to go into CCP/CRS operation in 2026 at a cost of X, or not. If yes, this saves the fixed and ops costs of Dragon/F9 starting in 2027, so fixed ops costs of Y for the four years 2027-2030.
Mission costs and prices for four CCP flights and 8 CRS flights shift from Dragon/F9 to StarshipCCP.

My guess: the development is worth it for four years, not worth it for one year, unless StarshipCCP will also serve other stations.

This ignores other considerations such as combined CCP/CRS flights.


Offline Robotbeat

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #495 on: 09/27/2022 03:18 pm »
I was hoping for actual date guesstimates: timing is everything. If there are only one or two Crew Dragon flights left after Starship is certified, then SpaceX will eat the loss and fly Crew dragon at a loss once or twice, and maybe keep flying Cargo Dragon for CRS. If there are (say) four more CCP flights after Starship is certified, they might get creative and come up with a way to use Starship.
Even with many remaining Dragon flights, SpaceX would need to trade off purely operational (development is done, certification is done, the Dragon capsules are already built, the ground infrastructure is already built, the first stages are mostly already built) costs of continuing Dragon operations, vs. the costs of developing and certifying Starship to meet existing Commercial Crew standards (and adding any additional hardware and infrastructure needed), plus operational costs.
Considering Starship will need crew certification anyway
Only if they intend to bid it for NASA astronaut surface-to-orbit tasks (e.g. Commercial Crew for Commercial Destinations). All other crew surface-to-orbit does not require certification (as no such certification exists), and NASA have already demonstrated willingness to fly on Starship as long as crew transfer to it in orbit (skipping the abort issue entirely). For all private spaceflight, NASA certification is not a requirement.
Now, how many NASA astronaut missions will there be to justify the costs of certification (including any demanded modifications to meet abort requirements) vs. SpaceX either keeping Dragon around for that handful of missions, or just hiring one of the other commercial Crew providers for the handful of NASA missions?

tl;dr is the assumption that SpaceX will want to bid Starship for Commercial Crew a valid one?
Of course it is valid. Heck, Starship will already need to go halfway there by certifying Starship for landing and taking off (surface-to-orbit) from the Moon with NASA astronauts, and they're being paid $3 billion to do it already.

They've shown multiple renderings of Starship docked to ISS (which might be deorbited by the time it's certified, but still shows intent). The burden of proof lies pretty heavily on those who claim they'll never certify Starship for launching NASA crew. It beggars belief to claim they'll never do it.
« Last Edit: 09/27/2022 03:20 pm by Robotbeat »
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Offline edzieba

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #496 on: 09/27/2022 04:12 pm »
I was hoping for actual date guesstimates: timing is everything. If there are only one or two Crew Dragon flights left after Starship is certified, then SpaceX will eat the loss and fly Crew dragon at a loss once or twice, and maybe keep flying Cargo Dragon for CRS. If there are (say) four more CCP flights after Starship is certified, they might get creative and come up with a way to use Starship.
Even with many remaining Dragon flights, SpaceX would need to trade off purely operational (development is done, certification is done, the Dragon capsules are already built, the ground infrastructure is already built, the first stages are mostly already built) costs of continuing Dragon operations, vs. the costs of developing and certifying Starship to meet existing Commercial Crew standards (and adding any additional hardware and infrastructure needed), plus operational costs.
Considering Starship will need crew certification anyway
Only if they intend to bid it for NASA astronaut surface-to-orbit tasks (e.g. Commercial Crew for Commercial Destinations). All other crew surface-to-orbit does not require certification (as no such certification exists), and NASA have already demonstrated willingness to fly on Starship as long as crew transfer to it in orbit (skipping the abort issue entirely). For all private spaceflight, NASA certification is not a requirement.
Now, how many NASA astronaut missions will there be to justify the costs of certification (including any demanded modifications to meet abort requirements) vs. SpaceX either keeping Dragon around for that handful of missions, or just hiring one of the other commercial Crew providers for the handful of NASA missions?

tl;dr is the assumption that SpaceX will want to bid Starship for Commercial Crew a valid one?
Of course it is valid. Heck, Starship will already need to go halfway there by certifying Starship for landing and taking off (surface-to-orbit) from the Moon with NASA astronauts, and they're being paid $3 billion to do it already.
Landing and takeoff from the moon for HLS are:
a) Very different from doing so on Earth (no atmospheric effects, no staging, different gravity, no ground support available, etc)
b) NASA tolerates higher risk than for Commercial Crew, out of necessity.
Quote
It beggars belief to claim they'll never do it.
Lots of what SpaceX does beggars belief (like deciding to build the largest vehicle in history to colonise Mars), so that's hardly a valid argument. "Of course SpaceX will do X!" has not been a good bet in the past.

Offline Robotbeat

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #497 on: 09/27/2022 06:11 pm »
SpaceX is betting the company on Starship. They fully intend to certify it for crew eventually. NASA crew will be on it for the most dangerous portions of a lunar mission (including ascent and landing), plus Polaris Project and Dear Moon will launch with people on it. If they fail, then they fail, but if you’re going to try to claim they don’t intend to qualify Starship for crew launch, then YOU are the one who bears the burden of proof.

Again, your original claim was about what SPACEX’S plans are and how they’ll weigh them. So you can’t dodge this by saying it might not succeed. That’s irrelevant. SpaceX is betting the company; we know what their plans are in this specific case.
« Last Edit: 09/27/2022 06:12 pm by Robotbeat »
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Offline OTV Booster

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #498 on: 09/27/2022 06:45 pm »
Every form of transport is reusable and every form of transport has more than 1000 tons of payload per year. EXCEPT space launch. The business constraints are therefore entirely different.
Wha happened? It all disappeared.


Now that reusability is here it's a new ballgame. The constraints are not all different. There is a core set common to all passenger/cargo carriers. Some constraints are different.


Trucks and trains have different restraints. Trains have to build their own rails. Trucks use public highways. Ignoring intermodal, train customers have to generate enough business to justify a spur. Truck customers need to be within easy reach of adequate roadway and invest in a relatively inexpensive loading dock. Airplanes need airports and ships need harbors, but airports never need to dredge to keep the runways open. Etc, etc.


As I said, the technologies are different but the core business environment is similar for all carriers. Because of the different technologies the details in the business models have different impacts on business decisions but the same concerns cross over between transport modes.


In the 'Developing a Mars Export Economy' thread, argument was made that transit costs would prohibit meaningful export. Let's ignore what would be exported. It's a rabbit hole and deflects from the issue at hand. This was countered by a common problem faced in trucking. Florida.


Florida is far and away a net importer. This is analogous to Mars. It has tourism, retirement, a much truncated citrus industry and space flight. Driving a load to Miami, way to the south, leaves a truck stranded without a load more often than not. There is a port facility at the north end in Jacksonville, Atlanta, Mobile and Birmingham. The only possible responses are to pick up local freight at ruinous rates to get to a freight rich area, deadhead to a freight rich location or wait while suffering fixed costs.  They all suck. Smart truckers make sure a load to Miami generates enough revenue to justify the crappy backhaul.


To translate this into a space flight business model, a load of martian bubbly water (don't ask) need only pay the marginal costs of shipping - extra propellant, for the rocket company to carry the load and not loose even more money on the backhaul. Charge a bit more than marginal costs and the carrier reduces backhaul costs.


To bring this closer to current reality, if a trucking company regularly picks up a less than max load from shipper A for receiver B, then discovers that receiver B also gets small loads from shipper C that is along the way, they will offer the option of picking up this load for a relatively small increase in costs. This is little different than a ride share.


This discussion of the transport industry is superficially off topic in discussing the viability of a mini-SS or a whole new 5m build. In truth it isn't. It addresses the business of transport and opens the possibility that new builds might have positive business impact. Possibility and might. Not a done deal. This is where specific technology comes up for discussion within the context of the transport industry.


To blanket claim that spaceflight in the era of reuse is so different than other transport industries that it constitutes an entirely different industry is an expression of ignorance of the shipping industry. Ignorant as in lack of knowledge. Not as in 'you be ignorant, dude'. Peace bro. ✌️

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Offline OTV Booster

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #499 on: 09/27/2022 07:30 pm »
Purely to throw some facts into the discussion, the US glider program (which became defunct after the end of World War II) produced 14,612 gliders of all types and trained over 6,000 glider pilots between 1941 and 1945. The vast bulk of these gliders were one-use transport vehicles. Other countries also produced significant numbers of gliders, including the Messerschmit 'Gigant', the biggest one ever constructed (a variant of which was fitted with engines and became a normal, albeit large, transport aircraft).

So: throwaway actually aircraft existed in large numbers (and some of these were reused).

Also: most liquid rocket engines have been reusable in the sense that they were fired multiple times. Only a small number were used again after they were flown, but had the will been there then they could have been.

What this suggests to me is that decisions relating to reusability are not about the technical feasibility of doing so, but about managerial decisions based on specific use cases and logistics (for example, STS).
The fundamental problem with reuse and space applications is the demand is just too low.

One of the main reasons why it doesn't make sense to hyper-optimize the launch vehicle size for the payload size for REUSABLE launchers is that the marginal cost is very low, and the fixed costs and development costs are high, so to first order, if you have 5 totally different launch vehicles of different payload classes, your fixed costs and development costs are increased by about a factor of 5, just to allow a slight reduction in the marginal costs, which is already approximately zero. So you'd be better off with just one reusable launch vehicle that can handle all 5 launch classes.  That's what the whole discussion is about.

And I don't know why it's so hard to get this obvious fact through to people, who seem obsessed with the idea that there should be hyper-optimization of reusable vehicle size just because some other modes of transport (which have totally different constraints and FAR LARGER annual tonnage) do it.

So yeah, ignoring arguments related to dissimilar redundancy, it really does make sense to kill off Falcon 9 and just use Starship. No amount of analysis by analogy (i.e. cargo cult thinking) will change that, no matter how popular such reasoning is.
It's all changing. The entire launch industry is in turmoil because of SX and reuse. It will never be the 'old space' same again. It's not just reuse. It's also becoming routine. High level finicky routine but routine none the less. Hard to build a routine if you only launch a few times a year. To shoot a sitting duck, an SLS launch will never be routine.


There is no evidence that a 5m fully reusable methane powered rocket would cost as much to develop as the SS. OTOH, there's no evidence that it wouldn't. That's part of what this discussion is about.


My gut says that a 5m two stage rocket based on SS construction techniques is technically feasible. This does not mean that it would be financially viable. Again, part of the reason for this discussion. IMO, the R&D would be significantly less than SS. Think back to all the fabrication refinements we've seen since Hoppy. It's all done. There would be differences. Thickness of skin, extent of reinforcing. But how to weld for consistent results, types of testing needed, and engineering dead ends (remember the blown out thrust puck?) have been explored and discarded.


The F9 was a learning experience for SS design. F9 and SS bracket a 5m design. What's amazing about SX is not that they can learn but that they learn how to learn. Excluding engines I'd wag that a 5m would have 20% of the R&D of SS.


NOW if they were to work on a 5 and a 7m design I'd agree that they're hyperoptimizing.
We are on the cusp of revolutionary access to space. One hallmark of a revolution is that there is a disjuncture through which projections do not work. The thread must be picked up anew and the tapestry of history woven with a fresh pattern.

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