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SpaceX set to re-fly a Block 5 rocket for the first time tonight

arstechnica.com

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Re: SpaceX set to re-fly a Block 5 rocket for the first time tonight

#51

Post by mikeash »

fooker wrote: post #38
mikeash wrote: post #35

Earlier quoted context omitted.

You need supplies to keep those humans alive for a week, and a huge amount of fuel to boost the ship into a moon-intersecting orbit. Not a tiny payload by any means.

What if it is refueled in orbit? The BFS presentations hinted at that ability.

You could, but I’d hesitate to call the result an SSTO, and you’d be better off using the whole BFR stack anyway.

Orbital refueling is critical for the Mars plans. BFR can’t launch for Mars without it, so the capability will definitely be there.

Re: SpaceX set to re-fly a Block 5 rocket for the first time tonight

#52

Post by TangoTrotFox »

thekingofh wrote: post #27
gliptic wrote: post #25

Earlier quoted context omitted.

The refurbishing costs of even their first reused booster was less than half the price of a new booster [1], so something above 50%*70% = 35% saving assuming that the booster is 70% of the cost of the launch. The new block 5 version rocket is supposed to reduce that refurbishing cost by a lot. However, they have development costs of something like a billion dollars to pay back, and no reason to lower the price drasti…

From that link. Holy cow: "“Looking forward for reusability, we don’t believe it really, really counts unless you can turn it around rapidly, or almost as rapidly, as you turn around an aircraft,”. I had no idea they were aiming for this level. That is just mind boggling how drastic a change it's going to be.

You should check out their presentation [1] from 2017. The whole thing is incredibly interesting but if you want to see some jaw dropping stuff, check the tail end. They plan to use the BFR (big.. falcon.. rocket) to carry out suborbital missions. In other words, you hop on the BFR. Take off in New York, enjoy some silky smooth zero g travel, and less than 30 minutes later you're landing in London.

I have serious doubts about this, but it's about time that people who have the means and ability to make incredible things happen became so aggressively technological that their ideas seemed doubtful. It wasn't that long ago that many believed that complete rocket reusability impossible (to say nothing of autonomous retropulsive landings on barges getting rocked around in the middle of the ocean). Then it changed it uneconomical. Then it changed to 'oh shit, we're now a decade behind technologically.' I now find myself on the doubter side and look anxiously and happily forward to being proven wrong!

[1] - https://www.youtube.com/watch?v=E4FY894HyF8

Re: SpaceX set to re-fly a Block 5 rocket for the first time tonight

#53

Post by JumpCrisscross »

Lanzaa wrote: post #48
JumpCrisscross wrote: post #43

Earlier quoted context omitted.

> It was a epoch defining change Not yet. Costs haven't fallen. The epoch-defining change would be back-to-back commercial launches with the same booster in a short period of time with zero or little retrofitting.

> Costs haven't fallen. I disagree. I highly doubt reusing a booster has been more expensive to SpaceX than building new boosters. It is also speculated that at least the first few customers of reused boosters were given a discount. If you are saying customer cost has not fallen, you may be correct. I would counter with the fact that SpaceX is already a low cost provider, lowering their price more may not increase th…

> I highly doubt reusing a booster has been more expensive to SpaceX than building new boosters

Well, they are. Which is natural, because the program is still R&D more than mass production.

> This is basically the design that SpaceX hopes will enable that zero or little retrofitting reuse

When that rapid re-use is demonstrated, it will mark the epoch. We could retcon to the original re-use, or even booster recovery. But that's premature.

(I'm still super excited about everything SpaceX does.)

Re: SpaceX set to re-fly a Block 5 rocket for the first time tonight

#54

Post by TomK32 »

wahern wrote: post #36
thekingofh wrote: post #27

Earlier quoted context omitted.

From that link. Holy cow: "“Looking forward for reusability, we don’t believe it really, really counts unless you can turn it around rapidly, or almost as rapidly, as you turn around an aircraft,”. I had no idea they were aiming for this level. That is just mind boggling how drastic a change it's going to be.

Musk's Mars plan depends on reducing the marginal costs of launching so much that SpaceX could with minimal expenditure chuck dozens of rockets at Mars every year loaded with supplies and crew. This is important to keep in mind when wondering why a corporation would continue pushing its costs down after obtaining an effective monopoly. As long as Mars is the goal SpaceX won't turn into a ULA or Ariane. But if for som…

one mission to Mars, just think about the workload that ground control would have to deal with. Will there be extra communication satellites involved outside earth's system?

Re: SpaceX set to re-fly a Block 5 rocket for the first time tonight

#55

Post by TomK32 »

TangoTrotFox wrote: post #52
thekingofh wrote: post #27

Earlier quoted context omitted.

From that link. Holy cow: "“Looking forward for reusability, we don’t believe it really, really counts unless you can turn it around rapidly, or almost as rapidly, as you turn around an aircraft,”. I had no idea they were aiming for this level. That is just mind boggling how drastic a change it's going to be.

You should check out their presentation [1] from 2017. The whole thing is incredibly interesting but if you want to see some jaw dropping stuff, check the tail end. They plan to use the BFR (big.. falcon.. rocket) to carry out suborbital missions. In other words, you hop on the BFR. Take off in New York, enjoy some silky smooth zero g travel, and less than 30 minutes later you're landing in London. I have serious dou…

I think the use case for the suborbital hops is to reduce transport costs for those BFR that go from CA to FL and then to Mars. Shipping them trough the canal is something I'd like to see close up but also a bit mental. But then, western Europe's launches happen from South America...

Re: SpaceX set to re-fly a Block 5 rocket for the first time tonight

#56

Post by stetrain »

fooker wrote: post #42
stetrain wrote: post #39

Earlier quoted context omitted.

To get other BFSes up there with enough fuel to transfer a useful amount would require them to use the first stage booster instead of just being SSTO. Really there's no point to doing an SSTO launch in practice since the BFR first stage will in theory be just as reusable (if not more so) than the BFS second stage. Using the first stage booster greatly improves payload to orbit and has relatively low marginal cost onc…

For a single launch, sure. What happens if there are regular launches? Logistically, to me it seems that it would be a great idea to have a refueling station in orbit which is supplied by BFR cargo ships ..say.. once a month. Launching a BFR for each launch of BFS would require a lot of transportation and duplicated effort. Is this intuition wrong?

The plan is that the BFR lands back at the launch pad in the same cradle it launched from which would reduce operational complexity.

The fuel for your station has to get there somehow, and so does the station itself. The BFS-tanker ships would need to be launched with a BFR booster to bring up a meaningful amount of fuel, and there are going to be way more of those than there will be BFS-crew launches (ignoring the Earth-to-Earth transportation segment, where a centralized fuel station wouldn't make sense since each route will take a very different orbital path).

SSTO-ing the BFS-crew would require another BFR booster-plus-cargo launch anyway to replace the fuel and cargo you could have carried up in the BFS if you had launched it on the BFR booster to begin with.

The only angle that makes sense to me for doing a BFS-crew SSTO with minimal payload would be if it is deemed to be less risky for loss-of-crew. In that case you could have a BFS-tanker already on orbit and fully loaded by multiple BFR-plus-tanker launches, ready to rendevous with the BFS-crew ship after it reaches orbit on fumes.

I think that is unlikely though since such a launch might leave the BFS-crew without the fuel margin required to divert or de-orbit and land propulsively without refuelling.

Re: SpaceX set to re-fly a Block 5 rocket for the first time tonight

#57

Post by evgen »

golem14 wrote: post #19
InTheArena wrote: post #10

Earlier quoted context omitted.

The first stage represents about 75% of the cost of the vehicle, not 50%. This represents the actual cost of the metal on the launchpad, but not the services around the rocket, including launch control costs, etc. You can't take a rocket to India and you can't manufacturer that rocket in India (Skilset, US based corporation, ITAR) so you can't achieve your savings that way. Even Russia - which is using a very old tri…

"You can't take a rocket to India and you can't manufacturer that rocket in India (Skilset, US based corporation, ITAR) so you can't achieve your savings that way." Out of curiosity -- can they _fly_ a rocket to India (maybe have a booster return to India instead of a drone ship ? Too far/out of the way ? That may not help much since stage 2 would still have to be shipped around, which is probably not cost effective,…

As soon as it lands you have violated ITAR, so no.

Re: SpaceX set to re-fly a Block 5 rocket for the first time tonight

#58

Post by mikeash »

fooker wrote: post #42
stetrain wrote: post #39

Earlier quoted context omitted.

To get other BFSes up there with enough fuel to transfer a useful amount would require them to use the first stage booster instead of just being SSTO. Really there's no point to doing an SSTO launch in practice since the BFR first stage will in theory be just as reusable (if not more so) than the BFS second stage. Using the first stage booster greatly improves payload to orbit and has relatively low marginal cost onc…

For a single launch, sure. What happens if there are regular launches? Logistically, to me it seems that it would be a great idea to have a refueling station in orbit which is supplied by BFR cargo ships ..say.. once a month. Launching a BFR for each launch of BFS would require a lot of transportation and duplicated effort. Is this intuition wrong?

Once your payload exceeds the SSTO capability of a single BFS launch, you save effort by doing a two-stage launch. The two-stage launch is more complex and difficult, but the added capacity is far greater.

For intuition, consider moving to a new house. What’s better, renting a tiny car with room for one suitcase, or renting a big truck? The car is cheaper and easier to drive, but unless all of your stuff fits in one suitcase, the truck is going to be much cheaper and easier for this task.

Re: SpaceX set to re-fly a Block 5 rocket for the first time tonight

#59

Post by avmich »

oh_sigh wrote: post #41
lorenzhs wrote: post #23

Earlier quoted context omitted.

You're missing the point of Ariane. Its purpose is providing independent access to space for ESA member nations at a reasonable price, and as insurance against a launch monopoly (it upper-bounds what others can charge ESA). Ariane 5 is also extremely reliable, which is very important for some launches (NASA's James Webb telescope is going to launch on Ariane 5, for example). Ariane's goal is not to win the most comme…

What happens with the JWT if the rocket blows up on launch? How long(and how much $$$) would it take to build another one, having already built one? Is this an instance where the government should follow the maxim from Contact : "Why build one, when you can build two for twice the cost?"

> Is this an instance where the government should follow the maxim from Contact: "Why build one, when you can build two for twice the cost?"

The maxim in Contact was different - "Why build one, when you can build two, but keep the second one secret", right?

I do hope JWT could be recreated cheaper than costs to create it in the first place. No matter though, we'll still need other space telescopes anyway, so both reliability and price to orbit are important.

Re: SpaceX set to re-fly a Block 5 rocket for the first time tonight

#60

Post by thebluehawk »

vertline2 wrote: post #2

This blows my mind and I have naive questions. How can the materials withstand such forces? Is a piece inside replaced (he said without taking it apart)? Is ablation a factor at all?

It's important to note that the first stage (which is about 70% of the rocket) is the part that is being reused. The top of the rocket (the second stage, the fairings, and the payload) are not reused (At least not yet. They are working on recovering fairings and there are rumors of second stage reuse).

When the stages separate, the first stage is going about 1.5 - 2.5 km/s. Then the second stage takes the payload the rest of the way to orbital speeds of 7+ km/s, and the first stage returns to earth.

So the first stage is going fast (several thousand miles per hour) but not as fast as things that re-enter from orbit. It still does need heat shielding, but not as much as the space shuttle or a capsule.

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