daniel l.

SpaceX BFR Discussion.

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This thread is specifically about the BFR spacecraft. I would appreciate it if it isn't merged with the common SpaceX discussion thread.

Anyway, what do you guys think of the BFR? The versatility of the design reminds me of a Federation Starship, which makes me hope we'll see the creation of some sort of Starfleet-style organization for exploration and colonization and peacekeeping within our solar system. A fleet of specially-fitted BFR's would be a good start for that.

http://www.spacex.com/sites/spacex/files/mars-entry.mp4

Here's a gallery of artist's conceptions:

Spoiler

bfr-payload.jpg

bfr-iss.jpg

moon-bfr.jpg

 

What are your hopes for this thing?

Edited by daniel l.

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I'm not much of a rocket scientist but I do know that it's going to be some time before we see that launch. If we see it launch. There's many a slip between the lip and the cup.

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6 minutes ago, The Dunatian said:

I'm not much of a rocket scientist but I do know that it's going to be some time before we see that launch. If we see it launch. There's many a slip between the lip and the cup.

I dunno. SpaceX is pretty ambitious, and they usually deliver on their promises (even if they do have to delay a couple years). From what I've read, they've already got the factories under construction, and are going to build the first prototype at the beginning of the 2nd quarter of this year. Test flights begin in early 2019.

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1 minute ago, daniel l. said:

I dunno. SpaceX is pretty ambitious, and they usually deliver on their promises (even if they do have to delay a couple years). From what I've read, they've already got the factories under construction, and are going to build the first prototype at the beginning of the 2nd quarter of this year. Test flights begin in early 2019.

No way. Where'd you see that?

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I think it's a fantastic approach to the problem of getting to space. It's kinda the philosophy of Elon: use what you have now instead of waiting for new technologies. If you can't have a fancy SSTO, use a dual stage in the best way possible. If you can't have Nuclear or Powerful Ion engines for vacuum, use the reusability system to refuel the traditional combustion engines.

I'm concerned about the reentry of the second stage, what will be something new for SpaceX.

Will the rocket be able to turn almost 180º for the landing burn? I guess the center of mass and center of lift will need to be very close for this to be possible, or changeable.

It will decelerate significantly in orbit with the engines to prevent damage in the reentry? How about the heat shield tiles? What will be done to avoid the nightmare this was in the Shuttle Orbiter?

Edited by MaximumThrust

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I'll believe it after its 10th or so launch. Same as New Glenn, Falcon Heavy and SLS: big rockets are cool and showing people that they work is cool as well, but there is still no market. Maybe demand will appear when supply becomes available but I doubt it: even without launch costs, payloads are still very expensive (your average GEO bird is usually in the 9 figures, a large programme and the corresponding payload is in the 10).

As for reusability, presentations are cool but if you believe BFR will be sub-$10M with 1000 possible reuses without several major technological breakthroughs, you're at the very best extremely gullible.

Edited by Gaarst

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The test flights are supposed to be the second stage as a "grasshopper" to start, since the spacecraft is the hard part. The booster they are unconcerned about (except for the composites, it's just a big F9).

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If it ends up working then it ends up working. I suspect that governments will be a large customer if it becomes operational. I personally think that there are better ways to get to space, but if they can reduce launch costs and potentially inspire reductions in payload costs, then everyone benefits.

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First issue: it's a long, long way from CGI videos and powerpoint slides to a flying rocket.

Second issue: all the cost benefits he claims only work if there is a fleet of these things making hundreds or thousands of flights each. And they are huge. Is there any way the payload demand is going to be that big? Even if the launch price/tonne is low?

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24 minutes ago, mikegarrison said:

Second issue: all the cost benefits he claims only work if there is a fleet of these things making hundreds or thousands of flights each. And they are huge. Is there any way the payload demand is going to be that big? Even if the launch price/tonne is low?

It's said they could somehow be cheaper per launch than F9...

I had no idea overnight mail is cheaper on An-225 !

Edited by YNM

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Yeah, assuming it works, the reuse is the key, since launch costs are propellant, and the per use share of building the craft. There is no need for thousands of them at all.

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18 minutes ago, YNM said:

It's said they could somehow be cheaper per launch than F9...

That was because the cost of the non-reuseable bits of the F9 outweigh the fuel costs from the supposedly fully-reuseable BFR. But that means you have to fly the BFR so many times that you amortize the capital costs and the tooling costs and the handling costs and ... well, as I said -- the whole key is that you have to use it a *lot*. There have only been about 50 F9 launches in total, but for the BFR to pencil out that needs to be something like the number of launches per month maybe.

A 747 is fully reusable, but if you only fly it once a month it's still gonna be a really long time before you pay off the costs to buy it.

SpaceX is really making a huge "if you build it, they will come" gamble here.

12 minutes ago, tater said:

There is no need for thousands of them at all.

Not thousands of BFRs, no, but if there is only one then all the development costs, tooling costs, etc. all end up on that one rocket. There is a trade between the number of rockets you build and the total market for payload and the number of times you expect to reuse the rocket and the schedule demand (can't launch one rocket to two orbits at the same time), etc. So I think a fleet of 20-100 or so would be needed to do everything that Elon promised in his announcement. I don't remember if he ever said exactly how big the fleet would be.

Edited by mikegarrison

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6 hours ago, MaximumThrust said:


Will the rocket be able to turn almost 180º for the landing burn? I guess the center of mass and center of lift will need to be very close for this to be possible, or changeable.

You mean like the Delta Clipper managed last century?

 

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1 hour ago, mikegarrison said:

But that means you have to fly the BFR so many times that you amortize the capital costs and the tooling costs and the handling costs and ... well, as I said -- the whole key is that you have to use it a *lot*. There have only been about 50 F9 launches in total, but for the BFR to pencil out that needs to be something like the number of launches per month maybe.

We had launches within days of each other. Perhaps when everyone drops off other launchers or something.

 

But I guess this is indeed what Elon wants - an LCC to space. I will go hands up for the engineering details (apart from the apparently magical manufacturing costs they've got) but the idea is there.

Considering that many major LCCs actually take such approaches (just... go and fly there, someone will eventually go), maybe it'll work ?

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The BFR is going to beat all the other rockets, but i will have to say, i have no clue if this thing will fly to LEO or not. Its absolutely bogus but absolutely great at the same time. Im looking forward to the development this year.

If this will really send normal citizens to space, this will be my ride, without a doubt. If the BFR will build a moon hotel (wich it in theory could), just shut up and take my money. The Moon would create a great place for my 120 year old spine lol.

Edited by NSEP

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4 minutes ago, NSEP said:

The BFR is going to beat all the other rockets, but i will have to say, i have no clue if this thing will fly to LEO or not. Its absolutely bogus but absolutely great at the same time. Im looking forward to the development this year.

If this will really send normal citizens to space, this will be my ride, without a doubt. If the BFR will build a moon hotel (wich it in theory could), just shut up and take my money. The Moon would create a great place for my 120 year old spine lol.

Let’s say it’s 5 million per BFR launch (saw this figure somewhere on SpaceX thread). To go to the Moon and back you need multiple in-orbit refuelings, 5 to 10. That’s 25-50M for the entire trip. Divide it by 100 tourists that SpaceX can fit in one BFR, and you get $250-500k per ticket. That’s assuming the hotel is already there and its construction is not contributing to the ticket cost. 

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1 hour ago, sh1pman said:

Let’s say it’s 5 million per BFR launch (saw this figure somewhere on SpaceX thread). To go to the Moon and back you need multiple in-orbit refuelings, 5 to 10. That’s 25-50M for the entire trip. Divide it by 100 tourists that SpaceX can fit in one BFR, and you get $250-500k per ticket. That’s assuming the hotel is already there and its construction is not contributing to the ticket cost. 

At least its below 500 million :wink:

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11 hours ago, MaximumThrust said:

If you can't have a fancy SSTO, use a dual stage in the best way possible.

Actually, when it isn't carrying payload, the second stage is an SSTO!

4 hours ago, Rakaydos said:

You mean like the Delta Clipper managed last century?

 

Whoa!  I never heard of that!  If NASA has that, why aren't they using it for stuff?  

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Wait until it really exists before calculating dV. There isn't even a full featured engine yet, nor structural parts ...

Edited by Green Baron

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5 hours ago, Rakaydos said:

You mean like the Delta Clipper managed last century?

 

Or last millennium :P I knew something about the project, but never saw that flight test. The almost 180º flip don't see too hard now.

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8 hours ago, mikegarrison said:

Not thousands of BFRs, no, but if there is only one then all the development costs, tooling costs, etc. all end up on that one rocket. There is a trade between the number of rockets you build and the total market for payload and the number of times you expect to reuse the rocket and the schedule demand (can't launch one rocket to two orbits at the same time), etc. So I think a fleet of 20-100 or so would be needed to do everything that Elon promised in his announcement. I don't remember if he ever said exactly how big the fleet would be.

SpaceX has to build a next gen LV anyway. BO is going to hit the market like a freight train. SpaceX might be WalMart (Sears?) at the moment, but Bezos is still Amazon. Any people down on SpaceX ( :wink: ) need to internalize this. Bezos is serious. They haven't done anything spectacular yet... but they will. NG is almost Saturn sized, and NA might make BFR look like a toy.

So the dev costs, while substantial, have to happen even for a slightly improved (and larger) F9. The point of BFR is not (proximally, at least) to land colonists on Mars, but to deal with the upcoming competition from Blue, I think.

Forget his promises of Mars, etc. I think those are part of the show. How many they need? Dunno.

Based on what they said the costs were for ITS, I think a BFR/BFS stack is around 250 million $.

Assume an F9 launch costs 30 M$, and they pocket 35M$.

While their info says that the BFR booster would be reused 1000 times, and the BFS 100, let's assume that is grossly optimistic, and they both last the same # of flights.

Assume that they set launch costs pretty close to F9, or maybe slightly cheaper. What they'd want is to be much cheaper, however, to compete with NG, etc, but let's talk where they'd otherwise just have F9, but now have BFR, instead.

If they last only 10 flights, the per launch cost of a stack is... 25 M$. Propellant costs several hundred thousand. They are still cheaper to launch than F9, even if they deliver an F9 sized payload, but they could deliver a 150 ton payload for the same cost to them (~26M$). Reuse 5 times? Now BFR is costing 50M$/launch. They'd not lose money sending up a 2 ton sat, but they'd be leaving money on the table at the same launch price as F9, or be competitive with a lower margin.

So take the 10 use case. Launching F9 sized payloads is not super competitive if they want to make more money per launch, though they can charge a little less, and make the same. Comanifesting, or launching large payloads, however, becomes a cash cow. With an SLS launch costing billions (since the customer actually paid the dev costs), SpaceX can charge what a Delta OV Heavy costs, and pocket hundreds of millions, and it's still a steal for the customer (NASA).

I think that a clean sheet design is going to be reused more than 10 times, honestly, that;s the point of the exercise. Assume they learn something from Block 5 operations.

Edited by tater

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13 hours ago, The Dunatian said:
13 hours ago, daniel l. said:

I dunno. SpaceX is pretty ambitious, and they usually deliver on their promises (even if they do have to delay a couple years). From what I've read, they've already got the factories under construction, and are going to build the first prototype at the beginning of the 2nd quarter of this year. Test flights begin in early 2019.

No way. Where'd you see that?

I think there's a pretty good chance of seeing a subscale composite vehicle powered by at least one production SL Raptor doing grasshopper tests by mid-2019. Maybe even suborbital entry tests. I wouldn't expect to see the full-size version until early 2020.

13 hours ago, MaximumThrust said:

I think it's a fantastic approach to the problem of getting to space. It's kinda the philosophy of Elon: use what you have now instead of waiting for new technologies. If you can't have a fancy SSTO, use a dual stage in the best way possible.

The nerd in me (okay, let's be fair, the nerd in me IS me) would really like to see a true SSTO, albeit one with zero payload, using crossfed parallel boosters to achieve desired payload. 

In other words, "This is an SSTO. It can go to orbit and come back and land, but it can't carry any payload. But it can carry 10 tonnes of payload to LEO for each parallel crossfed RTLS booster you strap on. And it has room for 6."

But since even that wouldn't necessarily permit airplane-like operations...the BFR architecture is probably better.

13 hours ago, MaximumThrust said:

I'm concerned about the reentry of the second stage, what will be something new for SpaceX.

Will the rocket be able to turn almost 180º for the landing burn? I guess the center of mass and center of lift will need to be very close for this to be possible, or changeable.

It's a valid concern. The DC-X tests didn't have big tail fins to deal with. The Falcon 9/H boosters have a very low center of mass, so they automatically orient themselves engine-first. But the only way I see the BFS being able to orient itself tail-first is if it does an aerodynamic pitch-up followed by an RCS-controlled stall, which strikes me as rather risky idea.

13 hours ago, MaximumThrust said:

It will decelerate significantly in orbit with the engines to prevent damage in the reentry? How about the heat shield tiles? What will be done to avoid the nightmare this was in the Shuttle Orbiter?

It would not perform an entry burn, no. 

Thermal stresses for typical LEO entry would actually be lower than for the Shuttle, since it carries its own tanks and thus has a much greater surface area for its mass. The Shuttle would have done far better with a single composite heat shield than those horrible tiles. The tiles were a political thing.

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9 hours ago, mikegarrison said:

SpaceX is really making a huge "if you build it, they will come" gamble here.

And it's going to fall flat on its face.

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