Author Topic: BFS - without BFR eats the launch market.  (Read 37955 times)

Offline FinalFrontier

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Re: BFS - without BFR eats the launch market.
« Reply #20 on: 03/01/2018 05:53 AM »
I am actually really glad this thread popped up, because I was just thinking about BFS today and a few things that I think have been overlooked occurred to me.

Consider for a moment the magnitude of BFS alone and what it means. Since the space age began the world's greatest minds have tried to devise an economically feasible human rated fully re-usable SSTO and they have all failed until this point to do so. BFS if it works would succeed at this, and it has very good data backing it up.

Consider what this also means. You could launch a manned variant of BFS to orbit quite cheaply and easily. I am not sure yet how the cost would work out, but I think it works out that a BFS going ONLY to LEO being used in the role of a man rated shuttle would be extremely low cost. This essentially gives you a rapidly re-usable shuttle for easy human access to LEO. With potential engine upgrades if raptor can be scaled further or pushed higher you might get even further while remaining in the same price range.

This is a big big big deal. Nobody has ever had human access to space like this system could provide before. And then of course there is all the implications here already being discuss wrt cargo.

BFS could easily be used to build a space tourism market in LEO all by itself, forget everyone else who has been trying for years or is trying only for sub orbital hops.

These are just things right off the top of my head.
« Last Edit: 03/01/2018 05:54 AM by FinalFrontier »
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Offline MikeAtkinson

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Re: BFS - without BFR eats the launch market.
« Reply #21 on: 03/01/2018 06:21 AM »
Some big assumptions there, and a lot of optimism.

1. Is BFS initial block(s) SSTO? Which LEO orbit?
2. Is BFS initial block(s) SSTO with enough fuel left to land again?
3. Is BFS initial block(s) SSTO with 10 tonne payload and still has enough fuel to land again?
4. Can BFS initial block(s) rendevous in LEO and transfer significant propellant?
5. Are the BFS initial block(s) launch rates high for multiple refueling?
6. How long does a BFS initial block(s) tanker take to launch, rendezvous, dock, transfer fuel, undock and land (what is the crossrange)?

If the answers to all these questions are positive then, maybe the BFS can eat the launch market.

Note: I'm fairly confident that the answers to the above questions are yes eventually. However the initial few blocks are likely to have lower performance, particularly as there are so many things about the BFS that are difficult.

I missed one:

7. Can BFS do SSTO with engine out capability? Without this SSTO is great for testing, but not really suitable for operational use (particularly passengers).

Offline CJ

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Re: BFS - without BFR eats the launch market.
« Reply #22 on: 03/01/2018 06:44 AM »
I'm a bit skeptical of BFS being able to do SSTO unless massively stripped down, because that needs one heck of a skinny mass ratio.

But if that's even plausible, why would they need BFR to do the point-to-point suborbital passenger flights they've proposed?

As for why BFS first, I'd have been amazed had they not gone this route. Part of the reason is probably insurance; if BFS development indicates a bit heavier BFS than they'd planned (as it well might, because the mass ratio budget is ambitious, to say the least) then BFR can be redesigned to be a bit larger, if needed. 


Offline Elmar Moelzer

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Re: BFS - without BFR eats the launch market.
« Reply #23 on: 03/01/2018 07:06 AM »
7. Can BFS do SSTO with engine out capability? Without this SSTO is great for testing, but not really suitable for operational use (particularly passengers).
If has enough payload so that they can put a Dragon 2 on top of it, it would still be feasible for passengers too.

Offline Elmar Moelzer

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Re: BFS - without BFR eats the launch market.
« Reply #24 on: 03/01/2018 07:07 AM »
I'm a bit skeptical of BFS being able to do SSTO unless massively stripped down, because that needs one heck of a skinny mass ratio.

But if that's even plausible, why would they need BFR to do the point-to-point suborbital passenger flights they've proposed?
I believe people are thinking of a version derived from the tanker with a small payload fairing (or Dragon2) on top. That would obviously not be big enough for point to point passenger flights.

Offline hkultala

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Re: BFS - without BFR eats the launch market.
« Reply #25 on: 03/01/2018 08:56 AM »
It's 2020, and BFS turns out to work just fine on first tests (or BFR is delayed), what can BFS do?

In short - eat every other launch vehicle, except perhaps FH expendable at max load.
Assuming relaunch costs $3m(*) (cost price).

Assuming 10 tons to LEO is possible

You talk about 10 tonne here but you are using 10+20 tonnes in your calculations. That 10+20 tonnes is not a so reasonable assumption anymore.

AND Elon musk clearly said using those vacuum raptors on atmosphere is not recommended.


Offline DreamyPickle

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Re: BFS - without BFR eats the launch market.
« Reply #26 on: 03/01/2018 09:13 AM »
Elon musk clearly said using those vacuum raptors on atmosphere is not recommended.

At least the first BFS will be build specifically for atmospheric tests, wouldn't this have a different engine configuration anyway? They plan to also test reentry dynamics with BFS-only flights, this would push it towards SSTO as much as possible.

Has anyone looked at what an BFS engine configuration optimized for sea-level liftoff would look like? It might make sense to add sea-level engines for high thrust and then shut them off later in flight to improve ISP.

Offline guckyfan

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Re: BFS - without BFR eats the launch market.
« Reply #27 on: 03/01/2018 10:20 AM »
Elon musk clearly said using those vacuum raptors on atmosphere is not recommended.

At least the first BFS will be build specifically for atmospheric tests, wouldn't this have a different engine configuration anyway? They plan to also test reentry dynamics with BFS-only flights, this would push it towards SSTO as much as possible.

Has anyone looked at what an BFS engine configuration optimized for sea-level liftoff would look like? It might make sense to add sea-level engines for high thrust and then shut them off later in flight to improve ISP.

He also said the full version for tests would have full vac engines.

Online speedevil

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Re: BFS - without BFR eats the launch market.
« Reply #28 on: 03/01/2018 11:53 AM »
It could also eat the lunch of a lot of commercial LEO station plans. It's a BA330 (actually several) that can get to orbit all by itself.

Good point - and for this role, at least the shell only needs to launch once, so it can carry some 30 tons up with it.
(on the above assumptions).
You would need to add moderately complex sun/earthshades for any manoeuvring fuel not to boil off rapidly, as even if designed for Mars cruise, it's in a very different thermal environment, and pointing at the sun won't cut it.

Offline Darkseraph

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Re: BFS - without BFR eats the launch market.
« Reply #29 on: 03/01/2018 03:20 PM »
BFR booster is built from 1000 uses. BFS is built for significantly less uses (10-100) because it goes through harsher reentry conditions. Using BFS as an SSTO would mean rapidly burning through the usable life of a very expensive asset for a modest payload to orbit each time, eating SpaceX's finances. Falcon 9 and FH as they are have been paid for and are enough for SpaceX to capture a large market for itself. They just have to freeze the design, mass manufacture it and turn them into real workhorses now.

It's boring but building a two stage booster really just is more sensible, not withstanding incredible future improvements in materials. Even a mini-BFS to replace the upperstage and fairing on Falcon Heavy would be more pragmatic and make that system completely reusable. If there are delays in the BFR-BFS program this could be a good way to go: mini-BFS on FH, later followed by a scaled down raptor powered single core booster to replace the three FH cores.
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Online speedevil

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Re: BFS - without BFR eats the launch market.
« Reply #30 on: 03/01/2018 03:29 PM »
BFR booster is built from 1000 uses. BFS is built for significantly less uses (10-100) because it goes through harsher reentry conditions.
Err - citation needed?
This disagrees with every statement I have seen pretty much from Musk about BFS. You may perhaps be thinking about the statement about wear coming back from Mars, doing earth entry, which is significantly harsher than normal entries.

It also clearly makes the P2P service wholly impossible, and makes refuelling in orbit much more expensive (for the nominal BFR+BFS).

Quote
For Mars, there will be some ablation of the heat shield. So it's just like a sort of brake pad wearing away. It is a multi-use heat shield, but unlike for Earth operations, it's coming in hot enough that you really will see some wear of the heat shield.
- Elon - IAC2017
« Last Edit: 03/01/2018 03:39 PM by speedevil »

Offline Negan

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Re: BFS - without BFR eats the launch market.
« Reply #31 on: 03/01/2018 04:20 PM »
If you look at the 2016 cost amounts, one tanker mission only costs 1.6 million. Even if off by a factor of ten, that launch still costs less than a F9 launch so if there's a less than 10 ton payload, why stack? Launch SSTO. Modifications to make this operationally possible for one or two BFS seem likely unless you believe the <10 ton payload need is going to disappear (and these numbers don't pan out of course).
« Last Edit: 03/01/2018 04:22 PM by Negan »

Offline envy887

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Re: BFS - without BFR eats the launch market.
« Reply #32 on: 03/01/2018 05:45 PM »
BFR booster is built from 1000 uses. BFS is built for significantly less uses (10-100) because it goes through harsher reentry conditions.
Err - citation needed?
This disagrees with every statement I have seen pretty much from Musk about BFS. You may perhaps be thinking about the statement about wear coming back from Mars, doing earth entry, which is significantly harsher than normal entries.

It also clearly makes the P2P service wholly impossible, and makes refuelling in orbit much more expensive (for the nominal BFR+BFS).

Quote
For Mars, there will be some ablation of the heat shield. So it's just like a sort of brake pad wearing away. It is a multi-use heat shield, but unlike for Earth operations, it's coming in hot enough that you really will see some wear of the heat shield.
- Elon - IAC2017

The 2016 IAC presentation has Booster: 1000 flights; Tanker: 100 flights; Crew Ship: 10 flights (presumably to Mars and back).

BFS SSTO would basically be the tanker version, so 100 flights is not unreasonable. I think that these are estimates for number of flights between major rebuilds (e.g. complete new heatshield/engines/etc.)

Offline JamesH65

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Re: BFS - without BFR eats the launch market.
« Reply #33 on: 03/01/2018 06:21 PM »
BFR booster is built from 1000 uses. BFS is built for significantly less uses (10-100) because it goes through harsher reentry conditions.
Err - citation needed?
This disagrees with every statement I have seen pretty much from Musk about BFS. You may perhaps be thinking about the statement about wear coming back from Mars, doing earth entry, which is significantly harsher than normal entries.

It also clearly makes the P2P service wholly impossible, and makes refuelling in orbit much more expensive (for the nominal BFR+BFS).

Quote
For Mars, there will be some ablation of the heat shield. So it's just like a sort of brake pad wearing away. It is a multi-use heat shield, but unlike for Earth operations, it's coming in hot enough that you really will see some wear of the heat shield.
- Elon - IAC2017

P2P service is, I suspect, just Musk brainstorming possibilities. I doubt it will happen for decades if at all. The cost to set it up is so colossal that it would really get in the way of the Mars plans. Once Mars colonisation is underway, then maybe.

So given that, a 10-100 reentry lifetime for the BFS sounds about right.



Offline niwax

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Re: BFS - without BFR eats the launch market.
« Reply #34 on: 03/01/2018 06:26 PM »
BFR booster is built from 1000 uses. BFS is built for significantly less uses (10-100) because it goes through harsher reentry conditions.
Err - citation needed?
This disagrees with every statement I have seen pretty much from Musk about BFS. You may perhaps be thinking about the statement about wear coming back from Mars, doing earth entry, which is significantly harsher than normal entries.

It also clearly makes the P2P service wholly impossible, and makes refuelling in orbit much more expensive (for the nominal BFR+BFS).

Quote
For Mars, there will be some ablation of the heat shield. So it's just like a sort of brake pad wearing away. It is a multi-use heat shield, but unlike for Earth operations, it's coming in hot enough that you really will see some wear of the heat shield.
- Elon - IAC2017

P2P service is, I suspect, just Musk brainstorming possibilities. I doubt it will happen for decades if at all. The cost to set it up is so colossal that it would really get in the way of the Mars plans. Once Mars colonisation is underway, then maybe.

We might see Mars P2P service before Earth. Pack a couple scientists and some supplies and head out for a few days.

Offline Darkseraph

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Re: BFS - without BFR eats the launch market.
« Reply #35 on: 03/01/2018 06:34 PM »
Musk has flat out declared Earth SSTO a bad idea due to the large gravity well and that two stage is way more optimal for Earth. For Moon and Mars it is great. In the long term SSTO and P2P vehicles stationed permanently on the Moon and Mars is likely.
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." R.P.Feynman

Online speedevil

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Re: BFS - without BFR eats the launch market.
« Reply #36 on: 03/01/2018 06:43 PM »
The 2016 IAC presentation has Booster: 1000 flights; Tanker: 100 flights; Crew Ship: 10 flights (presumably to Mars and back).

BFS SSTO would basically be the tanker version, so 100 flights is not unreasonable. I think that these are estimates for number of flights between major rebuilds (e.g. complete new heatshield/engines/etc.)
And is clearly in the context of Mars.
If you read the full transcript, the '10 flights' is set by the fact that it's taking 20+ years to do those flights in.
This is also a much larger vehicle, with somewhat less work done on it, and without the thought of possibly desiring lots and lots of reflights.

For the 2016 Mars case,  you don't care at all if the tankers last 'only' a hundred flights, because that is about when you stop caring about the cost reduction, because it's dominated by the cost of BFS being away on Mars.

There is also the point that '10 flights' are round trips to mars, with a very, very aggressive reentry that is much higher energy than a normal earth one.


Online docmordrid

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Re: BFS - without BFR eats the launch market.
« Reply #37 on: 03/02/2018 02:41 AM »
>
P2P service is, I suspect, just Musk brainstorming possibilities. I doubt it will happen for decades if at all.
>

They've already added a third sea level Raptor to BFS for better engine-out and to enhance it for P2P. 

Reddit AMA after IAC2017

Quote
Btw, we modified the BFS design since IAC to add a third medium area ratio Raptor engine partly for that reason (lose only 1/3 thrust in engine out) and allow landings with higher payload mass for the Earth to Earth transport function.
« Last Edit: 03/02/2018 02:42 AM by docmordrid »
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Offline BeamRider

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Re: BFS - without BFR eats the launch market.
« Reply #38 on: 03/02/2018 02:35 PM »
#30 that’s what I’ve been thinking for a while. The way to get BFS operational “quickly” is the “Saturn I” approach of a Falcon 9/H-derived interim booster, built for the same reason NASA built the S-I, to get low-risk heavy-lift quickly to support the main event.

BFS evolve into true SSTO? Yes that could happen and it would be amazing... a real rocket ship! Now, if they could they put fins on it... ;-)

Online speedevil

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Re: BFS - without BFR eats the launch market.
« Reply #39 on: 03/02/2018 02:42 PM »
#30 that’s what I’ve been thinking for a while. The way to get BFS operational “quickly” is the “Saturn I” approach of a Falcon 9/H-derived interim booster, built for the same reason NASA built the S-I, to get low-risk heavy-lift quickly to support the main event.

In principle, a 'test article' BFR that is three times overweight, with legs, and has very limited or no TPS, would enable nearly all of the desired things other than rapid passenger transport.

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