Author Topic: BFS - without BFR eats the launch market.  (Read 39273 times)

Offline speedevil

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BFS - without BFR eats the launch market.
« on: 02/28/2018 02:38 PM »
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, and refuelling is easy. (Elon said at IAC SSTO is possible with BFS, since then, they added an engine). Also assuming re-usability works well immediately.

LEO, 10 tons = $3M. (*)
GTO, 10 tons = $18M
GTO, 30 tons = $25M
GEO, 30 tons = $90M
ISS, 3 tons, $3M.
ISS, 30 tons, $18M
Mars landing, 150 tons, $450M (plus cost of BFS, and on-orbit outfitting) (two years early)
JOI, 120 tons, $450M, expended BFS. (March 2020, extra free Uranus)
Moon landing/return, 20 tons to and from moon, $450M

Refuelling twice in orbit lets you use the landing fuel to launch, so 30 tons, and you need to top off to land.

BEO is technically possible, but, you're looking at of the order of a hundred flights to top it off, at which point it's almost always going to be worth it to just wait for BFR. Unless of course you're constrained by Mars launch windows, and willing to load your payload in 30 ton chunks, and fuel in 10s.
You can get really, really energetic if you expend the BFS - Jupiter insertion with over a hundred tons is quite possible if tanked fully in LEO.

Refuelling for a trip to GTO , you need some six flights, and as a bonus it lets you test the heatshield at higher velocities.
Add another couple of flights, and you can get a 30 ton payload to GTO.

Launching to ISS from 28N, starts off with about 50m/s more delta-v due to not going east, knocking a couple of tons off the nominal payload to LEO, and needs around 250m/s to do raising and approach and deorbit burns, and is only 3-4 tons without refuelling.

(above figures approximate, and you probably can't land at the launch site, unless Elon was meaning that as 'can do SSTO'. )

On the more speculative.
The above all requires two BFS.

*)

Can we make it cheaper?
Above I've been assuming $3m, for no particularly good reason, though I note BFS uses one quarter or so of the propellant, has less launch infrastructure, than a full stack.

How to halve the price?

Take two BFS, launched at the same time from the same place. Proceed as normal through the gravity turn to LEO as normal, but stop turning when you're at 45 degrees or so, a couple of minutes in and 30km altitude.
At this point, we're around 30 degrees over the normal thrust angle, so are losing 15% or so of horizontal accelleration, but gaining rapidly in vertical velocity.
At several minutes into the flight, as the apogee reaches 1000km, manoeuvre together, cut engines, dock, and begin transferring propellant. Transfer over 150 tons of propellant, leaving a significant amount in the source vehicle to enable a safe reentry.
We need to make up the 600m/s or so of horizontal velocity lost in the other BFS at this point.

We've gained a 'free' 1km/s or so, and payload is now 40-50 tons.

At this point in time,  refuelling in orbit would have been tested many times, as well as experience with different reentry conditions. If the fuelling is interrupted, neither vehicle is lost. (if the ground track has suitable abort sites).

This of course does need quite fast pumps, 25t/min.

Refuelling lots adds constraints of course, and will only work if you can launch very rapidly.

Online JamesH65

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Re: BFS - without BFR eats the launch market.
« Reply #1 on: 02/28/2018 04:54 PM »
Or you could just build the BFR.

Offline speedevil

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Re: BFS - without BFR eats the launch market.
« Reply #2 on: 02/28/2018 05:15 PM »
Or you could just build the BFR.

Which is being built after BFS.
The entire launch market being economically launchable by BFS a year earlier than BFR is around is interesting, and could be a reason to push BFS even harder.

As another point, if you have demonstrated through 'ridiculous' launch operations like the above, >>100 reuses per BFS, (which you do if you use it for all GTO flights in only one year), that becomes a really good starting point for negotiations about crew rating.

And might enable the bit that everyone in the industry seems to think was thrown in as comic relief - the passenger service.

« Last Edit: 02/28/2018 05:29 PM by speedevil »

Offline Johnnyhinbos

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Re: BFS - without BFR eats the launch market.
« Reply #3 on: 02/28/2018 05:30 PM »
I think from a new tech perspective - BFS is much more intense than BFR. They've already proven they can manage 27 engines - and in a config that's way more challenging than what is on the BFR. They've also worked out many hurdles of the vertical landing bit, and GSE dev will apply aptly to both BFS and BFR.


BFS, on the other hand, involves way more complexity and challenges. Look at even the fueling system - there's no umbilicals for that - that sucker is a butt loader (and a butt transfer-er), to put it bluntly. And TPS, and docking, and ECLSS, and and and.


Point being, Elon is tackling the hard thing first. If SpaceX sorts out the BFS then the BFR kinda just follows along...
John Hanzl. Author, action / adventure www.johnhanzl.com

Offline MikeAtkinson

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Re: BFS - without BFR eats the launch market.
« Reply #4 on: 02/28/2018 05:39 PM »
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.

Offline Negan

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Re: BFS - without BFR eats the launch market.
« Reply #5 on: 02/28/2018 05:44 PM »
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.

If 2 works, it would seem to have a good chance of eating the sub-orbital tourism market.

Offline Smrg

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Re: BFS - without BFR eats the launch market.
« Reply #6 on: 02/28/2018 06:01 PM »
One thing to consider when planning to have multiple refueling flights is you have to get into the orbital plane of the already-orbiting BFS. That means either a lot of geographically separated launch sites (therefore more than 2 BFS) or
wait at least 12 hours between launches to get into the orbital plane.
Launch windows become very short too, and
you might have to catch up with the orbiting BFS for halfway around an orbit, which could require a few extra orbits.

I don't think it's practical to refuel with just 2 BFS, unless you can do it in like 2 or 3 trips tops.

Offline speedevil

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Re: BFS - without BFR eats the launch market.
« Reply #7 on: 02/28/2018 06:04 PM »
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)?

I'm assuming that Elon, when he said at IAC 'can do SSTO without a booster' meant 'and land'. (20 tons of fuel)
Further that this was with 0 payload or so, and that the comments made after IAC on reddit about adding a medium area ratio engine lead to 10 tons payload.

The above was largely on the basis that inclinations of the launch site are OK, launch site is near the equator, and was neglecting boiloff.
In real life, inclinations far from the launch site inclination are expensive, either as you launch into the launch site inclination and then add a large amount of fuel, or launch not using the full eastwards momentum, which kills payload very rapidly for such a marginal launcher.
IS, for example,  is on the ragged edge of doable with a nominal payload of a ton or three, launching directly to the inclination.
For more than a nominal payload, you need to add 60 tons or so of fuel, launched into the launch inclination, and do the inclination change the hard way.

On rendevous, I'm basically assuming it happens at utterly, utterly ridiculous speeds, compared to normal ISS docking.
Instantaneous windows, and MECO only very nearby.
Refuelling - well - milligee and you in principle don't need pumps if you depressurise the receiving tanks, and how long it takes is set by the size of the lines.

Actual hardware that would need to be developed for this that would not be needed for Mars transport?
A cylindrical foil shield, with a closeable top, to cover the BFS and open when in shadow.

Everything on the BFS has to work, and work well, for this to happen, there is no margin.
There is huge margin on the BFR+BFS system.


Negan:
Quote
If 2 works, it would seem to have a good chance of eating the sub-orbital tourism market.

Indeed.
If BFS-SSTO actually works as outlined above, testing for BFS-passengers becomes actually free, or revenue generating.

At 'only' 3 million dollars for a dozen or more people, that's a moderately large market of its own.
(it's dwarfed by BFR+BFS of course)


Offline guckyfan

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Re: BFS - without BFR eats the launch market.
« Reply #8 on: 02/28/2018 06:18 PM »
Quote of Elon Musk in the reddit AMA



Quote
The "vacuum" or high area ratio Raptors can operate at full thrust at sea level. Not recommended.

IMO this pretty much rules out operational use. Just doable for reentry tests.

Offline speedevil

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Re: BFS - without BFR eats the launch market.
« Reply #9 on: 02/28/2018 06:28 PM »
Quote of Elon Musk in the reddit AMA



Quote
The "vacuum" or high area ratio Raptors can operate at full thrust at sea level. Not recommended.

IMO this pretty much rules out operational use. Just doable for reentry tests.

Hmm.
Unless upgraded medium area ratio raptors make up the difference (on all seven), or they properly qualify the engines when working overexpanded.
Or unless the sillier part of the post discussing suborbital refuelling comes to pass. (clearly not for passengers)
« Last Edit: 02/28/2018 06:32 PM by speedevil »

Offline guckyfan

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Re: BFS - without BFR eats the launch market.
« Reply #10 on: 02/28/2018 06:36 PM »
Quote of Elon Musk in the reddit AMA



Quote
The "vacuum" or high area ratio Raptors can operate at full thrust at sea level. Not recommended.

IMO this pretty much rules out operational use. Just doable for reentry tests.

Hmm.
Unless upgraded medium area ratio raptors make up the difference (on all seven), or they properly qualify the engines when working overexpanded.
Or unless the sillier part of the post discussing suborbital refuelling comes to pass. (clearly not for passengers)

Sounds easier to just build BFB.

Online JamesH65

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Re: BFS - without BFR eats the launch market.
« Reply #11 on: 02/28/2018 06:50 PM »
Or you could just build the BFR.

Which is being built after BFS.


Do you REALLY think they won't start building the BFR until the BFS is finished and flying? Once the BFS starts hopping, I'd be right on building the BFR in parallel with BFS testing. If it's more than a year after the BFS first flies to a decent height I'd be surprised.

Offline speedevil

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Re: BFS - without BFR eats the launch market.
« Reply #12 on: 02/28/2018 06:54 PM »

Do you REALLY think they won't start building the BFR until the BFS is finished and flying? Once the BFS starts hopping, I'd be right on building the BFR in parallel with BFS testing. If it's more than a year after the BFS first flies to a decent height I'd be surprised.

Of course they will. However, it is at least somewhat plausible to me that BFS may be flying without BFR for some period, be that six months, a year, or 18 months.
And I found it interesting to wonder what doing it this way, rather than BFR first might enable.
« Last Edit: 02/28/2018 07:06 PM by speedevil »

Offline Elmar Moelzer

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Re: BFS - without BFR eats the launch market.
« Reply #13 on: 02/28/2018 08:47 PM »
I still like the idea of a (modified) BFS as an SSTO. The main reason for SpaceX to do it, would IMHO be to launch their satellite constellation and at the same time gather A LOT of operational experience with BFS by launching and landing it often. That would probably also lead to improvements that would also apply to BFR.
And who knows after a couple of years of incremental improvements to the engines and the ship, the payload for BFS might increase enough to make it a viable launch vehicle for other commercial payloads to higher orbits. If the lifetime improvements to Falcon 9 since version 1.1 are any indication, that seems very likely.
A SSTO BFS with 15 tons payload to ISS orbit could launch a Dragon2 on top.
It seems credible to me that this would be cheaper than launching a whole stack of BFR and BFS for say delivering 6 people to a space station (ISS or some future commercial station).

Offline Norm38

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Re: BFS - without BFR eats the launch market.
« Reply #14 on: 03/01/2018 01:07 AM »
Getting kinda OT, but if we're going to go with BFS as SSTO to LEO, then an architecture could be built around a fuel/cargo depot supplied by unmanned BFRs, tankers and cargo haulers.
Passengers and crew ride up on BFS.

Does that buy anything?  BFR doesn't have to be human rated. But a lot more mass has to be transferred on orbit.

Offline speedevil

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Re: BFS - without BFR eats the launch market.
« Reply #15 on: 03/01/2018 01:34 AM »
Does that buy anything?  BFR doesn't have to be human rated. But a lot more mass has to be transferred on orbit.

I'm not sure it does.
I think if BFR works, you always want to use it, unless you have very, very small cargo - BFS alone in principle is really hard to put into a system where P2P makes sense - unless it's for fill-in flights where there is simply no reason for large cargo.
But, given the limits in pretty much all ways - if BFR exists, and you have more than five or so tons to move in a non-urgent manner, it's almost always going to make more sense to use it.

It could improve operational flexibility a lot - you don't need to use ferry flights of BFR to get BFS in the right place.

The only case I can sort-of-imagine it working would be the ultimate status symbol of personal spacecraft.

Also, it's plausible that the payload of a BFS outfitted for P2P may be 0, so it can carry around 0 passengers to orbit, but can self-ferry, so a 'low weight several passengers' mode would be needed, and ...
« Last Edit: 03/01/2018 01:39 AM by speedevil »

Offline Lar

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Re: BFS - without BFR eats the launch market.
« Reply #16 on: 03/01/2018 02:36 AM »
This is an interesting execise that shows what a robust architecture this is. Thanks, Speedevil.

But I suspect that BFR development will start somewhere around the 1/2 way point of BFS development, and possibly blow right past it and complete first.. As others, I think BFR is easy... well... "easy" compared to BFS.
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Offline Norm38

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Re: BFS - without BFR eats the launch market.
« Reply #17 on: 03/01/2018 03:08 AM »
The only case I can sort-of-imagine it working would be the ultimate status symbol of personal spacecraft.

Yes.  Elon's personal yacht.

Offline speedevil

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Re: BFS - without BFR eats the launch market.
« Reply #18 on: 03/01/2018 03:15 AM »
This is an interesting execise that shows what a robust architecture this is. Thanks, Speedevil.

But I suspect that BFR development will start somewhere around the 1/2 way point of BFS development, and possibly blow right past it and complete first.. As others, I think BFR is easy... well... "easy" compared to BFS.

Very possible!
It would be fascinating to learn what the details of the system are, and what their current pencilled in masses are.

This and next years conferences will be fascinating, for what they reveal and don't.
I can see arguments for trying to do this in deep stealth - not to upset the applecart before revealing their hand of nearly complete launcher.
Or for going entirely the opposite direction, and 'People, this is really happening, you need to make stuff for the Moon, space and Mars, and here is the incentive scheme for that'.

Offline Negan

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Re: BFS - without BFR eats the launch market.
« Reply #19 on: 03/01/2018 04:10 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.
« Last Edit: 03/01/2018 04:19 AM by Negan »

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