Author Topic: Spacex BFR clarification  (Read 15455 times)

Offline DenverXDXDXD

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Spacex BFR clarification
« on: 04/02/2018 07:42 am »
Hey guys,

Just heard about SpaceX launching their BFR ("Big Falcon Rocket") in 2019 which I am HYPED for but I just want some clarification for SpaceX new BFR.

Is the BFR the official Mars transport ship that will establish a Mars colony or is there an even bigger ship coming after this one. I found this https://en.wikipedia.org/wiki/SpaceX_Mars_transportation_infrastructure which looks to me like another ship bigger than the BFR. The BFR's main purpose is to transport cargo, and passengers to mars, moon and across orbit. so I'm a bit confused.

SpaceX BFR will also be used to transport cargo and passengers to the moon.



How are they going to return to earth? There is no water on the moon. There could potentially be ice on the moon but nobody is really sure of it and there cant be that much water to fuel a BFR back to earth.

How about you guys.
« Last Edit: 04/08/2018 12:07 pm by Chris Bergin »

Offline RotoSequence

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Re: Spacex BFR clarification
« Reply #1 on: 04/02/2018 08:24 am »
If you're okay with cursing, this is a solid overview.

SpaceX is starting with the ship that is economically viable for them to construct and is at a reasonable scale for commercial satellite operations around Earth Orbit. The solution for leaving Mars is In-Situ Resource Utilization. The rocket has enough performance and the Moon's gravity is low enough that refueling in orbit before making a departure for the Moon will leave them with enough fuel to land on the moon and then come back to Earth.

Offline KelvinZero

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Re: Spacex BFR clarification
« Reply #2 on: 04/02/2018 09:57 am »
(note, there are large threads already discussing these videos somewhere, so probably find those threads rather than discussing the videos here)

Old plan:


New plan:


I can't remember the exact rational for the step from 12m down to 9m, but one critical point of the new plan is that Elon has a scheme to fund it: this new rocket is meant to be fundable pretty much just by replacing F9, F9 Heavy, Dragon on existing and already lined up missions, and is intended to be cheaper than all those due to full reusability. I think that 9m size is scaled to hit that target. Also 9m is probably going to be disproportionately cheaper because 12m would probably involve resizing a bunch of roads and other infrastructure just for SpaceX.

The lunar missions are designed to be achievable without propellant ISRU. The BFR lands on the moon enough propellant left over to return home. This involves some slightly more complex orbital mechanics.. something todo with refuelling on an elliptical orbit that I guess means it starts much closer (in term of delta-v and propellant) to the moon.
« Last Edit: 04/02/2018 10:01 am by KelvinZero »

Offline speedevil

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Re: Spacex BFR clarification
« Reply #3 on: 04/02/2018 02:03 pm »
The mission to the moon is discussed in the thread ITS to the moon.

In broad terms, six refuellings get one BFS to the moon, and back, with payload of 20 tons or so, landing on the moon with no refuelling.
If you add a BFS in lunar orbit, you can store fuel for your return journey to earth and get some hundred tons per six launches to the moon.
Lunar propellant production makes these figures lots better - but adds a massive layer of complexity over what the bare vehicle can do.

Offline kdhilliard

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Re: Spacex BFR clarification
« Reply #4 on: 04/02/2018 03:32 pm »
... Just heard about SpaceX launching their BFR ("Big Falcon Rocket") in 2019 ...

SpaceX is developing the more challenging upper stage (BFS -- Big Falcon Spaceship) first, and the 2019 test launches are "short hopper flights" of the BFS without its lower stage (BFB -- Big Falcon Booster, though Musk once called it the BRB -- Big Rocket Booster / Be Right Back, as it lands back in its launch cradle just minutes after taking off).

Check out Musk describing the hopper flights at 21:10 in the Falcon Heavy post-flight press conference, and note where he says of the full BFR, "I think it's conceivable that we do our first test flight in three or four years.  Of a full up, orbital test flight, including the booster."

The BFR is a hugely ambitious vehicle, and there is little chance they will meet the 2022 aspirational date mentioned last year for the first cargo mission to Mars, but it is certainly inspiring that a company is not just designing such a vehicle, but has actually started construction of a prototype upper stage.

Offline Alkan

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Re: Spacex BFR clarification
« Reply #5 on: 04/02/2018 10:16 pm »
... Just heard about SpaceX launching their BFR ("Big Falcon Rocket") in 2019 ...

SpaceX is developing the more challenging upper stage (BFS -- Big Falcon Spaceship) first, and the 2019 test launches are "short hopper flights" of the BFS without its lower stage (BFB -- Big Falcon Booster, though Musk once called it the BRB -- Big Rocket Booster / Be Right Back, as it lands back in its launch cradle just minutes after taking off).

Check out Musk describing the hopper flights at 21:10 in the Falcon Heavy post-flight press conference, and note where he says of the full BFR, "I think it's conceivable that we do our first test flight in three or four years.  Of a full up, orbital test flight, including the booster."

The BFR is a hugely ambitious vehicle, and there is little chance they will meet the 2022 aspirational date mentioned last year for the first cargo mission to Mars, but it is certainly inspiring that a company is not just designing such a vehicle, but has actually started construction of a prototype upper stage.

I would say there's a larger chance than "little."

I'd give it about a 30% chance based on the fact that SpaceX is significantly more seasoned than it was when it started on Falcon 9 and Falcon Heavy. It shat out the Falcon 9 very quickly. The Falcon Heavy took longer, but the BFR/BFS is actually Elon Musk taking into account that he's overly ambitious about these things.

Since they're planning short hops in 2019, an actual launch may happen in 2020 or 2021. If an actual launch happens in 2020, refueling test could be 2021, and likewise a full cargo mission to Mars could be 2022. It has to be mid 2022.

Offline Slarty1080

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Re: Spacex BFR clarification
« Reply #6 on: 04/03/2018 12:53 pm »
I think it's unlikely there will be any BFR Mars mission before 2024. I might be wrong, but I would have thought they would need whatever ships they had to gain experience in launching and re-entry operations as well as launching Elon's world wide web global access constalation of sats in order to pay for a small fleet of BFR's to get to Mars.
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Offline Robotbeat

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Re: Spacex BFR clarification
« Reply #7 on: 04/03/2018 01:16 pm »
To get a ship to Mars requires just:
1 booster (which stays at Earth)
1 ship
1 tanker (which also stays near Earth and could be just another ship)

So SpaceX could send one ship to Mars using a booster and ship normally used for satellite launching. And it doesn’t take many launches for BFR to launch the satellites.

Just need one extra ship, could be an old version that doesn’t even have the payload deploy mechanism.
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Offline Robotbeat

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Re: Spacex BFR clarification
« Reply #8 on: 04/03/2018 01:17 pm »
But I also would bet they’ll miss the 2022 window. But they might still do it.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline rst

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Re: Spacex BFR clarification
« Reply #9 on: 04/03/2018 02:39 pm »
I'd give it about a 30% chance based on the fact that SpaceX is significantly more seasoned than it was when it started on Falcon 9 and Falcon Heavy. It shat out the Falcon 9 very quickly. The Falcon Heavy took longer, but the BFR/BFS is actually Elon Musk taking into account that he's overly ambitious about these things.

On the flip side, rocketry projects seem to be particularly subject to Hofstadter's law: It always takes longer than you think it will, even if you try to take Hofstadter's law into account.

Offline DenverXDXDXD

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Re: Spacex BFR clarification
« Reply #10 on: 04/04/2018 03:38 am »
How much can the BFR(spaceship) carry in tons? I can't find the amount of cargo the BFR(spaceship) can carry. It doesn't say on Wikipedia, the BFR video or anywhere else.

1. How much cargo can a fully fueled spaceship carry from the earth to the ISS and back?

2. How much cargo can a fully fueled spaceship carry from the earth to the lunar surface and back?

3. How much cargo can a fully fueled spaceship carry from the earth to the Mars?


Offline speedevil

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Re: Spacex BFR clarification
« Reply #11 on: 04/04/2018 03:46 am »
How much can the BFR(spaceship) carry in tons? I can't find the amount of cargo the BFR(spaceship) can carry. It doesn't say on Wikipedia, the BFR video or anywhere else.

1. How much cargo can a fully fueled spaceship carry from the earth to the ISS and back?

2. How much cargo can a fully fueled spaceship carry from the earth to the lunar surface and back?

3. How much cargo can a fully fueled spaceship carry from the earth to the Mars?

It's complicated.
The first perhaps least so - around 140 tons.
A fully refuelled (not refuelled can't do it at all) with six tanker flights or so gets you to the lunar surface and back with 20 tons.
A slightly more complex architecture gets 100 tons to the lunar surface (a spaceship acting as a tanker in LLO) without needing any external resources other than refuelling in earth orbit from tankers. (six again).

Fully fuelled gets around 150 tons to Mars - but it can't get back toearth even without that cargo unless you make fuel on Mars.
https://forum.nasaspaceflight.com/index.php?topic=41682.msg1731818#msg1731818 - ITS to the moon thread.

Offline DenverXDXDXD

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Re: Spacex BFR clarification
« Reply #12 on: 04/04/2018 03:54 am »
@speedevil

Thanks for that, I couldn't find this info anywhere.
« Last Edit: 04/04/2018 03:55 am by DenverXDXDXD »

Offline john smith 19

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Re: Spacex BFR clarification
« Reply #13 on: 04/04/2018 07:00 am »
But I also would bet they’ll miss the 2022 window. But they might still do it.
Probably.

But it'll be worth it.

There are basically 2 ways to run a development programme. I'll talk in terms of military aircraft but the principle's the same.

1) Build flight test aircraft and gradually, over time, extend what systems are on board. When you've got most of the bugs out commit to full production. Historically the first ones have the airframe and engines (possibly not even the final engines, if they are still in development). it gives you a baseline. The last test aircraft will have all systems installed and be more or less ready to deploy.
2) Build the flight test aircraft on the full mfg line and change the line as the flight test programme finds issues.

Option 2 was done in WWII and worked quite well provided you weren't pushing the envelope and you need something fast in fairly large numbers. 
1 works better when you're stretching the envelope a lot with lots of new tech, challenging mass and range targets, need high reliability (in a very aggressive environment)etc.

Note that the F35 is being built with method 2, causing a tail back of all the deployed aircraft that have to be fixed as well.

Remember the delay after the first F9 flight in 2010 before the first full Dragon?

With BFR the shape may be more or less frozen but the systems are likely to need several generations of roll out, although I doubt it will be obvious.  DC-X demonstrated you could run a reusable test programme without on board crew.
The trick will be to have enough hardware to accommodate a flight failure without loosing schedule.  Historically X planes did this with 3 vehicles. SX will probably want a few more.
A key question will be if a vehicle is severely damaged can it be  repaired, or does it need to be scrapped?
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Offline speedevil

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Re: Spacex BFR clarification
« Reply #14 on: 04/04/2018 02:18 pm »
A key question will be if a vehicle is severely damaged can it be  repaired, or does it need to be scrapped?
Another is how much cost is the shell, vs 'bits'.
Is the monolithic shell wholly dominant in terms of cost (as seems likely), or does swapping over legs, engines, actuators, ... actually represent a meaningful saving vs a whole new vehicle.

Some classes of damage may make the vehicle impossible to be economically reused for missions requiring reentry, but as long as there are tanker or other missions available, that's not taking a vehicle out of service.
A lot depends on flight rate.

Offline Slarty1080

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Re: Spacex BFR clarification
« Reply #15 on: 04/04/2018 05:45 pm »
A key question will be if a vehicle is severely damaged can it be  repaired, or does it need to be scrapped?
Another is how much cost is the shell, vs 'bits'.
Is the monolithic shell wholly dominant in terms of cost (as seems likely), or does swapping over legs, engines, actuators, ... actually represent a meaningful saving vs a whole new vehicle.

Some classes of damage may make the vehicle impossible to be economically reused for missions requiring reentry, but as long as there are tanker or other missions available, that's not taking a vehicle out of service.
A lot depends on flight rate.

I'm sure the shell will be expensive but 31 raptor engines won't be that cheap either. It would be interesting if anyone could estimate the cost split shell v engines v the rest.
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Offline niwax

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Re: Spacex BFR clarification
« Reply #16 on: 04/04/2018 06:10 pm »
A key question will be if a vehicle is severely damaged can it be  repaired, or does it need to be scrapped?
Another is how much cost is the shell, vs 'bits'.
Is the monolithic shell wholly dominant in terms of cost (as seems likely), or does swapping over legs, engines, actuators, ... actually represent a meaningful saving vs a whole new vehicle.

Some classes of damage may make the vehicle impossible to be economically reused for missions requiring reentry, but as long as there are tanker or other missions available, that's not taking a vehicle out of service.
A lot depends on flight rate.

I'm sure the shell will be expensive but 31 raptor engines won't be that cheap either. It would be interesting if anyone could estimate the cost split shell v engines v the rest.

For comparison a Boeing 787 costs about $200M to make with a large chunk of that the carbon airframe. Raptors are probably in the single-digit millions. So maybe $100M frame and $100M engines and avionics for the booster and $100M frame, $50M engines and avionics for the ship would put the price in the rough area that has been estimated before.
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Offline envy887

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Re: Spacex BFR clarification
« Reply #17 on: 04/07/2018 03:21 am »
...
A fully refuelled (not refuelled can't do it at all) with six tanker flights or so gets you to the lunar surface and back with 20 tons.
I know the OP specified "and back", but it "IT" was just landing cargo than BFS can do it unrefueled, in one launch.

The cargo BFS could land somewhere between 5 and 20 tonnes on the Moon with a single launch, fully expended 1-way. That would be an expensive launch ($500 million?), but I'm not aware of any other LV/lander combination under active development that could do this.

Falcon Heavy and SLS lack landers. Blue is working on a lander for 5 tonnes or less, presumably to work with New Glenn. Several companies (mostly former X-Prize contestants) are working on smaller landers that are mostly LV agnostic but deliver less than 1 tonne.

Except BFR/BFS, none of them can land enough payload to reasonably build a base or support a crew mission with one launch. Even Saturn V landed less than 5 tonnes, and that needed 5 stages - with 2 of them hydrolox. BFR can do that with only 2 methalox stages.
« Last Edit: 04/07/2018 03:24 am by envy887 »

Offline wannamoonbase

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Re: Spacex BFR clarification
« Reply #18 on: 04/07/2018 04:45 am »
...
A fully refuelled (not refuelled can't do it at all) with six tanker flights or so gets you to the lunar surface and back with 20 tons.
I know the OP specified "and back", but it "IT" was just landing cargo than BFS can do it unrefueled, in one launch.

The cargo BFS could land somewhere between 5 and 20 tonnes on the Moon with a single launch, fully expended 1-way. That would be an expensive launch ($500 million?), but I'm not aware of any other LV/lander combination under active development that could do this.

Falcon Heavy and SLS lack landers. Blue is working on a lander for 5 tonnes or less, presumably to work with New Glenn. Several companies (mostly former X-Prize contestants) are working on smaller landers that are mostly LV agnostic but deliver less than 1 tonne.

Except BFR/BFS, none of them can land enough payload to reasonably build a base or support a crew mission with one launch. Even Saturn V landed less than 5 tonnes, and that needed 5 stages - with 2 of them hydrolox. BFR can do that with only 2 methalox stages.

And what could it do if it got it’s return LOx on the lunar surface?

Making LOx on the lunar surface has to be very near the top of priorities.
« Last Edit: 04/07/2018 04:45 am by wannamoonbase »
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Offline DenverXDXDXD

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Re: Spacex BFR clarification
« Reply #19 on: 04/07/2018 04:58 am »
...
A fully refuelled (not refuelled can't do it at all) with six tanker flights or so gets you to the lunar surface and back with 20 tons.
I know the OP specified "and back", but it "IT" was just landing cargo than BFS can do it unrefueled, in one launch.

The cargo BFS could land somewhere between 5 and 20 tonnes on the Moon with a single launch, fully expended 1-way. That would be an expensive launch ($500 million?), but I'm not aware of any other LV/lander combination under active development that could do this.

Falcon Heavy and SLS lack landers. Blue is working on a lander for 5 tonnes or less, presumably to work with New Glenn. Several companies (mostly former X-Prize contestants) are working on smaller landers that are mostly LV agnostic but deliver less than 1 tonne.

Except BFR/BFS, none of them can land enough payload to reasonably build a base or support a crew mission with one launch. Even Saturn V landed less than 5 tonnes, and that needed 5 stages - with 2 of them hydrolox. BFR can do that with only 2 methalox stages.

And what could it do if it got it returns LOx on the lunar surface?

Making LOx on the lunar surface has to be very near the top of priorities.

I doubt that propellant production on the moon would actually work. The moon does not have sufficient C02 or water for actual refueling. The best way for SpaceX to maintain efficient lunar operations they are going to have to refuel in LLO or the surface with another BFR.

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