Author Topic: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)  (Read 284159 times)

Offline Patchouli

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #800 on: 10/05/2017 06:41 am »
Direct GEO insertion is going to need a few refills, depending on the payload.

You need ~4,200m/s to get to GEO from LEO, with the payload, then another ~1800m/s to get back to GTO, from there you can aerobrake.

You also might want to split reentry in two or more passes as well since returning from GTO is going to be similar to a lunar return and a vehicle like this probably would not survive an Apollo style reentry.



Cost per launch that SX could see with BFR would be lower than the smaller launchers. So for price per launch they would meet todays market and be ready for tomorrows market at the smaller launcher price, but at a launch mass of the HLV. And that is if their price is $20M per launch ( $8M for hardware and launch + $12M profit , based on last years cost estimate for ITS and about  20% of $62M for F9 launch ). Even if the price were $40M per launch that would be hard to bet, that is if they had half as many flights of reuse per unit made. What if the per launch price was $60M per launch, for smaller payloads they could launch 2 to 4 at a time, that brings the price per payload to $15M each.

They might make a small launcher later on, I've suggested this in the past. The BFR is the 747 and the small a corporate jet or 737 to compare.

I think some of Spacex's cost goals are a bit fanciful esp at this stage in development.
But if it just manages to be the same priced as F9 it would be a game changer.
« Last Edit: 10/05/2017 06:48 am by Patchouli »

Offline Semmel

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #801 on: 10/05/2017 06:56 am »
I would also see the costs and prices that are presented as a long term goal, not reached within the first years of operation. Also I expect them to be approached asymptotically over time and after many revisions of booster and spaceship. But the good point about BFR/BFS is, even if the first launches cost $50M and provide only 10 flights per booster and spaceship, there will be customers.

This would put the first iteration on a production cost plus 10 refurbishments of $500M, which does not seem unreasonable.
« Last Edit: 10/05/2017 06:59 am by Semmel »

Offline TomH

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #802 on: 10/05/2017 07:19 am »
You also might want to split reentry in two or more passes as well since returning from GTO is going to be similar to a lunar return and a vehicle like this probably would not survive an Apollo style reentry.

BFS' primary purpose is to go to Mars and return. Reentry from Mars is even higher velocity than from Luna. Aerobraking passes would add time to the return, but yea, I wonder whether they will be necessary.

Offline Semmel

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #803 on: 10/05/2017 07:53 am »
You also might want to split reentry in two or more passes as well since returning from GTO is going to be similar to a lunar return and a vehicle like this probably would not survive an Apollo style reentry.

BFS' primary purpose is to go to Mars and return. Reentry from Mars is even higher velocity than from Luna. Aerobraking passes would add time to the return, but yea, I wonder whether they will be necessary.

Why should it be more difficult for BFS to shed the velocity? The command module of Apollo had 12 m^2 of heat shield and weighted around 6 mT. Thats 0.5 mT per m^2. The reentry mass of a BFS is about 150 mT (85mT dry, plus prop, plus return payload) and has a surface area of about 430 m^2. That is a bit more than 0.3 mT per m^2. So the heat shield should be less stressed than Apollo, even if the reentry path is similar to Apollo, which it will not be. Due to the delta wing, its going to be even shallower.
« Last Edit: 10/05/2017 07:55 am by Semmel »

Offline Kaputnik

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #804 on: 10/05/2017 08:08 am »
You also might want to split reentry in two or more passes as well since returning from GTO is going to be similar to a lunar return and a vehicle like this probably would not survive an Apollo style reentry.

BFS' primary purpose is to go to Mars and return. Reentry from Mars is even higher velocity than from Luna. Aerobraking passes would add time to the return, but yea, I wonder whether they will be necessary.

Why should it be more difficult for BFS to shed the velocity? The command module of Apollo had 12 m^2 of heat shield and weighted around 6 mT. Thats 0.5 mT per m^2. The reentry mass of a BFS is about 150 mT (85mT dry, plus prop, plus return payload) and has a surface area of about 430 m^2. That is a bit more than 0.3 mT per m^2. So the heat shield should be less stressed than Apollo, even if the reentry path is similar to Apollo, which it will not be. Due to the delta wing, its going to be even shallower.

It may have different limits though, on structure, on g-loads, and on the heat capacity of the shielding material.
A Paveway bomb lands a lot harder than a 747. They both come to a stop but there's only one of them you'd put paying passengers on.
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Offline Lumina

Many people worry that SpaceX will be taking a risk by transitioning at some point from the cash-producing Falcon 9 to the BFR. But there is one contrarian thought which I haven't read in this thread (or anywhere for that matter).

Today's SpaceX is above all an organization that excels at designing and building innovative launch vehicles and spacecraft. After 16 F9 landings in a row, one can imagine a future where most flights use previously flown boosters. Today's design-and-build SpaceX is less relevant in such a future.

Hence, the greatest long-term risk for SpaceX, in my view, would be if it were to stand still. And that's why I believe that the all-in transition to BFR makes perfect strategic as well as financial sense.

Offline Robotbeat

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #806 on: 10/05/2017 01:41 pm »
Many people worry that SpaceX will be taking a risk by transitioning at some point from the cash-producing Falcon 9 to the BFR. But there is one contrarian thought which I haven't read in this thread (or anywhere for that matter).

Today's SpaceX is above all an organization that excels at designing and building innovative launch vehicles and spacecraft. After 16 F9 landings in a row, one can imagine a future where most flights use previously flown boosters. Today's design-and-build SpaceX is less relevant in such a future.

Hence, the greatest long-term risk for SpaceX, in my view, would be if it were to stand still. And that's why I believe that the all-in transition to BFR makes perfect strategic as well as financial sense.
Agreed. If they don't stay on the edge, they'll start bleeding those capable and driven employees that have made them so great.

BFR in its various incarnations as well as all the necessary Mars infrastructure will keep them busy for a while.

... And it'll be less enticing for SpaceX employees to join startups like Firefly if all those lesser vehicles are made obsolete by BFR... (Someone will make a rival for BFR eventually, tho)
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Offline JasonAW3

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #807 on: 10/05/2017 01:58 pm »
Many people worry that SpaceX will be taking a risk by transitioning at some point from the cash-producing Falcon 9 to the BFR. But there is one contrarian thought which I haven't read in this thread (or anywhere for that matter).

Today's SpaceX is above all an organization that excels at designing and building innovative launch vehicles and spacecraft. After 16 F9 landings in a row, one can imagine a future where most flights use previously flown boosters. Today's design-and-build SpaceX is less relevant in such a future.

Hence, the greatest long-term risk for SpaceX, in my view, would be if it were to stand still. And that's why I believe that the all-in transition to BFR makes perfect strategic as well as financial sense.
Agreed. If they don't stay on the edge, they'll start bleeding those capable and driven employees that have made them so great.

BFR in its various incarnations as well as all the necessary Mars infrastructure will keep them busy for a while.

... And it'll be less enticing for SpaceX employees to join startups like Firefly if all those lesser vehicles are made obsolete by BFR... (Someone will make a rival for BFR eventually, tho)

That's not necessarily true.

      There will always be a place for smaller launchers, as there will always be rush payloads that are too small to economically be viable for a BFR launch.  Timing a number of payloads to a single orbital inclination for one launch can and often is problematic.

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Offline John Alan

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #808 on: 10/05/2017 02:17 pm »
Many people worry that SpaceX will be taking a risk by transitioning at some point from the cash-producing Falcon 9 to the BFR. But there is one contrarian thought which I haven't read in this thread (or anywhere for that matter).

Today's SpaceX is above all an organization that excels at designing and building innovative launch vehicles and spacecraft. After 16 F9 landings in a row, one can imagine a future where most flights use previously flown boosters. Today's design-and-build SpaceX is less relevant in such a future.

Hence, the greatest long-term risk for SpaceX, in my view, would be if it were to stand still. And that's why I believe that the all-in transition to BFR makes perfect strategic as well as financial sense.
Agreed. If they don't stay on the edge, they'll start bleeding those capable and driven employees that have made them so great.

BFR in its various incarnations as well as all the necessary Mars infrastructure will keep them busy for a while.

... And it'll be less enticing for SpaceX employees to join startups like Firefly if all those lesser vehicles are made obsolete by BFR... (Someone will make a rival for BFR eventually, tho)

That's not necessarily true.

      There will always be a place for smaller launchers, as there will always be rush payloads that are too small to economically be viable for a BFR launch.  Timing a number of payloads to a single orbital inclination for one launch can and often is problematic.

Solve it... with thinking outside the box...  ;)
Load all the worlds ready to fly small payloads onto some common rotary mounting frame yet to be invented...
Launch the "SmallSat special'
Use more prop as needed for orbital plane changes and different orbits as needed...
Time tankers to meet the ship at intervals... to partially refuel as needed during the delivery "route"...
Once all the payloads are all delivered and the last tanker has left... fly it home...
Put it back in the hanger and start loading the next months delivery payloads...
Once a month... 12 times a year... Fly that one BFS to clear the backlog installed...

Remember... while on orbit and with tankers available on call...
They could run the fuel tanks way down near empty to minimize mass needing to change orbit...
It could require one last tanker 'splash' before having enough fuel to land with... no big deal...

Just saying... think outside the box when considering how to solve the worlds launch needs...  ;)
« Last Edit: 10/05/2017 02:25 pm by John Alan »

Offline jpo234

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #809 on: 10/05/2017 02:21 pm »



That's not necessarily true.

      There will always be a place for smaller launchers, as there will always be rush payloads that are too small to economically be viable for a BFR launch.  Timing a number of payloads to a single orbital inclination for one launch can and often is problematic.

That's only true if the smaller launcher is cheaper than BFR. And if BFR comes close to the Elon's promise of being cheaper to launch than the Falcon 1, than this will be a real hurdle. You could get 1000x the payload of the Electron for the same price or even cheaper.
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Offline Lumina




That's not necessarily true.

      There will always be a place for smaller launchers, as there will always be rush payloads that are too small to economically be viable for a BFR launch.  Timing a number of payloads to a single orbital inclination for one launch can and often is problematic.

That's only true if the smaller launcher is cheaper than BFR. And if BFR comes close to the Elon's promise of being cheaper to launch than the Falcon 1, than this will be a real hurdle. You could get 1000x the payload of the Electron for the same price or even cheaper.

Also, SpaceX could fill-in much of the empty space in BFR with SpaceX satcom constellation segments -- which will presumably be spread across different orbital inclinations -- and charge the cost to the satcom business. That would help BFR compete even with the cheapest expendable small launcher.

Offline oldAtlas_Eguy

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #811 on: 10/05/2017 02:53 pm »



That's not necessarily true.

      There will always be a place for smaller launchers, as there will always be rush payloads that are too small to economically be viable for a BFR launch.  Timing a number of payloads to a single orbital inclination for one launch can and often is problematic.

That's only true if the smaller launcher is cheaper than BFR. And if BFR comes close to the Elon's promise of being cheaper to launch than the Falcon 1, than this will be a real hurdle. You could get 1000x the payload of the Electron for the same price or even cheaper.
A smallsat launcher would have to be something more like the DARPA envisionment of the launch on demand within a day's notice smallsat launcher (up to 1mt size). A reusable gas and go aircraft operations like booster stage able to be staged from any long runway airport. A possible spaceplane like US similar to Sierra Nevada's Dream Chaser that can drop off up to 1mt to a LEO orbit and return. This would create a fully reusable TSTO smallsat launcher that has no specific ground infrastructure requirements. Able to do daily sorties to space from an airport anywhere in the world.

Such a smallsat launcher could get the launch costs for 1mt of payload down to the $100's/kg range. A direct competitor to the BFR for such smallsats although a little more expensive caters to the custom orbits wanted by the smallsat operator.

The key here is that a greater push by government funding and commercial innovations would result because of BFR to provide such a smallsat launcher.
« Last Edit: 10/05/2017 02:55 pm by oldAtlas_Eguy »

Offline Patchouli

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #812 on: 10/05/2017 03:46 pm »
I really think half the reason Musk has considered NTR is to just keep Mueller happy.

Mueller is pretty much the Steve Wozniak or Paul Allen of Spacex so you would want to keep him happy.
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Offline envy887

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #813 on: 10/05/2017 03:58 pm »
When you resort to including some (massive) costs in one side of your argument and not including them in the other you've pretty much lost the "moral high ground" and people are likely to view your arguments with doubt. :(
I didn't introduce the numbers.  I was responding to the person who did introduce those numbers.  The point remains the same even with lower numbers.  STS development in today's dollars was probably around $40 billion.  BFR - a larger launch vehicle - at only $4 billion development I simply do not believe.  Remember that SpaceX itself did not say "$4 billion", that came from someone's on this thread.  Remember also that Mr. Musk said his company spent $1 billion just to develop Falcon 9 first stage landing.

But this argument is hopeless, of course, because SpaceX won't tell us how much money it is spending, how big its debt really is, etc. 

 - Ed Kyle

$40B to $4B is approximately the right NASA to SpaceX development cost ratio, yes. BFR is somewhat larger than STS, but it has fewer technical risks at this point than the Shuttle program had in the early 1970s.

Offline envy887

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #814 on: 10/05/2017 04:01 pm »
...SpaceX will have to build a factory, test sites, a new launch pad or two, a couple of giant recovery ships apparently, etc.

 - Ed Kyle

Why would they need new recovery ships? BFR is intended to RTLS, and if they do want to land downrange the current ASDS would be fine. F9's landed footprint is already well over 20 meters, there's no need for more deck space.

Offline mme

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #815 on: 10/05/2017 04:06 pm »
...SpaceX will have to build a factory, test sites, a new launch pad or two, a couple of giant recovery ships apparently, etc.

 - Ed Kyle

Why would they need new recovery ships? BFR is intended to RTLS, and if they do want to land downrange the current ASDS would be fine. F9's landed footprint is already well over 20 meters, there's no need for more deck space.
Agree BFR will always RTLS.  I think ASDS is irrelevant.  I don't take the offshore pads as barges or even part of the short term plan.
Space is not Highlander.  There can, and will, be more than one.

Offline aero

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #816 on: 10/05/2017 04:07 pm »
Surface area is one thing, total cargo - the rockets - and center of mass is a totally different consideration. Wouldn't want to land perfectly centered then have the first swell that comes along capsize your barge.

But I didn't get the impression that there were any plans to land the BFR stages on mobile platforms such as the barges used for the Falcon 9 first stage.
« Last Edit: 10/05/2017 04:09 pm by aero »
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Offline envy887

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #817 on: 10/05/2017 04:22 pm »
Surface area is one thing, total cargo - the rockets - and center of mass is a totally different consideration. Wouldn't want to land perfectly centered then have the first swell that comes along capsize your barge.

But I didn't get the impression that there were any plans to land the BFR stages on mobile platforms such as the barges used for the Falcon 9 first stage.

The ASDS are rated to carry several hundred times weight of a single empty booster. The weight is not an all an issue, even if it lands off-center.

Offline tchernik

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #818 on: 10/05/2017 04:48 pm »
Solve it... with thinking outside the box...  ;)
Load all the worlds ready to fly small payloads onto some common rotary mounting frame yet to be invented...
Launch the "SmallSat special'
Use more prop as needed for orbital plane changes and different orbits as needed...
Time tankers to meet the ship at intervals... to partially refuel as needed during the delivery "route"...
Once all the payloads are all delivered and the last tanker has left... fly it home...
Put it back in the hanger and start loading the next months delivery payloads...
Once a month... 12 times a year... Fly that one BFS to clear the backlog installed...

Remember... while on orbit and with tankers available on call...
They could run the fuel tanks way down near empty to minimize mass needing to change orbit...
It could require one last tanker 'splash' before having enough fuel to land with... no big deal...

Just saying... think outside the box when considering how to solve the worlds launch needs...  ;)

When you want to (efficiently) send a product to a city, you don't send a bike with just a crate. You send a truck full of them and distribute them with smaller trucks/whatever local distribution method makes sense.

A payload ride sharing scheme is a must for BFR to be successful IMO.

Offline John Alan

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 2 (Post Speech)
« Reply #819 on: 10/05/2017 05:52 pm »
...SpaceX will have to build a factory, test sites, a new launch pad or two, a couple of giant recovery ships apparently, etc.

 - Ed Kyle

Why would they need new recovery ships? BFR is intended to RTLS, and if they do want to land downrange the current ASDS would be fine. F9's landed footprint is already well over 20 meters, there's no need for more deck space.
Agree BFR will always RTLS.  I think ASDS is irrelevant.  I don't take the offshore pads as barges or even part of the short term plan.

Agreed with one caveat...
If and ONLY if... somebody wants to send ~200+ tonnes to LEO repeatably... and is willing to pay for all costs upfront...
SpaceX could consider putting together a plan to land a BFR booster on a ship at sea...
Putting a landing fixture on a ship with good position keeping and such... is in theory possible...
But yes... I highly doubt we will ever see a BFR booster landing on a floating (IE moving) "thing"...

They would likely save the older/obsolete boosters back at some point...
... and then just expend it on that over 150+ heavy lift launch... with much profit margin involved...  ;)
A slide with 250 tonnes expendable to LEO noted was shown briefly on the 2017 presentation...
EM started to comment on it and the next slide came up... he dropped it and went on...  :(

On edit... added screen grab showing 250 tonnes expendable...
« Last Edit: 10/05/2017 06:34 pm by John Alan »

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