Author Topic: How many BFR Boosters will SpaceX need to build?  (Read 2770 times)

Offline John Alan

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How many BFR Boosters will SpaceX need to build?
« on: 10/04/2017 01:22 AM »
On paper... One per active BFR launch pad...  ???
Realistically, Two per pad... a spare on hand...
Maybe the spare covers several pads co located...

My point is there will not be many BFR Booster airframes built...
Unless they wreck some in mishaps...
Or the number of flight cycles before fatigue sets in is low...
Or I guess a better design is proved out and the whole fleet is rebuilt over time.

I mean... It's carbon fiber...
You don't repair it normally... past cosmetic stuff
If damaged...you strip the usable components off back to a bare air-frame...
Then landfill it...  :P

I guess the answer really boils down to how many pads they need to satisfy flight demands...  ???

Can anyone see a flaw in this thinking?... Or do you agree?
« Last Edit: 10/04/2017 01:29 AM by John Alan »

Offline Ludus

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #1 on: 10/04/2017 02:05 AM »
That would be the design goal. Depending on how reusable they actually are they’d need a pipeline with enough replacements to maintain the launch rates. Maybe refurb facilities.

That seems to me to be part of the reason for the floating launch platforms and point to point. They’ll need a lot of launch sites to support intense launching for Mars on the synodic cycle so mass producing them and finding more ordinary uses for them around the world supports that.

Online guckyfan

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #2 on: 10/04/2017 08:48 AM »
They need a structural test article. They will need a prototype. After that initially 2 boosters should do for a while. Maybe 3 if they have two launch sites.

Offline Nibb31

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #3 on: 10/04/2017 09:19 AM »
If we assume that ISRU development will be iterative, the first couple of BFRs will have to be one-way. I doubt that the entire ISRU process will work flawlessly on the first attempt.

Online nacnud

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #4 on: 10/04/2017 10:23 AM »
So they need a steady supply of BFS but the boosters? Not so much. This is why I think they will be built in Hawthorn for the medium term.

So leading on from the handful of boosters needed, how many spaceships per booster?

Offline jpo234

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #5 on: 10/04/2017 10:43 AM »


If we assume that ISRU development will be iterative, the first couple of BFRs will have to be one-way. I doubt that the entire ISRU process will work flawlessly on the first attempt.

The question was about the booster. It stays at the pad and will theoretically never be expended.
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Offline John Alan

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #6 on: 10/04/2017 02:08 PM »
So they need a steady supply of BFS but the boosters? Not so much. This is why I think they will be built in Hawthorn for the medium term.

So leading on from the handful of boosters needed, how many spaceships per booster?

So it's agreed that only a handful of BFR boosters will ever be around in flying condition... depending on how many launch pads exist worldwide...

BFS spaceships...
I could see at least 3 tanker BFS's located at each pad... One on orbit... One about to launch...One just back and in 24 hour turnaround... maybe a 4th spare hanging around in heavy maintenance...
(Assuming a 24 hour cycle time on a pad... once a day is as good as it gets)

After that... It will depend on what paying mission is coming up...
I could see BFS's being launched at times empty... just to relocate them to a remote pad somewhere else in the world...

I think BFS cargos and crew will tend to be unique and tailored to what they do...
This one here is a Starlink special with a rotary dispenser setup in the nose bay...
Here is one set up to take EELV spec mounting ring birds up... 5m wide doors on the bay
Here is a Mars transit 100 pass one... ready for the next synod..
Here is a 10 passenger small cargo package carrier set up to service space stations thru a docking ring...
Here is "big gulp" special set up to take max size stuff to orbit (like was shown 2017 EM)
Here is a 6 passenger crew with a small cargo bay and robotic arm... used for on orbit service and repair work
Here is a Moon lander... takes crated cargo and a small crew...
...offloads same on the Moon via a door crane...(as was shown 2017 EM)
I mean the list could get quite long... with more then one of some types in use...

Anyway... my opinion on subtopic of BRS numbers...  ;)
« Last Edit: 10/04/2017 02:45 PM by John Alan »

Offline Jim

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #7 on: 10/04/2017 02:27 PM »
This just a silly thread.  Nobody knows the answer.  Not even SpaceX.

Offline John Alan

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #8 on: 10/04/2017 02:36 PM »
This just a silly thread.  Nobody knows the answer.  Not even SpaceX.

Agreed... we don't know... but we can speculate the heck out of it with opinions...  :)

Offline Hotblack Desiato

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #9 on: 10/04/2017 02:38 PM »
In 2016, ant the IAC, Musk said, that the booster itself will last a 1000 launches. An incredible number, but if you can actually launch 5 times a day, that booster is worn out after about half a year.

So make it 2 boosters per launchpad per year, if you shoot for 5 launches per day. If they want to do a launch per hour, they'd need to go for 9 boosters per year per pad because one won't even last for 6 weeks of operation.

Add at least one spare booster to it, because there may be engine failures (I don't know how long it will take to replace an engine), which adds the question of how many engines that booster will require, or how many restarts the raptors will actually allow (maybe the booster can do 1000 launches, but the engines will need a replacement after 100 launches? then each booster with 31 engines will require 310 engines over its lifetime).

And that 1000 reflights value isn't even granted. 500 times would already be an incredible achievement, and yet it'd double the amount of boosters required according to my calculation. keep in mind, the best, that regular falcom 9s have achieved is currently 2 (or 10 on the teststand).

Online RonM

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #10 on: 10/04/2017 06:04 PM »
This just a silly thread.  Nobody knows the answer.  Not even SpaceX.

Saying SpaceX doesn't know is silly. Did NASA roll dice to determine how many Shuttles to build? Of course not. They had a plan and so does SpaceX.

Offline Peter.Colin

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #11 on: 10/04/2017 08:19 PM »
The amount of BFR's will be limited to the amount of launch pads.
The number of spaceships will not limited by the number of launch pads.

So let’s say there will be 4 launch pads (or launch droneships) for the current BFR design.
They can easily serve 10 passenger ships and 30 cargo/tanker ships.

The 4 BFR's will be on the launch pad most of the time, even if they launch a few times a day.
Of the 40 ships only 4 of them will be on an earth launch pad at any time, the rest will be in space or Mars or on the Moon.

The larger BFR design thereafter will hopefully be as numerous as there are airports now.
And the number of spaceships as many as there are airplanes now.
« Last Edit: 10/04/2017 08:32 PM by Peter.Colin »

Offline Semmel

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #12 on: 10/04/2017 08:49 PM »
You could almost see the booster to be part of the launch pad in this configuration.

Offline ZachF

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #13 on: 10/04/2017 09:00 PM »
This just a silly thread.  Nobody knows the answer.  Not even SpaceX.

Saying SpaceX doesn't know is silly. Did NASA roll dice to determine how many Shuttles to build? Of course not. They had a plan and so does SpaceX.

They don't really though... No one does

They want the booster to last hundreds or even thousands of times, there is a big possible range this could eventually fall in.

The low cost of BFR could lead to gigantic increases in the number of space launches, or more modest increases. Demand is therefore ultimately unknown, and falls within a large (many orders of magnitude) possible range.

The amount of BFBs you'll need is a unknown number with a huge variance (demand) divided by an unknown number with a smaller, but still large variance (life of BFB). The signal/noise ratio is unfavorable, getting it within even an order of magnitude would be tough.
« Last Edit: 10/04/2017 09:01 PM by ZachF »

Online AncientU

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #14 on: 10/04/2017 09:20 PM »
Probably need two boosters at each launch pad for continuity as boosters head to hanger for periodic inspection and/or rework.  Longer refurbishment will probably take a booster out for months.  The real question is how many launch pads does SpaceX intend to have in 5, 10, 15, 20 years... that, and the realized lifetime of each generation of booster, will define booster production.
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Offline dnavas

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #15 on: 10/04/2017 09:54 PM »
They want the booster to last hundreds or even thousands of times, there is a big possible range this could eventually fall in.

Let's be honest -- if they can get to a point where the failure rate would allow that kind of reuse, that will be a significant advance just by itself.


Online Robotbeat

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #16 on: 10/04/2017 11:43 PM »
A more interesting question:

How many BFRs can SpaceX afford to build? How many flights does that translate to?

Currently, they have a capacity of like 25 cores, or about 200-250 Merlins. Musk seems to think making Raptor about the same size means they'd probably get the same number built in the same production line.

(And this is one benefit of having so many engines: you get mass production even though you don't need that many rockets.)

About 2.5 boosters and 25 spaceships. That's 2500 flights per year.

Of course, Raptors are more complicated than Merlins but still about the same size and they've already made multiple of them, so let's say they are 2.5x as hard to make.

That's about 1 booster per year and 10 spaceships. That replaces like 20-30 cores and another 20 upper stages, plus 4 or so Dragons per year. That sounds about right. 1000 flights per year.

If they're off by a factor of 10 in the early days, so 100 reuses of the booster and 10 of the spaceship, that's 100 flights per year, or pretty close to what they expect for Falcon launches next year (30) plus dozens more for the constellation.
« Last Edit: 10/05/2017 12:02 AM by Robotbeat »
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Offline Lumina

Re: How many BFR Boosters will SpaceX need to build?
« Reply #17 on: 10/05/2017 01:39 AM »
A more interesting question:

How many BFRs can SpaceX afford to build? How many flights does that translate to?

[...]


Another interesting question is how many new land-based and sea-based launch pads will SpaceX own or lease every year.

Demand will be driven by launch cost and launch cost will be driven by how quickly and easily boosters can be turned around and flown again. The faster and cheaper this turnaround, the lower the launch costs, the faster the growth in the space economy, the greater the demand for launches and therefore the greater the need for new launch pads. I expect SpaceX to eventually operate launch pads all over the world. Certain small island nations in the equatorial Pacific will have a very interesting future, to say the least.

Online RonM

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #18 on: 10/05/2017 01:50 AM »
This just a silly thread.  Nobody knows the answer.  Not even SpaceX.

Saying SpaceX doesn't know is silly. Did NASA roll dice to determine how many Shuttles to build? Of course not. They had a plan and so does SpaceX.

They don't really though... No one does

They want the booster to last hundreds or even thousands of times, there is a big possible range this could eventually fall in.

The low cost of BFR could lead to gigantic increases in the number of space launches, or more modest increases. Demand is therefore ultimately unknown, and falls within a large (many orders of magnitude) possible range.

The amount of BFBs you'll need is a unknown number with a huge variance (demand) divided by an unknown number with a smaller, but still large variance (life of BFB). The signal/noise ratio is unfavorable, getting it within even an order of magnitude would be tough.

What, are we reading tea leaves to predict the future? How many boosters SpaceX needs over the lifetime of the program will change based on events no one can predict, but based on their plans over the next few years SpaceX has a target number for normal operations. Due to development issues or accidents the total number might change, but what if everything goes according to plan?

Let's see if we can make an educated guess.

Looks like two pads to start. Having a spare at each pad is a good idea to keep flying while a booster is being worked on or replaced. So a reasonable guess is four.

Eventually, the boosters will wear out and need to be replaced, but without expanding the number of pads, the fleet size will remain at four.

Offline TomH

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #19 on: 10/05/2017 02:02 AM »
They will likely manufacture in blocks. My guess would be 4 in Block I. Performance, tweeks, and emerging customer demand will determine advancements incorporated in and numbers produced in successive blocks.
« Last Edit: 10/05/2017 07:21 AM by TomH »

Offline Lars-J

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #20 on: 10/05/2017 09:03 PM »
They will likely manufacture in blocks. My guess would be 4 in Block I. Performance, tweeks, and emerging customer demand will determine advancements incorporated in and numbers produced in successive blocks.

4? I think you underestimate the cost of BFR booster. They will be valuable hardware costing many times more than expendable rockets. They'll want to make sure and perfect the design before they build any more than they have to. Two at most for "Block I" is all I see, although as with F9 the block divisions will hazy at best. But they certainly don't want to build too many in case a critical design flaw is discovered.

Offline TomH

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #21 on: 10/05/2017 11:11 PM »
They will likely manufacture in blocks. My guess would be 4 in Block I. Performance, tweeks, and emerging customer demand will determine advancements incorporated in and numbers produced in successive blocks.

4? I think you underestimate the cost of BFR booster. They will be valuable hardware costing many times more than expendable rockets. They'll want to make sure and perfect the design before they build any more than they have to. Two at most for "Block I" is all I see, although as with F9 the block divisions will hazy at best. But they certainly don't want to build too many in case a critical design flaw is discovered.

They may well do one single prototype as Block 0 (like STS Enterprise), then go to Block I. I'm still guessing 4 for Block I. And of course, that is a very wild @$$ guess. And I'm looking at the word block as meaning a production run. I would not be surprised to see that spread over several years with minor changes to each booster, just as was the case with STS. But we shall see. I have to say, this discussion of what lies ahead is much more optimistically enjoyable than the one we all had re. a different monster rocket over the last 8 or so years.

Offline Zed_Noir

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #22 on: 10/06/2017 03:04 AM »
Think there will be an initial build of 3 boosters with 2 additional projected builds when BFR ASDS become available to established initial Intercontinental P2P service and polar orbit capability.

#1.  trials & spare unit (inactive)

#2. LC-39A resident unit

#3. Boca Chica resident unit

#4. New England offshore resident unit (projected)

#5. California offshore resident unit (projected)

With one new booster as each additional offshore pad come online. Plus a spare boosters for every 8note 1 active boosters.


note 1 - Or what ever number that SX decide is appropriate

Online Robotbeat

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #23 on: 10/06/2017 03:14 AM »
If ships get 100 reuses and boosters get 1000, then to get 1000 flights per year on average (and both numbers include hull losses), they need 1 BFB per year and 10 BFSes per year. 111 Raptors per year.

Pretty easy math.

I suspect early numbers will be a factor of 10 worse, so again like 1 BFB per year (3 a year at first to fill out launch sites and provide spares) and 10 BFSes, for a total of 100 flights per year, which is about what they need if the constellation works out well.

It's possible they'll need more launches if they make the constellation satellites much bigger.

So SpaceX might keep a similar production rate as they have now.
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Offline RocketmanUS

Re: How many BFR Boosters will SpaceX need to build?
« Reply #24 on: 10/06/2017 06:44 AM »
What is the turn around time for the booster for relaunch once landed back on the launch pad?
After how many flights will it have to stand down for refurb?
How many launches will there be per year?

That is part of what is needed to know for how many boosters will be needed.
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Online RonM

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #25 on: 10/06/2017 05:57 PM »
What is the turn around time for the booster for relaunch once landed back on the launch pad?
After how many flights will it have to stand down for refurb?
How many launches will there be per year?

That is part of what is needed to know for how many boosters will be needed.

SpaceX will have estimates, but no one will really know the answers to those questions until production boosters are flying. For example, the Shuttle never got anywhere near the predicted flight rate. We'll have to wait and see if SpaceX is being overly optimistic or if they can successfully do rapid turnaround.

Offline AC in NC

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #26 on: 10/07/2017 02:53 AM »
Duh!  42.

Offline tdperk

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #27 on: 10/08/2017 03:40 PM »
This just a silly thread.  Nobody knows the answer.  Not even SpaceX.

Saying SpaceX doesn't know is silly. Did NASA roll dice to determine how many Shuttles to build? Of course not. They had a plan and so does SpaceX.

"Jim" is an instantiation of a vague grumble.

Offline oldAtlas_Eguy

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Re: How many BFR Boosters will SpaceX need to build?
« Reply #28 on: 10/08/2017 09:27 PM »
Some boundings to the problem.

1- Initially the life (number of launches) capable by the two elements will be close to the same.

2- Quickly the booster will extend its life first past 5 then past 20. This will be done in only a few design iterations.

3- But the spacecraft or US however one wants to refer to it will take awhile and quite a few launches and design iterations to get the life beyond 20 or even just 5.

4- This difference in the rate of the life expansion would be represented by the differences in the build rates between the booster and SC elements. With the booster possibly even decreaseing in rate with the SC rapidly increasing in rate. A booster with life of 100 gas-n-go matched with a SC life of 20 gas-n-go would need 5 SC built for every 1 booster something similar to what SpaceX faces now with F9.

5- The general rule would be that the factor difference between will grow rapidly to a significant number before the SC maturity catches up to the almost design frozen booster.

With all of this the numbers built [my WAG]:

in the first 2 years would be: 3 boosters and 5 SC [launch/yr rate at end of period = 15]

in the first 5 years would be: 6 boosters and 20 SC ->Flying 4 boosters Life (50), 15 SC Life (10) [launch/yr rate at end of period = 50]

in the first 10 years would be: 11 boosters and 70 SC->Flying 5 boosters Life (250), 50 SC Life (25) [launch/yr rate at end of period = 200]

after that the dichotomy of build rates would start to close back


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