Author Topic: How many BFR Boosters will SpaceX need to build?  (Read 2847 times)

Online 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.

Offline 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.

Offline 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?

Online 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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Online 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.

Online 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).

Offline 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.

Online 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 »

Offline 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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Online 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.

Offline 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 »

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