Author Topic: Mini-Super Heavy (BFR) ship F9 Second Stage  (Read 107468 times)

Offline Oli

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #200 on: 11/08/2018 10:36 pm »

Good assumptions:
- Non-destructive recovery...

I don't believe this is a good assumption. 

I think this is a test vehicle. It's main purpose is to gather data for the real BFS.

I'm sure they want to inspect the TPS after reentry.

Offline John Alan

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #201 on: 11/09/2018 12:01 am »
A test vehicle with proper instrumentation and sensors embedded in the OML hull is all that is needed to verify the TPS works good enough to risk the full size BFS test article later in re-entry testing...

My take is SpaceX wants to retire the question of
"we can really control a BFS re-entering in this fashion and it will arrive at under Mach 1 and X altitude in one piece"
... period.

It will be a self funded research program with no customer payloads and no starlink either...
Just use of a spare S1 which is recovered and reused...
The test stage will then fly over a SpX research ship, downloading reams of data before crashing into the sea...
May even be photographic assets on the same ship, taking hull pics for later review...
No Recovery... no time wasted and @ low cost by June '19

May even be a series of one a month for 6 months planned to make sure they can complete by time BFS get to that stage in it's test program... late '19/early 20'

On edit... point is...
They likely are thinking... we can build, fly and trash 6 mini's in 6 months for the cost of one BFS spare hull...
The data is priceless... the possible time savings huge.... just do it...

 ;)
« Last Edit: 11/09/2018 12:14 am by John Alan »

Offline speedevil

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #202 on: 11/09/2018 12:04 am »
A test vehicle with proper instrumentation and sensors embedded in the OML hull is all that is needed to verify the TPS works good enough to risk the full size BFS test article later in re-entry testing...
That isn't quite true.
There can be limited to no risk to the test article if you can refly the full scale BFS test article simply at gradually increasing heatloads, with adequate sensors.
It would be very useful for 'no, this isn't going to work at all' determination in that it could shave time from exploring dead ends.

Offline lonestriker

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #203 on: 11/09/2018 09:07 am »
A test vehicle with proper instrumentation and sensors embedded in the OML hull is all that is needed to verify the TPS works good enough to risk the full size BFS test article later in re-entry testing...

My take is SpaceX wants to retire the question of
"we can really control a BFS re-entering in this fashion and it will arrive at under Mach 1 and X altitude in one piece"
... period.

It will be a self funded research program with no customer payloads and no starlink either...
Just use of a spare S1 which is recovered and reused...
The test stage will then fly over a SpX research ship, downloading reams of data before crashing into the sea...
May even be photographic assets on the same ship, taking hull pics for later review...
No Recovery... no time wasted and @ low cost by June '19

May even be a series of one a month for 6 months planned to make sure they can complete by time BFS get to that stage in it's test program... late '19/early 20'

On edit... point is...
They likely are thinking... we can build, fly and trash 6 mini's in 6 months for the cost of one BFS spare hull...
The data is priceless... the possible time savings huge.... just do it...

 ;)

Paying for just the testing by itself would be very un-SpaceX-like.  If they are going to self-fund the tests, at a minimum, I would expect them to throw a bunch of Starlink satellites up before they do the mini-BFS reentry tests.  We know SpaceX likes to iteratively design and test as they fly, so I would expect them to do these tests as part of a normal launch (though with their own payload at least initially, as to avoid any risk or disruptions for paying customers.)  They can increase the cadence of the fairing recovery attempts at the same time and perfect that.  So it would eventually be down to the cost of S2, fuel and launch costs to put Starlink satellites up and get mini-BFR testing "for free".

Offline Slarty1080

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #204 on: 11/09/2018 11:53 am »
A test vehicle with proper instrumentation and sensors embedded in the OML hull is all that is needed to verify the TPS works good enough to risk the full size BFS test article later in re-entry testing...
That isn't quite true.
There can be limited to no risk to the test article if you can refly the full scale BFS test article simply at gradually increasing heatloads, with adequate sensors.
It would be very useful for 'no, this isn't going to work at all' determination in that it could shave time from exploring dead ends.

The problem is they are using a very novel solution with 4 adjustable "fins" on a new vehicle flying in an environment that is not properly understood and is very difficult to simulate. The first one or two attempts could easily fail and failure with a prototype BFS would be more expensive than failure with a SFS by an order of magnitude.
My optimistic hope is that it will become cool to really think about things... rather than just doing reactive bullsh*t based on no knowledge (Brian Cox)

Online JamesH65

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #205 on: 11/09/2018 12:12 pm »
I seriously doubt any customers would be happy for a completely different and untested 2nd stage to be used for their very expensive payload launch. Especially one with aero surfaces poking out.

Since SpaceX have reusable first stages, the actual cost of a flight for this vehicle is really just the cost of fuel, plus the cost the modified second stage. So actually, they don't need a paying customer, it's really only the cost of fuel they need to find extra (Minus any launch costs of course) since the 2nd stage would have to be built anyway.

Offline speedevil

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #206 on: 11/09/2018 12:20 pm »
A test vehicle with proper instrumentation and sensors embedded in the OML hull is all that is needed to verify the TPS works good enough to risk the full size BFS test article later in re-entry testing...
That isn't quite true.
There can be limited to no risk to the test article if you can refly the full scale BFS test article simply at gradually increasing heatloads, with adequate sensors.
It would be very useful for 'no, this isn't going to work at all' determination in that it could shave time from exploring dead ends.

The problem is they are using a very novel solution with 4 adjustable "fins" on a new vehicle flying in an environment that is not properly understood and is very difficult to simulate. The first one or two attempts could easily fail and failure with a prototype BFS would be more expensive than failure with a SFS by an order of magnitude.

If your launch costs you $3M for BFS, then a really gradual campaign increasing heat loads by only a handful of percent a time is quite plausible.
It would seriously risk the vehicle to go full orbital loads first.

Offline Slarty1080

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #207 on: 11/09/2018 12:44 pm »
A test vehicle with proper instrumentation and sensors embedded in the OML hull is all that is needed to verify the TPS works good enough to risk the full size BFS test article later in re-entry testing...
That isn't quite true.
There can be limited to no risk to the test article if you can refly the full scale BFS test article simply at gradually increasing heatloads, with adequate sensors.
It would be very useful for 'no, this isn't going to work at all' determination in that it could shave time from exploring dead ends.

The problem is they are using a very novel solution with 4 adjustable "fins" on a new vehicle flying in an environment that is not properly understood and is very difficult to simulate. The first one or two attempts could easily fail and failure with a prototype BFS would be more expensive than failure with a SFS by an order of magnitude.

If your launch costs you $3M for BFS, then a really gradual campaign increasing heat loads by only a handful of percent a time is quite plausible.
It would seriously risk the vehicle to go full orbital loads first.

Perhaps but Musk being Musk is impatient and it would seem that they want to get everything done in a rush. They will tackle the problem from both "ends" at once to keep the time scale tight. The first BFR prototype will hop higher and higher and faster and faster up to perhaps to sub orbital supersonic speeds. Meanwhile the SFS will drop out of orbit to tackle the orbital and hypersonic / re-entry side of the flight.

Also the launch cost for a prototype BFS will not be 3 million. The cost of construction will be large and the number of flights it will make will probably not be that large before they lose it bend it or retire it.
My optimistic hope is that it will become cool to really think about things... rather than just doing reactive bullsh*t based on no knowledge (Brian Cox)

Offline speedevil

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #208 on: 11/09/2018 12:49 pm »
They will tackle the problem from both "ends" at once to keep the time scale tight. The first BFR prototype will hop higher and higher and faster and faster up to perhaps to sub orbital supersonic speeds. Meanwhile the SFS will drop out of orbit to tackle the orbital and hypersonic / re-entry side of the flight.
Tackling the problem from both ends is of course the right solution here.
Either end can be stretched if the data is slow in coming because you're having problems with that end.
Being able to stretch all the way up to no external data needed for BFS is nice, but won't result in the fastest development.
It is good for development security.

Offline su27k

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #209 on: 11/09/2018 12:54 pm »
Paying for just the testing by itself would be very un-SpaceX-like. 

SpaceX paid plenty of tests by themselves: Grasshopper, F9R-Dev1/2, subscale Raptor (partially funded by USAF but majority is paid by SpaceX), first Falcon Heavy, recent fairing drop test with Mr. Steven.

Online edzieba

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #210 on: 11/09/2018 01:36 pm »
Existing materials will be used no composite tanks. IMO to keep things simple.
I think CF construction is a necessity of TPS tests. The TPS is not just the externally exposed material, but also the mounting hardware of that material to the vehicle itself (solid enough to hold it in place against significant force, insubstantial enough not to transmit heat through conduction).
SpaceX already have tooling for F9 diameter CF composite cylinders (interstage) and a F9 diameter nosecone (F9H nosecones), so using the same tube-and-cap assembly method as BFR and BFS will use allows for existing tooling to produce the mini-BFS.

Offline speedevil

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #211 on: 11/09/2018 02:18 pm »
Existing materials will be used no composite tanks. IMO to keep things simple.
I think CF construction is a necessity of TPS tests. The TPS is not just the externally exposed material, but also the mounting hardware of that material to the vehicle itself (solid enough to hold it in place against significant force, insubstantial enough not to transmit heat through conduction).
SpaceX already have tooling for F9 diameter CF composite cylinders (interstage) and a F9 diameter nosecone (F9H nosecones), so using the same tube-and-cap assembly method as BFR and BFS will use allows for existing tooling to produce the mini-BFS.
We know they changed the fairing construction in 2018, and have said that a stretched fairing is easy.

Is it ridiculous to imagine it might be a more-or-less stock fairing, stretched by some 6m or so, attached to S1 without the normal interstage?

Merlin engine is nearly wholly enclosed, additional aerosurfaces on the outside, not as faired in as the nominal BFS.

Initial launch may even be of a system without any way to get a payload out, prioritising chances of recovery.
Fairing payload volume may be reduced if this was developed to the point of flying cargo.

Offline lonestriker

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #212 on: 11/09/2018 02:43 pm »
Paying for just the testing by itself would be very un-SpaceX-like. 

SpaceX paid plenty of tests by themselves: Grasshopper, F9R-Dev1/2, subscale Raptor (partially funded by USAF but majority is paid by SpaceX), first Falcon Heavy, recent fairing drop test with Mr. Steven.

My point is that they would not waste "free" testing nor an opportunity to get multiple benefits from roughly the same amount of money spent.  Grasshopper/F9R-Dev, and Raptor development are just test or development platforms that you can't bolt-on more use.

Flying missions for customers and then using the "free" S1/fairings to test recovery options is quintessential SpaceX.  So it would be natural to extend this to S2.

Assuming Elon meant minimal changes to S2, then if they're going to be sending S2 into orbit for testing, there's no reason not to throw Starlink satellites up at the same time.  Fly it enough times for themselves and they could certify that configuration for customers (the wings should be passive on ascent, so should be relatively easy to show data and convince customers that it doesn't add more risk.)  If they can recover S2 (helicopters, bouncy castles, whatever), then it might eventually be possible to reuse the stage if BFR isn't ready for Starlink deployment on time.


Offline AncientU

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #213 on: 11/09/2018 03:01 pm »
They will tackle the problem from both "ends" at once to keep the time scale tight. The first BFR prototype will hop higher and higher and faster and faster up to perhaps to sub orbital supersonic speeds. Meanwhile the SFS will drop out of orbit to tackle the orbital and hypersonic / re-entry side of the flight.
Tackling the problem from both ends is of course the right solution here.
Either end can be stretched if the data is slow in coming because you're having problems with that end.
Being able to stretch all the way up to no external data needed for BFS is nice, but won't result in the fastest development.
It is good for development security.

This is exactly what they did with Falcon first stage... Grasshopper from ground up and water landing boosters from top down.  Recall that it was shortly after EM said 'we have all the pieces' that ASDS landing attempts began.
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Offline RoboGoofers

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #214 on: 11/09/2018 04:12 pm »
a lot of the confusion relates to how people are reading his tweet and filling in the left out words or letters.

a)
Quote
Mod to SpaceX tech tree build: The Falcon 9 second stage will be upgraded to be like a mini-BFR Ship
b)
Quote
Mod to SpaceX tech tree build: Falcon 9 second stages will be upgraded to be like a mini-BFR Ship
c)
Quote
Mod to SpaceX tech tree build: A Falcon 9 second stage will be upgraded to be like a mini-BFR Ship

Any of these readings are reasonable. I suspect it'll be like option c) because there are many unknowns that a test article will answer, so even if the might eventually move to a upgraded S2 it will be a couple years in the offing since they need the tests to prove it's worth switching over to.

Are MVacs even reusable, and if so, will they still be reusable after this type of reentry?
They would still need regular S2s for BLEOs

Offline John Alan

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #215 on: 11/09/2018 04:29 pm »
Are MVacs even reusable, and if so, will they still be reusable after this type of reentry?
They would still need regular S2s for BLEOs

My guess is they will use a regular M1D on these S2 test objects... Used ones even...
After all, it's just going to be crashed after the test, and data download phase, it's said...
They really don't NEED an Mvac's ISP performance to accelerate the test item to orbit and then lightly brake burn it into setup for a max aero braking re-entry... do they?...  ;)

Offline Slarty1080

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #216 on: 11/09/2018 04:32 pm »
Are MVacs even reusable, and if so, will they still be reusable after this type of reentry?
They would still need regular S2s for BLEOs

My guess is they will use a regular M1D on these S2 test objects... Used ones even...
After all, it's just going to be crashed after the test, and data download phase, it's said...
They really don't NEED an Mvac's ISP performance to accelerate the test item to orbit and then lightly brake burn it into setup for a max aero braking re-entry... do they?...  ;)

Good point. They could take an older pre-block 5 core that will not fly again and strip out the Merlins for use a stage 2 engines.
My optimistic hope is that it will become cool to really think about things... rather than just doing reactive bullsh*t based on no knowledge (Brian Cox)

Offline whitelancer64

Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #217 on: 11/09/2018 04:49 pm »
They will tackle the problem from both "ends" at once to keep the time scale tight. The first BFR prototype will hop higher and higher and faster and faster up to perhaps to sub orbital supersonic speeds. Meanwhile the SFS will drop out of orbit to tackle the orbital and hypersonic / re-entry side of the flight.
Tackling the problem from both ends is of course the right solution here.
Either end can be stretched if the data is slow in coming because you're having problems with that end.
Being able to stretch all the way up to no external data needed for BFS is nice, but won't result in the fastest development.
It is good for development security.

This is exactly what they did with Falcon first stage... Grasshopper from ground up and water landing boosters from top down.  Recall that it was shortly after EM said 'we have all the pieces' that ASDS landing attempts began.

Ah, history. Remember that the Grasshopper program was intended to perfect the landings to a greater extent than they actually did. The F9R Dev1 and the (ultimately unused) F9R Dev2 were supposed to launch up to 300,000 ft and then land, but SpaceX never used its leased pads at Spaceport America for that because they learned so much from the "soft splashdown" water landings after operational launches.

I suspect this "mini BFS" is bullring on the lessons learned from that. SpaceX now knows they can test both sides towards the middle.
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Offline Norm38

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Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #218 on: 11/09/2018 04:55 pm »

Flying missions for customers and then using the "free" S1/fairings to test recovery options is quintessential SpaceX.  So it would be natural to extend this to S2.

Assuming Elon meant minimal changes to S2, then if they're going to be sending S2 into orbit for testing, there's no reason not to throw Starlink satellites up at the same time.

I don't think minimal changes to S2 was implied, else he would have said that.  He would have said something like "We will be making incremental changes to S2 and perform re-entry experiments.  But he specifically said "mini-BFR" not "modded S2".

It isn't "free" to use the fairings as they are jettisoned shortly after staging.  There's no evidence they can be easily modified with hinges to remain attached, open up, and close back up, then survive re-entry stresses.  There is an insane amount of work to be done to make that happen, no data that the aerodynamics will work, and a large risk that if the fairings don't close back up properly, the experiment won't yield any data, which is the whole point.

They may very well want to get to that point, but my gut says they want to prove to themselves they can survive re-entry and lock down the outer mold line before going to the effort of making it be able to dispense a payload.

Offline whitelancer64

Re: Mini-Super Heavy (BFR) ship F9 Second Stage
« Reply #219 on: 11/09/2018 04:59 pm »

Flying missions for customers and then using the "free" S1/fairings to test recovery options is quintessential SpaceX.  So it would be natural to extend this to S2.

Assuming Elon meant minimal changes to S2, then if they're going to be sending S2 into orbit for testing, there's no reason not to throw Starlink satellites up at the same time.

I don't think minimal changes to S2 was implied, else he would have said that.  He would have said something like "We will be making incremental changes to S2 and perform re-entry experiments.  But he specifically said "mini-BFR" not "modded S2".

*snip*

"Falcon 9 second stage will be upgraded to be like a mini-BFR Ship"

https://twitter.com/elonmusk/status/1060253333116473344
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
"There are lies, damned lies, and launch schedules." - Larry J

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