Author Topic: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)  (Read 76728 times)

Online Chris Bergin

Fourth discussion thread for Elon's second BFR overview at the IAC.

Previous thread:
https://forum.nasaspaceflight.com/index.php?topic=43920.0

News Articles (more to follow - we're working a 10,000 word feature article in L2 that's getting close but probably needs some SpaceX approvals) :

 [September 29, 2017] The Moon, Mars, & around the Earth - Musk updates BFR architecture, plan

 [October 4, 2017] Sputnik at 60: Ambition ties first satellite to SpaceX’s BFR, Mars plans

 Previous major discussion thread:
  IAC 2017 -- ITS (BFR) v0.2 Pre and During Speech

 Live Thread from the event:
  IAC 2017 --Elon Speech

Full video:



Additional NSF Articles Of High Relevance:

 [March. 7, 2014] SpaceX advances drive for Mars rocket via Raptor power
 [Aug. 29, 2014] Battle of the Heavyweight Rockets – SLS could face Exploration Class rival
 [Sept. 27, 2016]SpaceX reveals ITS Mars game changer via colonization plan
 [Jul. 24, 2017] Includes Subscale BFR on 39A

 Major NSF L2 Resources:

 L2 Level: Evaluations And Renderings - Thread 2 (Includes link to Thread 1)
 ITS Cargo Modules AIAA - by the Author
 Rocket and Spacecraft Traj Sim
 The Evolution of the Interplanetary Transport System Overview
 SpaceX McGregor, includes Raptor Testing and photos
 Master All SpaceX Pads Updates, Photos and Status, including for BFR


NSF Public Threads:
 
   Discussion before and during the 2017 presentation:

      IAC 2017 -- ITS v0.2
      9m ITS Development Updates and Discussion Thread

   
   Discussion after the 2016 presentation:
 
      ITS Propulsion – The evolution of the SpaceX Raptor engine
      ITS Development Updates and Discussion Thread

9m ITS Development Updates and Discussion Thread 2

Elon's presentation at IAC 2016:



SpaceX: ITS Video from 2016:


Support NSF via L2 -- Help improve NSF -- Site Rules/Feedback/Updates
**Not a L2 member? Whitelist this forum in your adblocker to support the site and ensure full functionality.**

Offline testguy

  • Full Member
  • ****
  • Posts: 607
  • Clifton, Virginia
  • Liked: 625
  • Likes Given: 599
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #1 on: 07/02/2018 01:19 am »
Congratulations to Tesla meeting the Model 3 production target.  Elon pulled out all the stops even working the production line himself.  The reason I bring this up is maybe, just maybe, the “Elon time” curse may be abating.

There has been lots of negativity discussing Elon schedules pertaining to SpaceX and BFR.  Let us give him credit when credit is due.
« Last Edit: 07/02/2018 01:22 am by testguy »

Offline ppb

  • Full Member
  • *
  • Posts: 188
  • San Francisco Bay Area
  • Liked: 202
  • Likes Given: 159
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #2 on: 07/02/2018 01:23 am »
I hope he didn't burn himself out in the process.
Congratulations to Tesla meeting the Model 3 production target.  Elon pulled out all the stops even working the production line himself.  The reason I bring this up is maybe, just maybe, the “Elon time” curse may be abating.

There has been lots of negativity discussing Elon schedules pertaining to SpaceX and BFR.  Let us give him credit when credit is due.

Online meekGee

  • Senior Member
  • *****
  • Posts: 14158
  • N. California
  • Liked: 14046
  • Likes Given: 1392
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #3 on: 07/02/2018 06:35 am »
I hope he didn't burn himself out in the process.
Congratulations to Tesla meeting the Model 3 production target.  Elon pulled out all the stops even working the production line himself.  The reason I bring this up is maybe, just maybe, the “Elon time” curse may be abating.

There has been lots of negativity discussing Elon schedules pertaining to SpaceX and BFR.  Let us give him credit when credit is due.
All these schedules are so far in advance of what was considered normal beforehad that complaining about a time dilation factor should just be embarrassing to the complainers...

-----
ABCD: Always Be Counting Down

ABCD - Always Be Counting Down

Offline Star One

  • Senior Member
  • *****
  • Posts: 13997
  • UK
  • Liked: 3974
  • Likes Given: 220
IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #4 on: 07/02/2018 10:01 am »
I hope he didn't burn himself out in the process.
Congratulations to Tesla meeting the Model 3 production target.  Elon pulled out all the stops even working the production line himself.  The reason I bring this up is maybe, just maybe, the “Elon time” curse may be abating.

There has been lots of negativity discussing Elon schedules pertaining to SpaceX and BFR.  Let us give him credit when credit is due.

I would strongly suggest we stay away from that topic considering the many eyes on here.
« Last Edit: 07/02/2018 10:02 am by Star One »

Offline Lar

  • Fan boy at large
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13463
  • Saw Gemini live on TV
  • A large LEGO storage facility ... in Michigan
  • Liked: 11864
  • Likes Given: 11086
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #5 on: 07/02/2018 07:11 pm »
I would strongly suggest we stay away from that topic considering the many eyes on here.
That's really good advice. Congrats. Mention of applicability (check) and move on. Thanks.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline Negan

  • Full Member
  • ****
  • Posts: 739
  • Southwest
  • Liked: 210
  • Likes Given: 533
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #6 on: 07/03/2018 03:23 pm »
How many tanker flights would be needed for BFS to do a circumlunar mission?

Offline envy887

  • Senior Member
  • *****
  • Posts: 8144
  • Liked: 6801
  • Likes Given: 2965
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #7 on: 07/03/2018 03:32 pm »
How many tanker flights would be needed for BFS to do a circumlunar mission?

Possibly none, for sufficiently small payload, probably around 5 tonnes.

With a single refueling flight, it could put 40 tonnes of payload though TLI and land it back on Earth with a free return.

Offline speedevil

  • Senior Member
  • *****
  • Posts: 4406
  • Fife
  • Liked: 2762
  • Likes Given: 3369
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #8 on: 07/03/2018 03:38 pm »
How many tanker flights would be needed for BFS to do a circumlunar mission?

Zero, perhaps under some assumptions one.

Lunar slingshot needs 3200m/s over LEO, or so.
If we assume the 85 ton mass often quoted is with landing fuel included, then:
235 tons ->3200m/s@370ISP -> 97 tons.
So, there may even be a little margin.

This thread goes into the detail of more complex missions.

A refilled vehicle in LEO can get around 20 tons landed on the surface and back to the surface of earth.
A refilled BFS in LEO, refilled once in extended earth orbit, with a tanker in low lunar orbit to which it offloads fuel, lands, and then returns to earth after retanking, gets around 150 tons for 8 total launches from earth.

Offline Negan

  • Full Member
  • ****
  • Posts: 739
  • Southwest
  • Liked: 210
  • Likes Given: 533
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #9 on: 07/03/2018 04:04 pm »
How many tanker flights would be needed for BFS to do a circumlunar mission?

Possibly none, for sufficiently small payload, probably around 5 tonnes.

With a single refueling flight, it could put 40 tonnes of payload though TLI and land it back on Earth with a free return.

Wow. I can certainly see why they tabled the FH circumlunar mission. Especially since BFR might be able to do it with no refueling.

Offline Negan

  • Full Member
  • ****
  • Posts: 739
  • Southwest
  • Liked: 210
  • Likes Given: 533
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #10 on: 07/03/2018 04:15 pm »
A refilled vehicle in LEO can get around 20 tons landed on the surface and back to the surface of earth.

Thia scenario has always interested me when it comes to their testing. You know they will do a full tanker fill up as a test so might as well use it for this too.
« Last Edit: 07/03/2018 04:24 pm by Negan »

Offline su27k

  • Senior Member
  • *****
  • Posts: 6414
  • Liked: 9100
  • Likes Given: 885
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #11 on: 07/04/2018 04:47 am »
Looking at the high-res photo of CRS-15 Dragon near station, it occurs to me that Dragon 2's reusable nosecone has a lot of similarities with cargo BFS' big cargo door: Both use composite material (I think), have light heat shield protection, need to stay locked during ascend and re-entry, and need to be able to open/close in space. Designing and building the former could inform the design and build of the latter.

Offline speedevil

  • Senior Member
  • *****
  • Posts: 4406
  • Fife
  • Liked: 2762
  • Likes Given: 3369
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #12 on: 07/04/2018 09:46 am »
A refilled vehicle in LEO can get around 20 tons landed on the surface and back to the surface of earth.

Thia scenario has always interested me when it comes to their testing. You know they will do a full tanker fill up as a test so might as well use it for this too.
There are reasonable concerns and arguments why landing on the moon might entail risks.
Apollo largely sidetepped them due to leaving the descent stage on the ground.
Landing a vehicle with 350 ton thrust at landing that the engines have to work again is perhaps not risk free.

There are other reasonable strategies that make it much less risky to do stuff on the moon, for example, descent and hovering while translating slowly at 50m while spending 30s throwing stuff out the airlock and then going home.

A 'hard landing' with airbags at 30mph is very survivable indeed for Tesla vehicle sized payloads.
Light modifications get you to something controllable for a week to do really deep surveying and surface modification of the landing area, for next time.

Offline niwax

  • Full Member
  • ****
  • Posts: 1422
  • Germany
    • SpaceX Booster List
  • Liked: 2040
  • Likes Given: 166
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #13 on: 07/04/2018 11:02 am »
A refilled vehicle in LEO can get around 20 tons landed on the surface and back to the surface of earth.

Thia scenario has always interested me when it comes to their testing. You know they will do a full tanker fill up as a test so might as well use it for this too.
There are reasonable concerns and arguments why landing on the moon might entail risks.
Apollo largely sidetepped them due to leaving the descent stage on the ground.
Landing a vehicle with 350 ton thrust at landing that the engines have to work again is perhaps not risk free.

There are other reasonable strategies that make it much less risky to do stuff on the moon, for example, descent and hovering while translating slowly at 50m while spending 30s throwing stuff out the airlock and then going home.

A 'hard landing' with airbags at 30mph is very survivable indeed for Tesla vehicle sized payloads.
Light modifications get you to something controllable for a week to do really deep surveying and surface modification of the landing area, for next time.

There might be issues with even getting near the surface. Exhaust gas velocities are well above orbital speeds so a landing anywhere will contaminate the entire moon with fast dust particles. There was a great post by a post-Apollo researcher recently about an instrument returned by an Apollo mission. They were told to look for a white box but when they found it it was brown. Years later they found out that millions of dust particles had lodged themselves into the paint after flying around the moon for a bit.
Which booster has the most soot? SpaceX booster launch history! (discussion)

Offline speedevil

  • Senior Member
  • *****
  • Posts: 4406
  • Fife
  • Liked: 2762
  • Likes Given: 3369
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #14 on: 07/04/2018 11:33 am »
There are other reasonable strategies that make it much less risky to do stuff on the moon, for example, descent and hovering while translating slowly at 50m while spending 30s throwing stuff out the airlock and then going home.

There might be issues with even getting near the surface. Exhaust gas velocities are well above orbital speeds so a landing anywhere will contaminate the entire moon with fast dust particles.
'The entire moon' might be a bit of a reach.
However, dust particles impinging back on the BFR, when it's above the surface, and not thrusting directly down (mostly thrusting sideways until a stop is reached, then a little circle) are going to be a very much smaller concern than possibly dropping a leg in a hole, or excavating subsurface rocks.

Offline AncientU

  • Senior Member
  • *****
  • Posts: 6257
  • Liked: 4164
  • Likes Given: 6078
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #15 on: 07/04/2018 12:07 pm »
Just as on Mars, the first BFS or two that land could just stay there.  These vehicles will 'only' cost $300-$500M apiece -- when compared to many $Billions for expendable vehicles that could deliver 150t to the Lunar surface, this price is free.

After unloading and setting up the first Lunar Village, landing pad(s) could be constructed as will need to be done on Mars.  Future vehicles could then come and go without risk of engine damage by flying debris.  The original vehicles could serve as habs, work shops, water tankage, whatever...

Note: I believe that is what the IAC2017 Moon base picture shows -- two BFSs parked near Village, and third landing and being unloaded on a pad near by.  See attachment and article.
https://www.teslarati.com/elon-musk-spacex-cities-moon-mars/
« Last Edit: 07/04/2018 12:46 pm by AncientU »
"If we shared everything [we are working on] people would think we are insane!"
-- SpaceX friend of mlindner

Offline Cheapchips

  • Full Member
  • ****
  • Posts: 1030
  • UK
  • Liked: 861
  • Likes Given: 1931
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #16 on: 07/04/2018 12:32 pm »
A refilled vehicle in LEO can get around 20 tons landed on the surface and back to the surface of earth.

Thia scenario has always interested me when it comes to their testing. You know they will do a full tanker fill up as a test so might as well use it for this too.
There are reasonable concerns and arguments why landing on the moon might entail risks.
Apollo largely sidetepped them due to leaving the descent stage on the ground.
Landing a vehicle with 350 ton thrust at landing that the engines have to work again is perhaps not risk free.

There are other reasonable strategies that make it much less risky to do stuff on the moon, for example, descent and hovering while translating slowly at 50m while spending 30s throwing stuff out the airlock and then going home.

A 'hard landing' with airbags at 30mph is very survivable indeed for Tesla vehicle sized payloads.
Light modifications get you to something controllable for a week to do really deep surveying and surface modification of the landing area, for next time.

Cold gas thrusters could presumably do the job of airbags too.

Offline spacenut

  • Senior Member
  • *****
  • Posts: 5181
  • East Alabama
  • Liked: 2587
  • Likes Given: 2895
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #17 on: 07/04/2018 12:46 pm »
From what I understand, BFS (Big Falcon Spaceship) will be built first and tested.  It will be a SSTO vehicle with very little payload. 

For missions to and from the moon, it would require the BFR (Big Falcon Rocket) first stage booster to be built to lift the BFS.  That is unless the BFS can be refueled in LEO with tankers or a fuel depot. 

BFS requires far more development and testing.  They have already landed a first stage with F9.  So building a BFR would be much easier.

So unless you guys are talking about refueling a test BFS in LEO to do a moon mission test.  It would have to be refueled with a FH or multiple F9 vehicles.   

Offline AncientU

  • Senior Member
  • *****
  • Posts: 6257
  • Liked: 4164
  • Likes Given: 6078
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #18 on: 07/04/2018 07:20 pm »
From what I understand, BFS (Big Falcon Spaceship) will be built first and tested.  It will be a SSTO vehicle with very little payload. 

For missions to and from the moon, it would require the BFR (Big Falcon Rocket) first stage booster to be built to lift the BFS.  That is unless the BFS can be refueled in LEO with tankers or a fuel depot. 

BFS requires far more development and testing.  They have already landed a first stage with F9.  So building a BFR would be much easier.

So unless you guys are talking about refueling a test BFS in LEO to do a moon mission test.  It would have to be refueled with a FH or multiple F9 vehicles.

BFS will probably not even fly to orbit without BFR.  The spaceship is just getting a couple years head start in development because of the new flight regime of belly-first reentry, while flight testing the Raptors and carbon tankage.  Missions to the moon and significant cargo operations all assume BFR is operating.  2020 is target for testing the booster... which will probably quickly become orbital operations for the spaceship.  The factory is being built in LA; serious foundation work underway.
https://www.teslarati.com/spacex-bfr-factory-construction-mr-steven-arm-surgery/

As noted above, even using FH to refuel BFS is nearly impossible.  BFS is simply a vastly larger spaceship* and will need equivalent sized tankers. 

Oops... the mass figures below were for the 2016 version of BFS... 2017 version is ~30% more massive (BFS -- 1,335t =1185t wet mass plus 150t payload vs 1045t wet mass for the SLS core)
*Note: For calibration, the BFS is approximately the size and double wet mass of the SLS core stage with approaching double the propulsive thrust.  This is a B-I-G F'n Spaceship.
https://www.nasa.gov/sites/default/files/thumbnails/image/core_stage_infographic_reboot.jpg
« Last Edit: 07/04/2018 09:00 pm by AncientU »
"If we shared everything [we are working on] people would think we are insane!"
-- SpaceX friend of mlindner

Offline marsbase

  • Full Member
  • ****
  • Posts: 429
  • North Carolina
  • Liked: 480
  • Likes Given: 82
Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 4 (Post Speech)
« Reply #19 on: 07/04/2018 08:49 pm »

*Note: For calibration, the BFS is approximately the size and double wet mass of the SLS core stage with approaching double the propulsive thrust.  This is a B-I-G F'n Spaceship.
https://www.nasa.gov/sites/default/files/thumbnails/image/core_stage_infographic_reboot.jpg
In all the discussions of refueling I haven't seen an estimate of how may BFS tankers it takes to refuel an empty BFS in LEO.  Is it 150 tons of fuel per tanker? How many does it take?

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
1