Author Topic: Elon Musk Reddit AMA  (Read 24299 times)

Offline p18582010

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Elon Musk Reddit AMA
« on: 10/23/2016 02:45 pm »
Not sure if this is the right place to post this but, Elon Musk is doing an AMA on r/SpaceX subreddit at 22:00 UTC, today, October 23rd.
Announcement thread: https://www.reddit.com/r/spacex/comments/58yc14/elon_musk_will_be_doing_an_ama_on_rspacex_at_3pm/
« Last Edit: 10/23/2016 02:58 pm by p18582010 »

Online FutureSpaceTourist

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Re: Elon Musk Reddit AMA
« Reply #1 on: 10/23/2016 04:45 pm »
Quote
23/10/2016 13:17 UTC

Announcement: T minus 9 hours until @elonmusk's AMA in r/SpaceX. Get ready for an epic Q&A session to follow on from the epic IAC 2016!

https://twitter.com/rspacex/status/790180225749483523

Online FutureSpaceTourist

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Re: Elon Musk Reddit AMA
« Reply #2 on: 10/23/2016 07:24 pm »
Quote
This will be under /r/spacex, not the general AMA. Meant to be supplemental to the IAC talk.

https://twitter.com/elonmusk/status/790267936258666496

Offline yokem55

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Re: Elon Musk Reddit AMA
« Reply #3 on: 10/23/2016 10:30 pm »

Offline savuporo

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Re: Elon Musk Reddit AMA
« Reply #4 on: 10/23/2016 11:42 pm »
Some really important new insights in there, like

https://www.reddit.com/r/spacex/comments/590wi9/i_am_elon_musk_ask_me_anything_about_becoming_a/d94trp9/

Quote
I think we need a new name. ITS just isn't working. I'm using BFR and BFS for the rocket and spaceship, which is fine internally, but...
Orion - the first and only manned not-too-deep-space craft

Offline Rangers75

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Re: Elon Musk Reddit AMA
« Reply #5 on: 10/23/2016 11:50 pm »
Shame he only answered 10 or so questions, a few with a Jim style response ;D Not much new in there, mainly expansions on what he's talked about, but that was the point, per the IAC. At least the top question wasn't asking him what his favorite animal was this time! ;D Best responses come from him during post mission breifings on NASA TV where he tends to open him up as he's talking, not thinking too much as he's typing, but I'm glad he's active on social media. He started that trend and now we have Tory Bruno tweeting like crazy!

Online pippin

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Elon Musk Reddit AMA
« Reply #6 on: 10/23/2016 11:51 pm »
Argh. "Block 5". Is it a stated Elon goal to invent a new naming scheme for each iteration of F9?

Edit: and yes, simultaneously a new name for the SAME iteration of MCT/ITS/BFS,...
« Last Edit: 10/23/2016 11:52 pm by pippin »

Offline mfck

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Re: Elon Musk Reddit AMA
« Reply #7 on: 10/24/2016 12:20 am »
Quote

ElonMuskOfficial - CEO of SpaceX
46m

Those are the header tanks that contain the landing propellant. They are separate in order to have greater insulation and minimize boil-off, avoid sloshing on entry and not have to press up the whole main tank.



If they don't press main tanks for EDL, what does that suggest about BFS structure? We know carbon main tank IS a structural member from the IAC presentation, iirc. Does it mean the unpressurised tank can take a compression load of the payload mass times gravity times acceleration at landing? Or is it offloaded axially via the three ribs and only helps against twist and lateral forces?

« Last Edit: 10/24/2016 12:24 am by mfck »

Offline nacnud

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Re: Elon Musk Reddit AMA
« Reply #8 on: 10/24/2016 12:27 am »
Quick note:

ITS and Tanker to have split body flaps for roll and pitch, RCS for yaw

Offline savuporo

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Re: Elon Musk Reddit AMA
« Reply #9 on: 10/24/2016 12:34 am »
Shame he only answered 10 or so questions..

Nevertheless, these will be now carved in the Tablets of Stone Composite and placed in the Ark COPV i suppose by the followers.
Orion - the first and only manned not-too-deep-space craft

Offline nacnud

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Re: Elon Musk Reddit AMA
« Reply #10 on: 10/24/2016 12:34 am »
More:

Paraphrasing 'ITS tanks inside tanks are for the landing propellants, so don't have to pressurised/insulate whole tanks booster only has one header tank as the other is the feed line leading through the fuel tank.' 

Offline nacnud

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Re: Elon Musk Reddit AMA
« Reply #11 on: 10/24/2016 12:42 am »
Even more:

Paraphrasing (Talking about the development large composite tank) 'Going to test it to 2/3 burst pressure on a barge in the next few weeks'

Offline mfck

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Re: Elon Musk Reddit AMA
« Reply #12 on: 10/24/2016 12:44 am »


Shame he only answered 10 or so questions..

Nevertheless, these will be now carved in the Tablets of Stone Composite and placed in the Ark COPV i suppose by the followers.

The sarcasm ate the point of your comment. What was it you've been trying to convey?

Offline nacnud

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Re: Elon Musk Reddit AMA
« Reply #13 on: 10/24/2016 12:46 am »
The rest is mostly questions where the answer is TBC

Online gongora

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Re: Elon Musk Reddit AMA
« Reply #14 on: 10/24/2016 12:50 am »
Questions and Answers from the I am Elon Musk, ask me anything about becoming a spacefaring civ! AMA on the /r/spacex Reddit site pertaining to reentry and landing:


https://www.reddit.com/r/spacex/comments/590wi9/i_am_elon_musk_ask_me_anything_about_becoming_a/d94vcmw/?context=3
Quote
Question from __Rocket__

ITS Spaceship design question II.:

The ITS Spaceship has two mystical spherical tanks, marked green in this slightly edited image. The whole tank design looks very exciting, and there's rampant speculation on this sub about the purpose of those spherical tanks:

    are they for landing fuel?
    ... or are they storing 'hot' gaseous propellants as part of the autogenous propellant pressurization system?
    ... or are they used for on-orbit propellant densification to store vapor before it's liquefied again?

All of the above perhaps?



Answer from /u/ElonMuskOfficial

Those are the header tanks that contain the landing propellant. They are separate in order to have greater insulation and minimize boil-off, avoid sloshing on entry and not have to press up the whole main tank.


https://www.reddit.com/r/spacex/comments/590wi9/i_am_elon_musk_ask_me_anything_about_becoming_a/d94vdk1/?context=3
Quote
Question from /u/_rocketboy

Also, why does the booster only have one in 1 tank?



Answer from /u/ElonMuskOfficial

The liquid oxygen transfer tube serves as the header tank for ox

https://www.reddit.com/r/spacex/comments/590wi9/i_am_elon_musk_ask_me_anything_about_becoming_a/d94v8p8/?context=3
Quote
Question from /u/FoxhoundBat

    Overall is the landing architecture of ITS booster and distances needed to be covered to be same as Falcon 9s? Boostback, re-entry burn, landing burn?

    Could you give us nuggets on what changes the final Falcon 9 version (v1.3) you mentioned will have? Uprated engines obviously from 170k to 190k lbf, but what else? Is it mostly geared towards reusabilty over performance?

    Gwynne mentioned 2 weeks ago that F9 v1.2 will be reused only once or twice while v1.3 should be reused up to 10 times. Can you talk about what are the limiting factors for Falcon 9 reuse?



Answer from /u/ElonMuskOfficial
The big booster will have an easier time of things than Falcon, as the mass ratio of the stages is lower and it will have lower density. Net result is that it won't come in quite as hot and fast as Falcon, so Falcon should be a bounding case on the big booster.

Final Falcon 9 has a lot of minor refinements that collectively are important, but uprated thrust and improved legs are the most significant.

Actually, I think the F9 boosters could be used almost indefinitely, so long as there is scheduled maintenance and careful inspections. Falcon 9 Block 5 -- the final version in the series -- is the one that has the most performance and is designed for easy reuse, so it just makes sense to focus on that long term and retire the earlier versions. Block 5 starts production in about 3 months and initial flight is in 6 to 8 months, so there isn't much point in ground testing Block 3 or 4 much beyond a few reflights.

https://www.reddit.com/r/spacex/comments/590wi9/i_am_elon_musk_ask_me_anything_about_becoming_a/d94ukv8/?context=3
Quote
Question from /u/termderd

We got a pretty good idea of what a Mars EDL looks like, but can you explain how the ITS and the Tanker plan to do an Earth EDL? Having talked with you at IAC about the Mars entry, we learned that there's very powerful thrusters that can handle attitude control. These work great for the Martian atmosphere, but what about on earth? There doesn't appear to be grid fins and the thrusters obviously have less authority here on earth, so what's the trick?

Thanks for your time!

    Tim Dodd, The Everyday Astronaut



Answer from /u/ElonMuskOfficial

Good question -- that wasn't shown at IAC. The spaceship and tanker would have split body flaps for pitch and roll. Probably just use the attitude control thrusters for yaw.

https://www.reddit.com/r/spacex/comments/590wi9/i_am_elon_musk_ask_me_anything_about_becoming_a/d94ub7h/?context=3
Quote
Question from /u/Tesla_X_City:
If I recall correctly on one of the slides it mentioned that there it will be 4-6 G's upon reentry. It does not specify, however, whether that will be during the landing burn or aerobreaking. It would be nice if that is clarified as well.



Answer from /u/ElonMuskOfficial

The spaceship would be limited to around 5 g's nominal, but able to take peak loads 2 to 3 times higher without breaking up.

Booster would be nominal of 20 and maybe 30 to 40 without breaking up.

https://www.reddit.com/r/spacex/comments/590wi9/i_am_elon_musk_ask_me_anything_about_becoming_a/d94u6zk/?context=3
Quote
Question from /u/TheVehicleDestroyer

Hi Elon. Ive got 3 questions on the ITS vehicle specs:

    Can you divulge what the Vacuum Thrust+Isp figures are for the Sea-Level Raptor variant?

    The ITS booster is able to hover. Will it ever use this capability to better ensure a successful landing at the expense of some small gravity losses, or is it hoverslams all the way?

    What is the expected maximum acceleration that the ITS booster can withstand during entry/landing?

Thanks for everything.



Answer from /u/ElonMuskOfficial

    Approx 360 sec vacuum Isp and 290 metric tons of thrust
    A high acceleration landing is a lot more efficient, so there wouldn't be any hovering unless it encountered a problem or unexpected wind conditions. A rocket that lands slowly is wasting a lot of fuel.
    Aiming for 20 g's


« Last Edit: 10/24/2016 01:04 am by gongora »

Offline Seamus

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Re: Elon Musk Reddit AMA
« Reply #15 on: 10/24/2016 12:59 am »
The one answer that particularly piqued my interest was mentioning the plural "tests" of the Raptor not showing any degradation of the turbopump.  While that probably just meant tests on the turbopump and not the full engine, it would be nice to know if there have been any additional firings at McGregor.  Haven't seen a hint of that L2 or public....

Online gongora

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Re: Elon Musk Reddit AMA
« Reply #16 on: 10/24/2016 01:04 am »
Questions and Answers from the I am Elon Musk, ask me anything about becoming a spacefaring civ! AMA on the /r/spacex Reddit site pertaining to initial missions to Mars:

https://www.reddit.com/r/spacex/comments/590wi9/i_am_elon_musk_ask_me_anything_about_becoming_a/d94ss5a/?context=3
Quote
Question from /u/El-Psy-Kangaroo

What equipment and procedures will be required for refueling operations on Mars? Will they be designed to function autonomously for the initial unmanned test flight?

Also, are there any plans to introduce a third variant of the ITS with just a large shuttle-like payload bay to allow for transporting bulkier cargo?



Answer from /u/ElonMuskOfficial

We are still far from figuring this out in detail, but the current plan is:

    Send Dragon scouting missions, initially just to make sure we know how to land without adding a crater and then to figure out the best way to get water for the CH4/O2 Sabatier Reaction.

    Heart of Gold spaceship flies to Mars loaded only with equipment to build the propellant plant.

    First crewed mission with equipment to build rudimentary base and complete the propellant plant.

    Try to double the number of flights with each Earth-Mars orbital rendezvous, which is every 26 months, until the city can grow by itself.


https://www.reddit.com/r/spacex/comments/590wi9/i_am_elon_musk_ask_me_anything_about_becoming_a/d94t2bv/?context=3
Quote
Question from /u/Ulysius

As a follow-up, considering the synodal reuse of the ITS spaceships, what form of permanent habitation do you foresee? Shipped modules or an (eventual) shift to in-situ resource utilization such as Martian rigolith/plastic-reinforced concrete structures?

Thank you for your time.



Answer from /u/ElonMuskOfficial

Initially, glass panes with carbon fiber frames to build geodesic domes on the surface, plus a lot of miner/tunneling droids. With the latter, you can build out a huge amount of pressurized space for industrial operations and leave the glass domes for green living space.

https://www.reddit.com/r/spacex/comments/590wi9/i_am_elon_musk_ask_me_anything_about_becoming_a/d94txm0/?context=3
Quote
Question from /u/theZcuber

As an add-on, how differently will the ITS be configured internally for a smaller crew (such as the first one) vs. a full 100-man crew?



Answer from /u/ElonMuskOfficial

Probably just pack the pressurized space with cargo. Early missions will be heavily weighted towards cargo. First crewed mission would have about a dozen people, as the goal will be to build out and troubleshoot the propellant plant and Mars Base Alpha power system.


Offline Pipcard

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Re: Elon Musk Reddit AMA
« Reply #17 on: 10/24/2016 01:08 am »
Quote
First crewed mission with equipment to build rudimentary base and complete the propellant plant.

And you get the whole "they have no way to return" problem. A concerned comment (not mine) got downvoted for it, but I guess it's easier than automating the water mining process. But it has to work.
« Last Edit: 10/24/2016 01:13 am by Pipcard »

Offline Robotbeat

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Re: Elon Musk Reddit AMA
« Reply #18 on: 10/24/2016 01:08 am »
Big news to me seems to be he doesn't even plan on having the propellant plant necessarily fully operational before the first people arrive. That, I think, implies there won't be a full mission cycle done before the first crew launches  although there will be an uncrewed landing (and almost certainly many EDL tests near Earth beforehand) and there WILL be multiple BFSes on Mars at that time, so they could still do a test launch with one of them before boarding for a return trip. But that's different from what I understood before. Looks more and more like Musk is going for an architecture which embraces Mars as a permanent human establishment from the get-go, not pussy-footing it at all.
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Online docmordrid

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Re: Elon Musk Reddit AMA
« Reply #19 on: 10/24/2016 01:09 am »
The one answer that particularly piqued my interest was mentioning the plural "tests" of the Raptor not showing any degradation of the turbopump.  While that probably just meant tests on the turbopump and not the full engine, it would be nice to know if there have been any additional firings at McGregor.  Haven't seen a hint of that L2 or public....

The full answer implies they've been doing some materials development,

"It used to be developing a new metal alloy that is extremely resistant to oxidation for the hot oxygen-rich turbopump, which is operating at insane pressure to feed a 300 bar main chamber. Anything that can burn, will burn. We seem to have that under control, as the Raptor turbopump didn't show erosion in the test firings, but there is still room for optimization."
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