|
|
Thread Tools | Display Modes |
#21
|
|||
|
|||
BFS drops composite construction
On 10/12/2018 4:53 pm, Fred J. McCall wrote:
I saw a report today that SpaceX was dropping composites for tanks and main structure on BFS in favor of using "heavy metal" (Musk's phrase). It's unclear why the change, although it's probably a cost/schedule move. It's also unclear if this change is permanent or if it's only for early ships. Also unclear what impact this will have on payload, since BFR will now be lifting a much heavier BFS than was originally planned. All these changes are both bad and good. They're bad because of impacts to weight and such. They're probably good in that they indicate that we're close to actual development and that is driving changes. Scott Manley has a video about this. https://www.youtube.com/watch?v=VoegqRJKGE8 It may not be a reaction to technical difficulties with composite, but a design decision based on the specifics of the BFS. Sylvia. |
#22
|
|||
|
|||
BFS drops composite construction
Jeff Findley wrote on Mon, 24 Dec 2018
17:31:40 -0500: In article , says... JF Mezei wrote on Mon, 24 Dec 2018 12:38:00 -0500: The other argument made was that a shiny reflective surface might reflect much of the heat generated by the plasma around the skin instead of absorbing it. (but this would assume the ship's exterior is stainless steel and I doubt stainless steel has a high enough melting point, or does it?) Depends on which stainless alloy you're talking about and how high a melting point is 'high enough'. There are stainless steels that are good to temperatures of 1400 C (AISI 330). Elon Musk on Twitter 2:38 p.m. on Dec 22, 2018: Yup. Actually, the only significant design element in common with early Atlas is stainless steel & we?re using a different alloy mix. I super ?? 300 Series Stainless! The 300 series stainless is typically good to at least 1150 C with 330 being the best. -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw |
#23
|
|||
|
|||
BFS drops composite construction
JF Mezei wrote on Mon, 24 Dec 2018
21:54:31 -0500: On 2018-12-24 18:28, Sylvia Else wrote: Scott Manley has a video about this. https://www.youtube.com/watch?v=VoegqRJKGE8 It may not be a reaction to technical difficulties with composite, but a design decision based on the specifics of the BFS. That is the one I watched. It does indicate that the original plan was marketing powerpoints and as the engineers are getting to design the actual ship, they are having to make some "reality check" changes to the big picture design. That happens with every design. In a case where BFS goes above LEO, would the stainless steel skin provide protection from radiation? I doubt that it's enough to be significant. It could be that the heavy skin ends up saving weight when you factor in the need for re-entry shielding, radiation and micro meteorite that would be needed with composite skin. Last heard, SpaceX was going to use a ceramic named TUFROC-X for TPS on Starship. It's not possible to get that degree of thermal protection with metal. -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw |
#24
|
|||
|
|||
BFS drops composite construction
JF Mezei wrote on Tue, 25 Dec 2018
16:29:41 -0500: On 2018-12-24 23:46, Fred J. McCall wrote: Last heard, SpaceX was going to use a ceramic named TUFROC-X for TPS on Starship. It's not possible to get that degree of thermal protection with metal. In that case, is there really an advantage to using stainless steel for the skin instead of aluminium or titanium ? Yes, there are several. From a structural strength point of view: BFS ~ 9m diameter. A380 ~ 7m diameter. Now run the load numbers. They're nowhere near the same. Since a crewed BFS would need to support 14.7 PSI whereas an aircraft generally supports about 8PSI, does stainless steel have more strength ofor that diametre than would Aluminium or Titanium ? Aluminum is too weak and melts at half the temperature of 330 stainless. Titanium has an advantage in melting point, but is preposterously difficult to machine. -- "Ignorance is preferable to error, and he is less remote from the truth who believes nothing than he who believes what is wrong." -- Thomas Jefferson |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
(Drops of) Water on Mars! | Bluuuue Rajah | Astronomy Misc | 1 | March 27th 09 08:44 PM |
NASA Drops Requirement For Methane Engine From CEV | Space Cadet | Space Shuttle | 16 | February 6th 06 05:23 PM |
Armadillo drops peroxide... forever? | Tom Cuddihy | Policy | 36 | April 11th 05 09:22 PM |
The other shoe drops: Hubble... | Steven James Forsberg | Policy | 73 | February 5th 04 05:39 AM |
Linux is doomed as SCO drops the bomb. | Nomen | Space Shuttle | 21 | August 17th 03 07:14 PM |