From: nospam@127.0.0.1   
      
   On 2022-09-26 1:54 AM, JF Mezei wrote:   
   > On 2022-09-23 09:58, David Spain wrote:   
   >   
   >> This is just but one example of why it's more difficult to do this when   
   >> a government agency is trying to accomplish something via contractors vs   
   >> doing it yourself.   
   >   
   >   
   >   
   > NASA had over  25 years experience with Shuttle/hydrogen and quick   
   > disconnects.   
   >   
   > The whole SLS project was specced by NASA via political pressure to   
   > maintain jobs at the contractors that did Shuttle. I would have hoped   
   > that experience from shuttle would have been transferef especially sicne   
   > NASA had experience with those contractors.   
   >   
   > But there are other worrysome things like limited battery lifetime once   
   > out of VAB for so many systems instead of powering the rocket while at   
   > pad to not deplete batteries. Just curious why this wasn't implemented.   
   > Weather delays and scrubs for technical issues are not something that   
   > are unknown.   
      
   It's not a question of powering the rocket. These batteries are used as   
   part of the flight termination system, which operates independently of   
   the SRS and controlled by range safety. I'm not sure why NASA accepted   
   such a tight operating regime for these batteries. I believe I read it   
   is 20 days after roll-out. Air Force range safety can grant extension   
   waivers on this.   
      
   >   
   > Due to IAN,  the rocket is being rolled back to VAB, so I assume they   
   > will get to change batteries at that point.   
   >   
   > One can criticise NASA's design of the system (SRBs etc), but in the   
   > past, NASA was very pedantic on testing and validating designs, so it is   
   > very strange to see components arriving on pad with less than stellar   
   > reliability especially when NASA is fully aware of difficulties of   
   > working with LH2.   
      
   As Rand Simberg points out on his blog a whole set of clocks start   
   ticking once the SLS rocket rolls out of the VAB. Two of those are the   
   SRB's themselves. They were stacked back in January of ->2021<- and have   
   essentially sat ever since. The contractor has already granted NASA one   
   extension, since originally they were only spec'd to be able to sit up   
   until September of 2021 IIRC. The issues (once again) are joint   
   integrity and propellant 'sag'. If this doesn't launch by December it's   
   not clear NASA will get another waiver and it'll be back to the VAB for   
   a restacking.   
      
   That's not actually such a bad thing. Valuable data would be had should   
   that be done. In fact, it would be wise to stack one vertically on a   
   test stand for up to two years then take it apart and see how it did.   
   Maybe an unused bay in the VAB.   
      
   The other big issue with SLS that was not so big for the Shuttle was the   
   the fact that the rotating service structure allowed a lot of work to   
   continue on the Shuttle even after it had been rolled out to the pad.   
   SLS does not have this, because why would you need to service an   
   *expendable* rocket?   
      
   Dave   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)