From: niklas.holsti@tidorum.invalid   
      
   On 2024-02-24 13:44, The Running Man wrote:   
   > On 23/02/2024 21:51 Alain Fournier  wrote:   
   >> On 2024-02-23 6:34 p.m., Snidely wrote:   
   >>> On Friday, Snidely exclaimed wildly:   
   >>>> After serious thinking Alain Fournier wrote :   
   >>>>> Intuitive Machines had a lander touchdown on the moon a little over   
   >>>>> an hour ago.   
   >>>>>   
   >>>>> Unfortunately communications with the spacecraft seem to be iffy.   
   >>>>>   
   >>>>>   
   >>>>> Alain Fournier   
   >>>>   
   >>>> Faint signal detected after several minutes, with both ground and   
   >>>> robot systems expected to cycle, perhaps several times.   
   >>>>   
   >>>> We're now about an hour into the IM/NASA post-landing news   
   >>>> conference.? I've just got onto the stream, and a quick thumbnail scan   
   >>>> doesn't seem to have any imaging from the lander ... I'll rewind and   
   >>>> watch more carefully, but ....   
   >>>>   
   >>>> There's a hint where I jumped in that antenna orientation on the   
   >>>> lander is part of the issue.   
   >>>   
   >>> I've now gone back to the point where they talk about catching a toe and   
   >>> tipping over and being propped up by a rock.? Might affect antenna aiming.   
   >>   
   >> Japan's SLIM tipped over and now Odysseus.   
      
      
   It seems that SLIM tipped over because one of its two descent engines   
   broke apart during descent, leaving the lander unbalanced and apparently   
   making it gain horizontal velocity.   
      
      
   >> Staying up right on an   
   >> unprepared surface is not always that easy. That might be a problem for   
   >> SpaceX's Starship HLS. Starship being very tall, that might make it more   
   >> prone to tipping over.   
      
      
   Yes. However, Lunar Starship seems to have a multitude of descent   
   engines, likely giving it significant redundancy against a SLIM-type   
   failure.   
      
      
   > Somewhat disappointing that they couldn't stick the landing, despite   
   > having a functional LIDAR and Obstacle Avoidance System.   
      
      
   Someone at Intuitive Machines forgot to enable the IM LIDAR lasers   
   before launch, so they had to improvise and patch the SW quickly (in   
   lunar orbit) to use the NASA experimental descent LIDARs instead. Those   
   are mounted in a different location on the craft and have different   
   lines of sight, so require different geometrical computations. Possibly   
   the SW patch was not perfect in this regard. The descent velocity at   
   landing was a few times larger than intended.   
      
      
   > They couldn't measure the horizontal speed for some reason? Or   
   > attitude (this could explain the horizontal speed component)?   
      
      
   AIUI the horizontal speed was measured by down-looking cameras using   
   some kind of "optical flow" algorithm. If the descent engine kicks up a   
   lot of dust, it seems likely that the flow of dust might severely   
   interfere with that optical measurement. If this measurement and control   
   loop was continued to the very moment of touch-down this could lead to a   
   spurious horizontal velocity. Indeed IM said at the NASA/IM news   
   conference that the horizontal velocity at landing was about walking   
   speed. This is not healthy for a tall vehicle (and I was surprised that   
   there was not more discussion of this point in the conference).   
      
   Lunar Starship has its descent engines mounted high up on the ship and   
   their jets slanted outward. This should reduce the dust flow below the   
   ship. And of course we don't know how SpaceX plans to navigate the landing.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)