On 2024-02-24 13:44, The Running Man wrote:
On 23/02/2024 21:51 Alain Fournier <alain245@videotron.ca> 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
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