Another Scott Manley comment on the lander design:
How do you guarantee the tanks are empty? What if you don't need to use any contingency propellant and you land with a bunch of it still left?Idea! Next time they can put the tanks on top, so by the time they land all the mass is at the bottom and you have a bunch of empty tanks on top.
It seems pretty simple to me or am I missing something.
that’s a good point, but it leaves me wondering how much contingency they have? Also if that was the max then we are in deep trouble…How do you guarantee the tanks are empty? What if you don't need to use any contingency propellant and you land with a bunch of it still left?
I'm pretty sure they would have done all they reasonably could to lower the CG, regardless.
Seems a bit aerodynamic for the moon…
You introduce more failure modes by doing that (i.e. the detaching mechanism may not work), and you also have to deal with whatever disruptive reaction force on the lander comes from the tank detachment (Newton's third law).Seems a bit aerodynamic for the moon…
But I have a second bad idea, maybe they could have a drop tank, it has the fuel for transfer and deorbit after that it’s dropped and you land with a much lower center of gravity.
True but I think that 2 landers made by completely different companies both having the same problem means that someone needs to do something to stop it, remember we plan on landing people in a lander with the same basic design (tall and skinny) and we can’t copy the LEM because of size constraints. So we somehow have to make this design work…Not saying any of this is necessarily a showstopper, part of engineering is knowing which risks are and are not worth taking.
Since Starship apparently failed since it did not have a cargo load....we can’t copy the LEM because of size constraints....
We will see for what they modify for the 2nd lander that they plan on sending at the end of this year. They will have corrected or changed a few things, perhaps have a few different experiments too.You introduce more failure modes by doing that (i.e. the detaching mechanism may not work), and you also have to deal with whatever disruptive reaction force on the lander comes from the tank detachment (Newton's third law).
Not saying any of this is necessarily a showstopper, part of engineering is knowing which risks are and are not worth taking.
Unfortunately the safety for laser range finder was turned on so the laser was not operative. Having that enabled probably would have provided the necessary information to slow the spacecraft more and land on a more level area. As it was, the alternate distance finding that the lander used meant that the lander came in a little hotter and with more horizontal speed than desired leading to a bit of a bounce & drag of a lander leg upon touchdown. It came down with more force than it was designed to handle. The laser ranger finder was brought up for discussion in today's online update. Somebody forgot to renable it after loading onto the Falcon 9. Something to add to the checklist on IM-2 and IM-3.You would think that they would have an IMU on board and they could use that to confirm their velocity... they could have slowed it down a little early based on the camera and the IMU.
I read something similar this morning. The report said that the lander had about a 2 m/s horizontal velocity when it landed.Unfortunately the safety for laser range finder was turned on so the laser was not operative. Having that enabled probably would have provided the necessary information to slow the spacecraft more and land on a more level area. As it was, the alternate distance finding that the lander used meant that the lander came in a little hotter and with more horizontal speed than desired leading to a bit of a bounce & drag of a lander leg upon touchdown. It came down with more force than it was designed to handle. The laser ranger finder was brought up for discussion in today's online update. Somebody forgot to renable it after loading onto the Falcon 9. Something to add to the checklist on IM-2 and IM-3.
That supports my idea to make the lander shape less susceptible to tipping. I watched Scott Manley's short video about the current shape of the lander and his opinion was that modifying the lander shape would add too much mass and complication. He obviously knows more about contemporary spacecraft than I do so I can't dismiss what he said. I don't know how difficult it will be to improve the landing guidance of this lander design.As the one scientist said in the above video "it's very hard to land something on the moon."
Apparently not that difficult: install the pin to enable the altimeter laser before launch. The only thing wrong with the landing guidance is they couldn't turn it on.I don't know how difficult it will be to improve the landing guidance of this lander design
Whole different instrument, I believe. But they couldn't get it to provide real time data. My understanding is that they started with twelve minute old altimeter data, then computed altitude using inertial and other sensors to plot its movement after that point.So as I understand it, while they were able to switch to the NASA experimental lasers for altimetry, the craft couldn't process the data quickly enough? Was it a whole separate laser altimeter or just different lasers? Something in the story didn't stick with me. I thought they had celebrated altimetry worked with the quick patch to NASA lasers.
I could be wrong, but I thought that I had heard that because they were using instruments from the science package and not the intended lasers, that the computers had to process the data in some way before using it and simply couldn't process data fast enough.Seems like a good plan, I'm not sure how it ended up a hundred meters off. Maybe the time resolution on the other instruments was too low.
I was going to suggest that then I realized that it would be difficult to make an engine that thrusts in that direction, And tipping it seems like a bad idea.I could be wrong, but I thought that I had heard that because they were using instruments from the science package and not the intended lasers, that the computers had to process the data in some way before using it and simply couldn't process data fast enough.
That said, I completely understand when they say that the design is tall and skinny because that's a constraint imposed on it by the shroud size. But, while I'm sure that there's a reason this wouldn't work, why not make it even *taller* and then land it sideways on purpose?
I was thinking in terms of something that would unfold to be wider and not so tall. Landing sideways could be an improvement because it doesn't have to unfold as much to do that.That said, I completely understand when they say that the design is tall and skinny because that's a constraint imposed on it by the shroud size. But, while I'm sure that there's a reason this wouldn't work, why not make it even *taller* and then land it sideways on purpose?
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