3 ms·

Maybe for a small lander, an alternative to landing upright would be to avoid having an upright in the first place. Have a spherical/polyhedral design with legs

Maybe for a small lander, an alternative to landing upright would be to avoid having an upright in the first place. Have a spherical/polyhedral design with legs on all faces and redundant solar panels/cameras on each face.

jethro_tell 3y ago
Or even a design that allows for self righting. You can find many of these in highschool robotics club battle bots. Obviously much more complex, but probably cheaper than redundant everything.
- invalidator 3y ago
  Mars Pathfinder did exactly this. It was a tetrahedron which could land in any orientation. As it happened they rolled a 4, but if it was on one of the other 3 sides it would have pushed itself upright as the sides folded open. https://en.wikipedia.org/wiki/Mars_Pathfinder https://en.wikipedia.org/wiki/Mars_Pathfinder
johnwalkr 3y ago
Very easy solution until you realize you need solar panels facing the sun[1], radiators facing deep space[2], antennas facing earth, payloads facing x, y, and z, deployable payloads facing x, y, and z plus the lunar surface. And all of those things are fragile, at least in terms of mounting them on the outside of a bowling ball rolling across sharp gravel/sand. And of course multiply difficulty by the number of all configurations^2 for both design and testing. [1] and [2] are especially huge drivers, you need power and therefore heat input, but you also need radiators to expel heat. Depending on complexity, solar panels in shade act as passive radiators leaking heat at best, and at worst as heaters, actively taking battery power to heat up and become even better radiators. And radiators act, to some extent, less effectively or even as heaters if they are facing the sun, sunlit earth, or sunlit lunar surface instead of deep space. It's not only a matter of adding complexity, mass, money, etc. This kind of solution is simple on its face, but it is akin to being ignorant of why a car has windows (for the driver to see), doors (for the passengers to enter/exit) or a cooling system (to not overheat), and then reading that Jeeps (or to be more fair, a new Jeep prototype) are prone to tipping over on a trail after driving 1000km on a highway to a trailhead, and then commenting on how Chrysler should just make a dodecahedron Jeep with 20 wheels instead of 4. These spacecraft also made it past 99% of the hurdles, the next try will probably make it and overcome the final 1% without starting from scratch and adding all kinds of complexity that are far more likely to add failure. I work in the industry and opinions are mine and not of my employer.
- whycome 3y ago
  Or have the singular versions and just roll the thing after landing.
- HarHarVeryFunny 3y ago
  I think the economics of a one-off lunar lander are a bit different to those of Jeep! The cost of the lander hardware is only a small part of overall cost of the mission, and adding some (or even a lot) of redundancy would seem a small price to pay if that provides a high likelihood of mission success. Of course this needs to be compared to cost and reliability of alternate solutions. This is a lot different to adding a lot of redundancy and cost and compromised design to a mass-produced vehicle where you can iterate and test in deployed environment as many times as you like. Obviously N-way redundancy isn't optimal, but it would seem potentially simple if you had a modular design with multiple instances of the same "omniface" component. Perhaps use 1/2 of each redundant face for radiator and 1/2 for solar panel? I'm not suggesting a rolling design - just one with legs on every side such that if it did tip over (or worst case tumble if landing on an incline) from preferred engine-down orientation then it would not make any difference. Seeing as Intuitive Machines wanted to avoid deployable (spreadable) legs as a way to achieve a more stable low center of gravity, another alternative would seem to be to shrink the design (lose the height) to better work within the width of the faring, although I don't know how viable that would be given amount of propellant needed for the landing.
  - johnwalkr 3y ago
    Cost of hardware is actually a huge part of overall cost, and the economics are worse, not better when you need to prototype and test things for a one-off mission/vehicle made by a new company vs updating a vehicle that sells hundreds of thousands, and making it by a company that has sold millions. There's virtually no technical risk in designing the next iteration of Jeep. "Just put 1/2 radiator and 1/2 solar" and "just put legs on every side" is still really simplistic and nobody even mentioned thermal insulation yet, which is normally a much higher proportion of surface area compared to radiators and solar, at least if all three are on the main spacecraft body. I was being extreme in my last comment to make a point, but you still sound to me like a guy suggesting 20, and now 12 wheels on a Jeep instead of 4.
demondemidi 3y ago
The first mars lander was in a tetraheadron in an airbag. There was no way for it to land in the wrong orientation because the tetraheadron always unfolded in the correct orientation. And that was almost 30 years ago.
- HarHarVeryFunny 3y ago
  Yes - that was a great design. I've seen some people suggest that it wouldn't work on the moon due to lack of atmosphere and less gravity, but not obvious why that would prevent it. Of course it's a more complex design in a way given that you deploy this airbag at low altitude - something else to go wrong. It's interesting though that NASA has used that and the even more complex air-crane technique on Mars both successful first attempt. Even though they seem complex I'd assume NASA determined they were the least-complex approaches that had a high likelihood of success. Maybe the economics of doing this on the moon, and with a cheaper lander, are different - better to have a simpler system with higher chance of failure, and redo the mission if it fails ?
  - demondemidi 3y ago
    I didn’t realize the part about the atmosphere. That’s interesting!

jethro_tell 3y ago

Or even a design that allows for self righting. You can find many of these in highschool robotics club battle bots. Obviously much more complex, but probably cheaper than redundant everything.

invalidator 3y ago
Mars Pathfinder did exactly this. It was a tetrahedron which could land in any orientation. As it happened they rolled a 4, but if it was on one of the other 3 sides it would have pushed itself upright as the sides folded open. https://en.wikipedia.org/wiki/Mars_Pathfinder https://en.wikipedia.org/wiki/Mars_Pathfinder

johnwalkr 3y ago

Very easy solution until you realize you need solar panels facing the sun[1], radiators facing deep space[2], antennas facing earth, payloads facing x, y, and z, deployable payloads facing x, y, and z plus the lunar surface. And all of those things are fragile, at least in terms of mounting them on the outside of a bowling ball rolling across sharp gravel/sand. And of course multiply difficulty by the number of all configurations^2 for both design and testing. [1] and [2] are especially huge drivers, you need power and therefore heat input, but you also need radiators to expel heat. Depending on complexity, solar panels in shade act as passive radiators leaking heat at best, and at worst as heaters, actively taking battery power to heat up and become even better radiators. And radiators act, to some extent, less effectively or even as heaters if they are facing the sun, sunlit earth, or sunlit lunar surface instead of deep space. It's not only a matter of adding complexity, mass, money, etc. This kind of solution is simple on its face, but it is akin to being ignorant of why a car has windows (for the driver to see), doors (for the passengers to enter/exit) or a cooling system (to not overheat), and then reading that Jeeps (or to be more fair, a new Jeep prototype) are prone to tipping over on a trail after driving 1000km on a highway to a trailhead, and then commenting on how Chrysler should just make a dodecahedron Jeep with 20 wheels instead of 4. These spacecraft also made it past 99% of the hurdles, the next try will probably make it and overcome the final 1% without starting from scratch and adding all kinds of complexity that are far more likely to add failure. I work in the industry and opinions are mine and not of my employer.

whycome 3y ago
Or have the singular versions and just roll the thing after landing.
HarHarVeryFunny 3y ago
I think the economics of a one-off lunar lander are a bit different to those of Jeep! The cost of the lander hardware is only a small part of overall cost of the mission, and adding some (or even a lot) of redundancy would seem a small price to pay if that provides a high likelihood of mission success. Of course this needs to be compared to cost and reliability of alternate solutions. This is a lot different to adding a lot of redundancy and cost and compromised design to a mass-produced vehicle where you can iterate and test in deployed environment as many times as you like. Obviously N-way redundancy isn't optimal, but it would seem potentially simple if you had a modular design with multiple instances of the same "omniface" component. Perhaps use 1/2 of each redundant face for radiator and 1/2 for solar panel? I'm not suggesting a rolling design - just one with legs on every side such that if it did tip over (or worst case tumble if landing on an incline) from preferred engine-down orientation then it would not make any difference. Seeing as Intuitive Machines wanted to avoid deployable (spreadable) legs as a way to achieve a more stable low center of gravity, another alternative would seem to be to shrink the design (lose the height) to better work within the width of the faring, although I don't know how viable that would be given amount of propellant needed for the landing.
- johnwalkr 3y ago
  Cost of hardware is actually a huge part of overall cost, and the economics are worse, not better when you need to prototype and test things for a one-off mission/vehicle made by a new company vs updating a vehicle that sells hundreds of thousands, and making it by a company that has sold millions. There's virtually no technical risk in designing the next iteration of Jeep. "Just put 1/2 radiator and 1/2 solar" and "just put legs on every side" is still really simplistic and nobody even mentioned thermal insulation yet, which is normally a much higher proportion of surface area compared to radiators and solar, at least if all three are on the main spacecraft body. I was being extreme in my last comment to make a point, but you still sound to me like a guy suggesting 20, and now 12 wheels on a Jeep instead of 4.

demondemidi 3y ago

The first mars lander was in a tetraheadron in an airbag. There was no way for it to land in the wrong orientation because the tetraheadron always unfolded in the correct orientation. And that was almost 30 years ago.

HarHarVeryFunny 3y ago
Yes - that was a great design. I've seen some people suggest that it wouldn't work on the moon due to lack of atmosphere and less gravity, but not obvious why that would prevent it. Of course it's a more complex design in a way given that you deploy this airbag at low altitude - something else to go wrong. It's interesting though that NASA has used that and the even more complex air-crane technique on Mars both successful first attempt. Even though they seem complex I'd assume NASA determined they were the least-complex approaches that had a high likelihood of success. Maybe the economics of doing this on the moon, and with a cheaper lander, are different - better to have a simpler system with higher chance of failure, and redo the mission if it fails ?
- demondemidi 3y ago
  I didn’t realize the part about the atmosphere. That’s interesting!