3 ms·

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

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.
  - HarHarVeryFunny 3y ago
    > you still sound to me like a guy suggesting 20, and now 12 wheels on a Jeep instead of 4 No - on a lunar lander, not on a jeep. It makes a difference (I'm really not sure why you started talking about Jeeps). The difference is the cost to test a lunar lander (on the moon) vs cost to test a jeep, and the fact that we're only going to build one lunar lander vs a production run of millions for the jeep. For the Jeep it's cheap enough to iterate and test (on earth), and end up with an optimized design that has 4 wheels and not 12 or 20. Not only is this relatively cheap to do, but there's a huge incentive to do so since we're going to mass produce the Jeep and would therefore like to reduce build cost and maximize profit. In contrast, the lunar lander is very expensive to "test" since that means a failed mission to the moon. Maybe that mission costs $5M, so if we fail twice before getting it right we've added $10M to the cost. If we can avoid those failed tests by instead adding $1M of redundant hardware that makes it work first time, then we've saved a lot of money. We're only building one lunar lander, so there's no multiplier in front of that $1M we added to the hardware cost.
hinkley 3y ago
You're just trying to ruin our zorbing fun.

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.
- HarHarVeryFunny 3y ago
  > you still sound to me like a guy suggesting 20, and now 12 wheels on a Jeep instead of 4 No - on a lunar lander, not on a jeep. It makes a difference (I'm really not sure why you started talking about Jeeps). The difference is the cost to test a lunar lander (on the moon) vs cost to test a jeep, and the fact that we're only going to build one lunar lander vs a production run of millions for the jeep. For the Jeep it's cheap enough to iterate and test (on earth), and end up with an optimized design that has 4 wheels and not 12 or 20. Not only is this relatively cheap to do, but there's a huge incentive to do so since we're going to mass produce the Jeep and would therefore like to reduce build cost and maximize profit. In contrast, the lunar lander is very expensive to "test" since that means a failed mission to the moon. Maybe that mission costs $5M, so if we fail twice before getting it right we've added $10M to the cost. If we can avoid those failed tests by instead adding $1M of redundant hardware that makes it work first time, then we've saved a lot of money. We're only building one lunar lander, so there's no multiplier in front of that $1M we added to the hardware cost.

hinkley 3y ago

You're just trying to ruin our zorbing fun.