3 ms·

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 t

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.

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.