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Landers don't impact hard - they fire rocket engines down, which may be much more efficient at kicking up dust than an impact. (I still think this is overblowi
by azernik 3y ago
Landers don't impact hard - they fire rocket engines down, which may be much more efficient at kicking up dust than an impact.
(I still think this is overblowing the problem, because any lander that causes this big of an ejecta problem would also badly damage itself. All the designs will put a LOT of engineering work into minimizing debris, eg Starship putting separate landing engines high up on the vehicle.)
- Sharlin 3y ago> because any lander that causes this big of an ejecta problem would also badly damage itself Not necessarily because the relative speeds will be very slow. Not so in low lunar orbit, where an orbiting spacecraft will slam into the ejecta curtain at >1 km/s.
- azernik 3y agoThe paper estimates that if there's LLO debris, it'll be starting out with about 1.6km/s of surface-relative velocity. Not something you want to get even a small percentage of on your landing gear.
- LorenPechtel 3y agoThe ejecta would go out to the side and not harm the lander. I'm just amazed that the ejecta is being thrown hard enough to be a threat at orbital altitude.
- azernik 3y agoThat's a simplifying assumption (per the paper). In reality it would be a distribution, with a lot less going up than to the sides. Plus then you're dealing with damage to your hopefully-smooth landing site.
- adastra22 3y agoIt’s a combination of the moon’s orbital velocity being low and the exhaust velocity being high.
- LorenPechtel 3y agoI'm still surprised that it can impart that much velocity, though.
- adastra22 3y agoWell is it not intuitive that something being blown by a moving fluid approaches speeds equal to the speed of the fluid?
- icodestuff 3y agoThat doesn't bode super well for Blue Origin's lander then, since its engines are on the bottom.