From: sylvia@email.invalid   
      
   On 26-Feb-21 4:43 pm, JF Mezei wrote:   
   > Having the lander hover while lowering rover and then fly away and crash   
   > seems so wasteful.   
   >   
   > How much more fuel would ne needed to have lander drop Rover off and   
   > then just land near it?   
      
   And risk an explosion near the rover that could damage it.   
      
   >   
   > Fit it with antenna and solar panels, and couldn't it act as a weather   
   > station and perhaps have some web cams? (useful if you have a problem   
   > with rover to see what state it is in). And having weather at landing   
   > spot while rover gives you weather wherever it is would also be useful.   
      
   You're talking about additional weight and complexity.   
   >   
   >   
   >   
   > Alternatively, couldn't the lander have its thrusters on longer poles   
   > and land with rover still on its belly, and once landed then release it   
   > and let it move away? Would that take up more fuel than hovering while   
   > you're lowering it down and then going back up and away to go crash   
   > somewhere?   
      
   The poles would have to fold up to fit inside the aeroshell, and then   
   unfold once the aeroshell is jettisoned, and before the rockets can   
   fire, which is yet more complexity with risk of failure.   
      
   The whole point of the mission is to get the rover safely onto the   
   Martian surface. Anything that can compromise that is an unnecessary risk.   
      
   >   
   > Cue Starship:   
   >   
   >  From what I saw, Perseverance came from space alrady aimed at its   
   > landing point and entered atmpsphere diagonally but a ballistically   
   > straight line.   
   >   
   >   
   > Would Starship do the same and have a very quick and direct entry and   
   > landing?   
      
   I would expect so. Starship already needs reentry shielding for   
   returning to Earth.   
      
   >   
   > Would it first fire engines to slow down to make it survive re-entry and   
   > reach ground at a speed it can handle?   
      
   I would think that very unlikely.   
      
   >   
   > Would it aim higher up to do a partial orbit through MArs atmpshere to   
   > slow down and then fall ballistically at more manageable speed?   
   >   
   >   
   > I take it that going into orbit and then de-orbit to land would waste   
   > too much fuel? (but that would allow for flexibility of where you land   
   > not being so tied to when you left Earth).   
   >   
   > Would elliptical orbit with aerobraking at each perigee be considered?   
   >   
      
   A lot of speed would have to be lost on the first pass just to get into   
   any orbit, so I doubt it would be practical.   
      
   Side note on terminology - perigee is specifically the lowest point in   
   an orbit about Earth. There is the term pericynthion for the   
   corresponding point near the Moon. The generic term is periapsis.   
      
   Sylvia.   
      
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