Missions to Mars Q&A

• Missions to Mars Q&A by scienceguy on 08 Mar, 2008 17:07
• Does anyone here know the maximum amount of mass that one could bring to Mars and still use aerobraking?
  
  Does anyone here know the maximum amount of mass that one could bring to Mars and still use propellant to achieve Mars orbit?
• #1 by Jim on 08 Mar, 2008 17:17
• Quote

  scienceguy - 8/3/2008  1:07 PM
  
  1.  Does anyone here know the maximum amount of mass that one could bring to Mars and still use aerobraking?
  
  2.  Does anyone here know the maximum amount of mass that one could bring to Mars and still use propellant to achieve Mars orbit?

   
  
   It could be the size of one of the moons.  Just have a large enough  aeroshell or big propellant tank with big engines.
  
  The size is limited by the mass you can send to Mars, not how you brake into orbit
• #2 by scienceguy on 08 Mar, 2008 17:35
• Thanks for the quick response.
• #3 by tnphysics on 09 Mar, 2008 17:07
• Why are their limits on the mass/area of the Mars entry vehicle?
• #4 by Orbiter on 09 Mar, 2008 17:27
• So, during the trip to Mars, how are they going to solve a Problem with the Astronauts being so lonley from away from family?
• #5 by Kaputnik on 09 Mar, 2008 17:27
• The mass is limited by the area of the heatshield. The area of the heatshield is limited by the diameter of the payload fairing, which is itself related to the choice of LV.
• #6 by scienceguy on 09 Mar, 2008 19:37
• So even if a massive ship with AG was constructed in LEO, it would still be able to aerobrake at Mars if it had a wide enough heat shield?
• #7 by Kaputnik on 09 Mar, 2008 19:53
• Well... yeah, of course it would. There's no inherent limit on these things. It comes down to the density of the entry vehicle and the practical limitations of what can be assembled.
• #8 by Jim on 09 Mar, 2008 20:01
• Quote

  scienceguy - 9/3/2008  4:37 PM
  
  So even if a massive ship with AG was constructed in LEO, it would still be able to aerobrake at Mars if it had a wide enough heat shield?

  
  Yes
• #9 by khallow on 09 Mar, 2008 22:21
• Quote

  Orbiter - 9/3/2008  11:27 AM
  
  So, during the trip to Mars, how are they going to solve a Problem with the Astronauts being so lonley from away from family?

  
  I know of two ways. First, the plans I've glanced at have multiple astronauts (4 seems the favored number). Second, the astronauts would remain in contact with mission control and their families.
  
• #10 by tnphysics on 09 Mar, 2008 23:11
• The second method may not work owing to speed-of-light communication delays (up to 20 minutes+)
• #11 by Jim on 09 Mar, 2008 23:19
• Quote

  tnphysics - 9/3/2008  8:11 PM
  
  The second method may not work owing to speed-of-light communication delays (up to 20 minutes+)

  
  It will work, it is called email
• #12 by tnphysics on 09 Mar, 2008 23:23
• I ment telephone.
• #13 by Lampyridae on 09 Mar, 2008 23:31
• Quote

  khallow - 10/3/2008  9:21 AM
  
  

  Quote

  Orbiter - 9/3/2008  11:27 AM
  
  So, during the trip to Mars, how are they going to solve a Problem with the Astronauts being so lonley from away from family?

  
  I know of two ways. First, the plans I've glanced at have multiple astronauts (4 seems the favored number). Second, the astronauts would remain in contact with mission control and their families.
  

  
  By 2035, the computers will be able to hold a decent conversation with them. Until it goes mad, kills the crew and you have to pull the modules for its higher functions... additionally, they could have all sorts of robots as well.
  
  Plants also have a calming effect. Those will almost certainly be carried, albeit probably in pot plant form.
• #14 by A_M_Swallow on 10 Mar, 2008 02:54
• Quote

  Lampyridae - 10/3/2008  1:31 AM
  
  Plants also have a calming effect. Those will almost certainly be carried, albeit probably in pot plant form.

  
  Time to develop plants that are:
  a) edible
  b) like weak sun light
  c) and thrive in high levels of CO2.
  
  We can heat the greenhouse artificially and recycle the water.
• #15 by scienceguy on 10 Mar, 2008 03:18
• Quote

  A_M_Swallow - 9/3/2008  9:54 PM
  
  

  Quote

  Lampyridae - 10/3/2008  1:31 AM
  
  Plants also have a calming effect. Those will almost certainly be carried, albeit probably in pot plant form.

  
  Time to develop plants that are:
  a) edible
  b) like weak sun light
  c) and thrive in high levels of CO2.
  
  We can heat the greenhouse artificially and recycle the water.

  
  Spinach
  
  a) is edible
  b) does fine in weak sunlight
  c) thrives in high levels of CO2 (actually most plants if not all do better in high CO2)
  
  Also, spinach survives well under salty conditions (Zapata et. al. 2004), and water found on Mars would probably be salty. As a final kicker, spinach absorbs a lot of iron from soil and we know how important that would be in the rusty dunes of Mars.
  
  Reference
  
  Pedro J. Zapata, María Serrano, M. Teresa Pretel, Asunción Amorós and M. Ángeles Botella (2004) Polyamines and ethylene changes during germination of different plant species under salinity. Plant Science, Volume 167, Issue 4, Pages 781-788
• #16 by nedry on 10 Mar, 2008 07:13
• Perhaps with the correct sort of "pot" plants, they wouldn't care...
• #17 by MB123 on 10 Mar, 2008 07:20
• Will it be possible to return to Mars orbit on the same spacecraft that was used for entry.
  
  I have read some proposed architectures, many propose the ascent and descent vehicles are seperate spacecraft.
  
  Does anyone know why?
• #18 by Kaputnik on 10 Mar, 2008 08:18
• Quote

  Lampyridae - 10/3/2008  1:31 AM
  
  

  Quote

  khallow - 10/3/2008  9:21 AM
  
  

  Quote

  Orbiter - 9/3/2008  11:27 AM
  
  So, during the trip to Mars, how are they going to solve a Problem with the Astronauts being so lonley from away from family?

  
  I know of two ways. First, the plans I've glanced at have multiple astronauts (4 seems the favored number). Second, the astronauts would remain in contact with mission control and their families.
  

  
  By 2035, the computers will be able to hold a decent conversation with them. Until it goes mad, kills the crew and you have to pull the modules for its higher functions... additionally, they could have all sorts of robots as well.
  
  Plants also have a calming effect. Those will almost certainly be carried, albeit probably in pot plant form.

  
  I think the 'out of contact' 'problem' is over-stated. Given how long explorers used to have to go without contact, a 20-minute delay is absolutely nothing. When Franklin disappeared it was two whole years before anybody could be sure that something had gone wrong. Anyway, there was discussion of this on the 'would you go to Mars now' thread/poll in the Ares-V section.
• #19 by Kaputnik on 10 Mar, 2008 08:21
• Quote

  MB123 - 10/3/2008  9:20 AM
  
  Will it be possible to return to Mars orbit on the same spacecraft that was used for entry.
  
  I have read some proposed architectures, many propose the ascent and descent vehicles are seperate spacecraft.
  
  Does anyone know why?

  
  There are also architectures proposed which use a dual purpose ascent-descent vehicle.
  I can think of two reasons for having separate craft, though:
  1- landed mass bottleneck forces you to strip down a craft ot the bare minimum functionality
  2- you want the crew to land in their habitat module, a la Zubrin, for whatever reason- ascent vehicle needs to have refuelled itself, better chance for crew survivial if they go off course, etc.
  
  Note that in the first option, you wouldn't save all that much mass by having two dedicated and separate ascent and descent vehicles. The ascent vehicle has to descend to Mars safely at some point anyway, so you might as well stick a crew on it- if that's compatible with the rest of the mission plan.