Author Topic: Mars Direct with Solar Electric Propulsion viable?  (Read 1985 times)

Offline redliox

  • Senior Member
  • *****
  • Posts: 2537
  • Illinois USA
  • Liked: 683
  • Likes Given: 97
There could be many ways to Mars.  I favor the straightforward approach that minimizes bureaucracy and cost, but sometimes the straight path is hard to tread.  Mars Direct advocates ISRU and aerocapture whereas NASA-via-ARM SEP; short and dangerous versus tedious and safe.  There must be a way to compromise utilizing the strengths of both.

In Mars Direct, only 2 vehicles and launches are required.  In the Boeing scheme this is more like 5 or 6.  Reading through the Raftery report, I noticed something peculiar.  The timeline graphics, if indeed correct, imply that a Mars lander (both crew and cargo types) would each be launched with a prepped SEP tug from LEO to a spiral going first to EML-2 and then to Areosynchronous orbit.  2 out of 5 launches are actually dedicated to launching the inflatable transit habs, with the final launch being just an Orion delivering crew at the EML-2 staging point.  If the transhabs are eliminated, you only need 3 launches at best or 4 at worst to launch the SEP tug, the cargo lander, the crew lander, and the Orion (which ends up left at EML-2 anyway).

My biggest peeve against SEP, which otherwise is indeed an efficient technology I'd embrace, is the 'travel lag' that efficient...but extraordinarily weak...electric thrust tolls.  Plenty of papers gave pages of details on watts, array sizes, and evolving from ARM to crew-scale ops, but never gave a direct answer to: how long do you need to thrust to break into Mars orbit?  When you're talking propulsion systems to Mars, that is the bottom line.  Referring to the Raftery report via Boeing, after a roughly 7 month cruise with some thrusting toward Mars, the SEP does an about face and thrusts against Mars for 45 days.  Taken together, a one-way trip through interplanetary space takes 8.5 months.  I would not consider this ideal, especially with the crew weightless, but I think the history from Soviet/Russian stations and now ISS would confirm this is within human tolerance (but not exactly comfortable).

What I say is this: hook this SEP tug to the Mars Direct landers, safely park each leg in orbit, and then let them aerobrake to the surface.  The advantage is you safely deliver both equipment and crew sans aerocapture, whose main risk lies in accuracy; a descent from orbit closer to the planet allows for either a direct entry or aerobraking into low Mars orbit.  We have the technology for SEP and reentry - lets make the best of both.
« Last Edit: 04/24/2015 09:12 am by redliox »
"Let the trails lead where they may, I will follow."
-Tigatron

Offline sdsds

  • Senior Member
  • *****
  • Posts: 7201
  • “With peace and hope for all mankind.”
  • Seattle
  • Liked: 2050
  • Likes Given: 1962
Re: Mars Direct with Solar Electric Propulsion viable?
« Reply #1 on: 04/24/2015 10:18 am »
If the transhabs are eliminated

I'm pretty sure Raftery's proposal includes a kick stage launched with each hab. One powers Earth departure for the outbound crew. One powers Mars departure for the return. He provides values for the kick stages:
- 3500Kg Inert
- 21,000Kg LOX/Methane
- Isp 360

I'm pretty sure the proposal includes the habs themselves because NASA has studies showing the volume needed for long duration flights to keep crews performing well. They also presumably contain consumables for crew support.
— 𝐬𝐝𝐒𝐝𝐬 —

Offline Oli

  • Senior Member
  • *****
  • Posts: 2467
  • Liked: 605
  • Likes Given: 60
Re: Mars Direct with Solar Electric Propulsion viable?
« Reply #2 on: 04/24/2015 10:50 am »
In Mars Direct, only 2 vehicles and launches are required.

Mars Direct is a pipe dream.

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
0