View Single Post
  #6  
Old April 17th 17, 06:08 PM posted to sci.space.policy
Alain Fournier[_3_]
external usenet poster
 
Posts: 548
Default SLS launches likely delayed

On Apr/17/2017 Ã* 12:07 PM, JF Mezei wrote :
On 2017-04-16 22:46, Fred J. McCall wrote:
Looks like NASA's first two launches of the SLS for their lunar tests
will be delayed by a year or more. That means SpaceX will almost
certainly be there before them.



The announcement of the first flight being manned may have more to do
with the delay than budgets.

That article had a link to a NASA web page which describes its concept
for Mars. That page does not paint Orion/SLS as sending man to Mars.

NASA wants to build ISS-2 in lunar orbit to test the transit ship there.
So SLS/Orion act as shuttles to/from the vehicle in lunar orbit.

NASA admits Orion isn't big enough to being crews on months long mission
to Mars and back.

If you will assemble a transit ship in lunar orbit, you might need
something like SLS to bring modules up there.

Assembling in LEO costs less in module launches, but more in fuel to
escape from Earth. Assembling in Lunar orbit costs more in launches of
modules, but less to escape earth/moon orbit. Does the balance tip
heavily on one of those or is it more or less even ?


It is cheaper to do most of your acceleration low in the gravity well.
You can read on the Oberth Effect, for instance:
https://en.wikipedia.org/wiki/Oberth_effect


Alain Fournier