On Monday, February 23, 2015 at 6:35:01 PM UTC-5, Jeff Findley wrote:
In article ,
david.l.spain says...

On Sunday, February 22, 2015 at 10:48:08 PM UTC-5, Jeff Findley wrote:
In article ,
pedro1492 says...
Seems rather optimistic speculation.

Not at all. What was optimistic was the assumption that NASA funding
would continue at the same level as it was during the height of
Apollo/Saturn development. That assumption was proven false.

We need rockets about 10 times as powerful, and about 1/000th the cost
of 20th century technology.

In terms of size, no, we don't. Saturn V would have been enough.
Falcon Heavy would be big enough too, given enough launches.


Most Mars mission profiles from the 70's I recall, envisioned a nuclear upper stage. In the Saturn V configuration we're talking the 3rd stage, I believe.
Such technology was very close at hand in the early 70's but as you point out the funding had been cut off much earlier. Jeff, do you recall if there were other, pure chemical configurations based on Saturn V (either via fuel depot and/or multiple launches)? I keep remembering the timeline of ~1986 being tossed around as a "realistic" deadline for the first Saturn V derivative Mars missions. Of course that was all before we got the Space Truck fever!

Note that even with a nuclear upper stage, you still needed a lot of LH2
to "fuel" it, so the cryogenic storage problem would still need to be
solved (at least to the point of "good enough") with nuclear.

When you look at those sorts of details, nuclear wasn't really "needed".
It was part of the "everything and the kitchen sink" R&D that came with
Apollo/Saturn's blank checks.

Either a nuclear upper stage or cryogenic fuel depots could have been
used with conventional LOX/LH2 engines (J-2 wasn't a bad engine for its
time and had upgrade potential, just as the F-1 was being upgraded to
the F-1A).


Sorry to revive an old thread, but upon reflection and re-reading this some time later I realize what I remembered was a configuration of "assembled-in-orbit" cluster of Saturn V 3rd stages all feeding their own nuclear engine. I suppose in this configuration the 3rd stage was significantly modified to hold only LH2 or mostly LH2 with significantly reduced O2 tanks for air and water (with H2+O fuel cell combination?) for the trans hab module that sat on top of the core this cluster.

Dave