Apollo by Saturn IB

[Peter B]

I'm not sure if I've asked this before - apologies if I have - but could a manned lunar landing have been achieved EOR-style by using two Saturn IB rockets?

The idea I had would be:

1. S-IB 1 launches the crew into orbit.
2. S-IB 2 launches the LM into orbit, with propellant left over.
3. CSM docks with the S-IVB of S-IB 2.
4. S-IVB of S-IB 2 relights and heads off to the Moon (so eyeballs out for the crew).
5. Everything after this would be as per a normal Apollo mission.

The key thing would be how much fuel would be left over in the S-IVB of S-IB 2 after launching the LM into orbit. One minor weight saving would be that the SLA panels could be jettisoned much earlier in the flight, saving a bit of weight - I'm assuming that some sort of lattice would remain in place surrounding the LM which would include a docking target for the CSM so that it would be held securely during the TLI burn.

Anyone have any thoughts on the weight aspects of this hypothetical S-IB 2 launch?

Thank you!

[Obviousman]

As you say, I think the key thing is fuel.  IIRC, some type of on-orbit refueling would have been required. Don't take that as gospel, though... just something in the back of my little mind.

[Glom]

I'm sure I read somewhere that such a thing was considered.

Though it is not to be confused with the original EOR plan, which was to assemble an all-in-one spacecraft. This would have required two Saturn V launches.

[Obviousman]

It seems there were up to five planned launches: one for the LM, one for the CSM, and three for the LOX / H2. That would have been with the Saturn 1B. A development of the Saturn, the Saturn C-4, would have been used if possible and reducing the number of launches required to two or three.

[VQ]

Any good studies on this that can be linked for further reading?

[Count Zero]

Peter, you asked a similar question on the "old-old" AH board.  That is lost, but the question was asked again by Jairo 12 years ago on the "new-old" board.  That thread has been preserved:  Link.
The Saturn-1B discussion starts half-way down the first page.  You chime in with a suggestion at the bottom of the page.

Fun thread from back in the days when I had the time to think (i.e. before marriage & kids).

[Obviousman]

I'll see if I can find them.

[Obviousman]

Have a start with this one. I'll edit and put more references in as I find them.

http://www.thespacereview.com/article/150/1

From Page 23 of the next link:

"For the purpose of the manned lunar mission, the Saturn C-2 would be used to place into earth orbit an empty upper vehicle stage that would subsequently be used to propel the spacecraft toward the moon. Four or five additional C-2 payloads would be required to fill this empty stage with propellants. The last launching would propel the manned spacecraft together with the lunar take-off stage into earth orbit. Six or seven successful Saturn launchings, therefore, are required in order to place a space vehicle system into earth orbit that will then be capable of propelling an 8,000 pound spacecraft toward the moon, landing on the moon and returning it toward earth."

And from Page 58:

"II. 2. a: Earth Rendezvous Only.

On the basis of the preceding paragraph, the following weights at different stages of the mission pertain to the case of rendezvous in earth orbit only (based on H202 performance):
[4]
Weight returned to vicinity of earth 12, 500 pounds
Lunar take-off weight 28, 800 pounds
Weight landed on moon 31, 000 pounds
Weight in escape trajectory 73, 000 pounds
Weight in earth orbit 210, 000 pounds

These weights indicate that five C-2’s or two C-3’s are required in order to accomplish the mission.

https://history.nasa.gov/SP-4407vol7Chap2-Docs.pdf

[Count Zero]

And from Page 58:

"II. 2. a: Earth Rendezvous Only.

On the basis of the preceding paragraph, the following weights at different stages of the mission pertain to the case of rendezvous in earth orbit only (based on H202 performance):
[4]
Weight returned to vicinity of earth 12, 500 pounds
Lunar take-off weight 28, 800 pounds
Weight landed on moon 31, 000 pounds
Weight in escape trajectory 73, 000 pounds
Weight in earth orbit 210, 000 pounds

These weights indicate that five C-2’s or two C-3’s are required in order to accomplish the mission.

https://history.nasa.gov/SP-4407vol7Chap2-Docs.pdf

I note that these weight assume EOR only, which means that the vehicle which lands on the Moon and takes-off carries the fuel to return to Earth, the consumables for the trip home (air, food, water, power & maneuvering propellant) and the heat shield & parachutes for re-entry & landing.

When this paper was prepared in June, 1961 Lunar Orbit Rendezvous was still fighting an uphill battle against Direct Ascent and EOR concepts, both of which proposed landing the above-described vehicle on the Moon. The paragraph immediately following the one you cited discusses LOR, and remarks that:

"Calculations suggest,
however, that the amount of weight which must be put into an escape trajectory
for a given reentry vehicle weight might be reduced by a factor of two by use of
the lunar rendezvous technique. The earth booster requirement might therefore
be reduced to one C-3 with lunar rendezvous or two to three C-2 ‘s with earth
and lunar rendezvous."

Despite this savings, in the summary on page 61, EOR using multiple C-3 launches was the method preferred by the panel members.  LOR came in third, behind EOR using Nova & C-1 launches.

(This study examined rendezvous-based mission plans as an alternative to Direct Ascent)

[Obviousman]

There was also a mention of cost. Although it seemed like the cost per launch was lower, and thus the total cost was lower than a single Saturn V (C-5) launch, when ground preparation and other costs are considered, the overall cost was higher.

[ka9q]

One minor weight saving would be that the SLA panels could be jettisoned much earlier in the flight, saving a bit of weight - I'm assuming that some sort of lattice would remain in place surrounding the LM which would include a docking target for the CSM so that it would be held securely during the TLI burn.

In principle, this could also have been done with a Saturn V: just do transposition and docking before TLI. and extraction afterwards. The problem in both cases is that the structure of the relatively weak LM would have to handle the 28.8 tonne mass of a fully fueled lunar CSM. Acceleration peaked at 1.4 g at the end of TLI.

[ka9q]

Another problem is that a single Saturn V is worth considerably more than two Saturn 1Bs. Saturn V capacity to LEO is 140 tonnes; capacity to lunar injection is 48.6 tonnes. Saturn 1B capacity to LEO is only 21 tonnes; it could only orbit an earth orbital CSM lacking the full load of SPS propellant needed for a lunar mission.

[Count Zero]

Another problem is that a single Saturn V is worth considerably more than two Saturn 1Bs. Saturn V capacity to LEO is 140 tonnes; capacity to lunar injection is 48.6 tonnes. Saturn 1B capacity to LEO is only 21 tonnes; it could only orbit an earth orbital CSM lacking the full load of SPS propellant needed for a lunar mission.

Yes.  See my link to the previous thread (above).