Apollo concept designs?

[Tupin]

I read somewhere recently that the plan used to go to the moon during the Apollo missions, having the CSM orbit while the LM landed was initially unpopular. Are there any existing plans of what could have been, as with those Space Shuttle designs?

[ddavis425]

Here is a good picture showing some of the proposed designs, many of them were direct-descent designs like in KSP.

[Ziff]

They only considered 3 methods. Direct-ascent, which was pretty much your standard 'giant rocket all the way to the moon and back again.' They also considered Earth Orbit Rendezvous , where 2 smaller rockets would launch, 2 pieces would assemble in Earth orbit, and then that craft would go all the way to the moon and back. The 3rd method, Lunar Orbit Rendezvous wasn't seen as very favorable at first. Here's a NASA website that talks about it. http://www.nasa.gov/centers/langley/news/factsheets/Rendezvous.html

[rdfox]

For the record, even as much as people think of him as the champion of the Big Dumb Booster, von Braun preferred the Earth-Orbit Rendezvous profile. His proposal would have used three Saturn IB launches--one to put an Apollo CSM just like the one that actually flew into Earth orbit, one to put a lander stage into orbit (essentially, a modified Apollo Service Module with a bigger engine, minimal consumables other than propellant, and landing legs), and one to put a transfer stage into orbit (basically, that one would have flown without any payload, but with a lengthened S-IVB to provide enough fuel for the transfer. Once all three are in orbit (and I don't know the order of launch, sorry), they'd have the manned CSM dock with the lander stage, then have the combination of those two dock with the transfer stage, and off they'd go.

Interestingly, while the official reason for using LOR was that it allowed the lowest total mass (and thus, theoretically, the lowest total cost), there were other reasons it was selected, too. Of course, the big objection to it was, "We're not sure rendezvous in EARTH orbit is possible yet, and now you want to have one around the MOON?!", but it was quickly pointed out that EOR was even more reliant on rendezvous than LOR (with two required rendezvous rather than one), and the docking was going to be much easier when the CSM could point *towards* the vessel it was docking with. Even so, neither Direct Ascent nor EOR were fully killed until someone pointed out that the CSM atop the lander stage was going to be about seventy-five feet tall, and wouldn't be physically capable of having any windows that would allow the pilot to look down at the surface in the final stages of landing, so howinhell was he gonna LAND that monster?

(There were other suggestions. The craziest--which was shot down almost instantly--was to send a single man on a ONE-WAY landing mission, and keep sending him supply ships "until we can figure out a way to get him back." There was, however, a much more interesting idea that someone suggested that *might*, under certain circumstances, end up being a valuable option in the future, "Lunar Surface Rendezvous." You send up TWO ships, one a manned lander, and one an unmanned lander carrying all the supplies needed to refuel the manned lander for the return. Land the unmanned lander, land the manned lander next to it--i.e., "rendezvous on the surface of the moon"--refuel the manned lander, and then fly back home...)

[Nikolai]

(There were other suggestions. The craziest--which was shot down almost instantly--was to send a single man on a ONE-WAY landing mission, and keep sending him supply ships "until we can figure out a way to get him back."

Oh, yeah, the Pilgrim Project. Fun times. They even made a movie about it (starring James Caan) titled Countdown. It's interesting watching because it's pretty faithful to the science of the time -- including jagged mountains (which we figured should be everywhere because of the lack of erosion). I found the ending kind of abrupt, but it's still good watching for the realistic sci-fi fan. (Unfortunately, it was eclipsed when it came out -- as was every other sci-fi movie at the time -- by 2001.)

There was, however, a much more interesting idea that someone suggested that *might*, under certain circumstances, end up being a valuable option in the future, "Lunar Surface Rendezvous." You send up TWO ships, one a manned lander, and one an unmanned lander carrying all the supplies needed to refuel the manned lander for the return. Land the unmanned lander, land the manned lander next to it--i.e., "rendezvous on the surface of the moon"--refuel the manned lander, and then fly back home...)

It wasn't just the Americans floating ideas like that. The Soviet program kind of distrusted its pilots, and required automatic overrides on all their spacecraft. Between that and the fact that there were some upsetting design issues with their LK lander(*), the plan was to send two landers to the surface, one manned and one landed automatically. If anything happened to the manned lander, well, you had a backup.

(*) For example, the LM had two main engines -- one for descent and one for ascent. While this might seem wasteful, one of the advantages was that any damage caused to the descent engine by flying debris would not affect the ascent stage during its attempt to rendezvous with the CSM in lunar orbit. The LK, however, had only one engine for both tasks... so a backup would be nice to have around.

[Ziff]

Interestingly, while the official reason for using LOR was that it allowed the lowest total mass (and thus, theoretically, the lowest total cost), there were other reasons it was selected, too. Of course, the big objection to it was, "We're not sure rendezvous in EARTH orbit is possible yet, and now you want to have one around the MOON?!", but it was quickly pointed out that EOR was even more reliant on rendezvous than LOR (with two required rendezvous rather than one), and the docking was going to be much easier when the CSM could point *towards* the vessel it was docking with. Even so, neither Direct Ascent nor EOR were fully killed until someone pointed out that the CSM atop the lander stage was going to be about seventy-five feet tall, and wouldn't be physically capable of having any windows that would allow the pilot to look down at the surface in the final stages of landing, so howinhell was he gonna LAND that monster?

Von Braun switched from EOR to LOR for a number of official reasons, but he still seriously supported EOR. In fact one of the main reasons he supported LOR was because it would eventually lead to a more efficient EOR method, one based on a lighter and more efficient command module. At that time, with the current command module design and materials, LOR was preferable. He said, "We believe the Lunar Orbit Rendezvous mode using a single C-5 offers a very good chance of ultimately frowing into a C-5 direct capability."

You can read about those reasons, and other comments, in this actual NASA document from 1962. http://history.nasa.gov/Apollomon/apollo6.pdf

One of the more interesting thoughts that are rarely mentioned: "We agree with the Manned Spacecraft Center that the designs of a maneuverable hyperbolic re-entry vehicle of a lunar landing vehicle constitute the two most critical tasks in producing a successful lunar spacecraft. A drastic separation of these two functions into two separate elements is bound to greatly simplify the development of the spacecraft system."

In other words, the two craft could be designed separately at the same time with only very little consideration for each other. This allowed for a very simplified lander design that only had to consider landing and supporting 2 men on the moon and being able to dock back with the mothership.

Anyway, to the OP: There really aren't any official designs that are specific for the other methods, because they were knocked down before they went beyond concept stages. For example, you can see a diagram of a reduced size Apollo module for a direct-ascent 2 man mission craft with some explanations on this page here-> http://www.astronautix.com/craft/apot2man.htm. This document here-> http://smartech.gatech.edu/jspui/bitstream/1853/8042/3/SSEC_SE2_doc.pdf will explain the differences, with some old diagrams, of concepts of operations. It compares the operational steps of a LOR vs EOR vs Direct Ascent.

[Nibb31]

(*) For example, the LM had two main engines -- one for descent and one for ascent. While this might seem wasteful, one of the advantages was that any damage caused to the descent engine by flying debris would not affect the ascent stage during its attempt to rendezvous with the CSM in lunar orbit. The LK, however, had only one engine for both tasks... so a backup would be nice to have around.

The LM had the one big issue that if the ascent engine failed, they were toast. There was no redundancy. Which is why the engine was fully accessible through a cover inside the LM cabin, so that they could attempt to fix it or manually tamper or bang on it with a spanner during ascent... The ascent engine was also to be used to abort to orbit if the descent engine failed, which made it critical.

The LK on the other hand had 2 redundant landing/ascent engines. Only one was required, but the backup would kick in if necessary. There was no specific descent engine. The Block D stage would do most of the braking and powered descent, then be dropped, and the LK engine would only do the final landing burn and land with nearly full tanks. If something went wrong with LK engine, it would have aborted to a landing on the redundant engine.

[Nikolai]

The LM had the one big issue that if the ascent engine failed, they were toast. There was no redundancy.

Well, yes. My point was more that the ascent engine was not directly affected by damage that might be caused by flying debris during descent. In that sense, it was somewhat "shielded" until it was needed.

The LK on the other hand had 2 redundant landing/ascent engines.

I looked this up. Thanks for the correction. Serves me right for trying to post from memory.

[Milo Kurtiss]

The LOR Decision Lander and the Grumman Lander Look absolutley fantastic. pity they're not in KSP.