Moon Landing: Was Direct Ascent actually plausible

The rather length background to the question:

I recently saw “Moon Machines,” a six part miniseries about the development of various components of the Moon landing program. The various episodes dealt with the development of a) The Saturn V, b) The navigation computer, c) The Command Module, d) The space suit, e) The Lunar Module, and f) The Lunar Rover.
Anyway. . . The Lunar Module ep dealt with the three different options on the table for a landing a) Direct Ascent, b) Earth Orbit Rendezvous, and c) Lunar Orbit Rendezvous.

“Direct Ascent” was not practical because it was estimated that the rocket to launch off the moon might have to be as much as 60 feet tall (so bigger payload, more fuel, more fuel to help launch the extra fuel, lather , rinse, repeat).
Earth Orbit Rendezvous was ruled out. I understand why, but in the ep, they kinda glossed over.

The lone voice championing Lunar Orbit Rendezvous was one John Houboult (now probably in his 90s, and I guess not in good enough health to actually make an appearance in the ep). Despite being told to fuhgeddaboutit by Wernher von Braun himself, he repeatedly insisted that LOR was the only way to go. Von Braun was a proponent of Direct Ascent.

They also glossed over von Braun’s conversion to the LOR plan. It was just like, “You know this Direct Ascent might work, but I think we oughta go with LOR.”
Anyway, I came across this link, and it appears that this author’s contention is that if we had gone with two astronauts instead of three, that Direct Ascent would have been a good option, and we probably would have made the first landing even earlier (of course, assuming that we ever got there at all!).

Anyway, I don’t know that there is a completely factual response to this question, but wouldn’t might some opinion on just how plausible this contention is.

I don’t know if direct ascent would have been possible or not, but if you’re interested on another take of John Houboult’s story, check out the episode Spider from the excellent HBO Series From the Earth to the Moon.

Unless I recall incorrectly VonBraun was a proponent of Earth Orbit Rendezvous. And it was a question of what had the best chance of being done in the time frame of before the end of the decade.
Direct Ascent required a massive booster capable of launching from earth, landing on moon, launching from moon, landing. No specialized vehicles whose weight can be discarded when that purpose is served.
Apollo: Race to the Moon by Murray and Cox has an excellent recount of the decision making process.

Interesting topic. What do experts think of the Russian moon landing plan? This required a cosmonaut to leave the capsule, enter the LEM (or whatever the Russians called it), descend to the moon, return, and exit the LEM, then re-enter the capsule.
Sounds like a disaster waiting to happen-what odds were they that this would actually work?

Direct ascent was perfectly plausible, but would require either a bigger rocket or a smaller payload.

A bigger rocket would have involved one of the hypothetical designs generically referred to as “Nova”, such as the proposed Saturn C-8, which would have used eight F-1 engines in it’s first stage and eight J-2 engines in it’s second, instead of the five used in the Saturn 5. One objection to this is that it would be so big it would have required the building of new production facilities, when time was seen as of the essence. The Saturn 5 could be built in existing facilities.

Or a Saturn 5 could have lofted a smaller payload. In particular the USAF was pushing hard to establish a parallel manned space capacity, with it’s Gemini design as the USA’s standardized manned capsule. Even after the Saturn-Apollo design was finalized, there were still proposals for a Gemini-based “rescue” vehicle.

Encyclopedia Astronautica at has everything you would ever want to know about the subject.

Isn’t that what we did, too?

No, the Apollo Command module and Lunar module docked, and the Astronauts made the transfer via internally connecting tunnels/hatches.

The Soviet version (if I read correctly on Wiki) would have required space walks.

Chronos, he means by spacewalk.

ralph124c, US astronauts did perform a spacewalk on the exterior of the vehicle during the return flight, to retrieve camera film.

Odds that it would work? Yes? No? One in a whatever we wanted to make it? Not sure how to calculate that. It does place two spacewalks in the required path to execute the mission safely, rather than just as something to perform on the surface, not impacting landing and return.

Earl, I don’t know the details of what you ask, but thanks for an interesting question.

No, the Soviet concept actually had the cosmonaut performing an EVA to get to the lander, and then the reverse the other way. They also would have left the command module unmanned. It would have been truly a stunt mission, even more so than Apollo 11.

As for the OP, yes, I would have been at least plausible, and was seriously considered in early trade studies due to the schedule limitations versus specifying, designing, and qualifying two separate vehicles, each with their own habitat and propulsion systems. A hybrid concept, similar to the Soyuz layout (in which a return module with minimal life support and propulsion capability to minimize the mass that needs to be protected upon re-entry) might even be weight-positive despite carrying the RV down to the Moon’s surface and back up. However, despite the additional complexity, the CSM/LM system was selected due margin (separating the system allowed for growth of weight budgets on the then still only conceptual Apollo command module), flexibility (the base LM design could be modified to perform a variety of missions, including landing and deploying the Lunar Roving Vehicle), the flight history of the blunt-arsed conic RV (highly robust and successful from Mercury and Gemini), and safety (the CSM/LM offered larger habitat and redundant propulsion, life support, and communication systems.) (Unlike the portrayal in the film Apollo 13, the use of the LM as a lifeboat vehicle had been studied extensively by Grumman, although the use of the main descent engine for primary propulsion had not.)

Had the Apollo Plus/Apollo Applications program continued beyond the Skylab missions, the LM would have no doubt been put to use as an orbital ferry, lunar long-range exploration vehicle, and as a chassis for a variety of unmanned roles, so the Apollo configuration was really the best long-term choice for a general purpose space transportation system, which was recognized early in trade studies. There were even studies by NASA and Grumman to adapt the LM to the STS/Space Shuttle payload bay for a variety of uses. (The inclusion of a liquid fuel main propulsion system might have prevented its ultimate use, just as plans to use the Centaur-G were scrapped post-Challenger as a hazard in a Return-to-Launch-Site abort mode.)


I knew a guy who worked for NASA in the 60s. He said they knew the Russians did not have the ability to go to the Moon but downplayed that to get more money. Every time they needed more money they would say “Do you want the Russians to go to the Moon first”

The Soviet manned lunar program was real; it was only after the total failure of their lunar rocket that the Soviets backtracked and denied they had ever intended to go to the moon. Since the end of the Soviet Union information has come out of Russia documenting the extensiveness of the Soviet effort.

The Soviet lunar program started late, a full two years after Kennedy’s announcement that the US would seek to land on the moon by the end of the decade. The entire Soviet industrial system was based on five year plans in which the very materials like steel and concrete necessary for projects had to be allotted beforehand. The program never had the level of support that the US effort enjoyed, since the military complex in the Soviet Union considered a lunar landing irrelevant to more pressing national security concerns like ICBMs.

But the clincher was the rocket chosen for the lunar attempt, dubbed the N-1. It was the brainchild of Sergey Korolyov, the rocket engineer who had designed the R-7 rocket that boosted Sputnik, Gagarin and most of the Soviet Union’s early space efforts. This earned Korolyov tremendous cred within the system, but the N-1 was fatally flawed. Not only was it too small, meaning that despite promises to the contrary it could NOT boost a lunar mission in one shot (it would have needed Earth orbit rendevous AND lunar orbit rendevous), but the first stage design which used thirty combustion chambers was inherently unstable to catatrophic vibrational resonance. Korolyov himself died before the program matured and his successor was a bureaucrat who mismanaged the program. Four test flights were conducted and all were first stage failures.

Ironically, there was an alternative to the N-1. A rival rocket bureau that was responsible for the development of what became the Proton booster proposed a heavy-lift rocket based on clustering multiple units of the Proton’s core tankage. This rocket, dubbed the UR-700 (after the Proton’s official designation of UR-500) would if successful have had enough raw lift to support a direct ascent mission profile. However the design lost out because of political considerations, mainly Korolyov’s status and the shakeup that took place when Krushchev was deposed.

Thanks for all the very informative responses, but I believe in the wordiness of my OP, the specific question actually got lost, so with that all behind:

In the link I supplied, the author contends tha if we had gone with two astronauts instead of three, that Direct Ascent would have been a good option, and we probably would have made the first landing even earlier.

Was your friend a janitor? This isn’t even remotely true.


Answers still stand I’d say. I don’t believe the number of astronauts was a critical point in the decisions. And direct ascent carried a number of complications that made it the first possibility discarded, so in all likelihood it wouldn’t have made the first landing earlier.

Just finished reading the link. It does seem as if there was a commitment to the Apollo command module, which compared to Soviet designs (or even rival American designs) was the Cadillac of space capsules. For example, in the Apollo-Soyuz rendevous mission of 1975 the Soviets put their Soyuz capsule into orbit with a rocket with half the boost capacity of the Saturn-1B necessary to loft the Apollo Command/Service module.

Still, if they’d wanted to go ultra-cheap and dirty they could have landed one astronaut on the surface of the moon for an hour wearing a spacesuit and riding an open-frame lander. At some point it was decided to actually make a go of it rather than a stunt.

Asked and answered. Yes, it is plausible, yes, it would have had less complexity than the CSM/LM system with the LOR flight profile, and had it been based on the less technically sophisticated Gemini/Titan II (plus a man-rated Centaur upper stage) system, yes it is possible that we could have landed two astronauts on the surface of the Moon in a DA flight profile, albeit at significantly higher risk (in terms of technical and schedule risk, not flight hazards). More likely, it would have used a Gemini command and service modules with a LOR profile to a smaller (possibly open cockpit) lunar lander intended for a quick jaunt down to the surface for some sample collection and plant the flag, then return to the capsule. (Although a lander creates more operational complexity it places less of a burden on the weight budget of the overall vehicle and makes the development program less risky in terms of schedule milestones).

By analogy, the direct ascent concept is like holding the Q-K-A and hoping for a 10-J, while the Lunar orbit rendezvous approach is holding a pair of As and an 8 and betting on coming up with two pair or three of a kind.


Actually, the reason Apollo was budgeted for a crew size of three was to have the command module manned at all time, automated docking systems being uncertain risk. One of the main goals of the Gemini program (which was actually initiated after Apollo) was to test and validate rendezvous and docking systems and procedures. There was no crew workload rationale for three astronauts in the Apollo lunar missions, and in fact, one of the concerns about the Lunar Exploration Survey - Apollo missions was leaving the CSM pilot in orbit for an extended period (2-3 months). A three-man crew (and the associated expansion of life support and habitat space) was regarded as less technically risky, but nothing about the mission objectives of the lunar landing required a crew of three.


No he was an engineer. I am just telling you what he told me.

To be more specific he did not say the Russians had no plans to go to the Moon. He said the people at NASA felt they were no threat to beat the US to the Moon. Maybe a lot of that was simply arrogance of NASA people.

Your friend is either ignorant or lying. Far from being arrogant, the then fledgling NASA ,established in 1958 with a paltry budget of $100m from NACA–an almost purely research-oriented clearinghouse–realized that not only was the primary task assigned to the organization (“before this decade is out, of landing a man on the Moon and returning him safely to the Earth,”) a massively daunting one, on the scale comparable to the Manhattan Project in cost, schedule, engineering effort, logistical difficulty, and complexity of poorly understood technical problems, but that the United States was several years, if not a decade behind the Soviet Union in terms of rocket and space vehicle technology. By any rational estimate of technological achievement in 1961, the Soviets should have easily beat us to the Moon, just as they had proceeded the United States every major milestone in rocket technology to that point (deployment of the first operational ICBM system, first orbital launch, first probe to orbit the Moon, first to photograph the far side of the Moon, first soft landing on the Moon, first human in orbit, et cetera).

In fact, the reasons that the Soviets didn’t make it to the Moon were economic and political, not (strictly speaking) technical. The Soviets already had all of the basic elements for a lunar landing program; what they lacked was the ability to scale up their industry to support the order-of-magnitude increase of effort to support a Moon program, and the internecine fighting between design bureaus, the outcome of which was determined less by trade studies and concept demonstration than by which bureau chief had more draw with Khrushchev and the Politburo.

Although it is not quite correct to say that the US won the moon race by outspending the Soviets, it is fair to say that the concentration of resources allowed the exploration of multiple concepts which were then winnowed down to the optimum solution by a process that was as free of political chicanery as is possible for any major technical program. It is clear from even a cursory perusal of the initial trades that led into Apollo, though, that the system developers had only a crude idea of how they were going to get to the Moon, and at several times during Apollo/Saturn development there were significant concerns over achieving the goal of a lunar landing in the 1969 timeframe, not the least of which was the AS-204 pad fire that killed three astronauts and highlighted not only the gross design error of a hatch that couldn’t be opened from the inside (which had already been rectified in later models but hadn’t been flowed back down to the Apollo I mission) but a disconnect between risk assessment (the exact scenario that led to the tragic fire had already been identified and passed to NASA management as a risk) and systems integration, as well as numerous configuration control, quality control, qualification deficiencies, et cetera, came to light. Until mid-1967, McDonnell Aircraft held out variations on the Gemini-Titan system as an alternative to Apollo/Saturn (despite some of its technical limitations) and had substantial hearing from NASA management, if on the down low.

Until the flight of Apollo IX in early 1969, which proofed out the problematical development of the Lunar Module–there was not a high degree of confidence in meeting the 1969 deadline (although by that point it was pretty clear that the Soviets weren’t going to make it to the Moon by Christmas, either). And by 1969, nobody was handing blank checks to NASA; indeed, the J-class (extended duration) missions were already being curtailed, and the Apollo Applications Program (a plan to use the Apollo/Saturn system as the basis for numerous exploratory, scientific, and possibly even commercial ventures) had been severely hindered by stop-work orders on further Saturn INT-20 and Saturn V vehicles.

The claim of NASA engineers being unduly confident in beating the Soviets to the Moon doesn’t hold water.


I swear I have just read this thread, its 13:30 March 10 2010. Am in Baku and I just flicked channels to BBC Prime and Race to the Moon has the very same second started.

Stop it! You guy’s are now seriously starting to freak me out!:eek: