So JFK states that it should become a goal of the US to send a man to the moon and return him safely by the end of the decade. Very good.
So NASA has to start a huge engineering effort on all phases of the mission. Well, as anyone who has worked in a large company, on a large project or in a large bureaucracy knows, things always get bigger and more complicated the further you get into a project.
So it seems, in order to pull off a moon mission, just to be safe, the Saturn 5 had to have been conceptually designed to do a lot more that it was initially thought it might need to do. NASA couldn’t risk plowing a bunch of money into a rocket that, as the demands of the mission were better understood, couldn’t deliver. If that happened, the goal could never have been reached.
So how overpowered was the Saturn 5? Was it capable of doing 1 1/2x, 5x or 10x what was demanded of it? Or, was it just capable of doing what it had to do? Just asking.
The Saturn V was overdesigned, as far as rockets go. It had more payload capacity than it needed, and its engines operated within comfortable margins. But this is a relative thing–the margins were still thin by most standards.
So for instance, it had a capacity of 45 tonnes to TLI (trans lunar insertion), while Apollo 11 required 43.9 tonnes. Later missions pushed the mission mass closer to the limit.
Also, the F-1 engines were to have an uprating program to increase thrust by 33%. This never happened, but it gives you an idea as to the limits of the basic design. Note that this doesn’t mean you could plop the engines in and get 33% more payload–you need more fuel, too.
I suppose another question is if the program as a whole was overdesigned, in the sense that if you just had to put one man on the moon, how much could you save? Or heck–what if you didn’t retrieve him? I’d suppose you could save at least a factor of 2 in mass here; maybe more.
So in short, there are no large margin factors unless the mission is reconsidered. Rockets always operate on the bleeding edge. It’s the nature of the problem.
Very close to just right. Although the history of the mission is anything but that. The Saturn V was not the largest design, it was however about the largest they could manage within the launch pad design constraints. The mission profiles took some time to converge, and the whole question of lunar orbit rendezvous was the key element that allowed the mission design to converge. Before that, some mission designs used two Saturn V launches - one to launch a tanker with enough fuel to allow the rest of the mission to proceed.
The mass budgets were reasonably well understood early on, it isn’t hard to work them out - working backwards from the mission profile. But you are right that the Saturn V was in design before the mission was properly specified. As it was, keeping within the mass budget for the various vehicles was a nightmare - especially for the lunar module - which was the device at the pointy end of the equation. Designing a vehicle capable of taking off from the lunar surface with two guys on board to rendezvous with the command module sets in stone the mass budget of the rest of the configuration. Mooted designs were as stripped down as a platform that the guys simply stood on whilst suited up. It was the realisation that this vehicle didn’t need to do anything more - and didn’t need to be the vehicle they re-entered in - that allowed a single launch mission to be viable. So in the end, the answer is - the Saturn V was just capable. Once it was realised it was just capable, they made things fit. As the construction of vehicles progressed later versions got lighter, and thus there was more room for extending missions and adding equipment. The lunar module used for Apollo 10 was too heavy to perform a landing and ascent mission at all. The third block of lunar modules was light enough that they could add a lunar rover and run extended stay missions. Improvements in the Saturn V helped here too.
The physics of the system is a hard master. The myriad designers knew they had a set mass budget, and no amount of pleading with management was going to change the laws of physics. Not that every designer didn’t feel that their system was so important that they deserved a larger slice of the mass. Brutal simplification won the day in many areas.
History might have shown that had it not been quite possible, they might have ended up with hybrid missions - say the CM and astronauts launch on a Saturn I-B to meet with a LM/Saturn-IV stage, dock, and thence to the moon. That would have been riskier, but not much riskier than a single launch, with none of the really hard problems of fuel transfer envisaged with the early dual Saturn-V direct ascent missions.
You do get some payload increase with higher thrust and without using more fuel. Because the rocket travels faster, it spends less time opposing gravity. The ultimate example is a rocket that hovers, it uses infinite fuel to ‘achieve orbit’, with more powerful engines it will use a lot less fuel.
Not just the maximum inertial loading, but also the aeroloads on the vehicle at maximum aerodynamic pressure (“max Q alpha”) and the attendant heating rates that will require more thermal protection. For any particular vehicle profile, there is a maximum speed at any given altitude that you can realistically achieve, after which other factors start to increase total impulse required and the hazards experienced. Once you clear the atmosphere, the more impulse you can generate the better up to the maximum acceleration that can be tolerated by the payload, until you achieve orbit.
As for the question of the o.p., the Saturn V was optimally designed to delivery the Apollo CSM, Lunar Module, and (for later missions) the Lunar Roving Vehicle. This begs the question of how oversized the Apollo system itself ways, and while there is no definitive answer, we can note that it carried three people to Lunar orbit and two to the surface in a pressurized habitat, whereas a single guy with just enough of a rocket and habitat to land and take off again would have satisfied the base requirements of Kennedy’s speech. McDonnell Aircraft proposed a number of different modifications and configurations for the Gemini vehicle including a scaled down cislunar system and an open-cockpit lunar lander (which would have required a spacewalk from the capsule to the lander and back on return). This would have flown on an uprated Saturn I or Titan IIIM (uprated Titan II with solid rocket boosters, similar to the later Titan 34D configuration). Such missions would have been on the hairy edge of desperate, and the kind of failure that the Apollo XIII mission was able to survive would have been catastrophic for a Gemini-based lunar mission, so in retrospect, Apollo provided just enough margin to recover from a serious system failure.
Thanks for these very enlightening replies. I’m finding my question to be more intriguing than I thought when I posted it. IANA scientist or engineer. Can I take the liberty to synthesize the the information into pedestrian terms and you tell me if I’m understanding it.
The engineers mapped out a project and came up with parameters as to what they would need to accomplish the mission.
The rocket guys went to work on the launch vehicle and decided on the Saturn V. They were confident that a rocket of that capacity could do the job. They also had a plan to enhance the performance of it if necessary.
The moon landing guys were given the parameters of what the Saturn V could accomplish. They used those parameters in designing what they could launch, how many astronauts could be involved and what the limitations were as to what they could take with them.
The power of the Saturn V not only allowed three astronauts but it would be sufficient on future missions to take a lunar rover.
If the Saturn V specs had been less than what they it was actually capable of then the moon landing guys would have scaled back the scope of the mission. Two astronauts, no lunar rover, whatever.
This gets back to the OP. The Saturn V was designed to be the basis of the mission. The moon landers designed their mission around that. They modified accordingly.
Please correct me if I’m wrong. I guess what I’m getting at is, if I understand the information correctly, the Saturn V was an overpowered vehicle to accomplish the initial mission but it wasn’t an overpowered vehicle to accomplish the mission as it came to be designed. The moon lander guys designed within the Saturn V capabilities. The Saturn V guys didn’t design up or down to what the moon lander guys said they needed. Right or wrong?
Thanks for all the info. It’s been very enlightening. Just trying to fight ignorance.
This gives the wrong impression of how the Saturn V was developed. NASA, acting as its own prime contractor responsible for defining the system architecture, didn’t tell Boeing (the prime integrator for the Saturn V) to “go away and build us a big ass rocket,” and then hope is was enough. They performed what is now called the system requirements analysis process to define the key capabilities required by the functional elements of the system, and then decomposed those requirements down to lower levels, providing each contractor and subcontractor with a consistent set of requirements for their particular system (stages, CSM, LM, et cetera). As the designed matured from concept to preliminary design to final design, requirements are revised and reallocated so that there isn’t (in theory) a gross mismatch in capability. That the Saturn V had the capability to deliver the Extended LM and LRV for the J-class missions was no accident; it was the result of deliberate planning and weight budgeting to assure the desired capability that was defined well before any fabricator started bending steel.
The Saturn V was actually almost perfectly optimized for its intended role. To a certain extent, that optimization was actually a detriment; adding further capability became difficult without substantial modification (essentially redesign) and the cost was such that it was never suitable for nascent commercial interest in space. A Big Dumb Booster type concept that was not so tightly optimized might have offered better economies of scale and the ability to achieve design cost reductions concurrent with production, as done on the highly successful and long-lived Delta II medium class launcher.
It is worth mentioning a few aspects of the history of the Saturn-V to perhaps underline the interactive, and also modular nature of the process.
The engines, the F-1 an J-2 were being designed in the late 1950’s before any craft that would use them had been any more than notionally sketched out. Indeed the F-1 was initially envisaged as being used as a single engine for large military payloads.
The Saturn-V configuration was firm by the end of 1961, and NASA gave formal approval for development on 25 January 1962. It was only in November 1961 that John Houbolt wrote to NASA associate administrator Robert Seamans advocating lunar orbit rendezvous as the best (if not only) viable way of achieving a lunar landing. On 11 July 1962, NASA confirmed the choice of the LOR mode for the lunar mission. In the interim, a direct ascent mission, possibly based upon the mooted giant Nova rocket (which had between 8 and 10 F-1 engines) was notionally still on the cards, and had significant support within NASA. In some ways the Saturn-V was simply the best configuration that used the F-1 and J-2 engines to build a really big rocket. The precise configuration was tuned to the mission as both developed. But the genesis of mission configuration and basic rocket configuration were concurrent.
It is hard to imagine how fast things were moving back then.
And to think, NASA and its contractors did all this without the benefit of Microsoft Project or Powerpoint. It boggles the mind. I’m also pretty sure that no one involved with the program ever uttered the words “going forward” or “synergize”.
Interestingly many of the project management skills came from the ICBM programmes. (Something that was not always welcome in NASA.) There were plenty of serious issues in Apollo on the way through. I find the history of the project remarkable reading for just this reason. As much as I love the technology and the fantastic achievements, the lessons in how they managed it don’t grow old. That whole era just puts the current world to shame. We don’t have steely eyed missile men any more.
Then again, NASA changes dramatically through the 60’s and the senior guys knew that it would never be the same. They would never be entrusted with so much money, with so much freedom ever again.
One of (I think) the coolest possible missions the Saturn V could have done was a manned flyby of Venus! It was one of the possible missions proposed by the Apollo Applications Program. Unfortunately Skylab was the only post-Moon landing mission that got funding.
Huh. The Venus flyby simultaneously sounds like the coolest thing ever, and also a perfect example of something that can be done better with an unmanned mission. For the same cost you could probably send out a half dozen probes with more instruments, learn exciting new things, and still have plenty money left over.
Wow, never heard of the manned Venus mission. A whole year completely exposed to the radiation environment of the inner solar system…I wonder if NASA really understood the scope of that problem when they were profiling the mission? We still don’t have a good handle on how to protect astronauts from ionizing radiation during long-term flight outside the cover of the Earth’s magnetic field.