James Concannon writes...
In their 2009 book Dark Mission, Richard Hoagland and Mike Bara wrote (p. 280) "While the spacecraft [the Apollo 10 LM, Snoopy] was theoretically fully capable of landing on the moon, inexplicably, it was not given the capability to do so."
In expat's critique of the book, he wrote: « FACT: Snoopy was emphatically NOT capable of landing (well perhaps, technically, it was, but not of successfully taking off again.) Grumman engineers had not yet implemented SWIP (the Super Weight Improvement Program) and the spacecraft was too heavy. More accurately, it would have been too heavy if it had been fully-fueled for a landing and takeoff. »
It's not a widely-known fact that George Mueller, Director of NASA's Office of Manned Spaceflight, was actually in favor of a landing by Snoopy. He felt that, even if the astronauts couldn't exit the LM and walk on the lunar surface, just the fact of a brief touchdown would sufficiently fulfill JFK's challenge to land a man on the Moon.
In Foothold in the Heavens (2010), Ben Evans wrote this, on the basis of an interview with Tom Stafford:
"Stafford told Mueller in no uncertain terms that if Apollo 10 was rescheduled to make a landing, "The flight crew won't be on it. There was just so much to do." The main problem was that 'his' lunar module, designated LM-4 and shortly to be re-named Snoopy, was overweight; it was only by a few kilograms, but still too much to satisfy the safety margins for a successful lunar liftoff. Grumman engineers had long known that LM-4 was earmarked for an Earth-orbital or lunar-orbital test flight, rather than a lunar landing, and had not subjected it to their Super Weight Improvement Program (SWIP)."STATS: The mass of Snoopy, unfuelled, was 9,484 lb cf. 9,287 lb for Apollo 11 's Eagle. An overweight of 197 lb or 89 kg.
On the basis of an online discussion with a space fan (in French, as it happens) I fell to wondering how come, if 197 lb overweight was a show-stopper for Apollo 10, it became possible to add a Lunar Rover weighing 463 lb for the later J Missions (Apollos 15-17). I'm a member of a Facebook group that regularly discusses space history and has several experts (James Oberg is one) who take an interest. So I posted to that group yesterday and got immediate response:
James Concanon: Snoopy was too heavy to have landed on the Moon and taken off again, right? The Descent Stage was 220lb heavier that that of Apollo 11. So how come for the J Missions it was OK to add a 463lb LRV?
Ronald Purviance: Many things. Saturn V mods to increase payload, changes in way the LM was released for descent to the surface, and changes to the LM itself.
Alan McEwen: ...
Rolf Karlastad: Alan: If you're not too heavy to take off, more fuel = more delta V.
Even if you had too much fuel for takeoff, due to a lack of thrust, one could simply burn fuel until the thrust to weight ratio was greater than one, and you would lift off.
Sort of the opposite of a plane where you rely on lift.
Alan McEwen: I deleted my previous response because I realized it was wrong. Snoopy was short fueled in the ascent stage. That is why it could not have completed and an ascent to orbit. Thrust was not an issue. As I said it could lift off. There was just not enough energy potential in the amount of fuel to carry out a full ascent. The weight issue came into play with The descent. As you may remember , Buzz and Neil landed with almost empty tanks. If I'm not mistaken they also had 2 PLSSs and basic science cargo. Snoopy did not have those things if I remember correctly. Had Snoopy been fully fueled, plus carrying the cargo, it would not have enough descent propulsion fuel to make a landing.
John Breaux: Bigger descent engine is the main thing. Also in later missions the LM would be taken closer to the surface before undocking meaning it needed less fuel for the descent. I'm sure some of the bigger brains here can give you exact figures.
Shane Barry Penington: Absolutely Correct...BINGO you get the $64,000.00 prize! They also figured a more direct descent trajectory from a lower orbit...
David Paul: Yes, in later missions they used the SM engine for the initial descent orbit insertion, letting that engine do some of the delta-v needed. Also, by the J missions, they had changed the fuel mixture ratio on the Saturn (I think it was the S-II) so they could get more payload up.
Greg Bigelow: At approx. 2:20 Tom Stafford himself says it was too heavy to land. https://youtu.be/DkS2BMeA2Io
Rolf Karlstad: he over simplified. Perhaps it didn't have enough delta V to land. Unless for some reason the landing legs were weak. See? Weight doesn't really factor in, only delta V. It didn't have enough delta V to land because it didn't have enough fuel, perhaps because it was too massive, and the tyranny of the delta V equation Delta V = natural log (mass fueled/mass empty) *isp *g
It's really the only factor at play here.
That's the History, now for the Mythology
So, OK, I got my answer. But perhaps predictably it stirred up a well-known controversy about that mission. Gene Cernan must take part of the blame for this, because he himself suggested an alternative reason why Apollo 10 was not cleared to land.
"A lot of people thought about the kind of people we were: 'Don't give those guys an opportunity to land, 'cause they might!' So the ascent module, the part we lifted off the lunar surface with, was short-fueled. The fuel tanks weren't full. So had we literally tried to land on the Moon, we couldn't have gotten off." --Cernan, quoted in Rocket Men by Craig Nelson...and of course, some of those Facebook experts couldn't resist reviving the controversy:
Steve Pietrowski: NASA intentionally short-fueled the LEM so there was no way they could have landed and gotten back. Management assumed that the X crew would have tried for the surface if they had a viable chance. For the J-missions, they had better PDI, as well as a redesigned engine bell for the descent stage. I don't think the engine was uprated powerwise, just made more efficient.
Sarah Bowyer: I don't think NASA short-fuelled the LM because they didn't trust the crew not to try and land on the surface! Yes, they were competitive, but not to the extent of ignoring orders and trying to land before the procedures had been worked out. Remember, when A10 flew, they had a good chance of being on a later lunar mission.
Steve Pietrowski: I'm pretty sure I read it in "Chariots for Apollo." I don't recall management explicitly forbidding a landing either. They sort of just didn't bring it up; then mentioned, "by the way, you won't have the fuel." I know I've seen this story in the wild elsewhere. If anything it adds a layer to the legend.?????
James Concannon: That was not the reason for the half-empty tanks. The reason was they needed the spacecraft's mass at the moment of rendezvous to be exactly what it would have been if it had taken off from the surface.
Tom Faber: Will this myth that Snoopy's ascent stage was short fueled to keep the crew from trying to land ever die out? No, that is NOT the reason. It had a reduced propellant load so that the rendezvous maneuvers with the CSM were flown with the ascent stage at close to the same mass as one had after an actual ascent from the surface. If it had a full load its handling characteristics would have been very different.
Besides, these men were professionals. They would not have disobeyed orders. And what would have happened if they did? They would NOT have been heroes. They would have forever been branded as the crew who would follow orders. It would have cast a pall over the whole program. Congress may have pulled the plug on the rest of the program right there.
Ronald Purviance: Every time I hear this BS rumor, it makes me mad. It totally dishonors the crew.
Greg Kennedy: I’ve posted to similar threads several times. Suggest you check NASA history publication “Apollo by the Numbers”. It has statistical data for all the missions including vehicle weights, propellant loads, etc.
Just the facts
I took Greg Kennedy's recommendation, and looked up the document. Here's a link to the ToC. In the tabulations labeled Spacecraft Key Facts, I found two very interesting facts.
FIRST, Although the Descent Stage of Snoopy is confirmed as overweight, the Ascent Stage was actually lighter than that of Eagle: 4,781 lb cf. 4,804 lb. So if that's true, why would there be any concern about Snoopy's capability to take off?
SECOND, The rated thrust of the Apollo 10 Ascent Stage engine is given as 1,650 lbf cf. 3,218 lbf for Apollo 11 and all subsequent missions. Even the Apollo 9 figure cited is 2,524.
Nobody in the expert group ventured any explanation. So there is a mystery—two mysteries—about Apollo 10 after all.
All I can say is that the fact that Patrick actually posted this thread, finally gives him a modicum of credibility, as usually he simply dismisses anything mysterious, as if mundane. Come on Patrick, don't give up now and tarnish your perfect record. Isn't there some obvious imaginative mundane explanation you can toss like sand in the machine?
Well, I can think of one for the wieght of the Ascent Stage. Perhaps some equipment was counted as part of the essential spacecraft. Snoopy would not have needed the EVA suits and oxygen support PLSSs -- that would account for 400 lb, which is too much in theory.
As for the apparent lack of thrust in the ascent stage engine, at this point I have NFI.
No fair, James. Good answer, but I was asking Patrick, not you. Or, are you just one of his many ghost accounts?
Apollo by the Numbers is not definitive. Why? Because it is alot of numbers. Take a look at the chart and compare it with actual source documents.
The Apollo 10 press kit (before the flight) says the Ascent Propulsion System is " 3500 pound (1589 kg)" (same in the Apollo 11 press kit).
The "Apollo 10 LM-4 Ascent Propulsion System Final Flight Evaluation" report (http://hdl.handle.net/2060/19690026326) says it is (note from actual flight data) 3432.1 pounds force.
The "Apollo by the Numbers" seems to be in kilograms not pounds force. This kg and lb things seems to happen sometimes.....
As to mass, they definitely "off-loaded" or "half-loaded" the accent module tanks. The flight data shows there was 1650.1 lbm of oxidizer and 981.4 lbm of fuel in Apollo 10 ascent module tanks. For Apollo 11 is shows 3218.5 lbm of oxidizer and 2019.9 lbm of fuel. Not sure why they did that.... not spelled out in bold font words.
« The "Apollo by the Numbers" seems to be in kilograms not pounds force. This kg and lb things seems to happen sometimes..... »
I can't accept that. The line is clearly labeled lb (in context it clearly means lb-f not lb-m) If a metric figure somehow crept in it would be newtons, not kg. 1650 kg would convert to 3,638 lb-m -- way too big.
« As to mass, they definitely "off-loaded" or "half-loaded" the accent module tanks. The flight data shows there was 1650.1 lbm of oxidizer and 981.4 lbm of fuel in Apollo 10 ascent module tanks. For Apollo 11 is shows 3218.5 lbm of oxidizer and 2019.9 lbm of fuel. Not sure why they did that.... »
It's quite clear from many sources why they did that. The mass of the ascent stage at the moment of rendezvous had to be the same as if the spececraft had taken off from the Moon surface.
Thanks for the xomment
Having worked on government projects many years ago. I can tell that when we truly did not know how something would pan out from too many unknowns. We actually tested our equipment just short of the actual application.super computers were a few years off.
Considering we truly didn't know everything about potential variables concerning gravity anomalies, ground condition etc. I'm with the facts. They needed to replicate everything short of a landing.
Remeber, even when they landed. Nixon had a second speech if they could not leave the moon. So even then, things were uncertain.
Nixon's backup speech was written by William Safire at the suggestion of Frank Borman. It began:
Fate has ordained that the men who went to the moon to explore in peace will stay on the moon to rest in peace.
These brave men, Neil Armstrong and Edwin Aldrin, know that there is no hope for their recovery. But they also know that there is hope for mankind in their sacrifice.
These two men are laying down their lives in mankind's most noble goal: the search for truth and understanding.
Others will follow, and surely find their way home. Man's search will not be denied. But these men were the first, and they will remain the foremost in our hearts.
For every human being who looks up at the moon in the nights to come will know that there is some corner of another world that is forever mankind.
I think that's pretty good stuff.
Expat, do you know 'how' Armstrong and Aldrin were told to die, if they couldn't leave the moon? Were they to remain in the spacecraft, or go outside, or what? Were they to take a suicide pill, or just run out of oxygen? Do you know the details?
No I don't. I've always assumed it would be their own personal decision. If it were me, I'm not sure whether I'd prefer to cark it inside or outside the LM.
Mr. Concannon writes:
>>I can't accept that. The line is clearly labeled lb (in context it clearly means lb-f not lb-m) If a metric figure somehow crept in it would be newtons, not kg. 1650 kg would convert to 3,638 lb-m -- way too big.
You are right. I withdraw the "kg" idea.
In "Performance analysis of the ascent propulsion system of the Apollo spacecraft" at http://hdl.handle.net/2060/19740005391 , Table VI shows the various kinds of thrust data for Apollo 10. They list the calculated flight performance (based on flight data) as 3432 lbf. Table VII shows for Apollo 11 that the thrust is 3442 lbf. By the way, Table V shows Apollo 9 data too, 3380 lbf. The tables show the engine acceptance test data too and none are as low in Apollo by the Numbers' "maximum rated thrust".
My prior posting reference and analogous ones for other Apollo flights show the post-flight data reduction of thrust. None show the odd low values for Apollo 9 or 10 and they don't even match the other flights.
Without references, these Apollo by the Numbers should not be considered primary source data.
Also, this ascent module engine is nonthrottleable. This means you can't change its thrust. It is one thrust. So, changing the amount of fuel only changes the time of operation, not its thrust level.
Mr. Concannon states: "Although the Descent Stage of Snoopy is confirmed as overweight, the Ascent Stage was actually lighter than that of Eagle: 4,781 lb cf. 4,804 lb. So if that's true, why would there be any concern about Snoopy's capability to take off?"
If the Apollo 10 Ascent Stage and Descent Stage fuel tanks were completely fueled, then because the Descent Stage was 220 lbs too heavy, it doesn't matter if the Ascent Stage was 23 lbs lighter and theoretically could take off, the combined modules will go splat because on landing they were too heavy. Now, you could examine the ullage fuel they carry and ask yourself whether they could offload 200 lb. They put ullage fuel in there for a good reason and you can't count on it not being needed. I am sure the Ascent Stage had ullage fuel too. You don't drive your car until you use up the gas in the tank.
The ascent stage weight dry weight or fully fueled?
Every minute and second of these missions was planned out and practiced over and over again. The crew could not have just inserted a landing into the flight. Plus, these guys were the ultimate professional test pilots. They would not have done something as crazy as landed on the Moon even if they could have.
The myth that they might have is perpetuated by people who have absolutely no concept of who the Apollo astronauts were. It's completely absurd.
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