Author Topic: Apollo 10: What prevented a landing? carmelo

Member Posts: 1051

From: Messina, Sicilia, Italia

Registered: Jun 2004 posted 02-07-2005 11:17 AM If Apollo 10 astronauts Tom Stafford and Gene Cernan landed with the lunar module "Snoopy," could they have been able to perform a short EVA on the moon? bruce

Member Posts: 917

From: Fort Mill, SC, USA

Registered: Aug 2000 posted 02-07-2005 11:44 AM Gene Cernan has said that they were short-fueled with their lunar module, thereby making a (safe) landing impossible. Also, I don't believe they had all the suit equipment for an EVA. Even if they managed to land Snoopy on the lunar surface, I dare say it would have been a single, very, very short EVA! nasamad

Member Posts: 2141

From: Essex, UK

Registered: Jul 2001 posted 02-07-2005 12:16 PM I have heard quite a few people say that the Apollo 10 lunar module was too heavy to land on the surface, but having just checked out the numbers it seems the the Apollo 11 lunar module was 3500 pounds heavier, so I don't know why I have heard that so often... Blackarrow

Member Posts: 3160

From: Belfast, United Kingdom

Registered: Feb 2002 posted 02-07-2005 05:20 PM Without checking the statistics, surely the extra weight on Apollo 11 was the extra fuel which "Snoopy" lacked? Also, surely its not as simple as weight. It's a matter of thrust-to-weight ratio. Snoopy wasn't designed to land. Eagle was. nasamad

Member Posts: 2141

From: Essex, UK

Registered: Jul 2001 posted 02-07-2005 05:52 PM I knew it wasn't purely as simple as weight, it's just that more than one person has told me that was the reason it couldn't land (apart from the fact it wasn't a lunar landing mission). I checked the figures and the descent stages on Snoopy and Eagle both carried around 18,200 pounds of fuel. The ascent stages carried 2,631 pounds on Snoopy and 5,238 on Eagle, a difference of around 2600 lbs.



I would expect the extra weight difference would soon mount up in Eagle when you consider, two PLSS backpacks, two OPS Units (I don't know if Snoopy carried these), consumables, a fully loaded MESA, the EASEP, lunar surface tools etc. Another telling bit of info I noticed in the statistics is the thrust of the ascent engines, Eagle had 3218 pounds of thrust, while Snoopy only had 1650 pounds! So even though Snoopy was lighter it may not have had enough power to leave the surface. spacecraft films

Member Posts: 802

From: Columbus, OH USA

Registered: Jun 2002 posted 02-07-2005 06:27 PM There were a lot of things worked out on Apollo 10 that really built confidence for 11, and would have made a landing on 10 a much more risky adventure - even if the LM had been capable of landing. There were final software issues to be completed, more modeling of the mascons and how they would affect trajectories, and the LM communication system had not been tested at lunar distances. Apollo 10 was a very important mission for making 11 work, and an overweight LM was a convenient reason for not attempting a landing more than a negative that held back a landing on 10. The system just wasn't ready yet. One of the things we've started adding on our disc sets is including a number of pre-mission interviews with crew, and on the Apollo 10 set these really drive home some of the loose issues settled on the mission that helped 11... I'm a little jaded right now because I've just spent so much time with the 7, 9 and 10 missions, but they were so critical to pulling off the landing. An interesting question is, however - It's November or December 1969, and Apollo 10 (with 7, 8, and 9 flown as they were historically) sits on the pad with a landing-ready LM. I suspect you go for it. Blackarrow

Member Posts: 3160

From: Belfast, United Kingdom

Registered: Feb 2002 posted 02-08-2005 09:27 PM Adam, interesting figures. I assume you get them from "Apollo By the Numbers." It looks, at face value, as if Snoopy did not have enough fuel loaded to fire back into orbit in the event of an unscheduled landing, but that doesn't explain why there was such a light fuel-load. I suspect that's where Mark's arguments kick in... By the way, Snoopy's ascent stage is the only FLOWN lunar module ascent stage still intact, floating somewhere in solar orbit (unless it's been hit by a large meteoroid, which is unlikely.) In the far future, maybe the Smithsonian will retrieve it. spaceuk

Member Posts: 2113

From: Staffs, UK

Registered: Aug 2002 posted 02-09-2005 06:03 AM My recollections from the time period of Apollo 10 are that suitable prime landing site photography still did not exist at that time to have sufficient confidence in trying to undertake a first manned landing. Besides testing all components of the manned landing system for the first time in lunar orbit, one of Apollo 10's prime tasks was to acquire detailed high grade photography of the Apollo 11 target sites including what was to become 'Tranquillity Base' site. spaceuk

Member Posts: 2113

From: Staffs, UK

Registered: Aug 2002 posted 02-09-2005 11:18 AM I went through various pre and post mission reports, voice transcripts and other available material to try and get to the bottom of the Apollo 10 versus Apollo 11 LM DPS propellant weights. Apollo 10 was loaded with 17,741 lbs of DPS propellants



Apollo 11 was loaded with 17,921 lbs of DPS propellants. Apollo 10 used only 759 lbs of DPS propellants during its DPS burns while Apollo 11 — because it was going to land on the Moon — used 17,477 lbs of DPS propellant and had just 444 lbs of remaining DPS propellant at touchdown. Apollo 10 would have been loaded with basically the same amount of DPS propellants to simulate the propellant load and conditions that the later Apollo 11 landing mission would have. With 16,982 lbs of DPS propellant remaining when the Apollo 10 descent stage was jettisoned I wonder how much is now still left in the tanks with the Apollo 10 LM descent stage still in a selenocentric orbit. nasamad

Member Posts: 2141

From: Essex, UK

Registered: Jul 2001 posted 02-09-2005 03:45 PM My source for the fuel quantities was "Apollo by the Numbers." The source for the data below is the Apogee Apollo 10 Mission Reports. I can't understand why the Snoopy ascent stage would be loaded with so much less fuel than Eagle's ascent stage. According to the mission report the LM Descent engine only burnt for a total of 67.5 seconds during the entire mission, they had over 95% left over. They burnt the LM ascent engine until it ran out of fuel! Surely they could have had extra fuel in case of emergency and done a timed burn. Phill, are you sure about the descent stage being in lunar orbit? I thought the ascent stage was in heliocentric orbit but the descent stage had impacted. spacecraft films

Member Posts: 802

From: Columbus, OH USA

Registered: Jun 2002 posted 02-09-2005 06:49 PM The ascent stage burn-to-depletion was executed after the ascent stage separated from Charlie Brown. This was done for data purposes. There was good reserve left beyond nominal rendezvous for contingencies. And the descent stage is not still in orbit. spaceuk

Member Posts: 2113

From: Staffs, UK

Registered: Aug 2002 posted 02-10-2005 06:46 AM I would think the reason why the descent stage was 'fully loaded' was to emulate what the propellant load would be like for Apollo 11. I also pondered whether there may have been anything in having the tanks 'fully loaded' from a pressurisation viewpoint? spaceuk

Member Posts: 2113

From: Staffs, UK

Registered: Aug 2002 posted 02-11-2005 08:20 AM I'm pretty interested now to know if and when it did 'crash' to lunar surface. What date? What location - if known? Anyone who has definitive details - please publish. With the stage being almost fully loaded the impact could have left a sizable crater on the lunar surface? Did the propellants ignite on impact? Did the tanks rupture and spill - and therefore possibly stain - onto the lunar surface? Can we view the impact site and any crater or staining in any Clementine images (doubtful) or in later images from - say - SMART1 or future lunar orbiter(s)? spaceuk

Member Posts: 2113

From: Staffs, UK

Registered: Aug 2002 posted 02-16-2005 09:01 AM I had a reply from the tracking sites. No one knows for certain when or where the Apollo 10 LM DPS actually crashed onto surface of Moon. It was anticipated that it was in late 1969 but no one knows for certain. Fra Mauro

Member Posts: 1624

From: Bethpage, N.Y.

Registered: Jul 2002 posted 03-27-2010 01:16 PM I've heard Gene Cernan say, most recently on a Discovery Channel special, that they short-changed the Apollo 10 ascent stage propellant since NASA didn't fully trust Stafford and Cernan not to try and land. Any thoughts? I think he is just horsing around -- if you didn't trust a crew then why fly them? Editor's note: Threads merged. MCroft04

Member Posts: 1647

From: Smithfield, Me, USA

Registered: Mar 2005 posted 03-27-2010 02:59 PM My recollection is that the Apollo 10 LM was too heavy, so I think Cernan was just horsing around. However, trust has to be earned. When von Braun was preparing to launch one of his early rockets (1956 I believe), apparently there were some who did not trust him. The fourth stage was supposed to be a "dummy" stage, but if "live" could have probably put a satellite into orbit. In the book "Von Braun" by Michael Neufeld, he writes that "The Pentagon actually sent an inspector to the Cape (to inspect the fourth stage) in case the Army was planning to launch a satellite 'by accident.'" bernoullis

Member Posts: 14

From: UK

Registered: Feb 2009 posted 03-27-2010 04:13 PM I am not convinced that Cernan was 'horsing around' at all. The Apollo 10 LM was too heavy, as already mentioned, to make a landing as planned for Apollo 11. Nevertheless, weight reduction was already 'in force' for the Apollo 11 LM. Because the Apollo 10 mission was planned to closely replicate everything expected on the Apollo 11 mission, bar the final 50 000 ft to the lunar surface, the heavier Apollo 10 LM was balanced by carrying less fuel. Could a landing have been made? Maybe, but not safely, thats for sure. moorouge

Member Posts: 2458

From: U.K.

Registered: Jul 2009 posted 03-27-2010 04:49 PM The decision to take Apollo 10 close to the Moon but not land had little to do with weights or fuel. To fly to with 47,000 feet of the lunar surface was a natural cut-off point and eliminated all the remaining unknowns before committing a crew to an actual landing. It was the point at which a landing LM would initiate the final DPS burn; it was the altitude at which the landing radar became effective; it was the minimum altitude at which the CSM could come to the aid of the LM in the event of a problem. It was part of a logical development programme leading to the actual landing by Apollo 11. Lou Chinal

Member Posts: 1332

From: Staten Island, NY

Registered: Jun 2007 posted 03-27-2010 06:20 PM It wasn't so much as the extra weight prevented the landing as it would have prevented a take off. The Apollo 10 lunar module would not have been able to get back into an orbit of 47,000 feet. The command module couldn't go any lower for a rendezvous. I think they were playing it close to the vest by off loading some fuel. Jay Chladek

Member Posts: 2272

From: Bellevue, NE, USA

Registered: Aug 2007 posted 03-27-2010 07:44 PM I highly doubt Stafford would have tried to land, even if Snoopy had the fuel. Reason being is George Low apparently came up with a plan for Apollo 10 to use LM-5 for the flight since it was capable of landing to give them an earlier shot at landing on the moon and Stafford turned down the idea saying there were too many unknowns to do a safe landing. Stafford was not one prone to making decisions like that since he knew fully well what it meant to test pilot a mostly unproven spacecraft. As such, I think Cernan is just stirring the pot a little. As for the PLSS backpack situation (or at least OPS chest packs), I believe Apollo 10 may have had enough equipment onboard for an EVA since that was one of the contingencies in case a CM and LM were unable to dock. Granted none of the LMs had docking problems (Apollo 14 did during initial extraction from the S-IVB, but it still got docked), but it would have been a bad day public relations wise if there was a problem with docking Snoopy to Charlie Brown after the ascent from the moon and Stafford and Cernan were unable to get back to the CSM because they didn't have the proper equipment to make a safe transfer. MCroft04

Member Posts: 1647

From: Smithfield, Me, USA

Registered: Mar 2005 posted 03-27-2010 08:00 PM Cernan states in "The Last Man on the Moon" page 184 that "our lander, LM-4... was still too heavy to guarantee safe margins for a moon landing." In addition, Rodney Rose stated several years back that he was very much against an Apollo 10 lunar landing because they needed additional data on mascons; he felt the Apollo 10 mission was critical to a successful Apollo 11 landing. Lou Chinal

Member Posts: 1332

From: Staten Island, NY

Registered: Jun 2007 posted 03-27-2010 08:12 PM I belive it was Rodney Rose who said, "we need to mature the system." ilbasso

Member Posts: 1522

From: Greensboro, NC USA

Registered: Feb 2006 posted 03-27-2010 09:16 PM One wonders if the Soviets were secretly worried that the US would pull off an unannounced landing on Apollo 10. It would have been something out of the USSR's bag of tricks. Obviousman

Member Posts: 438

From: NSW, Australia

Registered: May 2005 posted 03-27-2010 10:29 PM It seems the terminology may be causing the confusion. As a few people have said, the Apollo 10 DPS had sufficient propellant for a nominal landing, but the designers wanted greater safety margins. The ascent phase was another ball game; there they did not have sufficient propellant. That was because - again as people have said - the amount on board was meant to simulate the amount of propellant onboard the ascent stage after it had lifted off from the lunar surface, giving the ascent stage the correct mass for that phase of flight and thus accurate data points for study prior to the first lunar landing. If you look at the Apollo 10 transcripts, you'll see that whilst they were in lunar orbit after the LM manoeuvres they saw the descent stage a couple of times in lower orbit. It crashed on the lunar surface.

spacemal

Member Posts: 30

From: Glasgow, Scotland

Registered: Aug 2014 posted 01-16-2019 05:05 AM Many sources, such as Chris Kraft's "Flight", state a principle reason for Apollo 10 not attempting a landing was the weight of the LM being too heavy. Referring to "Apollo by the Numbers" this does not seem to hold true. The Apollo 10 LM was the lightest of all LMs having a weight of 31,166 pounds at separation for landing, whereas all LMs that did land were in excess of 33,000 pounds. Does anyone have some insight as to why the weight issue was put forward as a reason for not landing? Editor's note: Threads merged. Jim Behling

Member Posts: 1488

From: Cape Canaveral, FL

Registered: Mar 2010 posted 01-16-2019 08:03 AM The Apollo 10 LM weight in "Apollo by the Numbers" is not a relevant comparison to other mission LMs, unless they were carrying the same items. As stated before, Apollo 10 did not have: "two PLSS backpacks, two OPS units (I don't know if Snoopy carried these), consumables, a fully loaded MESA, the EASEP, lunar surface tools, etc." Also, crew items like food, drinking water, hygiene kits, etc. And then there is electrical power, did Snoopy have the same amount of batteries/capability for a standard mission duration? As for DPS propellant, most of it was loaded to provide the necessary mass for the Saturn V. MSFC likely didn't want to do all the analyses required for off nominal payload mass. Much like the reason the LTA flew on Apollo 8.