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Apollo 11 Issues: LM Oxygen Usage, other issues

grmcdorman

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Apollo 11 Lunar Module O2 Consumption
Abstract
In a posting in the James Randi Education Forums, the individual known as Apollo20, who is Dr. Frank Greening, posted a claim that the O2 usage in the Apollo 11 Lunar Module, according to the published figures, was far below the minimal amount that should have been used, based on the expected consumption.

Definitions
CM|Command Module. The Command Module remained in orbit while the LM descended to and landed on the surface.
LM|Lunar Module. (Note that there is an obsolete term, LEM; this term was retired from use well before Apollo 11.)
JREF|James Randi Educational Forums, http://www.internationalskeptics.com/forums .
lbm|Pounds (mass).
GET|Ground Elapsed Time; time from launch of the mission.

Sources
The original post, at JREF: http://www.internationalskeptics.com/forums/showpost.php?p=2764883&postcount=143.

My original rebuttal, also at JREF: http://www.internationalskeptics.com/forums/showpost.php?p=2766085&postcount=169. The original rebuttal contains much the same argument as this post with regards to the basic oxygen consumption.

Discussion at the ApolloHoax forums, http://apollohoax.proboards21.com/: http://apollohoax.proboards21.com/index.cgi?action=display&board=theories&thread=1184426948.

Apollo 11 Lunar Landing Press Kit, NASA, July 6, 1969; available online at http://www.hq.nasa.gov/office/pao/History/alsj/a11/A11_PressKit.pdf (8.5 Mb).

Apollo 11 Mission Report, MSC-00171, November 1969, NASA, available online at http://www.hq.nasa.gov/alsj/a11/A11_MissionReport.pdf (12 Mb).

ECS Quick Reference Data, NASA, last modified 22 September 2005; available online at http://history.nasa.gov/alsj/alsj-ECSQuickRef.html; accessed 15 July 2007.

The History of Manned Spaceflight, David Baker, Ph.D., New Cavendish Books, revised 1985.

Values
Initial O2 Loading
The LM contained three oxygen tanks in the two stages. The descent stage contained one tank, which initially held 48.2 lbm of oxygen. The ascent stage contained two tanks, each containing 2.5 lbm of oxygen (Apollo 11 Mission Report, page 9-34, or page 162 in the PDF). This is a total of 53.2 lbm.
The History of Manned Spaceflight lists standard LM oxygen loading as 21.7 kg (47.8 lbm) in the descent stage, and 1.1 kg (2.4 lbm) in the ascent stage. Given rounding errors and that this was the standard values across all missions, these values are sufficiently close.

Consumption of O2
There were three main items that consumed the oxygen:
  1. Astronaut respiration.
  2. Cabin depressurizations (or more precisely, repressurizations after a depressurization).
  3. Cabin leaks.
In his initial post, Dr. Greening uses a baseline of 0.05 lbm/hr for astronaut respiration. This agrees with estimates made on the ApolloHoax board. I will accept this for the purposes of these calculations.

For cabin depressurizations, there were two during the stay on the surface. The first was at the start of the EVA; the second was prior to lift-off to jettison unwanted materials. According to the ECS Quick Reference Data, each subsequent repressurization required 6.6 lbm of oxygen, for a total of 13.2 lbm (note, however, that this does not specify if it applied specifically to the Apollo 11 LM, or is a generic average across all LMs). Dr. Greening estimated 12 lbm, which is acceptably close.

For cabin leaks, there are actually two values. The nominal value – which is the design target – was 0.2 lbm/hr. Post mission, however, it was found that the Apollo 11 LM had an actual leak rate of 0.05 lbm/hr (Apollo 11 Mission Report, page 9-33; page 161 in the PDF). Dr. Greening uses the former rate, from page 102 of The NASA Mission Reports. Volume One: Apollo 11, (Robert Godwin, ed., Apogee Books, 1999). The value therein is apparently taken from the Apollo 11 Lunar Landing Press Kit, page 186 (or page 190 of the PDF). In the latter, it is clearly marked as the nominal value.
As such, the actual value must be used when comparing expected oxygen consumption to actual values.

Reported O2 Consumption
The Apollo 11 Mission Report, page 9-34, (page 162 in the PDF) reports the total consumed oxygen, among other figures. For the descent stage, which is the item of interest here, the total consumed oxygen in the descent stage was reported as 17.2 lbm.

Note that all of these values – initial load and consumed mass – are based on telemetered data. According to Jay Utah at the ApolloHoax boards, the sensor “runs the whole dimension of the tank and is spoofed by stratification of temperatures along its length.” In other words, the values can be inaccurate; the level of inaccuracy in the reported values is not clear in the sources I have examined.

There is also some question with regards to reported remaining O2 in the transmission logs; I will return to that later.

Calculations
The period during which the LM was on the descent stage oxygen tank would be the time from the sealing of the docking tunnel between the LM and CM, and the switchover to the ascent stage tanks shortly prior to lunar lift-off. Lacking specific times for these in the record, we can use the undocking for the former and lunar-lift off for the latter; hopefully the two will cancel out. Undocking of the LM and CM occurred at 100:12:00 GET; lunar lift-off occurred at 124:22:00.8 GET, for an elapsed time of 24 hours and 10 minutes (The History of Manned Space-Flight, page 568). I will use 24 hours for the calculations, as this is an approximation anyway. Dr. Greening uses a 25 hour period; it is not clear what this figure is derived from.

Thus, based on this 24 hour period, the expected non-respiration consumption will be (using the above figures) 24x0.05=1.2 lbm for leakage and 12 lbm for cabin re-pressurizations. This is a total of 13.2 lbm, and leaves 17.2 – 13.2 = 4.0 lbm for respiration. The minimal respiration for this period would be 24x0.05x2=2.4 lbm, so the actual respiration usage was actually well above the minimum.

If I use Dr. Greening's 25 hour figure, this is only one additional hour, or an additional 0.05 lbm of leakage, for a respiration of 3.95 lbm versus a minimum of ~ 2.5 lbm.

Conclusion
The claim that the O2 usage figures as reported by NASA for the Apollo 11 LM is not correct. It appears that this claim was made due to inadvertently using the nominal 0.2 lbm/hour leak rate for the LM instead of the actual measured 0.05 lbm/hour.

Transmission Logs
An additional issue raised by Dr. Greening is this transmission (times are GET):
114:31:45|McCandless: Okay. RCS (Reaction Control System, the steering jets) Alpha is 81 percent: RCS Bravo, 75 percent. Coming up on 115 hours GET, descent oxygen is 31.8 pounds or 59 percent; descent amp hours 858 (remaining), and ascent amp hours 574. Over. (Pause)
114:32:28|Aldrin: Roger. Copy. Thank you very much.
First, Dr. Greening calls attention to the figures, stating that the percentage quoted doesn't correspond to the mass quoted. This is true if only the descent stage tank is taken into account; if the full load of 53.2 lbm (i.e. both ascent and descent tanks) is used, 31.8 lbm does correspond to 59 percent.

Secondly, Dr. Greening calculates, correctly, that this shows that only 0.9 lbm of oxygen from the descent stage was apparently used in the roughly 10 hour interval between this transmission and lift-off at 124:22:00.8 GET. However, there are several items confounding this conclusion:
  1. The values reported are based on the (telemetered) sensor data. As mentioned above, if there is a temperature stratification in the tank, the sensor can report incorrect data.
  2. For a substantial portion of this period – 114:52:57 to 120:59:04 GET, to be precise, or 6 hours – the crew was sleeping (or attempting to sleep, at least). This would reduce the crew's metabolism and therefore oxygen consumption.
  3. The crew would have switched to the ascent stage tanks prior to the lift-off at 124:22:00.8 GET. Thus, the time will be less – possibly substantially less, depending on when the switchover occurred. (The transmission logs do not show when this occurred).
  4. Further, a subsequent transmission provided a new value for the oxygen levels:
    123:14:45|Evans:And, Tranquility, I have a LM consumables update for you.
    123:14:53|Aldrin: Roger. Ready to copy.
    123:14:55|Evans: Okay. At plus 123 plus 00, RCS Alpha 78, (repeating) seventy eight percent, PQMD; Bravo is 76 percent PQMD; descent O 2 is 62, sixty-two percent. Descent ampere hours are 590...590 remaining; ascent ampere hours are 574, 574 remaining. Over.
    Note that the reported descent O2 is 62 percent. This is actually greater than the previous report, and corresponds to 33 lbm. The discrepancy, presumably, is due to the sensor inaccuracy in one or both reports.

In conclusion, I must reject the claim that the reported O2 levels in the transmission is anomalous.

Addendum: Further Data
The Apollo 11 Mission Report contains a fairly detailed breakdown of the astronauts' metabolism and oxygen usage during the EVA, in a table on page 10-3 (page 167 in the PDF). The interested student could use this to further refine the calculations.

Credits & Acknowledgments
I wish to thank Bob B. and Jay Utah on the ApolloHoax forums for providing reference information and information on the tank sensors, respectively. Obviousman also provided a link to the LM ECS summary which included specific values for the amount of oxygen required for LM cabin repressurization. alex04 also made a minor contribution.
 
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I would also like to know how the information on the Van Allen Belts and the high-altitude nuclear weapons tests in this post by Apollo20 (Dr. Greening) is connected to the Apollo program. To date, I have not seen a response from Dr. Greening replying to my query about that at all.
 
Dr Greening's works in his area of expertise are excellent. With all due respect outside of this expertise, however, is another story altogether; the Apollo program and space science in general seems to fall into the 'outside his expertise' category.
 
Well even though I have already been accused of being "out of my depth".....

And, no doubt, NASA's finest will correct me on this:

An indication of the potentially damaging effects of the Starfish radiation belt is evidenced by the fact that three artificial satellites orbiting the earth at that time, namely Ariel, Transit 4-B and Traac, ceased to function within 4, 24 and 36 days, respectively, of the July 9, 1962, Starfish explosion. It was concluded at the time, (See: W. Hess, J. Geo. Res. 68, 667 (1963)), that the greater than 100,000 rad/day radiation field to which these satellites were being exposed was more than enough to fry their solar cells within a month or so!

In order to fully comprehend the type of radiation hazard created by the Starfish test, the changes induced in the Inner Van Allen Radiation Belts, especially with regard to the energy, spatial distribution and decay of the injected electrons, needs to be considered.

Given that the Van Allen Radiation Belts were only discovered in 1958, research scientist’s understanding of this remarkable natural phenomenon was still in its infancy in the early 1960’s mainly because of the relative paucity of space radiation data available at that time. Nonetheless, satellite data prior to the Starfish test indicated that, at an altitude » 1000 km, electrons were present at a flux of about 10^6 /cm^2/s and with an average energy of about 200 keV. This corresponds to a dose rate of about 2 rad/min.

It was also known by 1961 that the Inner Van Allen belt is far from uniformly distributed around the globe. It was realized that, because the earth’s magnetic field is not truly dipolar, regions of weaker than average field strength create radiation “islands” at low altitudes. The most significant of these “hot-spots” was found between Brazil and South Africa in a region dubbed the South-Atlantic anomaly. Here pre-Starfish electron fluxes up to 10^6 electrons/cm^2/s were measured at altitudes as low as 600 km. In fact, trapped electrons were found at altitudes as low as 300 km at fluxes up to 10^3 electrons/cm^2/s. However, calculations showed that, in these regions electrons slowly leak or “precipitate out” of the trapped zone as a result of scattering by atmospheric atoms and ions.

The Starfish test injected fission product beta-particles into the radiation belts. Beta-particles are relativistic electrons with average energies » 1.2 MeV. The difference in energy between the natural and man-made electrons allowed the artificial Starfish radiation belt to be differentiated from the natural belt, and thereby to be effectively mapped.

The earliest radiation measurements carried out after the Starfish test were obtained by the satellites Injun I, Ariel and TRACC, and confirmed that a new belt of trapped electrons was centered at an altitude of about 1300 km. The initial flux immediately after the July 9, 1962 test was extrapolated to be as high as 10^9 electrons/cm^2/s, or well in line with the predictions previously discussed

The situation with regard to the fate of the Starfish electrons after their initial injection is described in an article written at the time (See: Space Science Reviews Vo1 1, 1962), by B. O’Brien, a prominent University of Iowa physicist:

“(The Starfish test) populated the entire region underneath the old natural inner belt, where we can consider qualitatively that the atmosphere had worn down the inner zone intensity or prevented it from becoming high over the preceding years. Following Starfish, the atmosphere had to wear away the artificial belt from its underside. This it did, effectively removing electrons which mirrored at altitudes as low as 100 to 200 kilometers in a few hours, while the intensity of those with minimum mirror altitudes of about 350 kilometers was greatly reduced in a few weeks. At higher altitudes, however, large intensities still persist several months later, and it appears that the artificial belt will remain at higher altitudes in measurable intensities for many months.

On the final point regarding the longevity of “higher altitude” Starfish electrons, O’Brien’s prediction has since proved to be erroneous. In fact it would have been more accurate had he said “many years” rather than “many months”.

Reports in the open literature show that scientists were able to detect high energy Starfish electrons above the “natural background” for almost a decade after their July ’62 injection. This is precisely the most active period of the US/USSR race to the moon. One is compelled to ask: Why would the Americans create a radiation hazard in space precisely at the start of its race with the Soviets to get to the moon?
 
Apollo20 said:
Well even though I have already been accused of being "out of my depth".....

[snip]

This is precisely the most active period of the US/USSR race to the moon. One is compelled to ask: Why would the Americans create a radiation hazard in space precisely at the start of its race with the Soviets to get to the moon?
Click to expand...
Thank you! This is obviously a post you took some care with, and has some notable (and interesting) detail.

Possibly because they didn't know it would happen? Or possibly because the people doing the tests - in the Air Force - were not that closely linked with the people doing the space program - in NASA? Or, more likely, both?

In particular, the EMP effects of Starfish Prime were not at all anticipated, as I understand it. Likewise, you yourself point out in your post that the lifetime of the injected electrons was not fully appreciated until later.

In any event, the hazard posed by the VAB to humans (and machines) traversing it was well known by the time Apollo had to go through it. As pointed out elsewhere, since the VAB is largely charged particles rather than ionizing radiation, and since the astronaut's transit was relatively short, it was relatively easy to provide them with quite adequate shielding. Electrons, in particular, do not have much penetrating power.

However, I will post your information over on ApolloHoax and see what the experts there have to say. (There are quite a number of very good people, including some with substantial knowledge of the space program.)

(FYI, some of the Air Force pilots - notably Chuck Yeager - had, or have, rather dim views of the original astronauts. Yeager, in his autobiography, pretty much says he didn't think much of Neil Armstrong. This would tend to corroborate the idea that there wasn't much communication going on.)
 
Just a quick update on this. I'm pulling together the sources, and hope to post a full response soon. It may take a bit of time, though, as I do have this time-sink called a job that I have to attend to.

However, at the moment it looks like the effects of Starfish Prime were not a problem because:
  • The levels of injected high-energy particles, principally electrons, apparently decay to non-significant levels within a year or less. (One source, talking about using high-altitude nuclear explosions as a way of intentionally destroying satellites, speaks of being unable to replace the destroyed satellites for a year).
  • Most of the injected particles are in low earth orbit; at higher altitudes, not only does the quantity of the particles decline, but also the energy.
  • Detectable is not hazardous. The injected particles were indeed detectable long after the event; however there are no recorded satellite failures after the initial cluster that were attributed to Starfish Prime that I can find. I have not yet found statements of the particle levels, however.
  • An unsourced claim is that the particle levels decayed by two orders of magnitude after the first 10 hours.
  • The failure of the satellites was blamed on damage to the solar cells; not only are those most vulnerable but no manned America spacecraft had solar cells until Skylab, about a decade later.
  • The objective of Starfish Prime was to see if such a weapon could be used to interfere with radar and similar equipment directly below the explosion. It appears that the effect on the near earth environment, and the satellites, was not anticipated.
  • Starfish Prime was on July 9, 1962. The first few flights following Starfish Prime were:
    1. MA-8, October 3, 1962, Walter Schirra, in Sigma 7, 6 orbits, 9 hours 13 minutes, apogee 282.9 km, perigee 161 km
    2. MA-9, May 15, 1963, Gordon Cooper in Faith 7, 22.5 orbits, 34 hours 19 minutes, 267 km /161.4 km
    No further manned flights occurred until the first Gemini flight in 1965; so the highest risk was to Walter Schirra, four months after the shot for a little over 9 hours. This was in a Mercury capsule, which is metal-skinned with a single porthole, so he (and the equipment in the capsule) was probably reasonably well shielded against the remaining particles.
 
Apollo 20, I'm unsure but barring further evidence I presume you would agree that the calculations are correct? There might be discussion about the sources of figures and which are the more accurate but if the the rates used above are accurate, you have no problem?

I actually like these kind of things - sometimes. Someone questions your assumptions - not with the usual "no it isn't" but a thought out and reasonable challenge. You then have to examine the challenger's calculations, determine what assumptions they have made, how they have determined their formulas, etc. In many cases it leads to you discovering facts you were not previously aware of (such as leakage rates or pressure loss from cabin repress).

It's all great!
 
Some additional items:
 
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This might also be of some interest:

raddata2.jpg


raddata.jpg


Source:
SPACE RADIATION CANCER RISK PROJECTIONS FOR EXPLORATION MISSIONS: UNCERTAINTY REDUCTION AND MITIGATION

FRANCIS A. CUCINOTTA, WALTER SCHIMMERLING, JOHN W. WILSON, LEIF E. PETERSON, GAUTAM D. BADHWAR, PREMKUMAR B. SAGANTI, AND JOHN F. DICELLO

JSC-29295
 
Estimates of the Electron Flux and Dose in the Radiation Belts:

W. Hess: J. Geophysical Research 68, 667, (1963)
Uses the conversion factor 1R = 3 x 10^7 electrons/cm2
Hess gives the following electron fluxes at the specified altitudes:
260 km: 2.8 x 10^4 electrons/cm2/s
594 km: 7.9 x 10^6 electrons/cm2/s
1067 km: 3.2 x 10^7 electrons/cm2/s

C. E. McIlwain: Science 142, 355 (1963)

Gives flux maps of Starfish electrons. Assuming a fission beta-spectrum:
2000 km: 1.0 x 10^8 electrons/cm2/s

SPENVIS website gives the formula:

Dose (rad) = 1.6 x 10^-8 dE/dx Flux,

Where dE/dx (in MeV cm2 g-1) is the electron stopping power in the material of interest. For 1 MeV electrons in Si, for example, dE/dx ~ 2
Dose (rad) ~ 3.2 x 10^-8 Flux.
Hence, 1 rad = 1/ 3.2 x 10-8 electrons/cm2 = 3.125 x 10^7 electrons/cm2

These and othe published data show that, immediately after the Starfish test, the electron dose rate at an altitude of 1000 km was about 1 rad/s.
 
Indeed. It is pretty clear that, immediately after the test, there was concern, but it turned out to be not a problem for the Mercury astronauts, as they were not at an altitude where there were long-lived effects - even three months afterwards. By the time there were high-orbit missions (i.e. Apollo) the residual effects were no longer a problem. (One document even speaks of the effect of a solar flare, which, in effect, "renewed" part of the belts - which implies, to my mind, that the test-introduced electrons were of similar magnitude at the time.)

Fundamentally, the only thing I haven't been able to find an absolutely clear answer to yet is the lifetime at high altitudes (at L =~ 1.75). One document states 1 to 2 years, as mentioned above, but it is not really corroborated anywhere else that I can find (save once, where it is stated that satellites destroyed by a HANE could not be replaced for a year; this would tend to corroborate the 1-2 year lifetime). The 1964 document may have more but the math is a bit dense for me; it does have an extensive discussion of lifetimes.

ETA: The open issue, as far as I am concerned, is the lifetime. The initial density is clear; it's also clear in the literature that the lifetime is fairly short at low altitude (low L) and high L; the lifetime is longer at intermediate L (i.e., as above, L =~ 1.75).
 
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