Talk:Project Mercury

message: Check out the following differing figures from the article, given for the Mercury capsule's volume:
*Spacecraft section: Only 12.13 cubic meters of volume (...)
*Data table: Volume: 60 ft³  1.7 m³
I wonder if a typo mighirockt've crept into the Spacecraft sec's number. My guess so far is that the correct number should be, say, 1.213 m³, and that it represents the capsule's internal volume. Any comments? --Wernher 19:54, 12 Oct 2004 (UTC)
replies: text: states that the habitable volume was 1.7m³. There is often a bit of descepancy between various sources on things like volumes, capacities etc. --enceladus 21:23, 12 Oct 2004 (UTC)

text: What are you on about, then? The number has been corrected in the article (1.7 cubic meters), which is about as good as we're likely to get. JustinTime55 (talk) 21:34, 2 October 2012 (UTC)
thread_title: Capsule volume discrepancy

message: What is it? Why is it not labeled?
* It is the Mercury program monument at pad 14. The entry in the article to include the image was missing the word "thumb". I believe that I have fixed it. Vaoverland 12:37, 13 November 2006 (UTC)
thread_title: Image on the Left

message: During reentry, the astronaut would experience about 4 g-forces. The separate mission articles say otherwise: Mercury-Redstone 3: 11.6 g, Mercury-Redstone 4: 11.1 g, Mercury-Atlas 6: 7.7 g, Mercury-Atlas 7: 7.8 g, Mercury-Atlas 7: 8.1 g, Mercury-Atlas 9: 7.6 g. So this might need to be corrected. --Proofreader 18:16, 10 January 2007 (UTC)
replies: text: Not necessarily; the booster numbers are obviously giving the launch accelleration. Re-entry g-force is completely different, caused by the friction of the air, and is totally unrelated to the acceleration at launch, and would mainly be driven by re-entry speed.  I would expect the orbital flights (M-A) to be perhaps a bit different (bigger?) than the suborbitals (M-R). JustinTime55 (talk) 22:29, 26 February 2010 (UTC)

text: Opps--I mis-spoke.  The articles explicitly quote re-entry g's and are fuzzy or silent about the launch g's, so Proofreader is correct.  The sub-orbitals probably pulled much higher re-entry g's because of the steeper ballistic trajectory. JustinTime55 (talk) 22:47, 26 February 2010 (UTC)
thread_title: g-Forces

message: The article says the LES generated 52,000 lbs of thrust.  With a launch weight of 4265 lbs, that works out to a little over 11 Gs.  Is that really possible?    Can people survive 11 Gs? -- RoySmith (talk) 01:29, 5 May 2008 (UTC)
thread_title: Launch Escape System

message: The space capsule stuff should be expanded, perhaps into a separate article Mercury space capsule 70.55.203.112 (talk) 08:15, 28 September 2008 (UTC)
thread_title: space capsule

message: The article describes Gordon Cooper as the "Last American to orbit the Earth solo", but isn't that actually David Scott, the Command Module pilot of Apollo 9? He orbited the Earth solo while the Lunar Module was being test flown. 70.153.127.71 (talk) 03:09, 27 July 2009 (UTC)
replies: text: Cooper was the last American to orbit the Earth solo.  No one else was in orbit at the time.  To be more definitive, though, he was unequivocally the last American to be launched into orbit alone.  —Preceding unsigned comment added by SEWalk (talk • contribs) 02:58, 23 October 2009 (UTC)

text: Bruce McCandless could also be considered an astronaut flying in solo orbit. I have modified the table remark. ShelbyBell (talk) 23:30, 24 June 2012 (UTC)
thread_title: Last American to orbit the Earth solo

message: I think this section should be removed.  NASA never considered using women.  This was all the idea of Lovelace, who had tested the Mercury Seven.  Bubba73 (You talkin' to me?), 04:02, 4 July 2010 (UTC)
replies: text: There have been no objections, so I removed that section.  It is mentioned in the See also section.  Bubba73 (You talkin' to me?), 15:24, 15 July 2010 (UTC)
thread_title: Mercury 13 section

message: The removal of the lists of unmanned and manned Mercury launches diminishes the utility of this article, to no discernible purpose.  Relevant information should be grouped together for easy reference and comparison; having to go to several different articles for the relevant information significantly impairs the encyclopedic usefulness of the article. RandomCritic (talk) 03:42, 28 October 2011 (UTC)
replies: text: Since there was no objection, I completed the merge. RandomCritic (talk) 19:06, 15 November 2011 (UTC)
replies: text: I agree with this merge.--Craigboy (talk) 00:31, 20 November 2011 (UTC)
thread_title: Merge

message: I had changed cubic meters to decimeters/liters since cubic meters seemed like a large metric to describe the volume and used both cubic decimeters and liters because cubic decimeters are the recognized but uncommon SI unit. I also added cubic feet in parentheses for three reasons: 
1. The spacecraft was built by McDonnel in the 1950s in the US, and most likely designed to specifications described in US customary units. 
2. As a convenience and courtesy to the smaller yet significant portion of the English language wikipedia readers who lack an intuitive scope of area defined by SI units.
3. A secondary metric of 60 cubic feet is also helpful to those readers familiar with both SI and US customary units.
The change was reverted, and while I concede to the reversion of the SI volume back to "cubic meters" on the proposed basis that liters are not as intuitive as cubic meters when describing volume, I object to the removal of the secondary metric given in "cubic feet".  I intend to edit the secondary metric using "cubic feet" following "cubic meters" into the article in parentheses following the primary description in cubic feet.  If it is removed afterwards I will accept the change and refrain from editing this detail in the future. 
173.67.242.156 (talk) 11:05, 30 March 2012 (UTC)
replies: text: Thank you for obtaining the accurate volume number. And thanks so much for your "convenience and courtesy" extended to the "smaller yet significant portion". There is a strong national tie to Project Mercury, since it was undertaken by the US, which in 1958 did not (and to this day, still in most of the aerospace industry, does not primarily) use metric units; therefore the English units should go first. That's the most authoritative way to obtain the correct value for the historical US space programs, as that was what was originally used in the design, and the metrics were/are a conversion extended as a courtesy. (NASA didn't switch officially to metric units until the 1970's.) We also have the Template:convert to maintain accurate unit conversions. JustinTime55 (talk) 16:28, 6 June 2012 (UTC)

text: Please see: Talk:Project Mercury#Capsule volume discrepancy, is this helpful? Soerfm (talk) 14:25, 4 April 2012 (UTC)
replies: text: Not really, as the old value was determined to be inaccurate. JustinTime55 (talk) 16:28, 6 June 2012 (UTC)
thread_title:  Interior volume of spacecraft 

message: I have a problem understanding just what this sentence is trying to say:
:"Twelve companies bid to build the Mercury spacecraft, an unusually high number for a $20 million contract, given the project's great prestige."
Exactly why would one expect fewer than 12 contractors to bid? The $20 million is in 1958 U.S. dollars, which doesn't give modern readers a good handle on it (would be equivalent to much more today.) And what is the assumed relationship of price to attraction? (One would assume it's positive.) And then, "given the project's great prestige" is thrown in at the end, which should attract more bidders. The use of "given" is confusing, and probably not what you intended? The phrase "given [the fact that...]" is usually used to reinforce an expectation when used in such a sentence. Is this the essence of what you were trying to say?
:"It was surprising that as many as 12 contractors bid, since [here's where "given" would be more appropriate], it was only worth $20 million; yet it had a great deal of prestige."
JustinTime55 (talk) 15:55, 6 June 2012 (UTC)
thread_title:  Clarification needed 

message: The US Centennial of Flight Commission has a mistake on its Mercury page; the volume of the capsule could not possibly be 428.5 cubic feet, when the Apollo Command Module had only 218 cubic feet. (This is why we need verification!) I believe the 60. figure, because I tabulated a comparison with the others (Vostok for reference, is 63 cubic feet) but unfortunately I can't remember where I got that. Can someone help, please? JustinTime55 (talk) 21:27, 13 July 2012 (UTC)
thread_title:  Cabin volume: source needed 

message: In the mission profile page it talks about how the orbital version needed a bigger rocket as compared to the sub-orbital version so that it can achieve a "higher altitude".  This is misleading, the biggest reason why an orbital mission needs a more powerful rocket is the substantially higher speed needed to achieve orbit.
166.250.33.101 (talk) 04:44, 19 July 2012 (UTC)
thread_title:  Mission Profile 

message: This was the article a year ago, this is it now. A lot of information was removed for reasons not entirely clear to me, if it was removed because someone believed it was beyond the scope of the article than a page should have been created specifically for the Mercury spacecraft. Can we do anything to rectify this?--Craigboy (talk) 02:29, 29 September 2012 (UTC)
thread_title:  Article insufficiently covers the Mercury spacecraft 

message: I have made a revision mostly based on 
*
*
I have deleted some information: 
*claim in lead about planet Mercury (original research and not verified in body)
*claim about spacecraft being worn not ridden (no citation)
*claim about minor participants (no citation)
*claim that MJ-1 was proposed as a heat shield test (no citation)
*claim that MJ-2 was deemed unnecessary (no citation, contradicts budget constraint claim)
I reduced the information about T.J. O'Malley pushing the button to a footnote. I found a citation for the volume of the spacecraft, on the other hand, but it was 100 cubic feet and not 60 cubic feet. As requested, I have expanded the spacecraft section. I have also maximized the use of pictures. Finaly, I have deleted dead links and links overlapping Bibliography from External links section.
By the way, have you noticed that the kindle version of This New Ocean on Amazon includes an old version of the Wikipedia article? Soerfm (talk) 17:30, 9 July 2013 (UTC)
thread_title:  Revision July 2013 

message: This dubious footnote was just added:
:"...a frustrated politician compared the spacecraft-Atlas combination to "a Rube Goldberg device on top of a plumber's nightmare" and John Glenn was invited to the White House to explain the delays."
This New Ocean verifies the senator's remark, but makes it clear that JFK, while disappointed like everyone else, believed NASA knew best what was required to make the flight with reasonable safety, and describes Glenn's February visit (incidental to his visiting family in Virginia) as "a brief visit with President Kennedy, who asked him many semitechnical questions about plans and systems for the orbital flight" (citing several newspaper reports), but says nothing at all about Kennedy demanding Glenn "explain delays". This would seem totally out of character for JFK; I removed it. I have no idea who this Brit John Catchpole is, but I would suggest being cautious about regarding his Project Mercury - NASA's First Manned Space Programme as a reliable source about certain things. JustinTime55 (talk) 17:32, 18 September 2013 (UTC)
thread_title:  JFK "invited" Glenn to explain delays? 

message: "It is estimated to have cost $1.71 billion and have involved the work of 2 million people." - this should be clarified to specify either the cost in 1950s/60s dollars, or the cost in ~2013 dollars. Apparently this is the cost accounting for inflation?  — Preceding unsigned comment added by 199.212.215.11 (talk) 13:49, 11 October 2013 (UTC)
replies: text: Look further: in the infobox and down in the article body, it says that's today's cost. JustinTime55 (talk) 16:46, 11 October 2013 (UTC)
thread_title: Cost

message: Both pressure and friction seem to create heat during reentry...
 
I must admit I didn't think of the pressure drag when I wrote the paragraph. Can anyone suggest a better explanation? - Soerfm (talk) 22:04, 7 November 2013 (UTC)
replies: text: You are probably referring to my revert of the anon's change of the page text on this issue. As the issue is more complex than either friction or a pressure wave and the change was not ref'd, I reverted it assuming I'd come back to it later (which I didn't). That being said, the sentence probably needs to be changed to reflect the more complex description of what is actually going on. The returning capsule causes the atmosphere to be compressed and heated while the bow shock causes frictional drag - both of which contribute to the capsules heating. Ckruschke (talk) 13:53, 8 November 2013 (UTC)
thread_title:  Reentry: pressure vs friction 

message: I like to expand the paragraph about cabin pressure and air composition based on Giblin. 
Suggestion:
:The choise of cabin air composition and pressure was a matter of controversy. Pure oxygen presented a risk of fire in the cabin at least at launch. In space, without gravity, it was believed that combustion products would gather around the fire and smother it and; in any case, the pilot could vent the oxygen into empty space to the same effect. In addition, the long-termed health effects of breathing pure oxygen were not known. On the other hand, a cabin air of oxygen and nitrogen was difficult to control. On the launch pad, the pressure and composition would be like the surrounding air (20% oxygen and 80% nitrogen at the pressure of one atmosphere (15 psi)). During launch the pressure inside the cabin would be gradually reduced and nitrogen replaced with oxygen; the fragile spacecraft would not allow too big af pressure difference between its inside and outside. In orbit, the craft would contain about 67% and 33% nitrogen at a pressure 5 psi, although the astronaut would be able to breathe pure oxygen from his space suit. I all, the oxygen/nitrogen-solution was complicated and added weight to venting system. Further, it gave a health risk since a reduction in nitrogen level of inhaled air could led to a potentially lethal formation of nitrogen bubbles in the blood. Eventhough the atmospheric air-solution was complicated and added weight to the venting system, NASA originally favored it, but an accident during a ground test in 1960 changed their mind as a test pilot nearly died when the pure oxygen in his space suit was somehow diluted by nitrogen from the cabin. Unable to eliminate the problem, NASA decided to use pure oxygen for Mercury—not only in space but on the ground as well. [Note: the Soviet spacecraft used oxygen and nitrogen at atmospheric pressure, but their spacecraft was heavier and more strongly build than the American. The controversy in USA was not over and the risk of ground fire was proven by the Apollo 1 accident.] 
From The pure oxygen atmosphere and the existence of combustibles in the cabin had long been controversial among aerospace engineers, but until Apollo 1 NASA was firm in its resolve. The earth’s atmosphere is about 21 percent oxygen and 78 percent nitrogen. In space flight, to avoid putting a strain on the craft’s thin shell, the internal pressure is reduced to about one-third of that on earth. The partial pressure of oxygen in normal air under such conditions would be much too low to support life. In fact it takes only a moderate drop in the partial pressure of oxygen to affect brain activity.
In addition, the presence of nitrogen in the spacecraft presents a danger of its own. Astronauts exposed to a sudden change in pressure—whether due to an accident or malfunction or after donning space suits filled with low-pressure oxygen—could develop the condition known as the bends, in which nitrogen escapes from body tissues and forms gas bubbles in the bloodstream, blocking circulation. (Oxygen presents no such threat.) This illness, which was first noticed among sandhogs and is most often associated today with scuba-diving accidents, can cause neuralgic pain, difficulty in breathing, paralysis, or even death.
A pure oxygen atmosphere would provide sufficient oxygen even at the reduced pressure used in space and would purge nitrogen from the bloodstream to prevent the bends. But there was no consensus about the possible health effects of long-term exposure to pure oxygen. Soviet spacecraft had equipment that duplicated the fullpressure, two-gas environment found on earth, but they needed a thicker shell. Complex air locks were also required, and the cosmonauts had to purge the nitrogen from their bodies for hours before leaving the cabin for a space walk to protect against the bends. NASA thought that the complicated sensing and regulating system that such a scheme would require was too unreliable, and the additional tanks, piping, and controls as well as the heavier shell needed for a two-gas system would add too much weight to the spacecraft. Also, because a pure oxygen system could operate at one-third the pressure, leaks through any joints in the shell into the vacuum of space were less likely.
From NASA’s point of view, then, the case for using pure oxygen in space was overwhelming. For ground operations, the argument was less clear-cut. Indeed, the original design for the Mercury spacecraft had called for the cabin to be filled with normal air while on the launch pad. As it ascended into orbit, the air would be bled from the cabin and replaced with pure oxygen as the external atmosphere thinned. By the time it reached space, the craft would contain about two-thirds oxygen and only one-third nitrogen at a total pressure of approximately 5 psi, although the astronaut would breathe pure oxygen at the same pressure through his space suit at all times (unlike Apollo, whose astronauts would mostly breathe the cabin atmosphere). The primary reason for this arrangement was precisely to reduce the risk of an oxygen-rich fire on the ground. Fire in space was not considered to be as serious a problem, since scientists believed that with no gravity to make hot gases rise, the flames would smother themselves in their own combustion products. In any case, an astronaut could always vent the cabin into the vacuum of space to extinguish the flames.
AN ACCIDENT DURING A ground test in April 1960 changed NASA’s thinking. A McDonnell test pilot was about one hour into a test of the environmental control system when he fell unconscious and nearly died from oxygen depletion. Because of a difference in pressure, nitrogen had leaked into his space suit from the cabin, diluting the oxygen he was breathing. Unable to eliminate the problem reliably, NASA decided that a pure oxygen environment was the best option for Mercury—not only in space but on the ground as well.
This policy was questioned within the space-flight community. In 1964, for example, two separate scientists working for NASA warned of the hazards posed by pure oxygen, which can cause fires that are virtually inextinguishable. In February 1966 an editor of Science Journal, reviewing the proceedings of a conference held the previous fall, noted a general lack of attention to launch-pad safety and predicted, “The odds are that the first casualty in space will occur on the ground.” Yet a conversion to oxygennitrogen for ground use would have introduced complications of its own at a time when NASA already had plenty to worry about. Pure oxygen at all times remained official policy in the Gemini and Apollo programs.
The question of combustible materials was raised again when CSM 012 was delivered to NASA in August 1966. Joe Shea had reiterated the firesafety requirements for the spacecraft and asked North American to investigate the problem. Within six weeks North American documented the results of a “walk-through” inspection of CSM 012 and requested specific direction from NASA on addressing them. NASA responded in turn, but given the volume of concurrent design revisions in the works, compliance was never verified.
Comment: 
* Giblin has: Because of a difference in pressure, nitrogen had leaked into his space suit from the cabin, diluting the oxygen he was breathing. This seems unlikly to me since the spacesuit is under internal pressure, meaning that any leak will result in oxygen leaving the space suit and not nitrogen entering it.
*It is still not clear to me how the internal pressure was maintained at ground level. Did they use pure oxygen at a pressure of one atmosphere or did they mix oxygen with helium (there is a helium tank on the spacecraft cutaway - what was it for)?
- Soerfm (talk) 15:53, 28 May 2015 (UTC)
thread_title:  Cabin pressure and air composition 

message: I have split the flight tables which means that the remarks per default are hidden. They could also be shown if the majority thinks so, it is up to you.  - Soerfm (talk) 09:56, 10 July 2016 (UTC)
thread_title:  Split of flight tables 

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*Added archive https://web.archive.org/web/20130823200222/http://www.astronautix.com/flights/meryma12.htm to http://www.astronautix.com/flights/meryma12.htm
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*Added archive https://web.archive.org/web/20120617195355/http://www.astronautix.com/flights/merr2mj2.htm to http://www.astronautix.com/flights/merr2mj2.htm
*Added archive https://web.archive.org/web/20050117174129/http://images.ksc.nasa.gov/photos/1964/captions/KSC-64C-5517.html to http://images.ksc.nasa.gov/photos/1964/captions/KSC-64C-5517.html
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thread_title:  External links modified 

message: It is true that the sources don't support the claim that perigee is the insertion point, however, the fact that the orbital flights all have the same perigee seems to suggest this. The difference in apogee then comes from a difference in speed at insertion. Soerfm (talk) 22:18, 2 October 2018 (UTC)
thread_title:  Perigee and apogee 

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