Editing Apollo (spacecraft) (section)

==Spacecraft–lunar module adapter (SLA)==
[[File:ApolloSpacecraftLMAdapterDiagram.png|thumb|left|Apollo spacecraft-to-LM adapter]]
The spacecraft–LM adapter (SLA), built by North American Aviation (Rockwell), was a conical aluminum structure that connected the service module to the Saturn [[S-IVB]] rocket stage. It also protected the LM, the service propulsion system engine nozzle, and the launch-vehicle-to-service-module umbilical during launch and ascent through the atmosphere.<ref>No CSM was carried on the [[Apollo 5]] uncrewed LM flight, and an aerodynamic nose cone was fastened to the top of the SLA instead.</ref> 

The SLA was composed of four fixed {{convert|7|ft|m|adj=mid|-tall}} panels bolted to the [[Saturn V Instrument Unit|Instrument Unit]] on top of the S-IVB stage, which were connected via hinges to four {{convert|21|ft|m|adj=mid|-tall}} panels which opened from the top similar to flower petals.

The SLA was made from {{convert|1.7|in|mm|adj=mid|-thick}} aluminum honeycomb material.<ref>[https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730010176_1973010176.pdf NASA.gov]</ref> The exterior of the SLA was covered by a thin ({{cvt|0.03|–|0.2|in|mm|disp=or}}) layer of cork and painted white to minimize thermal stresses during ascent.<ref>{{cite web|url=http://www.hq.nasa.gov/office/pao/History/SP-4204/ch20-3.html|title=Moonport, Ch20-3|first=Roger D.|last=Launius|access-date=11 October 2016|archive-date=July 14, 2019|archive-url=https://web.archive.org/web/20190714121441/https://www.hq.nasa.gov/office/pao/History/SP-4204/ch20-3.html|url-status=dead}}</ref>

The service module was bolted to a flange at the top of the longer panels, and power to the SLA [[Redundancy (engineering)|multiply-redundant]] pyrotechnics was provided by an umbilical. Because a failure to separate from the S-IVB stage could leave the crew stranded in orbit, the separation system used multiple signal paths, multiple detonators and multiple explosive charges where the detonation of one charge would set off another even if the detonator on that charge failed to function.

[[File:Apollo 7 Rondevouz.jpg|thumb|upright|One of the SLA panels on [[Apollo 7]] did not fully open to the designed 45°.]]
{{multiple image
| align     = right
| direction = horizontal
| header    = Transposition of CSM, docking and extraction of LM
| image1    = apollo11-03.jpg
| width1     = 170
| alt1      = Adapter panels fall away from the LM as the CSM turns around
| caption1  = Adapter panels are jettisoned and the CSM is turned 180 degrees
| image2    = apollo11-04.jpg
| width2     = 173
| alt2      = The CSM pulls the LM away from the Saturn 5 third stage
| caption2  = The CSM docks with the LM and pulls it away from the Saturn V third stage.
}}
Once in space, the astronauts pressed the 'CSM/LV Sep' button on the control panel to separate the CSM from the launch vehicle. [[Detonating cord]] was ignited around the flange between the SM and SLA, and along the joints between the four SLA panels, releasing the SM and blowing apart the connections between the panels. Dual-redundant pyrotechnic thrusters at the lower end of the SLA panels then fired to rotate them around the hinges at 30–60 degrees per second.

[[File:Apollo Spacecraft-Lunar Module Adaptor Structural Stiffener.jpg|thumb|Apollo 7 did not carry a Lunar Module. A structural stiffener is used to provide sufficient stiffness of the SLA.]]

On all flights through [[Apollo 7]], the SLA panels remained hinged to the S-IVB and opened to a 45-degree angle, as originally designed. But as the Apollo 7 crew practiced rendezvous with the S-IVB/SLA containing a dummy docking target, one panel did not open to the full 45 degrees, raising concern about the possibility of collision between the spacecraft and the SLA panels during docking and extraction of the LM in a lunar mission. [[Wally Schirra]] compared it to the "angry alligator" from [[Gemini 9]]. This led to a redesign using a spring-loaded hinge release system which released the panels at the 45-degree angle and pushed them away from the S-IVB at a velocity of about {{cvt|8|kph|mph|order=flip|sigfig=1}}, putting them a safe distance away by the time the astronauts pulled the CSM away, rotated it through 180 degrees, and came back for docking.

The LM was connected to the SLA at four points around the lower panels. After the astronauts docked the CSM to the LM, they blew charges to separate those connections and a guillotine severed the LM-to-[[Saturn V Instrument Unit|instrument-unit]] umbilical. After the charges fired, springs pushed the LM away from the S-IVB, and the astronauts were free to continue their trip to the Moon.

===Specifications===
*Height: {{convert|28|ft|m|abbr=on}}
*Apex diameter: {{cvt|12|ft|10|in}} Service module end
*Base diameter: {{cvt|21|ft|8|in}} S-IVB end
*Weight: {{convert|4050|lb|kg|abbr=on}}
*Volume: {{convert|6700|ft3|m3|abbr=on}}, {{convert|4900|ft3|m3|abbr=on}} usable