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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Apollo command and service module | 7/7 | https://en.wikipedia.org/wiki/Apollo_command_and_service_module | reference | science, encyclopedia | 2026-05-05T12:35:22.001294+00:00 | kb-cron |
=== Specifications === Length: 24.8 ft (7.6 m) Diameter: 12.8 ft (3.9 m) Mass: 54,060 lb (24,520 kg) Structure mass: 4,200 lb (1,900 kg) Electrical equipment mass: 2,600 lb (1,200 kg) Service Propulsion (SPS) engine mass: 6,600 lb (3,000 kg) SPS engine propellants: 40,590 lb (18,410 kg) RCS thrust: 2 or 4 × 100 lbf (440 N) RCS propellants: MMH/N2O4 SPS engine thrust: 20,500 lbf (91,000 N) SPS engine propellants: (UDMH/N2H4)/N2O4 SPS Isp: 314 s (3,100 N·s/kg) Spacecraft delta-v: 9,200 ft/s (2,800 m/s) Electrical system: three 1.4 kW 30 V DC fuel cells
== Modifications for Saturn IB missions ==
The payload capability of the Saturn IB launch vehicle used to launch the Low Earth Orbit missions (Apollo 1 (planned), Apollo 7, Skylab 2, Skylab 3, Skylab 4, and Apollo–Soyuz) could not handle the 66,900-pound (30,300 kg) mass of the fully fueled CSM. This was not a problem, because the spacecraft delta-v requirement of these missions was much smaller than that of the lunar mission; therefore they could be launched with less than half of the full SPS propellant load, by filling only the SPS sump tanks and leaving the storage tanks empty. The CSMs launched in orbit on Saturn IB ranged from 32,558 pounds (14,768 kg) (Apollo–Soyuz), to 46,000 pounds (21,000 kg) (Skylab 4). The omnidirectional antennas sufficed for ground communications during the Earth orbital missions, so the high-gain S-band antenna on the SM was omitted from Apollo 1, Apollo 7, and the three Skylab flights. It was restored for the Apollo–Soyuz mission to communicate through the ATS-6 satellite in geostationary orbit, an experimental precursor to the current TDRSS system. On the Skylab and Apollo–Soyuz missions, some additional dry weight was saved by removing the otherwise empty fuel and oxidizer storage tanks (leaving the partially filled sump tanks), along with one of the two helium pressurant tanks. This permitted the addition of some extra RCS propellant to allow for use as a backup for the deorbit burn in case of possible SPS failure. Since the spacecraft for the Skylab missions would not be occupied for most of the mission, there was lower demand on the power system, so one of the three fuel cells was deleted from these SMs. The command module was also partially painted white, to provide passive thermal control for the extended time it would remain in orbit. The command module could be modified to carry extra astronauts as passengers by adding jump seat couches in the aft equipment bay. CM-119 was fitted with two jump seats as a Skylab Rescue vehicle, which was never used.
== Major differences between Block I and Block II ==
=== Command module ===
The Block II used a one-piece, quick-release, outward opening hatch instead of the two-piece plug hatch used on Block I, in which the inner piece had to be unbolted and placed inside the cabin in order to enter or exit the spacecraft (a flaw that doomed the Apollo 1 crew). The Block II hatch could be opened quickly in case of an emergency. (Both hatch versions were covered with an extra, removable section of the Boost Protective Cover which surrounded the CM to protect it in case of a launch abort.) The Block I forward access tunnel was smaller than Block II, and intended only for emergency crew egress after splashdown in case of problems with the main hatch. It was covered by the nose of the forward heat shield during flight. Block II contained a shorter forward heat shield with a flat removable hatch, beneath a docking ring and probe mechanism which captured and held the LM. The aluminized PET film layer, which gave the Block II heat shield a shiny mirrored appearance, was absent on Block I, exposing the light gray epoxy resin material, which on some flights was painted white. The Block I VHF scimitar antennas were located in two semicircular strakes originally thought necessary to help stabilize the CM during reentry. However, the uncrewed reentry tests proved these to be unnecessary for stability, and also aerodynamically ineffective at high simulated lunar reentry speeds. Therefore, the strakes were removed from Block II and the antennas were moved to the service module. The Block I CM/SM umbilical connector was smaller than on Block II, located near the crew hatch instead of nearly 180 degrees away from it. The separation point was between the modules, instead of the larger hinged arm mounted on the service module, separating at the CM sidewall on Block II. The two negative pitch RCS engines located in the forward compartment were arranged vertically on Block I, and horizontally on Block II.
=== Service module ===
On the Apollo 6 uncrewed Block I flight, the SM was painted white to match the command module's appearance. On Apollo 1, Apollo 4, and all the Block II spacecraft, the SM walls were left unpainted except for the EPS and ECS radiators, which were white. The EPS and ECS radiators were redesigned for Block II. Block I had three larger EPS radiators located on Sectors 1 and 4. The ECS radiators were located on the aft section of Sectors 2 and 5. The Block I fuel cells were located at the aft bulkhead in Sector 4, and their hydrogen and oxygen tanks were located in Sector 1. Block I had slightly longer SPS fuel and oxidizer tanks which carried more propellant than Block II. The Block II aft heat shield was a rectangular shape with slightly rounded corners at the propellant tank sectors. The Block I shield was the same basic shape, but bulged out slightly near the ends more like an hourglass or figure eight, to cover more of the tanks.
== CSMs produced ==
== See also ==
Orbital module Reentry capsule Space capsule Space suit Space exploration U.S. Space Exploration History on U.S. Stamps Apollo Lunar Module Mars Piloted Orbital Station
== Footnotes == Notes
Citations