Exploring the Unknown: Selected Documents in ... - The Black Vault

28 First Steps into Space: Projects Mercury and Gemini
neering team’s important decisions was to use a pure oxygen atmosphere at 5 psi.
This atmosphere would become the standard for American spacecraft until the
Space Shuttle, but it had a fundamental drawback as a fire hazard, something that
proved fatal in the Apollo 1 accident of 1967. 89
The Mercury capsule that emerged from this process stood 115 inches high
with a tapering cylinder from 74 inches at its base so that it appeared to all as an
upside-down ice cream cone. The pressurized cockpit for the pilot was the largest
portion of the capsule, with most other systems packed throughout the cramped
interior. Indeed, the astronaut had very little room for movement, being placed
in an individually fitted contour seat for the duration of the flight. A smaller
cylinder at the top housed other electronics as well as a parachute for recovery.
Attitude control jets allowed the astronaut to orient the spacecraft during flight.
An ablative heatshield with a ceramic coating affixed to the capsule’s base would
protect the spacecraft during reentry. Designed to adhere to strict weight restrictions
and maximum strength, much of the spacecraft was titanium, but heatresistant
beryllium made up the upper cone of the vehicle since, other than the
heatshield, it would suffer the greatest heat during reentry. Underneath the heatshield
a retrorocket pack of three solid rocket motors served to slow the vehicle
down and return it to Earth. Each motor produced 1,000 pounds of thrust for
only about 10 seconds. The Mercury spacecraft also had 3 smaller posigrade rockets
that produced 400 pounds of thrust each for a second, used for separating the capsule
from its booster. Atop the capsule stood a launch escape tower with solid rocket
motors producing 52,000 pounds of thrust that could shoot the capsule away from the
rocket during an emergency on the launchpad or during ascent. The capsule proved
a spare but serviceable space vehicle. 90
Adapting Launch Vehicles
During Project Mercury two different boosters proved their mettle in sending
astronauts into space. The first was the Redstone, built by Wernher von Braun’s
rocket team at the Army Ballistic Missile Agency (ABMA) in Huntsville, Alabama,
as a ballistic missile and retrofitted for human flights. 91 NASA Administrator T.
Keith Glennan materially aided this effort by securing the transfer of ABMA
Historical Reference Collection, NASA History Division, NASA Headquarters, Washington, DC.
89. This was discussed in “Report of the Ad Hoc Mercury Panel,” 12 April 1961. Folder 18674,
NASA Historical Reference Collection, NASA History Division, NASA Headquarters, Washington, DC.
The report stated: “The idea of using a single gas, O 2
, atmosphere, in both the suit and capsule
to simplify the system appears to be reasonable from an engineering standpoint if it meets the biomedical
requirements. The environmental control system is capable of operating completely automatically
if required and still provide redundancy in many areas against failure. In the automatic
mode the only single point of failure without backup appears to be with the emergency oxygen rate
valve. However, with man functioning in the system, this valve can be manually operated.”
90. A description of the Mercury spacecraft may be found in Swenson et al., This New Ocean, pp.
223–262; Linda Ezell, NASA Historical Data Book: Volume II, pp. 134–139.
91. See Wernher von Braun, “The Redstone, Jupiter, and Juno,” in Eugene M. Emme, ed., The
History of Rocket Technology (Detroit, MI: Wayne State University Press, 1964), pp. 107–121.