Jumat, 03 Maret 2017

An Ideal Home in orbit (1959-1960)

As Beyond Apollo readers in the United Kingdom may know, this weekend the 103rd Ideal Home Show draws to a close at Earls Court in London. Typically, the Ideal Home Show has had little to do with spaceflight. This has not, however, always been true. The Ideal Home Show in March 1960 had the theme of "A Home in Space." With help from Douglas Aircraft Company, the show's organizers built a life-size mockup of a plausible four-man Astronomical Space Observatory (ASO). W. Nissim, an engineer in the company's Advance Design Section, designed the ASO and wrote a report describing it to guide the builders. As many as 200,000 people toured the mockup, which stood more than three stories tall.

The ASO was envisioned as a spent-tank space station; that is, it would start out as a rocket stage filled with liquid propellants and would be converted into a pressurized habitat for astronauts after it expended its propellants by placing itself into low-Earth orbit. The spent-tank station concept may have originated with Wernher von Braun in the 1940s. In the late 1950s, several space engineers, including Krafft Ehricke of General Dynamics and Kurt Strauss and Caldwell Johnson of NASA's Manned Spacecraft Center, developed spent-tank station designs. Beginning in late 1964, von Braun urged that the concept be made part of NASA's proposed Apollo-based post-Apollo space program. By 1966, the Saturn S-IVB stage-based "wet workshop" (images at top) had become a key element of the Apollo Applications Program (AAP).
Nissim proposed that the ASO be built into the second stage of a 107-foot-tall, 17-foot-diameter chemical-propellant rocket. He envisioned launching the ASO from near-equatorial Christmas Island, located in the Indian Ocean northwest of Australia. The rocket's first stage, with three engines generating 150,000 pounds of thrust each, would expend 154,266 pounds of liquid hydrogen fuel and liquid oxygen oxidizer during 145 seconds of operation, boosting the second stage to a velocity of 9800 miles per hour.

The second stage would separate from the spent first stage, coast for eight seconds, then ignite its single 150,000-pound-thrust engine to boost itself to a velocity of 16,300 miles per hour. Following engine shutdown, the second stage would coast to an apogee (highest point above the Earth) of 300 nautical miles. At apogee, the engine would ignite a second time to boost the second stage to an orbital velocity of 17,000 miles per hour and circularize its orbit, which would be inclined 40° relative to Earth's equator. The second stage would burn a total of 86,788 pounds of liquid hydrogen and liquid oxygen to achieve its operational orbit.

A = second-stage rocket engine; B = tanks holding gaseous oxygen and nitrogen for liquid hydrogen tank purging and pressurization; C = streamlined launch shroud segment with solar cells on concave inner surface (one of four); D = Schmidt telescope; E = star tracker for accurate telescope pointing; F = Cassegrain telescope; G = loop antenna for radio astronomy; H = emergency reentry vehicle; I = airlock hatch for spacewalks; J = emergency reentry vehicle launch escape/deorbit rocket motor (in airlock); K = relaxation area restraint positions (one of two); L = hatch from central column to interior of liquid hydrogen tank; M = central column; N = common bulkhead separating liquid hydrogen and liquid oxygen tanks; O = food lockers; P = life support equipment; Q = sleep area; R = radiation-shielded compartment; S = space suit storage.
During launch and ascent to orbit, the initial four-man crew would ride in a conical emergency reentry vehicle with a dome-shaped nose, three fins, and a single solid-propellant motor. The emergency reentry vehicle would be mounted atop a six-foot-diameter cylindrical central column embedded in and protruding from the top of the second-stage hydrogen tank.

In the event of launch vehicle trouble during launch and ascent, the solid-propellant motor would ignite, blasting the emergency reentry vehicle to safety. The spent motor would then separate and the vehicle would descend to Earth nose first. During ascent, the astronauts would face forward in the direction of the vehicle's nose; during descent, their couches would pivot so that they would face in the direction of its tail. Shortly before landing, the emergency reentry vehicle would deploy a parachute to slow its descent.

Assuming, however, that they arrived safely in orbit, the astronauts would immediately begin to prepare the second stage for occupancy. First, they would turn it to maximize the amount of sunlight striking it and open valves in the second-stage engine. Solar heating would speed escape of any residual hydrogen through the engine nozzle into space.

Next, a space-suited astronaut would open a hatch in the emergency reentry vehicle leading into the airlock at the top of the central column. After sealing the hatch behind him, he would open a hatch into the radiation shelter, a section of the central column embedded within the hydrogen tank. There he would open a valve that would release into the hydrogen tank nitrogen gas stored in spherical tanks at the bottom of the second stage. The nitrogen would escape through the engine nozzle, purging the tank of any remaining hydrogen. The engine valves would then be closed.

A = second-stage rocket engine; B = tanks holding gaseous oxygen and nitrogen for liquid hydrogen tank purging and pressurization (five clusters); C = lower liquid oxygen tank bulkhead; D = liquid oxygen tank; E = common bulkhead separating liquid oxygen and liquid hydrogen tanks; F = bottom of central column; G = central column; H = sleep area; I = space suit storage; J = life support equipment access panel; K = lavatory; L = crew personal lockers; M = ventilation duct.
The astronaut would next open a hatch leading from the central column into the hydrogen tank and move to the tank's bottom end. There he would permanently seal the hydrogen outlet port leading to the engine by welding a cover over it or by injecting a plastic sealant. He would then return to the central column, seal the hatch behind him, and release nitrogen into the hydrogen tank to check for leaks. While his shipmates monitored the tank's internal pressure, he would return to the emergency reentry vehicle.

Assuming that pressure in the tank remained steady, a space-suited astronaut would enter the central column to release oxygen into the hydrogen tank. According to Nissim, the pressure in the tank would equal the atmospheric pressure on Earth at 10,000 feet of altitude. The atmosphere in the tank would, however, contain as much oxygen as occurs at Earth's sea level. Located in the same area as the nitrogen tanks, the spherical oxygen tanks would contain enough gas to supply the ASO crew for 45 days.

The three astronauts waiting in the emergency reentry vehicle would then enter the hydrogen tank and doff their space suits. They would cut away metal covers welded over pre-installed equipment and openings (for example, air ducts), then would remove equipment and furnishings stowed in the central column and install them in the tank.

The crew would also point the emergency reentry vehicle's nose at the Sun and open four petal-like streamlined launch shroud segments located between the top of the second stage and the bottom of the emergency reentry vehicle. Besides revealing a "storage area" containing folded astronomical instruments, this would expose to the Sun electricity-generating solar cells covering the concave inner surfaces of the shroud segments. Attitude control thrusters and gyroscopes would keep the station properly oriented as it revolved around the Earth. (Nissim, by the way, proposed fueling the attitude control thrusters with crew urine.)

Pointing the emergency rentry vehicle at the Sun would also help to regulate temperature on board the ASO. The open shroud segments, telescopes, and emergency reentry vehicle would partially shade the spent stage part of the station. Alternating blue and white stripes of equal area would cover its hull. The blue stripes would absorb sunlight while the white stripes would reflect it. Most heating in the converted hydrogen tank would come from on-board equipment and the astronauts' bodies. Nissim estimated that the interior of the spent stage would maintain a temperature of 72° Fahrenheit.

The emergency reentry vehicle would be powered down, so would lack a significant internal heat source. It would, however, be in direct sunlight whenever the ASO was over the Earth's day side, so would be colored white with thin blue stripes so that it would reflect most of the sunlight striking it.

With ASO electricity, life support, and thermal control up and running, an astronaut would don a space suit, enter the central column airlock, pump the air it contained into the converted hydrogen tank, and open a hatch leading to the station's exterior. Linked to the airlock by a thin cable, he would deploy astronomical instruments from the storage area between the top of the stage and the bottom of the emergency reentry vehicle. By operating above Earth's obscuring atmosphere, Nissim explained, the ASO's instruments would for the first time in history permit astronomical observations of the entire electromagnetic spectrum from gamma rays to very long radio waves.

After deploying and checking the instruments, the spacewalker would return to and repressurize the airlock, then rejoin his colleagues in the tank. After doffing his space suit, he would settle into a routine that would see two crew members on duty, one asleep, and one off duty at all times.

In their explanatory text for the mockup, the Ideal Home Show organizers wrote that the initial crew would return to Earth in the emergency reentry vehicle, which they called the "reentry Vehicle (nosecone)." This would mean that only the initial crew could reside in the station before it was abandoned. According to its designer, however, the ASO would operate "forever," with new four-man crews and supplies arriving by ferry spacecraft every 30 days.

Nissim did not specify how astronauts would transfer between ferry and ASO. His design lacked docking ports, so he might have meant for astronauts to spacewalk between the two vehicles. Ferry spacecraft would remain at the ASO only long enough to rotate crews and drop off supplies. The emergency reentry vehicle, on the other hand, would remain part of the ASO throughout its career, enabling crews to evacuate immediately in the event of catastrophic meteoroid puncture, fire, or massive life support failure.