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SPC Facility Description

Space Power Chamber No.1 with Centaur setup. — The SPC No. 1 vacuum chamber could subject spacecraft to long duration testing in a simulated space environment.

In the early 1960s, NASA converted the AWT into two large altitude test tanks known as the Space Power Chambers (SPC).

Overview

After becoming part of the new National Aeronautics and Space Administration (NASA) in the fall of 1958, the Lewis Research Center shifted nearly all of its resources to space-related research. This dramatically reduced the need for the Altitude Wind Tunnel (AWT) and other aeronautics-based facilities. Management decided to repurpose the facility by constructing two large chambers capable of simulating altitudes. This required the removal of the tunnel’s drive fan, exhaust scoop, and turning vanes from the east end and the insertion of bulkheads to seal off the new chambers within the tunnel. The eastern section of the tunnel, SPC No. 1, became a vacuum chamber capable of simulating 100 miles altitude. The larger SPC No. 2 in the western leg of the tunnel could simulate altitudes of 100,000 feet. These chambers were used for a variety of tests on the Centaur second-stage rocket until the early 1970s.

Documents

Aerial view of Space Power Chambers. — The SPC contained two test chambers for testing space flight hardware. SPC No. 1 is at the left and SPC No.2 to the right (1979).

SPC No. 1 blueprint. — Blueprint drawing of SPC No. 1 and its control room (1963).

Cutaway drawing of SPC No.1. — Drawing of a Centaur stage in the SPC No. 1 vacuum tank (1964).

Interior of SPC No. 2. — The interior of the 51-foot diameter and 100- foot long SPC No. 2 (1965).

Space Power Chamber No. 1

The 100-foot-long SPC No. 1 was located in the east leg of the tunnel, which was 31 feet in diameter at one end and 27 feet in diameter at the other. It was necessary to reweld the 1-inch-thick chamber shell during the conversion in order to maintain the low pressures necessary to simulate the space environment. The insulation and outer weather shield were permanently removed from this section at that time. The chamber was segregated from the rest of the tunnel by bulkheads at the southwest and northwest sections. Access to the chamber was provided by a 15-foot diameter door in the latter. SPC No. 1 included an overhead rail crane, various instrumentation ports, and numerous fixed eyehooks and other fittings that were used for various test setups.

Crane removes tunnel outer shell and insulation. — Removal of the AWT’s outer shell and insulation in July 1961 during its conversion into the SPC.

Removal of Altitude Wind Tunnel Turning Vanes. — The AWT’s turning vanes, drive fan, and other tunnel components had to be removed to create the SPC test chambers (7/20/1961).

Crane inserts bulkhead into new Space Power Chambers. — Insertion of a 31-foot diameter cap into the AWT to separate the two new vacuum test chambers (11/21/1961).

Bulkhead with shut swing door inside Space Power Chambers . — This 27-foot diameter bulkhead with its swinging door was installed at the north end of SPC No.1 in 2005. The former tunnel test section is located on the other side of this bulkhead.

A small vacuum pump house was built beneath SPC No. 1 to accommodate the ten diffusion pumps and several roughing pumps necessary to create a deep vacuum. Access ports in the chamber’s floor connected directly to the pumps in the building below. The vacuum was brought down slowly in several phases to prevent excessive airflow over the pumps. The center’s central exhauster system could evacuate the SPC to 100,000 feet pressure altitude in about 15 minutes. Then, two piston pumps simultaneously removed 12.5 cubic feet of air per second during the roughing stage. A rotary positive displacement pump pulls additional air at 500 cubic feet per second. The final vacuum is pulled down by the ten 32-inch-diameter oil diffusion pumps, which could remove 17,650 cubic feet air per second.

Construction of Vacuum Pump House for Space Power Chamber No.1. — Construction of the Vacuum Pump House underneath the eastern end of the AWT (9/13/1961).

Men working inside Vacuum Pump House. — Interior of the Vacuum Pump House below SPC No. 1. The building had 12 diffusion pumps to evacuate the chamber to pressures altitudes found in space (5/11/1962).

Vacuum Port in Space Power Chamber No.1. — One of ten portals in the floor of SPC No.1 linking the chamber to the diffusion pumps below (8/21/1962).

Vacuum Pump House beneath Space Power Chambers. — This Vacuum Pump House beneath SPC No. 1 in 2007.

Modifications for Centaur

NASA intended to use the SPC No. 1 vacuum tank to test satellites, space power systems, and small space vehicles. In the fall of 1962, however, Lewis assumed responsibility for the Centaur upper-stage rocket. Lewis management decided to modify SPC No. 1 to accommodate the stage. A vertical 17.5-foot extension with a removable cap was added to the top of the chamber so that a Centaur could be placed vertically within the tank. The 22.5-foot-diameter lid could be removed using a crane so that the Centaur or other test articles could be lowered into the chamber. An elevated catwalk was erected around the dome to allow access to the instrumentation portals and cable trays.

SPC No. 1 dome area and equipment. — Dome area of the SPC No.1 facility. The elevated separation tank at the left supplied the chamber’s cold wall with liquid nitrogen (1/6/1967).

Crane removes lid from SPC No. 1 dome . — A crane removes the 22.5-foot diameter dome from SPC No. 1 in January 1964. The dome created a 45-foot vertical space inside the chamber.

Space Power Chamber No.1 rusting exterior and dome . — SPC No. 1 extension and removable dome in October 2005.

Rusting Interior of Space Power Chamber No.1 . — The interior of SPC No.1 with extension leading to dome above (10/12/2005).

SPC No. 1 was already capable of creating the vacuum of space, but the test engineers also wanted to simulate the cryogenic temperatures and solar radiation found in space. A 42-foot-high copper cold wall was created specifically for these tests and assembled around the Centaur. Cryogenic liquid nitrogen flowed through vertical ribs in the wall and the shroud’s interior was coated with heat-absorbing black paint to generate the low temperatures. In addition, six panels of 500-watt tungsten-iodine lamps were arranged around the Centaur to simulate the effect of the Sun’s heat on the rocket performance. Four of these arrays were on the upper end of the Centaur, and two were located near the RL–10 engines. Certain lamps could be turned on at different times to recreate the changing areas of the rocket exposed to sunlight during a mission.

The actual setup of the Centaur included a pneumatic system to keep the vehicle’s thin fuel tanks pressurized so that they would not collapse, a hydraulic system to rotate or “gimbal” the engines as they would be during flight, and a liquid-hydrogen pumping system to fill the propellant tank. The telemetry for these tests included a high-powered system for powered flight, a lower power system for coast periods, camera and data transmission systems to view the liquid hydrogen tank, ground support equipment that controlled and monitored the operation of the Centaur, and extensive instrumentation.

Centaur stand lowered into Space Power Chamber No. 1. — The Centaur rested on this approximately 9-foot tall triangular stand inside SPC No. 1 (1/16/1964).

Diagram of nitrogen-filled copper cold wall built around the Centaur rocket in SPC No. 1. The cold wall simulated the low temperatures found in outer space.

View up at Centaur in Space Power Chamber No.1 surrounded by cold wall. — The Centaur 6A rocket surrounded by a ribbed liquid-nitrogen filled cold wall in SPC No. 1 to simulate the cryogenic temperatures of space (1984).

Centaur in SPC No. 1 with radiant lamps. — A radiant heater system simulated the effect of the sun’s heat on the Centaur in SPC No. 1. Lamps are visible at lower end of the photograph (1967).

Space Power Chamber No. 2

SPC No. 2 was the larger of the two chambers in the former AWT. It consisted of the entire southern and western legs of the tunnel, as well as the throat section. SPC No. 2 was sealed off from the other chamber by a 31-foot bulkhead near the southeast corner and from the tunnel test section by a 20-foot-diameter bulkhead in throat section, which effectively made SPC No. 2 a large J-shaped chamber. The 51-foot-high chamber in the west leg allowed the vertical erection of full-scale rocket shrouds so that the jettison systems could be tested at high altitudes.

Unlike the vacuum tank in SPC No. 1, SPC No. 2 did not require a major overhaul to be used as a high-altitude test chamber. The existing AWT exhauster and refrigeration systems were powerful enough to achieve the desired altitudes up to 100,000 feet. During the conversion to the SPC, this chamber only required the two bulkheads that sealed it off, some upgraded crane equipment, and a new coat of paint.

In order to work on the tall shrouds, an oval platform elevator was built on two vertical steel girders. The elevator could be raised the entire length of the chamber, and its 11-foot-diameter opening allowed it to be placed around payload shrouds to assist in test preparations. The catwalk along the western wall provided access to lighting and cameras used to record the tests. An overhead crane was installed over the chamber to permit the transfer of large test articles.

Atlas/Centaur separation test in Space Power Chamber No.2. — Setup of Atlas-Centaur separation test inside the massive SPC No. 2. A net at the far end caught the Centaur model after the separation (11/6/1963).

Interior of Space Power Chamber No. 2. — Technicians prepare SPC No. 2 for a shroud separation test in May 1965.

Contraction area in Altitude Wind Tunnel. — The AWT’s throat section before the test section contracted from 51 to 20 feet in diameter. This area was used for the Project Mercury MASTIF tests in 1960 (2007).

Control Rooms

The SPC had separate control rooms for each of its two test chambers. The former AWT control room next to the test section was used for the tests in SPC No. 2. The conversion primarily involved rewiring the telemetry and updating the control panels. The floor-mounted pneumatic engine controls were also removed. The original acoustic tiles on the walls and ceiling remained, as did the overhead fluorescent light fixtures. The eastern panel, which had the system laid out schematically on the panel with toggle switches and indicator lights, controlled the exhaust flow. The next panel operated the liquid nitrogen system. The panel at the west end contained a large number of controls for cameras inside SPC No. 2.

Operator in Space Power Chamber No.2 control room. — An engineer in the SPC No. 2 control room monitors the chamber’s conditions during a test of the Atlas/Centaur retrorockets in September 1963.

Crowded SPC No. 2 control room. — Lewis researchers and General Dynamics technicians crowd into the control room for SPC No.2 for Atlas/Centaur retrorocket tests (9/27/1963).

General Dynamics personnel in Space Power Chamber No.2 control room. — K.G. Smits, R.G. Sims, and J.E. Rogers of General Dynamics in the SPC No. 2 control room (10/8/1963).

A new control room for SPC No. 1 was constructed underneath the former tunnel’s test section. Efforts were made to make this control room as much like the Centaur launch controls at Cape Canaveral as possible. The eastern wall contained the primary controls, including Centaur pressure and tanking controls; hydrogen peroxide, hydraulic, stretch, pneumatic, and canister purge systems; the cold wall and vacuum systems, and solar simulator temperature monitor. The northern section consisted of monitors for temperature, pressure, and the solar simulator. The western wall controlled the guidance system, nose cone, and tank vents. The southern section had data and event recorders as well as radio frequency and range safety monitors. Racks in the center of the room contained the test conductor and engine controls, ground programmer, a vehicle power monitor, and data recorders.

Construction of Space Power Chamber No. 1 control room. — Construction of a new control room for SPC No.1 underneath the former tunnel test section (11/28/1961).

Space Power Chamber No.1 vacuum system control panel. — This panel in the SPC No. 1 control room monitors the diffusion and mechanical pumps that create the vacuum inside the test chamber (2/28/1964).

Researchers in Space Power Chamber No. 1 Control Room. — Larry Ross (right) and Ben Dastoli prepare for a Centaur systems test in SPC No. 1 during 1964.

Man examines data recorders in control room. — An engineer examines the electrical drawings for the new SPC No. 1 control room (1/10/1964).

Since the tunnel’s test section no longer needed to be enclosed, the large clamshell lid was removed. Flat, steel grating was installed in the bottom of the test section and a pedestrian bridge was built over the 20-foot-wide gap. A new rail crane was installed in the tunnel between the test section and bulkhead so the test articles could be transported into SPC No. 1. The surrounding test chamber room was used as a work area for mechanics in the 1960s and storage area in recent years.