 | Agena Target Vehicle
Credit - © Mark Wade
|
Manufacturer's Designation: Lockheed. Class: Tug. Destination: Maximum Payload Orbit. Nation: USA. Agency: NASA. Manufacturer: McDonnell. To provide the Gemini spacecraft with a rendezvous and docking target, Agena D rocket stages were modified with the addition of a docking collar, status panel display, and restart capabilities for the Gemini program. After docking, the Agena had sufficient fuel reserves to boost the Gemini into high earth orbits, to the edge of the Van Allen radiation belts.
The Gemini-Agena Target Vehicle design was an adaptation of the basic Agena-D vehicle using the alternate Model 8247 rocket engine and additional program-peculiar equipment required for the Gemini mission. This GATV was divided into:
- The program-peculiar forward auxiliary section. This section consisted of the auxiliary equipment rack, the McDonnell Aircraft Company-furnished docking-adapter module, and the clamshell nose shroud.
- The Agena-D forward and mid-body sections. The Agena-D forward section housed the main equipment bay, and the mid-body contained the main fuel and oxidizer tanks which supplied propellants through a feed and load system for the main engine. (3) the program-peculiar aft section. The Model 8247 multi-start main engine and the smaller Model 8250 maneuvering and ullage orientation engines were located in this section.
Orbital length of the GATV was approximately 26 feet. Vehicle weight-on-orbit was approximately 7200 lb. This weight included propellants still remaining in the main tanks and available for Model 8247 engine operation after the Agena achieved orbit.
The Gemini-ATV propulsion system consisted of the following:
- Model 8247 rocket engine, also known as XLR-81-BA-13, and its controls, mount, gimbals, and titanium nozzle extension
- Pyrotechnically operated helium-control valve (POHCV) and associated pressurization plumbing
- Fuel and oxidizer feed and load system, including propellant tanks, vents, and fill quick disconnects
- Propellant isolation valves (PIV's)
- All associated pyro devices and solid-propellant rockets.
The XLR-81-BA-13 engine thrust chamber was an 80-percent bell-shape with an expansion ratio of 45:1. This thrust chamber assembly performed satisfactorily throughout a gimbaling orientation of plus 5 deg in a square pattern from the associated planes, with a gimbal acceleration of 30 rads/sec/sec. The nozzle was regeneratively cooled up to the point at which the area ratio was 13.3: I. The remaining portion of the nozzle (13.3:1 to 45:1) was a radiation-cooled titanium extension.
The propulsion system was designed to inject the GATV into an orbital path which has an altitude varying between 161 nautical miles (nm) and 87 nm when measured at a latitude of 28. 34 deg. A minimum of five main-engine burns were available to complete the mission requirements; one burn was required for injection into orbit and four subsequent burns were available to perform orbital plane and phase changes, as required and selected from ground stations or from the spacecraft. All launches took place from AMR Pad 14.
Once the GATV was in orbit, the PPS provided the thrust necessary for the following maneuvers :
- Adjusting the orbits so that they were coplanar and making the radius of one apside of the Agena orbit equal to the rendezvous radius
- Circularizing the Agena at the rendezvous radius and proceeding to an inertial location which was a point lying on the line of the apsides of the catch-up orbit
- At the initial location of the injection point, transferring the Agena to a catch-up orbit for placing the vehicle at the rendezvous point when specified.
The XLR-8I-BA-13 was a liquid bi-propellant rocket engine with a minimum capability of five starts and a demonstrated capability of fifteen starts under vacuum conditions. This rocket engine consisted of the following major components:
- Thrust-chamber assembly
- Multiple-restart assembly
- Turbine-pump assembly
- Overspeed shutdown electronic-gate and cable assembly
- Turbine-exhaust duct
- Propellant manifolds
- Thrust-chamber nozzle extension
Fuel used was unsymmetrical dimethylhydrazine (UDMH); oxidizer used was inhibited red fuming nitric acid (IRFNA). The propulsion system provided the thrust necessary to place the GATV into a selected orbit and to accomplish major orbital changes. A minimum of five starts was available for performing these maneuvers.
The Gemini-ATV Status Panel (ASP), was mounted on the forward end of the Target Docking Adapter of the Agena Target Vehicle where it was visible to the astronauts in the Gemini spacecraft during and after the docking maneuver. The panel displayed information on the status and safety of the Agena propulsion, guidance, electrical power, and docking systems. Originally, only eight Agena parameters were to be displayed in the Gemini spacecraft; however, the number of parameters increased to the point that the spacecraft no longer had the space or weight capability to accommodate them. Accordingly, the panel was placed on the Target Docking Adapter. The ASP system consisted of a display panel with nine display lights and three analog dials and the necessary circuitry which was distributed throughout the Gemini-ATV. When not in use, this system was normally de-energized in order to save power; however, the PPS and SPS Time Remaining Clocks were energized whenever the PPS or SPS engines fire. Three of the twelve parameters displayed on the ASP panel, indicated PPS status and three indicated SPS status. The Primary Propulsion System displays were as follows:
- PPS Burn Time Remaining Clock
- "MAIN" Red Light
- "MAIN" Green Light
The Secondary Propulsion System displays were as follows:
- SPS Burn Time Remaining Clock
- "SEC HI" Green Light
- "SEC LO" Green Light
Requirements received from the astronauts stated that a dimming circuit must be added to the ASP system, because the panel lights were found to be too bright when the spacecraft docked with the GATV on the night side of the earth. Consequently, a dimming circuit was added to reduce or increase the brightness to the desired level. The dimming circuit functions on all lights except MAIN Red which was always bright when "ON". In order to improve reliability, two lamps were incorporated in each indicator light.
Typical orbit: 279 km x 301 km at 29 degrees inclination. Length: 7.93 m (26.01 ft). Basic Diameter: 1.52 m (4.98 ft). Maximum Diameter: 4.90 m (16.00 ft). Mass: 3,260 kg (7,180 lb). Associated Launch Vehicle: SLV-3 Atlas / Agena D.
Gemini Agena Target Vehicle Chronology - 1965 October 25 - Gemini 6 Agena Target - Program: Gemini. Flight: Gemini 6, Gemini 7. Launch Site: Cape Canaveral. Launch Vehicle: Atlas. FAILURE: Exploded 6 minutes after takeoff. Failure. Mass: 3,261 kg (7,189 lb).
The Agena target vehicle failed to reach orbit. Gemini 6, awaiting launch, was cancelled. In the ashes of this setback, the idea of launching Gemini 6 to rendezvous with Gemini 7 was born.
- 1966 April 12 - Gemini Agena target vehicle 5005 completed modification and final assembly with the installation of a number of electrical and electronic components for which it had been waiting. -
 | Gemini-Agena
Gemini docked to Agena...
Credit- © Mark Wade |
These included the guidance module, flight control junction box, and flight electronics package. The vehicle was transferred to test complex C-10 at Sunnyvale to begin Vehicle Systems Tests. Preliminary test tasks were completed by April 23, with preliminary inspection on April 26-27.
- 1966 May 17 - Gemini 9 Agena Target - Program: Gemini. Flight: Gemini 9. Launch Site: Cape Canaveral. Launch Vehicle: Atlas. FAILURE: Control system failure. Mass: 3,248 kg (7,160 lb).
Bibliography:- McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: http://www.planet4589.org/jsr.html.
- JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Web Address when accessed: http://msl.jpl.nasa.gov/home.html.
- Baker, David, The History of Manned Spaceflight, Crown, New York, 1981.
- Bramscher, Robert G, Spaceflight, "A Survey of Launch Vehicle Failures", 1980, Volume 22, page 351.
- Hall, Edwin H, "Memorandum to Deputy Director, Gemini Program, "Circumlunar Missions"", June 29, 1965.
- Lockheed Martin Coporation, Atlas Family Fact Sheets, September 1998.. Web Address when accessed: http://www.lmco.com/ILS/txtmain/ils_lsysinfo.htm.
- NASA Report, Agena Technical Summary (partial) , Web Address when accessed: http://prdownloads.sourceforge.net/mscorbaddon/agena_partial_summary.pdf?download.
- NASA Report, Agena Performance Summary, Web Address when accessed: http://prdownloads.sourceforge.net/mscorbaddon/agena_perf_summary.pdf?download.
- NASA Report, Propulsion Subsystem Engineering Analysis Report Gemini-Agena Target Vehicle, Web Address when accessed: http://ovh.dl.sourceforge.net/sourceforge/mscorbaddon/ee.pdf.
- NASA Report, Agena Command Summary, Web Address when accessed: http://prdownloads.sourceforge.net/mscorbaddon/agena_commands.pdf.
- NASA Report, A Study of Gemini-Agena Docking Using a Fixed-Base Simulator Employing a Closed-Circuit Television System, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660002865_1966002865.pdf.
- NASA Report, Effect of target angular oscillations on pilot-controlled Gemini-Agena docking, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660013632_1966013632.pdf.
- NASA Report, Investigation of tethered station keeping, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19680002173_1968002173.pdf.
- NASA Report, Comparison of results of two simulations employing full-size visual cues for pilot-controlled Gemini-Agena docking, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660030611_1966030611.pdf.
- NASA Report, Effect of target angular oscillations on pilot-controlled Gemini-Agena docking, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660013632_1966013632.pdf.
- NASA Report, Gemini/Agena target vehicle 5002 systems test evaluation (45 day report), Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19750069069_1975069069.pdf.
- NASA Report, Visual Aspects of A Full-Size Pilot-Controlled Simulation of The Gemini-Agena Docking, Web Address when accessed: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650006980_1965006980.pdf.
- NASA Report, Agena Command Functions, Web Address when accessed: ftp://sf.gds.tuwien.ac.at/2/m/ms/mscorbaddon/agena_commands.pdf.
Contact us with any corrections, additions, or comments.
Conditions for use of drawings, pictures, or other materials from this site..
To contact astronauts or cosmonauts.
© Mark Wade, 1997 - 2008 except where otherwise noted.
|
