What was the Commercial Titan III?
An infographic about the Commercial Titan III which explains many of its systems. Credit: NSF Forums
History
From 1989 to 1992, the Commercial Titan III launched only 4 times to satisfy the needs of customers such as SKY Perfect JSAT group, the United Kingdom’s Ministry of Defence, Intelsat, and NASA. The development of the Commercial Titan III started in the mid-1980s. CT-III was developed by Martin Marietta for the U.S. Air Force’s Medium Launch Vehicle competition to launch their GPS NAVSTAR Block II satellites. Unfortunately, the Commercial Titan III lost the competition, and McDonnell Douglas’ Delta II rocket won the competition to launch GPS satellites. However, by September 1986, a few commercial buyers have already placed orders for their spacecraft to be launched on the Titan. Because the Titan 34D’s service was coming to an end, the CT-III would end up being the final Titan III, ending a legacy of almost 30 years.
What made up the Commercial Titan III?
The Commercial Titan III utilized two UA1206 solid rocket motors which created 2,800,000 pounds of thrust at liftoff. The two UA1206 motors were manufactured by Chemical Systems Division of United Aircraft, later known as United Technologies Corporation. The UA1206 motors ran on Ammonium perchlorate composite propellant (APCP) solid propellant, using a Polybutadiene acrylonitrile (PBAN) binder. Because the solid motors didn’t have the capability to gimbal to provide control during flight, they used a liquid injection thrust vector control system. The large red tanks you see on the side of the boosters were for this purpose, and they contained nitrogen tetroxide (NTO).
A UA1206 motor is shown on the pad at LC-40. To the left of the image, you can see the red LITVC tank. Credit: NASA
The Titan 3B-1 core stage used an LR-87 engine, like all other Titan boosters in the past. The LR-87 engine was manufactured by Aerojet-General. Titan boosters had a unique staging system. At liftoff, they were carried to the sky under the power of only the solid rocket motors. Shortly before the solid motor burned out, the LR87 engine would ignite and provide the rocket with 547,950 pounds of thrust. Unlike the SRMs, the core used liquid fuel. Aerozine50 was used as fuel and NTO was used as an oxidizer. After the LR-87 ignited, it would continue burning for ~200 seconds before the engine shut off. The engine lacked the need of an ignition system due to its usage of hypergolic propellants.
The core tank of a CT-III is shown. Credit: An NSF Forum
For the second stage, the rocket used the Titan 3B-2. The second stage used the LR-91-11 engine, also made by Aerojet. Shortly before the LR-87 engine shut off, the LR91 engine would ignite, and the second stage would separate from the rocket. The LR91 provided 105,000 pounds of thrust. Because the second stage used no ullage motors or any other ways to combat ullage, the engine ignited while the other was burning so that the propellants would stay at the back of the tank rather than float around. This is a process known as hot staging. The LR91 would burn for ~250 seconds more before placing the payload into low earth orbit.
The second stage & fairing of the Commercial Titan III are shown. This is the rocket that launched NASA’s Mars Observer mission. Credit: NASA
Capabilities of Commercial Titan III - How Far it Could Send Something
In the basic, two-stage configuration, the launch vehicle could only place a satellite in low earth orbit due to the LR91 having no restart capability. This means that to have your payload placed into a higher orbit, you’d need an upper stage. None of the launches had no third stage. 5 upper stages were designated for use aboard CT-III:
Payload Assist Module (PAM)
Transfer Orbit Stage (TOS)
Centaur-G Prime (never flown)
Expendable Shuttle Compatible Orbit Transfer System (ESCOTS)
Of these upper stage options, only 2 of them were flown, those being the Transfer Orbit Stage and the PAM-D2, made for Delta vehicles. The Orbus-7S and Orbus-21S were also flown on launches. Using the simple two-stage configuration, the rocket could deliver a 31,530 pound payload into low earth orbit. With a third stage, the rocket could deliver a 10,980 pound payload into geostationary transfer orbit. CT-III could deliver a 7,480 pound probe to the Moon, and a 5,720 pound probe to either Mars or Venus.
Another special capability that was carried by the Commercial Titan III was the ability to carry two satellites. The fairing and the dual payload system is derived from Europe’s Ariane 4 rocket. The dual payload system used Europe’s Speltra system. One satellite was placed on top of Speltra, and the other was inside. The satellite on top of Speltra would be released first at around 1 hour into flight. After the first satellite was deployed, the Speltra system would be jettisoned from the rocket, exposing the other payload to space. The satellite that was encapsulated by Speltra gets deployed around 2 and a half hours into flight. Only 1 of the 4 launches would use the dual payload system, that being its inaugural launch.
Launches Conducted by CT-III
From 1989 to 1992, the Commercial Titan would only make 4 flights. The launch vehicle only had access to one launch pad: LC-40 at Cape Canaveral. Because LC-40 was under renovation for a year, the rocket didn’t fly for long periods of time. These flights were done for commercial entities and government entities.
Inaugural launch: JCSAT-2 and Skynet-4A
On December 31, 1989 (local time), the Titan III lifted off on its first flight from Cape Canaveral. The liftoff occurred on January 1, 1990 at 0:07 GMT, making the launch happen across two different decades. The rocket carried JCSat-2 for SKY Perfect JSAT group, and Skynet-4A for the British Ministry of Defence. A PAM-D2 motor placed Skynet-4A into geostationary orbit at 6 degrees east, and an Orbus-7S motor placed JCSat-2 into geostationary orbit at 154 degrees east.
JCSAT-2 and Skynet-4A launch from LC-40. Credit: X/Cosmic_Penguin
Intelsat 603
On March 14, 1990, the CT-III lifted off once again to bring an Intelsat satellite into geostationary orbit. The launch was a partial failure. While the launch vehicle did the launch as normal, deploying the motor and satellite was coming up. Because of a wiring error in the stage separation electronics, the kick motor couldn’t be deployed from the second stage, therefore Intelsat 603 had to be jettisoned from the kick motor. The satellite was stranded in low earth orbit until STS-49, the Space Shuttle Endeavor’s maiden flight came to rescue the satellite and attach a new kick motor.
Intelsat 603 lifts off from Cape Canaveral Air Force Station. Credit: Intelsat
Intelsat 604
This launch was a complete success. On June 23, 1990, the rocket successfully lifted off from LC-40. The Orbus-21S motor was successfully deployed from the rocket this time, and Intelsat 604 was deployed into a geostationary orbit at 27 degrees west. Intelsat 604 would continue operating normally, providing service to Europe, Africa, Latin America, and the eastern portion of North America.
Intelsat 604 sits on the pad at LC-40. Credit: Intelsat
Final Launch: Mars Observer
Mars Observer was a NASA probe that was headed to Mars, like the name states. This was the final launch of a Titan III rocket. Mars Observer was NASA and the USA’s return to Mars after the Viking 2 mission. On September 25, 1992, the rocket successfully thundered off the pad at Cape Canaveral Air Force Station. The Transfer Orbit Stage was successfully deployed from the rocket, and the TOS begun its burn to send the probe to Mars. The probe was successfully deployed from the motor on its way to Mars. Unfortunately, 2 days before the probe’s planned orbital insertion into Mars, the probe lost contact with NASA, and the payload was considered lost. Mars Observer’s launch costed $90M, but the total cost was $813M.
Mars Observer lifts off from LC-40. Credit: NASA
References:
Gunther’s Space Page
planetary.org
Spaceline.org
futura-sciences.us
planet4589.com
Space Shuttle Missions Summary - STS-49 (nasa.gov)
