Titan IV

Titan IV-A flew with steel-cased solid rocket motors (SRMs) produced by Chemical Systems Division.

Years later, the Titan IV-B evolved from the Titan III family and was similar to the Titan 34D. While the launcher family had an extremely good reliability record in its first two decades, this changed in the 1980s with the loss of a Titan 34D in 1985 followed by the disastrous explosion of another in 1986 due to a SRM failure.

The Titan IV-B vehicle was intended to use the new composite-casing SRMs manufactured by Alliant Technologies. However, after numerous development problems the first few Titan IV-B launches flew with the old-style SRMs.

• Builder: Lockheed-Martin Astronautics
• 

  Bottom of first stage of Titan IVB rocket
  Power Plant:
  • Stage 0 consisted of two solid-rocket motors.
  • Stage 1 used an LR87-AJ-11 liquid-propellant rocket engine.
  • Stage 2 used the LR91-AJ-11 liquid-propellant engine.
  • Optional upper stages included the Centaur and Inertial Upper Stage.
• Guidance System: A ring laser gyro guidance system manufactured by Honeywell.
• Thrust:
  • Stage 0: Solid rocket motors provided 1.7 million pounds force (7.56 MN) per motor at liftoff.
  • Stage 1: LR87-AJ-11 provided an average of 548,000 pounds force (2.44 MN)
  • Stage 2: LR91-AJ-11 provided an average of 105,000 pounds force (467 kN).
  • Optional Centaur (RL10A-3-3A) upper stage provided 33,100 pounds force (147 kN) and the Inertial Upper Stage provided up to 41,500 pounds force (185 kN).
• Length: Up to 204 feet (62 m)
• Lift Capability:
  • Could carry up to 47,800 pounds (21,700 kg) into low Earth orbit
  • up to 12,700 pounds (5,800 kg) into a geosynchronous orbit when launched from Cape Canaveral AFS, Fla.;
  • and up to 38,800 pounds (17,600 kg) into a low Earth polar orbit when launched from Vandenberg AFB.
  • into geosynchronous orbit:
    • with Centaur upper stage 12,700 pounds (5,800 kg)
    • with Inertial Upper Stage 5,250 pounds (2,380 kg)
• Payload fairing:[7]
  • Manufacturer: McDonnell Douglas Space Systems Co
  • Diameter: 16.7 feet (5.1 m)
  • Length: 56, 66, 76, or 86 ft
  • Mass: 11,000, 12,000, 13,000, or 14,000 lb
  • Design: 3 sections, isogrid structure, Aluminum
• Maximum Takeoff Weight: Approximately 2.2 million pounds (1,000,000 kg)
• Cost: Approximately $250–350 million, depending on launch configuration.
• Date deployed: June 1989
• Launch sites: Cape Canaveral AFS, Fla., and Vandenberg AFB, Calif.

In 1988-89, The R. M. Parsons Company designed and built a full-scale steel tower and deflector facility, which was used to test the Titan IV Solid Rocket Motor Upgrade (SRMU). The launch and the effect of the SRMU thrust force on the space shuttle vehicle were modeled. To evaluate the magnitude of the thrust force, the SRMU was connected to the steel tower through load measurement systems and launched in-place. It was the first full-scale test conducted to simulate the effects of the SRMU on the main space shuttle vehicle.[8]

In the early 1980s, General Dynamics developed a plan to assemble a lunar landing spacecraft in-orbit. A Space Shuttle would lift a Lunar Module into orbit and then a Titan IV rocket would launch with an Apollo-type Service Module to rendezvous and dock. The plan required upgrading the Space Shuttle and Titan IV to use lighter aluminium-lithium alloy propellant tanks. The plan never came to fruition, but in the 1990s the Shuttle was converted to aluminum-lithium tanks to rendezvous with the highly inclined orbit of the Russian Mir Space Station.

By the mid-1980s the United States government worried that the Space Shuttle, designed to launch all American payloads and replace all unmanned rockets, would not be reliable enough for military and classified missions. In 1984 Under Secretary of the Air Force and Director of the National Reconnaissance Office (NRO) Pete Aldridge decided to purchase Complementary Expendable Launch Vehicles (CELV) for ten NRO payloads; the name came from the government's expectation that the rockets would "complement" the shuttle. Later renamed Titan IV,[9] the rocket would only carry three military payloads[10] paired with Centaur stages and fly exclusively from LC-41 at Cape Canaveral. However, the Challenger accident in 1986 caused a renewed dependence on expendable launch systems, with the Titan IV program significantly expanded. At the time of its introduction, the Titan IV was the largest and most capable expendable launch vehicle used by the USAF.[11]

The post-Challenger program added Titan IV versions with the Inertial Upper Stage (IUS) or no upper stages, increased the number of flights, and converted LC-40 at the Cape for Titan IV launches. As of 1991, almost forty total Titan IV launches were scheduled and a new, improved SRM (solid rocket motor) casing using lightweight composite materials was introduced.

In 1990, the Titan IV Selected Acquisition Report estimated the total cost for the acquisition of 65 Titan IV vehicles over a period of 16 years to US$18.3 billion (inflation-adjusted US$ 35.8 billion in 2021).[12]

In October 1997, a Titan IV-B rocket launched Cassini–Huygens, a pair of probes sent to Saturn. It was the only use of a Titan IV for a non-Department of Defense launch. Huygens landed on Titan on January 14, 2005. Cassini remained in orbit around Saturn. The Cassini Mission ended on September 15, 2017 when the spacecraft was manoeuvered into Saturn's atmosphere to burn up.

While an improvement over the shuttle, the Titan IV was expensive and unreliable.[9] By the 1990s, there were also growing safety concerns over its toxic propellants. The Evolved Expendable Launch Vehicle (EELV) program resulted in the development of the Atlas V, Delta IV, and Delta IV Heavy launch vehicles, which replaced Titan IV and a number of other legacy launch systems. The new EELVs eliminated the use of hypergolic propellants, reduced costs, and are much more versatile than the legacy vehicles.

In 2014, the National Museum of the United States Air Force in Dayton, Ohio, began a project to restore a Titan IV-B rocket. This effort was successful, with the display opening June 8, 2016.[13] The only other surviving Titan IV components are on outdoor display at the Evergreen Aviation and Space Museum in McMinnville, Oregon, including the core stages and parts of the solid rocket motor assembly.[14]

Titan IVA K-11 moments before the August 1993 failure.

On August 2, 1993, Titan IV K-11 lifted from SLC-4E carrying a NOSS SIGNIT satellite. Unusually for DoD launches, the Air Force invited civilian press to cover the launch, which became more of a story than intended when the booster exploded 101 seconds after liftoff. Investigation found that one of the two SRMs had burned through, resulting in the destruction of the vehicle in a similar manner as the earlier 34D-9 failure. An investigation found that an improper repair job was the cause of the accident.[15]

After Titan 34D-9, extensive measures had been put in place to ensure proper SRM operating condition, including X-raying the motor segments during prelaunch checks. The SRMs that went onto K-11 had originally been shipped to Cape Canaveral, where X-rays revealed anomalies in the solid propellant mixture in one segment. The defective area was removed by a pie-shaped cut in the propellant block. However, most of CSD's qualified personnel had left the program by this point and so the repair crew in question did not know the proper procedure. After replacement, they neglected to seal the area where the cut in the propellant block had been made. Post repair X-rays were enough for CC personnel to disqualify the SRMs from flight, but the SRMs were then shipped to Vandenberg and approved anyway. The result was a near-repeat of 34D-9; a gap was left between the propellant and SRM casing and another burn-through occurred during launch.

1998 saw the failure of Titan K-17 with a Navy ELINT Mercury (satellite) from Cape Canaveral around 40 seconds into the flight. K-17 was several years old and the last Titan IV-A to be launched. The post-accident investigation showed that the booster had dozens of damaged or chafed wires and should never have been launched in that operating condition, but the Air Force had put extreme pressure on launch crews to meet program deadlines. The Titan's fuselage was filled with numerous sharp metal protrusions that made it nearly impossible to install, adjust, or remove wiring without it getting damaged. Quality control at Lockheed's Denver plant, where Titan vehicles were assembled, was described as "awful".

The proximal cause of the failure was an electrical short that caused a momentary power dropout to the guidance computer at T+39 seconds. After power was restored, the computer sent a spurious pitch down and yaw to the right command. At T+40 seconds, the Titan was traveling at near supersonic speed and could not handle this action without suffering a structural failure. The sudden pitch downward and resulting aerodynamic stress caused one of the SRMs to separate. The ISDS (Inadvertent Separation Destruct System) automatically triggered, rupturing the SRM and taking the rest of the launch vehicle with it. At T+45 seconds, the Range Safety Officer sent the destruct command to ensure any remaining large pieces of the booster were broken up.[16]

An extensive recovery effort was launched, both to diagnose the cause of the accident and recover debris from the classified satellite. All of the debris from the Titan had impacted offshore, between three and five miles downrange, and at least 30% of the booster was recovered from the sea floor. Debris continued to wash ashore for days afterward, and the salvage operation continued until October 15.

The Air Force had pushed for a "launch on demand" program for DOD payloads, something that was almost impossible to pull off especially given the lengthy preparation and processing time needed for a Titan IV launch (at least 60 days). Shortly before retiring in 1994, General Chuck Horner referred to the Titan program as "a nightmare". The 1998-99 schedule had called for four launches in less than 12 months. The first of these was Titan K-25 which successfully orbited an Orion SIGNIT satellite on May 9, 1998. The second was the K-17 failure, and the third was the K-32 failure.

After a delay caused by the investigation of the previous failure, the 9 April 1999 launch of K-32 carried a DSP early warning satellite. The IUS second stage failed to separate, leaving the payload in a useless orbit. Investigation into this failure found that wiring harnesses in the IUS had been wrapped too tightly with electrical tape so that a plug failed to disconnect properly and prevented the two IUS stages from separating.

The fourth launch was K-26 on April 30, 1999, carrying a Milstar communications satellite. During the Centaur coast phase flight, the roll control thrusters fired open-loop until the RCS fuel was depleted, causing the upper stage and payload to rotate rapidly. On restart, the Centaur cartwheeled out of control and left its payload in a useless orbit. This failure was found to be the result of an incorrectly programmed equation in the guidance computer. The error caused the roll rate gyro data to be ignored by the flight computer.[17]