Less than three months after the spectacular—though catastrophic—loss of a Proton-M booster in July, International Launch Services (ILS) is primed to return the venerable vehicle to flight. Liftoff of the three-stage Proton and its troubled Briz-M upper stage from Pad 39 at Site 200 at the Baikonur Cosmodrome in Kazakhstan is scheduled for 3:38 a.m. local time Monday (5:38 p.m. EDT Sunday), carrying the Astra 2E communications satellite into 22,300-mile geosynchronous orbit. The 191-foot-tall Proton was rolled horizontally out to the launch pad on Thursday, 26 September and raised into a vertical orientation, with propellant loading operations slated for early Sunday.
This launch is long-awaited, coming on the heels of the last Proton mission, which failed seconds after launch on 2 July. As highlighted in dramatic YouTube imagery, the 1.5-million-pound Proton started pitching wildly to the left and right along its vertical axis shortly after leaving the pad. Efforts to bring these unwanted motions under control by the guidance system were unsuccessful, and the vehicle entered an unmanageable pitchover and hit the ground in a fireball at T+30 seconds. Last month, the Russian government formed the United Rocket and Space Corporation to consolidate the space sector, with Deputy Prime Minister Dmitri Rogozin announcing that it was “so troubled that it needs state supervision to overcome its problems.” The corporation is expected to gain a controlling interest in the Energia rocket engine manufacturer, in which the Russian government already held a 38-percent interest level.
On 13 August, the ILS Failure Review Oversight Board (FROB) and Russia’s State Inter-agency Commission revealed that three angular velocity sensors for yaw control of the Proton’s first stage had been installed incorrectly and formed the root cause of the accident. Moreover, it was suggested that an umbilical separated prematurely, with the vehicle leaving the pad a few tenths of a second early, before the engines had reached full thrust. As it pitched over in its final seconds, the upper stages of the rocket and the payload—a trio of GLONASS navigation satellites—were torn away from the burning Proton and destroyed. “We very much appreciate the time, effort and participation of our customers, the insurance underwriters and technical experts in the FROB process,” said John Palmé, ILS Vice President of Programs and Operations. “They worked tirelessly with us to ensure that the review was conducted thoroughly. As we work towards the return to flight of the Proton vehicle, we thank all of our customers for their continued support.” The accident marked the first failure by a Proton during first-stage flight in over 30 years.
At the time of the accident, efforts had entered high gear for the launch of Astra 2E aboard the very next Proton. The cube-shaped spacecraft—built by the Luxembourg-based SES global satellite provider—arrived at Baikonur in mid-June, followed by the Proton’s restartable Briz-M upper stage a few days later. Liftoff was scheduled for the night of 20/21 July, but was put on indefinite hold in the wake of the accident. Eventually, ILS announced that it was tracking a new launch date in mid-September, but technical troubles rendered this target unachievable. Detoxification of the accident zone and reports from ILS relating to “an out-of-tolerance reading in the first stage of the vehicle” conspired to delay the launch by two weeks. On 22 September, a new launch date and time of 3:38 a.m. local time Monday, 30 September (5:38 p.m. EDT Sunday the 29th) was scheduled. Rollout of the Proton-M and Astra 2E payload to Pad 39 at Site 200 occurred on 26 September.
Flown 70 times since April 2001, with six failures and two partial failures, the Proton-M comprises three main stages and on this launch will also utilize the restartable Briz-M upper stage. This allows it to inject payloads weighing up to 14,800 pounds into geosynchronous transfer orbit and up to 7,700 pounds directly into a 22,300-mile geosychronous orbit. The vehicle is built by the Khrunichev Research and State Production Centre, and its heritage extends back to the mid-1960s, with a launch history of almost 400 flights and one of the most reliable track records in the world. All of its stages, including the Briz-M, utilize nitrogen tetroxide and unsymmetrical dimethyl hydrazine propellants. Its first stage consists of a central oxidizer tank, surrounded by six outboard fuel tanks, each fed by an RD-276 engine, and these will provide the initial impetus to boost Astra 2E toward orbit.
Fueling of the main three stages is expected to begin about nine hours ahead of liftoff. Ignition of the six RD-276 engines will commence at T-2 seconds, ramping up to 100 percent to produce 2.3 million pounds of thrust at liftoff. A little over a minute into the ascent, the Proton will encounter the period of maximum aerodynamic turbulence (known as “Max Q”) on its flight surfaces, with the separation of the first stage scheduled at the two-minute point. The second stage will then pick up the baton, with its four engines generating a combined 540,000 pounds of impulse for a little over 3.5 minutes. Shortly after the second stage separates from the vehicle, the Payload Fairing (PLF) will be jettisoned and the single-engine third stage will add an extra 138,000 pounds of thrust for the next four minutes of flight. Shutdown of the third stage is expected about 10 minutes after launch, by which time the vehicle will have been placed onto a suborbital trajectory.
The turn will then come for the single-engine Briz-M upper stage, which has exhibited a mixture of success and failure since its maiden voyage, back in May 2000. In August 2012, a premature shutdown of the Briz-M left Indonesia’s Telkom-3 and Russia’s Ekspress-MD2 satellites in useless orbits, and in December 2012 another launch glitch impacted the Yamal-402 satellite. Last March, a Proton-M/Briz-M successfully injected Mexico’s Satmex-8 communications satellite into orbit. Capable of restarting up to eight times in flight, the Briz-M has a battery-powered lifetime of 24 hours and is scheduled to execute five “burns” to insert Astra 2E into orbit.
Its first burn will last 4.5 minutes and is due to commence about 11 minutes into the mission, after which the Briz-M/Astra 2E combo will enter a circular “parking orbit” and coast for almost an hour, preparatory to the second burn. This will be a much longer firing of almost 18 minutes, followed by a two-hour period of coasting, then a third burn of 11.5 minutes and a fourth of about six minutes in duration. After the fourth burn, the combo will coast for about five hours, ahead of the final scheduled Briz-M firing at T+8 hours and 53 minutes. This six-minute burn will position Astra 2E into geosynchronous transfer orbit, and at T+9 hours and 12 minutes the 13,200-pound satellite will separate from the upper stage.
Owned and operated by the Luxembourg-based SES global satellite provider, Astra 2E will be positioend at 28.2 degrees East in geosynchronous orbit. Equipped with three Ku-band downlink beams covering Europe and the Middle East, it will provide digital television and satellite broadband services for Europe and the Middle East. It forms the second of three “second-generation” satellites assigned to the 28.2 degrees East orbital position. Astra 2F was launched by Europe’s Ariane 5 in September 2012, and Astra 2G will fly in spring 2014. Upon arrival in its orbital slot and after initial checkout, Astra 2E will take over the channels currently broadcast by the Astra 1N satellite. Together with Astra 2F, the new satellite will deliver programs to 13 million satellite homes and 3 million cable homes. The satellite weighs 13,200 pounds and is expected to operate for 15 years.