Thursday, June 8, 2017

Proton-M Returns to Flight with Launch of EchoStar 21

Launch of the Proton-M / EchoStar 21 mission rocket. Photo Credit: Roscosmos

After a delay of nearly one year, International Launch Services (ILS) launched the EchoStar 21 communications satellite atop a Proton-M rocket from Site 81/24 at Baikonur Cosmodrome in Kazakhstan. Liftoff took place at 11:45 p.m. EDT on June 7 (03:45 GMT on June 8), 2017.

The mission is tasked with delivering the EchoStar 21 satellite into a geostationary transfer orbit (GTO). The flight will last slightly more than nine hours, counting from launch until spacecraft separation.

EchoStar 21 has come a long way to get to this point. The project dates back to 2005 when TerreStar Networks, Inc. finished final design reviews for the TerreStar-1 satellite that was launched into space in 2009. The TerraStar-2 spacecraft was ordered in 2006 and was renamed to EchoStar 21 in 2012 when Englewood, Colorado-based company EchoStar acquired all of TerreStar Network’s assets.

An agreement to launch the EchoStar 21 satellite was signed with ILS in May 2013, initially targeting the end of 2015 for liftoff. However, the mission has faced several delays. First, it was postponed to June 2016; however, in May of that year, it was rescheduled to August 29, 2016.

Later, on July 28, it was decided the launch needed to be postponed to October 2016 due to the prolonged investigation into the problem with the Proton-M’s second stage that occurred after the June 9, 2016, liftoff. Then it was rescheduled for December 2016 before being delayed into 2017.

Then in early 2017, problems were discovered with the launch vehicle’s engines, prompting further investigation.

Finally, in late May 2017, a firm launch date of June 7 (June 8 local time) was set. By this time, Proton had experienced its longest delay in its history: about 364 days. The record before this was 247 days in 1966 into 1967.

The 190-foot (58-meter) tall Proton-M booster measures some 13.5 feet (4.1 meters) in diameter along its second and third stages. Its first stage has a diameter of 24.3 feet (7.4 meters). The total overall height of the rocket’s three stages is about 138.8 feet (42.3 meters).

The first stage consists of a central tank containing the oxidizer surrounded by six outboard fuel tanks. Each fuel tank also carries one of the six RD‑275M engines that provide power for the first phase of flight. The cylindrical second stage is powered by three RD-0210 engines along with a single RD‑0211 engine.

A single RD-0213 engine and a four-nozzle vernier engine powers the third stage. Guidance, navigation, and control of the Proton-M during operation of the first three stages is carried out by a triple-redundant closed-loop digital avionics system mounted in the third stage.

Topping off the rocket is the Breeze-M upper stage. It is powered by a pump-fed gimbaled main engine. This stage consists of a central core and an auxiliary propellant tank (APT) that is jettisoned in flight after the depletion of its fuel. The stage’s control system includes an onboard computer, a three-axis gyro stabilized platform, and a navigation system.

The countdown that led the Proton-M rocket to the ignition of its engines commenced about 11.5 hours ahead of liftoff. The launch vehicle and its systems were activated about six hours before the launch, enabling fueling operations. The campaign entered its final phase approximately 45 minutes before ignition when final checkouts of all systems were performed and the launch abort system armed.

The last five minutes of the pre-launch phase was the most crucial as the automated countdown sequence began, switching the launch vehicle to internal power. About two minutes before liftoff, propellant tank pressurization took place and engineers had their last opportunity to conduct health checks of the rocket’s Breeze-M upper stage. With all systems declared “go”, the Proton-M ignited its six RD-275M boosters to begin climbing toward space.

Maximum dynamic pressure, or max Q, occurred about 62 seconds after liftoff. It was at this point the vehicle endured its maximum stresses.

Stage one and two separated less than a minute later at two minutes after liftoff. The second stage continued burning for about 3.5 minutes before it too cut off and separated.

At this point, the third stage had taken control. It fired at 5 minutes, 26 seconds after liftoff. Nineteen seconds later, the payload fairing jettisoned, revealing the Breeze-M upper stage and the EchoStar 21 satellite.

At 9 minutes, 41 seconds after leaving the launch pad in Baikonur, the third stage cut off and separated from the Breeze-M. About 1.5 minutes after that, it too ignited to finish the climb to orbit.

Fifteen minutes, 32 seconds after liftoff, Breeze-M with EchoStar 21 was in a parking orbit. The first of five burns the upper stage needed to do was complete.

After coasting for 54 minutes, the Breeze-M ignited again and burned for about 18 minutes. This intermediate orbit had a low point of 168 miles (270 kilometers) and a high point of 3,107 miles (5,000 kilometers).

The Breeze-M and EchoStar 21 then coasted again for about two hours before the third upper stage ignition occurred. This burn started 3 hours, 37 minutes, and 36 seconds after liftoff; it continued for just under nine minutes. At its conclusion, the APT jettisoned.

About 1.5 minutes later, the fourth burn started. This seven-minute burn concluded at a mission elapsed time of 3 hours, 47 minutes, 53 seconds.

Coasting again, the Breeze-M upper stage had a five-hour break before its final burn.

That burn occurred 8 hours, 52 minutes, 58 seconds after leaving Baikonur. The primary objective of this 4.5-minute burn was to change the inclination of the vehicle and satellite from 51.5 degrees relative to the equator to just 30.5 degrees. The low point of its orbit was now 1,429 miles (2,300 kilometers) and the high point was 22,236 miles (35,786 kilometers).

At 9 hours, 13 minutes mission elapsed time, the EchoStar 21 satellite separated from the Breeze-M.

The 6.8-metric ton EchoStar 21 is based on SSL’s 1300 spacecraft platform and features two deployable solar arrays and a large unfurlable reflector.

Once the spacecraft’s onboard propulsion to circularize its orbit, EchoStar 21 will be in a geostationary orbit at the 10.25 degrees East orbital slot where it will provide its services for 15 years.

EchoStar describes the newest addition to its in-orbit fleet as a state-of-the-art S-band satellite designed to provide mobile connectivity throughout Europe.

This was the first ILS Proton launch in 2017 and the 94th ILS Proton launch overall. Additionally, six EchoStar satellites have now been launched by the company atop Proton rockets.

In total, 413 Proton rockets have launched since 1965. Since 2001, 90 Proton-M variants have launched using the Breeze-M upper stage.

This was the third launch from Baikonur Cosmodrome in 2017. The next mission from that spaceport will be the Progress MS-06 cargo ship bound for the International Space Station. It will take to the skies at 5:20 a.m. EDT (09:20 GMT) on June 14, 2017.

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