Tuesday, January 24, 2017

Japanese H-IIA Rocket Delivers DSN-2 Military Communications Satellite to Orbit

H-IIA rocket launches with DSN-2 military communications satellite. Credit: asahi.com

The Japan Aerospace Exploration Agency (JAXA) successfully conducted its first launch of 2017 with the delivery of the DSN-2 military communications satellite to a geostationary transfer orbit. Carrying the payload was an H-IIA rocket configured in its 204 arrangement. Liftoff took place at the opening of a 74-minute launch window at 2:44 a.m. EST (07:44 GMT) Jan. 24, 2017, from Japan’s Tanegashima Space Center (TNSC).

H-IIA rockets, built and operated by Mitsubishi Heavy Industries, stand some 174 feet (53 meters) tall. The 204 configuration has two stages and four strap-on solid rocket boosters.

Seconds before lifting off the launch pad, the first stage’s main engine, the LE-7A, roared to life as the turbopumps built up 200,000 pounds (870 kilonewtons) of thrust. Once the flight computer determined the engine start was nominal, the four supplemental SRB-A3 solid-fueled boosters were ignited.

With each of the SRB-A3 motors providing nearly 520,000 pounds (2,305 kilonewtons) of additional thrust, the vehicle quickly left the pad, clearing the launch tower a few seconds later.

As it soared into a partly cloudy sky, the vehicle executed its pitch, roll, and yaw maneuver to ensure the rocket was in its proper flight attitude.

Heading eastward out over the Pacific Ocean, the H-IIA rapidly gained velocity as the vehicle exceeded Mach 1 – the speed of sound – and encountered the greatest stress on the vehicle from aerodynamic forces, a part of the flight regime known as max Q.

The four SRBs continued to burn until their solid fuel was exhausted, approximately two minutes after ignition. No longer needed, the spent boosters were jettisoned nearly ten seconds later. The carbon-polymer booster casings are not designed to be reused and were allowed to fall into the Pacific Ocean.

Weighing significantly less than it did at liftoff, the lone LE-7A continued to push the remainder of the vehicle to orbit. As the atmosphere thinned, the LE-7A’s output jumped to 247,000 pounds (1,098 kilonewtons) of force. Roughly three-and-a-half minutes after launch, the payload fairing was jettisoned.

After burning for approximately six-and-a-half minutes, the first stage’s liquid oxygen and liquid hydrogen propellants were consumed and the LE-7A was shut down. Ten seconds later, the first and second stages separated.

Following a short coast, the second stage’s single LE-5B engine was ignited. Like the first stage’s main engine, the LE-5B is a cryogenically-fueled (liquid hydrogen and liquid oxygen) power plant.

Providing nearly 31,000 pounds (137 kilonewtons) of thrust, the upper stage’s engine performed three burns in order to place the DSN-2 payload into an “upgraded” geostationary transfer orbit.

The first burn of the LE-5B placed the vehicle into a nearly circular low-Earth parking orbit. A few minutes later, the engine fired again; this time as it was crossing the equator. This burn ensured that the vehicle’s apogee would center above the equator.

The third, and final, burn corrected for inclination offsets and raised the perigee. Utilizing this three-burn profile allows for the payload to be placed in a higher orbit, which precludes the satellite from having to use as much of its own propellant to raise its orbit as would be the case with more traditional geostationary transfer orbits.

Shortly after this third burn, the DSN-2 satellite was released from the second stage, concluding the H-IIA’s mission. The communication satellite will go through a series of check-out procedures before raising its orbit and assuming its slot in geostationary orbit.

This was JAXA’s 32nd overall launch of the H-IIA vehicle, and third of the 204 variant.

Written by: Curt Godwin
Original source: spaceflightinsider.com

1 comment:

  1. The primary blaze of the LE-5B put the vehicle into an almost round low-Earth stopping circle. A couple of minutes after the fact, the motor let go once more; this time as it was intersection the equator. This smolder guaranteed that the vehicle's apogee would focus over the equator. See here