Japan’s SS-520 fails during TRICOM-1 launch to demo small rocket capability

by William Graham

Japan conducted an experimental launch, using a modified SS-520 sounding rocket to place a CubeSat, TRICOM-1, into low Earth orbit. The mission lifted off from the Uchinoura Space Centre at 08:33 local time (23:33 UTC on Saturday), aiming to mark a new record for small rocket launch capability. However, the launch has been declared as a failure.

Japanese Launch:

A one-off demonstration mission, the launch aimed to prove the concept of using a minimally-modified sounding rocket to place small satellites into orbit.

Both IHI Aerospace and Canon have investigated partnerships with the Japan Aerospace Exploration Agency (JAXA) on the development of rockets to launch small satellites, and the launch will gather data which could aid these programs. The TRICOM-1 satellite is a CubeSat, carrying a communications experiment and cameras for Earth imaging.

The SS-520 is a two-stage solid-fuelled sounding rocket, designed to carry research payloads on suborbital missions to altitudes of around 800 to 1,000 kilometers (620 miles, 540 nautical miles).

For the mission, which has the flight designation SS-520-4, the vehicle has been modified with the addition of a small third stage to inject its payload into a low Earth orbit.

SS-520-4 will make the third flight of the SS-520, which first flew on 5 February 1998 from Uchinoura and made a second launch in December 2000 from Svalbard, Norway, carrying out geomagnetic research missions.

The first stage of the SS-520 is based on the S-520 rocket, with a smaller second stage mounted atop it to increase the maximum altitude the rocket can reach on suborbital missions. Fins at the base of the rocket provide spin stabilization.

A rhumb line control system using gaseous nitrogen thrusters mounted in the interstage between the first and second stages is used to reorient the vehicle during a coast phase between first stage separation and second stage ignition, firing as the vehicle spins to change its attitude by precessing its rotation. For Wednesday’s mission the third stage and payload are mounted within the rocket’s standard nose cone.

First introduced in 1980, the S-520 is used by JAXA, and its predecessor the Institute of Space and Aeronautical Science (ISAS), for research launches which typically reach an altitude between 200 and 400 kilometers (124-249 miles, 108-216 nautical miles). Thirty have been launched, with one failure which occurred in 1995.

In its three-stage configuration, the SS-520 is expected to be able to place a four-kilogram (8.8 lb) payload into low Earth orbit. The vehicle measures 9.54 meters (31.3 feet) in length with a diameter of 0.520 meters (1.71 feet), and has a mass at launch of 2,600 kilograms (5,700 lb).

Had the launch been classed as successful, SS-520-4 would have become the smallest rocket ever to deliver a payload into orbit. The only smaller vehicle – both in mass and length – to attempt an orbital launch was the US Navy’s NOTS-EV-1 vehicle, also known as Pilot. Air-launched from an F4D-1 Skyray, Pilot made six orbital launches and four ground-launched suborbital test flights between July and August 1958; all ten launches failed.

The smallest rocket to reach orbit prior to the launch was Japan’s Lambda-4S rocket, which made five launches between 1966 and 1970, scoring its only success with the February 1970 deployment of Osumi, Japan’s first successful orbital launch.

The TRICOM-1 CubeSat was the only payload aboard SS-520-4. Developed by the University of Tokyo, the satellite carries a store-and-forward communications payload and five cameras for Earth observation. It has a mass of approximately three kilograms (6.6 lb).

TRICOM-1 was built to the three-unit CubeSat standard. CubeSats have become a popular standard within the space industry for small scientific, educational, technology research and even commercial payloads. A variety of form factors have been launched, specified in terms of units – a single unit being a cube with sides of ten centimeters (3.9 inches).

The smallest CubeSat to have been launched was a 0.25-unit spacecraft, measuring 0.25 cm along one axis, and ten centimeters along the other two, while the largest is a twelve-unit satellite measuring 20 by 20 by 30 cm (7.9 x 7.9 x 11.8 inches).

A three-unit spacecraft like TRICOM-1 measures 10 by 10 by 30 centimeters, or 3.9 by 3.9 by 11.8 inches; although with its unique separation system and antennae deployed, TRICOM-1 is slightly larger, measuring 11.1 by 11.1 by 34.6 cm (4.6 by 4.6 by 13.6 inches).

Since the first CubeSats were deployed from a Rokot rocket in 2003, over 300 such spacecraft have been launched with the three-unit the most common configuration. CubeSats are typically carried as secondary payloads on the launches of larger satellites, and the launch is the first time a single CubeSat has been given a dedicated launch. Also unusually for a CubeSat, TRICOM-1 is designed to separate directly from the upper stage of the SS-520 rocket, rather than using a deployment pod.

The launch took place from the Uchinoura Space Centre, using the facility’s KS Centre launch complex. Uchinoura, which was known as the Kagoshima Space Centre prior to 2003, is one of two orbital launch sites in Japan, along with the Tanegashima Space Centre.

Uchinoura has two launch complexes; the KS Centre which is primarily used for sounding rocket missions, and the Mu Centre, about 350 meters (1150 feet) to the East, which is used for orbital launches with Epsilon, and formerly Mu, rockets.

The KS Centre is used by the S-310, S-520 and SS-520 rockets, Japan’s fleet of suborbital research vehicles. Historically the pad has also been used by Kappa, Lambda and MT-135 vehicles. Japan’s earliest orbital launch attempts, using the Lambda-4S rocket, were made from the complex, with the fifth and final launch on 11 February 1970 Japan’s first successful orbital launch, placing the Osumi satellite into orbit. The launch of Osumi is the most recent orbital launch from the KS Centre.

The KS Centre has a large integration building and launch dome, with rockets able to launch from within the building or from a concrete area outside, via mobile launchers. The S-310 and S-520 have separate launchers, with the SS-520 using the S-520’s launcher for its previous flight from Uchinoura.

Between 2012 and 2014, a permanent rail launcher was installed adjacent to the launch dome, which was first used for the August 2014 launch of an S-520 rocket, flight designation S-520-29. It is from this rail launcher that SS-520-4 will take flight.

The launch was to last seven and a half minutes from liftoff to spacecraft separation. At the zero-second mark in the countdown the first stage ignited, beginning a 31.7-second burn which accelerated SS-520-4 to a speed of 2 kilometers per second (4,500 mph), boosting it towards space.

Once its first stage had ignited, the rocket left the launch rail and began its ascent towards space. Following first stage burnout, the rocket coasted towards its apogee.

Sixty-five seconds after launch, with the rocket at an altitude of 78 kilometers (48 miles, 42 nautical miles), the vehicle’s nose cone separated. A second later, the spent first stage was jettisoned. Shortly afterward, at about 77 seconds elapsed time, the rhumb line thrusters began firing pulsed as the vehicle rotated, adjusting its spin to provide the correct orientation for second stage flight – a process which lasted twenty-nine seconds.

Two minutes and 27 seconds into the flight, the interstage, which houses the rhumb line thrusters, separated from the second stage. Ten seconds later a vehicle status check was conducted to determine whether the rocket was still capable of achieving orbit.

This verified that the vehicle’s spin rate, its position, speed and altitude, and its attitude were within expected parameters, that the vehicle was healthy and that any necessary adjustment to the second stage ignition time could be made. Had these checks passed the flight would have continued to second stage ignition, otherwise the mission would have been aborted and the rocket allowed to fall into the Pacific Ocean.

It took over an hour until news was provided that the vehicle suffered a problem before second stage ignition, resulting in the failure of the mission.

Had second stage ignition been authorized, it would have occurred 170 seconds after liftoff, at an altitude of 174 kilometers (108 miles, 94 nautical miles). The second stage would make a 24.4-second burn to raise the vehicle’s velocity to 3.6 kilometers per second. Then, a little under thirty seconds after its burn completed, the second stage would have separated, with third stage ignition taking place three seconds after staging.

The third stage would have burned for 25.6 seconds, completing orbital insertion and placing TRICOM-1 into a planned target orbit of 180 by 1,500 kilometers (112 by 932 miles, 97.2 by 810 nautical miles) at an inclination of 31 degrees. Spacecraft separation occurred at seven minutes, thirty seconds mission elapsed time. None of these events were tested with the flight telementry only noting first stage performance before the failure.

Despite the failure, the three-stage SS-520 was the first of several new small, low-cost, rockets to debut in 2017. US-New Zealand company Rocket Lab plans to introduce its Electron rocket later in the year, with the first flight of Virgin Galactic’s LauncherOne is currently targeting the end of the year.

InterOrbital Systems are also claiming to be planning launches of their Neptune rocket this year, including a Google Lunar X-Prize competitor – however, in the past, they have claimed to be close to conducting their first launch but that launch has never materialized.

The launch of SS-520-4 was Japan’s first of 2017 – although it will be classed as a failed mission – and the fourth worldwide following China’s successful launches of Chang Zheng 3B and Kuaizhou-1A rockets – and SpaceX’s Falcon 9 launch earlier on Saturday. Japan’s next launch is scheduled for 24 January, when an H-IIA will deploy the DSN-2 communications satellite in a mission to be flown from Tanegashima.

The next SS-520 launch is currently scheduled for December, flying a suborbital mission from Svalbard in its standard two-stage configuration. This will be pending the investigation into the failure.

(Images via JAXA and Rocket Labs).

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