WASHINGTON The Japanese space agency is in final preparations for the liftoff of the eighth H-II heavy lift space booster from the Tanegashima Space Center, the agency reported early Wednesday. The rocket, with the MTSAT aeronautical navigation satellite aboard, is under final checkout at Yoshingbu Launch Complex, officials of the National Space Development Agency (NASDA) reported.
Under the launch plan, NASDA officials must make their final determination of the exact time and date for liftoff to safety and range officials at the Tanegashima site no later than 3pm two days prior to the attempt. Thus the exact date of the launch attempt wont be finalized until next Wednesday.
This months launch is significant for two reasons, one related to the vehicles satellite payload and the other related to the rocket itself. The satellite is the first of a pair of test navigation spacecraft to be planned by Japan.
The Ministry of Transportation Satellite (MTSAT) will establish a rudimentary communications link with Japanese civil aircraft. The satellites will not transmit navigation signals like those used on the U.S. Global Positioning System or Russian Glonass satellites. Instead the satellites will relay voice and data communications between aircraft and two ground control Aeronautical Satellite Centers, one at Kobe and the other at Hitachi-ota.
The satellites will also be used for weather and environmental photography and monitoring. The second of the two MTSATs is to be launched in 2004, completing the constellation. Both vehicles will orbit at geostationary altitude 22,000 miles above the earth.
The H-II rocket, the eighth flight vehicle to be launched, contains a series of improvements and modifications largely overlooked in the public statements about the MTSAT mission, but which have significance to U.S. and European commercial launch service providers.
These include improvements to the core booster, mainly to the second stage. NASDA has created a new, separate bulkhead for the rockets fuel tanks, moving away from a common unit used on previous vehicles.
A change in the flight control system from a hydraulic to an electro-mechanical actuator system was installed, reducing cost.
More rocket fuel is being carried in the stage, from 2.4 to 2.8 tons of liquid oxygen and from 11.7 to 13.9 tons of liquid hydrogen. This will give flight planners greater freedom for longer burn times in flight and add additional reserves.
The LE-5A engine has been replaced with the LE-5B on the second stage. The newer engine thrust chamber has a new coolant system. The new design also has fewer parts and fewer welds during assembly, thus reducing potential areas of in-flight failure.
The engine also has a new series of turbine blades made in a new manufacturing process. The engine is also more powerful, going up to 14 tons from the previous 12.4, in a vacuum.
There were no changes to the rockets electrical system. The structural design of the fairing, the cover that protects satellites and payloads during launch, was changed to reduce costs.
An adapter was added to facilitate payload processing and standardization.
NASDA also added a gaseous oxygen/hydrogen thruster system to better control the second stage during coasts between firings.
The launch pad at Tanegashima was also modified, with new umbilicals for the second stage and a new disconnect system on the rockets launch tower.
In flight, the H-II rises vertically from the pad then pitches over at a 92.5 degree angle to bring the booster out over the western Pacific Ocean. The strap-on booster motors separate at about one minute 33 seconds in flight, followed by the cores first stage at about four minutes 15 seconds into the launch. Both fall into the ocean and are not recovered.
The second stage fires once to insert the MTSAT into a parking orbit briefly, then refires at 24 minutes 20 seconds when the rocket is on the other side of the world to send the satellite towards its final, geostationary altitude.
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