Day: December 7, 2015

It is not often that I get to report on a space event that is happening right as I’m wiring about it; but that is precisely what happened as I wrote this edition of Space Sunday.

As I was typing, high above Venus, a little cube-like space craft measuring just over a metre on a side and supported by two stubby solar panel “wings”, had been making a final desperate attempt to enter orbit around the planet.

Akatsuki (“Dawn”), is a Japanese space probe also known by the names Venus Climate Orbiter (VCO) and Planet-C. Its mission is to study the dense, intense atmosphere of Venus and gain greater insight into how it formed, whether it has active weather phenomena such as lightning, and whether Venus itself may still be volcanically active. It is also a vehicle which has taken “the long way around” in order to reach its target.

Originally launched on May 20th, 2010 Akatsuki should have entered orbit around Venus on December 7th of that year. In order to do so, the vehicle had to carry out a 12-minute “burn” of its main engine to slow itself to the point where it would be caught by Venus’ gravity and so swing into an elliptical orbit. However, while the engine did fire as expected, a fuel valve failed, preventing the burn from being completed as required, and Akatsuki failed to achieve the desired orbit, and instead was left strained in a heliocentric (Sun-centred orbit) which would bring the craft back into proximity with Venus five years later – on the evening (UK time) of the 6th / 7th December 2015.

Having managed to keep the little craft alive and functioning during the intervening years, this second encounter offer a final opportunity to get Akatsuki safely into orbit around Venus, where it might complete its primary mission. Final because the craft has already far exceeded its operational life span, and such an opportunity is unlikely to come again.

So it was that at around 23:51 UTC on Sunday, December 6th, Akatsuki fired one set of its reaction control system (RCS) thrusters for 20 minutes in an attempt to push itself into an extended orbit around Venus (VOI – for Venus Orbital Insertion – in the diagram above).  Entirely automated, the attempt could, if required, be followed by an additional motor firing if telemetry received on Earth indicated the first burn had failed.

At 00:24 UTC on December 7th, data received from the vehicle, having taken over 8 minutes to be transmitted to Earth and then be processed, indicated the initial motor firing had been successful, and that Akatsuki should have established itself in an extended elliptical orbit around Venus, between 300,000 to 400,000 km above the surface of the planet. This is somewhat greater than the original orbit for the craft, which would have varied between 300 to 80,000 km, but it still should be close enough for the probe to undertake most of its science mission, although it will be several hours before this is confirmed.

 Cosmic Girl Gets Ready to Launch

Virgin Galactic is probably best known for two things: Richard Branson and trying to develop a sub-orbital flight capability which will allow fare-paying tourists enjoy a few minutes of “weightlessness” at the edge of space, marketing itself as the “world’s first commercial space line”.

However, the company is also looking to enter the lucrative market of commercial satellite launches, using a vehicle they’ve christened LauncherOne. The vehicle is specifically intended to to provide a launch capability for “smallsats”, sub-500 kg satellites, an increasingly poplar market sector, but one where very often the main means of getting into orbit is by “hitch-hiking” aboard launchers carrying other payloads.

Unlike most boosters, LauncherOne is designed to be air-launched. That is, carried aloft by an aircraft to an altitude of some 10,770 metres (35,000 ft) before being released to allow its first and second stage motors carry its payload up to the required orbit.

The technique isn’t new – it is used most notably by the Pegasus launch system developed by Orbital ATK, and which first flew in 1990. However, the technique offers some significant advantages. The most obvious of these is that by lifting the booster a fair way out of the denser part of the Earth’s atmosphere, less fuel is required for the rocket to reach orbit, reducing its overall mass and cost. Air-launched missions also aren’t restricted to a launchpad; they can be undertaken from any airport where there are suitable facilities for handling the booster itself, thus maximising the potential launch profiles a customer might need. When all the benefits are put together, it means that Virgin Atlantic can offer tailor-made smallsat launch capabilities to clients for just US $10 million a shot.

Continue reading “Space Sunday: of Venus, Cosmic Girl and Cygnus” →