If you’ve been reading this blog for a while, you probably heard me talking about Elon Musk’s Space X and the plans to develop a reusable rocket system. The theory is that it’s the cost of space craft that overwhelmingly contributes to the high cost of getting into orbit. The fuel itself represents perhaps 1% of the total cost. So if you can develop a truly reusable rocket system you can potentially revolutionise space travel. There are a few parts wishful thinking in this, and a few parts hyperbole, but it’s an intriguing concept nonetheless. Meanwhile, Space X is forging ahead.
Space X have been developing a reusable system based on their Falcon 9 launch vehicle platform. This launch vehicle is a pretty familiar sort of beast – a two stage rocket powered by liquid oxygen and kerosene. It has established a solid performance record to date and was used by Space X for a visit to the International Space Station, the first by a commercial company.
The Space X Grasshopper is designed to take the place of the Falcon 9’s first stage. It has been in active testing since September last year. So far it has had six test flights, each gradually extending the height at which the rocket stops, hovers then touches back down. Both take off and landing are vertical (VTVL). The latest (check here for video) took the venerable Grasshopper to 325m (1066 feet), with an overall duration of 68 seconds. It’s likely the tests will extend substantially, perhaps reaching altitudes of up to 91 kilometres (57 mi) with the second generation of the test craft.
If you want a bit of entertainment, check out this video of one of the early tests that plays to Jonny Cash’s ‘Ring of Fire’. LOL.
The second generation of Grasshopper will have lighter-weight landing legs that actually fold up into the rocket. I can’t help but be reminded of those sleek 1950s art-deco SF rockets than come down to land on their legs in such a similar manner, except they (of course) had three legs whereas Grasshopper has four. The Grasshopper’s legs use a telescoping piston on an A-frame, actuated by high-pressure helium.
Plans are to start testing the decent of Falcon 9 first stages to confirm the technology. Each first stage of the Falcon 9 will be equipped and instrumented as a controlled descent test vehicle. They will initially do the propulsive return tests over water until they can complete a return to the launch site with a powered landing, perhaps as early as 2014.
Ultimately the first stage separation will occur at around Mach 6, rather than the current Mach 10 for the expendable version of the Falcon 9. This is to ensure there is sufficient fuel for deceleration, controlled descent and landing.
I have a feeling that once this system is up and running, expendable launch systems will seem like the crazy idea, not reusable ones!
But the Grasshopper, as impressive as it is, is only half the launch system. The first stage will separate and be back on the launch pad minutes after the launch. The reusable second stage will take up to 24 hours to return to the launch pad, to allow for orbital realignment and atmospheric re-entry. Both stages are envisaged to be available for reuse within hours of return.
Eventually the reusable launch system technology will be applied to both the Space X Falcon 9 and Space X Falcon Heavy launch vehicles.
I think we are watching history in the making.
