Putting things into space isn’t an easy thing to do. The amount of energy required to reach orbital speeds means that we really only have one option available to us: strapping whatever it is to a giant barrel of explosives and setting light to it. Whilst the science of this is now well understood it doesn’t mean that we’re immune from mistakes, especially those which arise from the inherently complex systems that these rockets have become. Indeed just last week we saw the even a long time space contractor, one with numerous launches under its belt, can suffer a catastrophic accident without any indication that things were going to go wrong. Unfortunately tragedy has struck another private space venture with Virgin Galactic’s SpaceShipTwo crashing, killing one of the test pilots.
This unfortunately isn’t the first tragedy to befall this project. Back in 2007, shortly after their X-prize winning journey and subsequent partnership with Virgin, Scaled Composites had a fatal accident that killed 3 of their engineers. Whilst this wasn’t a flight accident, it was a catastrophic failure of the nitrous oxide tank that the ship uses, it did make many people question just how safe this kind of craft could be made. To their credit the subsequent 7 years were incident free with the prototype undergoing numerous tests both in the air and back down on the ground. Last week however that streak was broken when the VSS Enterprise broke up over the desert in California, killing one of the pilots and destroying the craft.
Initial reports centred on the fact that SpaceShipTwo was testing a new fuel mixture which could have potentially exploded causing the craft to fail. For a motor like the one in SpaceShipTwo, namely a hybrid rocket engine, this is highly unlikely as the fuel doesn’t have the same capability to combust explosively as its liquid cousins do. Had the changes been with the oxidizer or tank design then I’d be more inclined to blame them for failure. Indeed current reports have shown that the motor has been found fully intact at the crash site, indicating that a mid air explosion was not the cause of the crash.
Investigators are now focusing on the events leading up to the crash, including the possibility that the wings were unlocked too early into their flight. SpaceShipTwo has an unique system for its re-entry, it’s wings fold up in a process called feathering that ensures it comes back down belly-first. Engaging this system is a 2 stage process, requiring the pilots to first unlock the wings and then engage the feathering process. Initial reports have suggested that the wings were unlocked during powered ascent although it’s still too early to say if that was the cause of the crash or not.
To his credit Richard Branson has committed himself to the project even in the face of this disaster which means we’ll still be seeing SpaceShipTwo make flights into space sometime in the future. This will definitely set them back but I’m sure that the new versions of the ship will ensure that an event of this nature cannot happen again. It’s an unfortunate reminder that things like this still carry some form of risk with them and those who dare to be on the frontiers like this really are risking their lives for our greater good.
There’s a saying that goes “The speed of light is greater than the speed of sound, which is why some people appear bright before they open their mouths”. Whilst I’m sure that we can all remember someone who fits that description exactly not many people appreciate just how vast the difference is between the speed of light really is. Indeed in everyday life you can pretty much consider light to travel instantaneously since it could reach any point on earth in under a millisecond. That also means that visually observed phenomena can help us determine other things, like how far away the boat in the below video was from the volcano that erupted:
From the first point where you can see the eruption beginning to the time when the shockwave hits the camera approximately 13 seconds elapses. Taking into account that the speed of sound in air (roughly 341 m/s, although it could be slightly faster depending on the temperature) that gives us an approximate distance of 4.4 km from the eruption site. To put that in perspective the light that brought the picture traveled the same distance in about 0.01 milliseconds, an imperceptibly short amount of time. If you were so inclined you could also figure out all sorts of other kinds of information from this video (like the height of the plume, it’s velocity, etc.) but they’re an exercise I’ll leave up to the reader.
This video also showcases one of the coolest (in my opinion) visual phenomena related to massive explosions like this. You can see the shock wave propagating out from the epicenter very clearly, something which always happens but isn’t usually visible to the naked eye. Here you can see it travelling outwards thanks to it compressing the air in front of it which changes the refractive index of light. With explosions of this magnitude the amount of compression, and the resulting shock wave, are enough to produce a significant bend in the light passing through it.
I probably wouldn’t want to be that close to the explosion though!
Cast your mind back 5 months, where were you then? I can remember where I was quite clearly: I was in a hotel room in a city called Bandar Seri Begawan, the capital of Brunei. With nothing much else to do in town apart from drink coffee and swelter in the unrelenting heat I had made myself comfortable on the bed with my laptop and tenuous Internet connection so that I could witness history in the making. It was there that I saw SpaceX’s Dragon capsule being captured by the crew aboard the International Space Station and brought to dock with the ISS, becoming the first ever private craft to do so.
SpaceX, not wanting to falter with their goal of being able to rapidly turn around craft, has today achieved the same feat again and the very first of their official missions, dubbed CRS-1 (Commercial Resupply Service), has just docked at the ISS. Just like its predecessor the payload its taking up isn’t anything to get excited about being mostly crew supplies, materials for new and current experiments as well as hardware for ongoing maintenance of the station itself. Just like its predecessor it will also be bringing back some payload back with it once its completed its 2 week mission attached to the ISS, something which is still a unique capability of the Dragon capsule.
Whilst the mission might be fairly rudimentary its launch has been anything but. Those of us who tuned into the launch live stream on Monday were treated to a pretty spectacular show due to the launch happening at night. There was also a curious incident where one of the engines appeared to suffer some kind of failure with many news outlets reporting that one of the engines on the Falcon 9 had exploded during the first stage. The failure didn’t appear to affect the launch however with the comms chatter saying everything was nominal and with the Dragon arriving successfully you can’t really fault them.
In fact the “explosion” was actually part of a system designed to relieve pressure in the engine bay when an engine out occurred. The system was triggered as the control systems aboard the Falcon 9 detected a loss of pressure in engine 1 and shut down the engine which lead to those panels being ejected in a rather spectacular fashion. To put this all in perspective the Falcon 9 can make it into orbit with 2 of its engines failing in this fashion and for many of the previous missions it has actually throttled down 2 of its engines because the additional thrust isn’t required. Thus whilst this was unexpected it was not a situation that they hadn’t accounted for and it was actually a great demonstration of the Falcon 9’s engine out capability, something which is currently unique to it (other launchers, which are no longer flying, have had this functionality).
A separate payload that wasn’t part of the CRS-1 mission is the prototype satellite for Orbcomm which was released once the Falcon 9 entered its second stage of flight. Whilst the payload was successfully released it was unfortunately dropped into the wrong orbit, much lower than the one required. Officials have stated that this was due to the engine out causing the other 8 engines to compensate, making them burn for longer than what was originally calculated for. Whilst they might be able to salvage it using the onboard propellant (which will reduce the useful life of the craft significantly) it’s still something of a faux pas on SpaceX’s part. I’m sure that for the next lot of flights it won’t be an issue as SpaceX has a phenomenal track record for fixing this problems as soon as they become apparent.
Despite these issues it’s still a great achievement for SpaceX to go from first dock to the ISS to being an official re-supplier all within the space of 5 months. Whilst they won’t make the deadlines that they originally had planned for this year (CRS-2 has slipped to be no earlier than January 2013) they’re still moving at a blistering pace compared to nearly all other players in the space industry. For now they’ll be slipping into the routine of launching cargo missions but it won’t be long before they start sending people up alongside the cargo and that’s an incredibly exciting prospect.