The Refined Geek

Even if you’re not a space nut like myself you’re likely familiar with Chris Hadfield, a Canadian astronaut who’s social media presence has captured the attention of hundreds of thousands of people. He’s been responsible for dozens of videos showcasing life aboard the International Space Station and has done numerous outreach programs during his time in orbit. As I write this he’s in the final stages of preparation for departure which will end his nearly 5 month tenure as the first Canadian commander of the ISS. As if he didn’t already have enough to do whilst he was up there he recorded this amazing video of him singing a (slightly modified) version of David Bowie’s Space Oddity, and it’s bloody brilliant:

There’s nothing more I can add to this, really

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.

There’s been something of a goal shift within the space industry recently. For quite a long time the focus was on returning to the moon and establishing a presence there which was born out of George W. Bush’s Vision for Space Exploration. However since then the goals of NASA, and indeed the goals of the most promising private space company, have shifted from going back to where we once visited to charting a course to virgin territory. Whilst its entirely possible that both NASA and SpaceX are just looking to capitalize on the attention that’s been focused on the Mars Curiosity Rover by announcing plans to send humans to our red sister there’s no denying that both of them are seriously considering the idea and it seems NASA might be looking at some rather radical ideas.

There’s been quite a lot of talk about what the best way to get to Mars would be and most of them involve a way station of some sort, something close to Earth that we can use as a staging ground whilst we prepare for the actual mission. The ideas have ranged from simply using the International Space Station to establishing a base on the moon. NASA has recently started investigating the idea of putting a base out at L-2 (Lagrange Point 2), beyond the orbit of the moon. Such a base would provide quite a few advantages and not just to potential manned missions to Mars.

You see the Lagrange points are special places where the gravitational effects of all the nearby bodies balances out so that you don’t really need to do a heck of a lot to remain there indefinitely. That’s quite desirable because it means you have to take up less station keeping equipment and fuel with you, making room for bigger and better payloads. It’s for this (and numerous other reasons) that the Hubble successor, the James Webb Space Telescope, will be placed at L-2. There’s also one other advantage to L-2 as well and that’s the fact that you don’t need very much energy to get anywhere in our solar system once you’re there, especially if you time it right and get some lovely gravitational boosts along the way.

Putting a station there and maintaining it would be no small feat however. At L-2 you’re well outside the  protective magnetic field of Earth which means that any potential space station has to be heavily shielded against the solar winds and cosmic radiation that will bombard it relentlessly. This either means a much smaller single launch station (ala Salyut and Skylab) or multiple successive launches. It’s not an insurmountable task but it’s definitely a step up from the ISS in terms of complexity and investment required. The L-2 location also makes getting to and from the station much more complicated than getting to the ISS or even the moon and that raises questions about how to handle things like emergency situations and resupply flights. Again there’s no technical limitation to this but you’re well into envelope pushing territory when you’re working out a L-2.

At the same time though I do believe that if you’re considering a base at L-2 you’d also better consider doing something similar on the moon, especially if landing on other planets is your end goal. You see we do have quite a bit of experience in building space stations and a base at L-2 would be an organic progression of that. However what we don’t have is any experience in building habitats on the surface of other planets and the moon, with its lack of atmosphere and harsh environment, would be an amazing test bed for potential habitats on other planets. This is not to say that a moon base is better than something at L-2, they both have their pros and cons, just that if L-2 is a consideration then the place 1.5 million kms before it might not be a bad idea either.

I think the most exciting thing to come out of all of this is the fact that NASA is investigating some things which really are pushing the limits of our capabilities in space. I’ve long said that this is where they need to be focused as the private space industry has shown that they’re quite capable of doing the day to day stuff which should leave NASA’s budget free to do some really incredible stuff. With that finally happening I could not be happier as it means that we’re not that far off from becoming an interplanetary species.

In principle, at least.

It was late Friday night. My companions and I had just finished up work as we stumbled out into the hot, humid air that surrounded us here in Brunei. After a nearly 12 hour day we had our sights fixed on grabbibng some dinner and then an early night as we would have to come in the next day to finish the job. As we chatted over our meals a curious image appeared on the television, one that I recognized very clearly as SpaceX’s Dragon capsule that was launched no more than a couple days earlier. At the time it appeared that they were performing some last manuevers before the docking would occur. I couldn’t take my eyes away from it staring intently at the capsule that was driftly serenely across the beautiful backdrop of our earth.

The time came for us to make our departure and we headed back to the hotel. I hit up Facebook to see what was going on when I saw a message from a long time friend: “I hope you’re not missing this http://on.msnbc.com/JxfRMS“.

I assured him I wasn’t.

I was fixated on the craft watching it intently from 2 different streams so that I’d never be out of the loop. I monitored Twitter like a hawk, soaking in the excitement that my fellow space nuts shared. I almost shed a tear when Houston gave SpaceX the go to make the final docking approach as, for some unknown reason, that was when it all became real: the very first private space craft was about to dock with the International Space Station. At 13:56 UTC on May 25th, 2012 the SpaceX Dragon became the first private space craft to be captured by the International Space Station and not 6 minutes later it was birthed on the earth side docking port of the American Harmony module.

It’s an incredible achievement for SpaceX and proves just how capable they are. This is only the second launch of both the Falcon 9 rocket and the Dragon capsule which demonstrates just how well engineered they are. Most of the credit here can go to the modularity of the Falcon series systems meaning that most of the launch stack has already seen a fair bit of flight testing thanks to the previous Falcon 1 launches. The design is paying off in spades for them now as with this kind of track record it won’t be long before we see them shipping humans up atop their Falcon rockets, and that’s extremely exciting.

The payload of the COTS Demo Flight 2 Dragon capsule is nothing remarkable being mostly food, water and spare computing parts and small experiments designed by students. What’s really special about the Dragon though is its ability to bring cargo back to earth (commonly referred to as downrange capability) something that no other craft currently offers. The ATV, HTV and Progress crafts all burn up upon re-entry meaning that the only way to get experiements back from the ISS now will be aboard the Dragon capsule. Considering that we now lack the enormous payload bay of the Space Shuttle this might be cause for some concern but I think SpaceX has that problem already solved.

Looking over the scheduled flights it would appear that SpaceX is looking to make good on their promise to make the launches frequent in order to take advantage of the economies of scale that will come along with that. If the current schedule is anything to go by there will be another 2 Dragon missions before the year is out and the pace appears to be rapidly increasing from there. So much so that 2015 could see 5 launches of the Dragon system rivalling the frequency at which the Soyuz/Progress capsules currently arrive at the ISS. It’s clear that SpaceX has a lot of faith in their launch system and that confidence means they can attempt such aggressive scheduling.

I have to congratulate SpaceX once again on their phenomenal achievement. For a company that’s only just a decade old to have achieved something that no one else has done before is simply incredible and I’m sure that SpaceX will continue to push the envelope of what is possible for decades to come. I’m more excited than ever now to see the next Dragon launch as each step brings us a little closer to the ultimate goal: restoring the capability that was lost with the Space Shuttle. I’ve made a promise to myself to be there to see it launch and I simply can’t wait to see when it will be.

It’s strange, looking back over all my space posts of the past 3 years I couldn’t find any that were dedicated to the European Space Agency’s cargo craft, the Automated Transfer Vehicle. Sure I mentioned it in passing back when JAXA sent its first HTV to the International Space Station but even its second flight, named Johannes Kepler, obviously wasn’t inspiring enough for me to take notice. The only good reason I can come up with is the maiden voyage happened well before I got into blogging, but that doesn’t excuse me ignoring the significance of the ATV.

The ESA’s ATV is the only craft that the ESA has that participates in the ISS program. It’s a derivative of the Multi-Purpose Logistics Module that the Shuttle used to carry up to the ISS and is  meant to work alongside the Russian Progress craft that have been resupplying the ISS for years. Compared the Progress its something of a monster being able to deliver almost 4 times the payload although that’s offset significantly by the fact that it’s current launch rate is about once per year. The majority of the payload is taken up by reboost and attitude control propellant as the ATV is capable of reboosting the ISS, something which no other craft is currently capable of doing (the retired Shuttle was the primary reboost craft prior to this). The rest of the payload consists of crew and station consumables, roughly equivalent to the amount that a Progress craft would deliver.

Today sees the ESA’s 3rd ATV docking with the International Space Station:

Whilst it’s not pushing any boundaries or developing new capabilities the successful docking of the Edoardo Amaldi shows that the ESA can make the yearly launches of the ATV without incident. That’s quite an achievement in itself and means that the 2 currently planned ATV launches should go off without a hitch. With the upcoming flights from companies like SpaceX and Orbital Sciences to the ISS you might be wondering why we’d bother having a craft like the ATV, especially when something like the Dragon has similar capabilities whilst also being reusable. The answer, from my perspective is two fold.

For starters neither of the upcoming private craft have the ability to reboost the ISS. Now doing this is non-trivial so its unlikely that either craft will gain that ability in the near term and as far as I can tell there are no other craft, current or planned, that have that ability. That surprises me as the second argument for the ATV’s existence, redundancy in capabilities, doesn’t exist with ISS reboosting. It’s possible that the upcoming Space Launch System with the Orion capsule might be able to do this but I can’t find anything that states that.

The second reason, as I alluded to before, is that when it comes to maintaining a human presence in space it doesn’t hurt to have redundancy for different capabilities. Whilst you can argue that there will be much better ways of doing things in the future it never hurts to have a backup that you can rely on. The ATV, with its rock solid yearly launch schedule, makes for a good fall back for other re-supply missions should they encounter any issues. Now all that’s required is finding another means by which to reboost the ISS and then we’ll have full redundancy across most of our manned space program activities.

I’ve seen my fair share of pictures and videos of earth in the past but none of them have been quite as captivating as this one by Michael König:

Hopefully that will be enough serenity to get you through the rest of the working day

(I’ve decided that instead of my usual 500+ word crap post that I’d churn out when I can’t find anything good to write about I’d instead just post something short that I found interesting. Those kinds of posts are mentally exhausting and I don’t particularly like them afterwards. At least I can’t be mad at something as beautiful as this!) 

Russia’s space program has a reputation for sticking to ideas once they’ve got them right. Their Soyuz (pronounced sah-yooz) craft  are a testament to this, having undergone 4 iterations since their initial inception but still sharing many of the base characteristics that were developed decades ago. The Soyuz family are also the longest serving series of spacecraft in history and with it only having 2 fatal accidents in that time they are well regarded as the safest spacecraft around. It’s no wonder then that 2 of the Soyuz capsules remain permanently docked to the International Space Station to serve as escape pods in the even of a catastrophe, a testament to the confidence the space industry has with them.

Recent news however has brought other parts of the Russia space program into question, namely their Proton launch stack. Last week saw a Proton launched communications satellite ending up in the wrong orbit when the upper orbital insertion model failed to guide it to the proper geostationary orbit. Then just this week saw another Proton launched payload, this time a Progress craft bound for the ISS, crashed shortly after launch:

The robotic Progress 44 cargo ship blasted off atop a Soyuz U rocket at 9 a.m. EDT (1300 GMT) from the central Asian spaceport of Baikonur Cosmodrome in Kazakhstan and was due to arrive at the space station on Friday.

“Unfortunately, about 325 seconds into flight, shortly after the third stage was ignited, the vehicle commanded an engine shutdown due to an engine anomaly,” NASA station program manager Mike Suffredini told reporters today. “The vehicle impacted in the Altai region of the Russian Federation.”

Now an unmanned spacecraft failing after launch wouldn’t be so much of a problem usually (apart from investigating why it happened) but the reason why this particular failure has everyone worried is the similarity between the human carrying Soyuz capsule and the Progress cargo craft that was on top of it. In essence they’re an identical craft with the Progress having a fuel pod instead of a crew capsule allowing it to refuel the ISS on orbit. A failure then with the Progress craft calls into question the Soyuz as well, especially when there’s been 2 launches so close to each other that have experienced problems.

From a crew safety perspective however the Soyuz should still be considered a safe craft. If an event such as the one that happened this week had a Soyuz rather than a Progress on top of it the crew would have been safe thanks to the launch escape system that flies on top of all manned Soyuz capsules. When a launch abort event occurs these rockets fire and pull the capsule safely away from the rest of the launch stack and thanks to the Soyuz’s design it can then descend back to earth on its usual ballistic trajectory. It’s not the softest of landings however, but it’s easily survivable.

The loss of cargo bound for the ISS does mean that some difficult decisions have to be made. Whilst they’re not exactly strapped for supplies at the moment (current estimates have them with a year of breathing room) the time required to do a full investigation into the failure does push other resupply and crew replacement missions back significantly. Russia currently has the only launch system capable of getting humans to and from the ISS and since they’re only a 3 person craft this presents the very real possibility that the ISS crew will be scaled back. Whilst I’m all aflutter for SpaceX their manned flights aren’t expected to come online until the middle of the decade and they’re the most advanced option at this point. If the problems with the Proton launch stack can be sorted expediently then the ISS may remain fully crewed, but only time will tell if this is the case.

The Soyuz and Progress series have proven to be some of the most reliable spacecraft developed to date and I have every confidence that Russia will be able to overcome these problems as they have done so in the past. Incidents like this demonstrate how badly commercialization of rudimentary space activities is required, especially when one of the former space powers doesn’t seem that interested in space anymore. Thankfully the developing private space industry is more than up to the challenge and we’re only a few short years away from these sorts of problems boiling down to switching manufacturers, rather than curtailing our efforts in space completely.

Whenever I find myself getting frustrated with the sorry state of government funded space programs overseas I don’t have to look much further than SpaceX to feel inspired once again. From their humble beginnings back in 2002 they have shown they are capable of designing, building and launching rockets on a fraction of the budget that is currently required. Their ambition also seems to have no bounds with their CEO, Elon Musk, eyeing off a trip to Mars with the intent of retiring there. SpaceX is also the USA’s only launch system provider who’s got a roadmap for delivering humans to the International Space Station, a real necessity now that the shuttle fleet has retired.

You can then imagine how exciting it is to hear that SpaceX has received in principle approval from NASA to combine the next 2 Commercial Orbital Transport Services (COTS) demonstration flights into one. That might not sound like much on the surface but it means that SpaceX’s Dragon capsule could be docking with the ISS this year:

Over the last several months, SpaceX has been hard at work preparing for our next flight — a mission designed to demonstrate that a privately-developed space transportation system can deliver cargo to and from the International Space Station (ISS). NASA has given us a Nov. 30, 2011 launch date, which should be followed nine days later by Dragon berthing at the ISS.

NASA has agreed in principle to allow SpaceX to combine all of the tests and demonstration activities that we originally proposed as two separate missions (COTS Demo 2 and COTS Demo 3) into a single mission. Furthermore, SpaceX plans to carry additional payloads aboard the Falcon 9’s second stage which will deploy after Dragon separates and is well on its way to the ISS. NASA will grant formal approval for the combined COTS missions pending resolution of any potential risks associated with these secondary payloads. Our team continues to work closely with NASA to resolve all questions and concerns.

That’s right, if everything stays on schedule (which, I’ll admit, isn’t very likely) then we’ll see a Dragon capsule docking with the ISS and the first time in history that a private company has docked with a space station. The mission will test all of the fligh avionics, communication systems and docking procedures that SpaceX have designed for the Dragon capsule. Whilst the Dragon going up there doesn’t appear to have a cargo manifest it will be bringing cargo back down from the ISS, which will be a good test to see if their current design has any flaws in it that can be rectified for future missions.

The current docking procedure for the Dragon capsule is surprisingly similar to that of JAXA’s HTV. For the COTS Demonstration 2 flight at least the Dragon capsule will fly very close to the ISS where it will then be captured by CANADARM2 which will guide it into a docking port. It’s interesting because from the past few missions I had assumed that the Dragon was capable of automated docking, especially with (what seemed to be) rather advanced DragonEye sensor being tested on previous shuttle flights. Still automated docking is quite a challenge and the captured route is a lot safer, both for SpaceX and the astronauts aboard the ISS.

The announcement also comes hand in hand with some improvements that SpaceX has made to their launch stack. They’ve installed new liquid oxygen pumps that now allow them to fully fill the Falcon 9 in under 30 minutes, a third of the time it use to require. This means that SpaceX could roll out, fuel and launch a Falcon 9 in under an hour something that hasn’t been possible with liquid fueled rockets in the past. They’re also ramping up their production facilities with an eye to have up to 16 launches per year, a phenomenal amount by any measure.

SpaceX continues to show that the private sector is quite capable of providing services that were for the longest time considered to be too expensive for anyone but the super power governments of the world. The announcement that a Dragon capsule could be visiting the ISS this year shows how much confidence NASA has in their capabilities and I’m sure that SpaceX will not fail to disappoint. We’re on the verge of a revolution in the space travel game and SpaceX are the pioneers who will lead us there.

There’s a saying amongst the space enthusiast community that the shuttle only continued on for so long in order to build the International Space Station and the ISS only existed so that the shuttle had some place to go. Indeed for the last 13 years of the shuttle program it pretty much exclusively visited the ISS taking only a few missions elsewhere, usually to service the Hubble Space Telescope. With the shuttle now retired many are looking now looking towards the future of the ISS and the various manned space programs that have contributed to its creation. It’s now looking very likely that the ISS will face the same fate as Mir did before it, but there are a multitude of possibilities of what could be done instead.

Originally the ISS was slated for decommission in 2016 and with it still not being fully constructed (it is expected to be finished by next year) that would give it a full useful life of only 4 years. The deadline was extended back in 2009 to 2020 in order to more closely match the designed functional lifetime of 7 years and hopefully recoup some of the massive investment that has gone into it. It was a good move and many of the ISS components are designed to last well beyond that deadline (especially the Russian ones which can be refurbished on orbit) and there’s still plenty of science that can be done using it as a platform.

The ISS, like Mir before it, has only one option for retirement: a fiery plunge through the atmosphere into a watery grave. Whilst there’s been lots of talk of boosting it up to a higher orbit, sending it to the moon or even using it as an interplanetary craft all these ideas are simply infeasible. The ISS was designed and built to be stuck in low earth orbit its entire life with many assumptions made that preclude it from going any further. It lacks the proper shielding to go any higher than say the Hubble Space Telescope and the structure is too weak to withstand the required amount of thrust that would get it to a transit orbit (at least in any reasonable time frame). The modifications required to make such ideas feasible would be akin to rebuilding the entire station again and thus to avoid cluttering up the already cluttered area of low earth orbit it must be sent back down to earth.

Russia however has expressed interest in keeping at least some of the parts of the ISS in orbit past the 2020 deadline. It appears they want to use them as a base for their next generation space station OPSEK. This space station would differ significantly from all the previous space stations in that it would be focused on deep space exploration activities rather than direct science like its predecessors were. It would seem that those plans have hit some roadblocks as the Russian Federal Space Agency has recently stated that the ISS will need to be de-orbited at the end of its life. Of course there’s still a good 8 years to go before this will happen and the space game could change completely between now and then, thanks in part to China and the private space industry.

China has tried to be part of the ISS project in the past but has usually faced strong opposition from the USA. So strong was the opposition that they have now started their own independent manned space program with an eye to set up their own permanent space station called Tiangong. China has already succeeded in putting several people into space and even successfully conducted an extravehicular activity (EVA), showing that they have much of the needed technology to build and maintain a presence in space. Coincidentally much of their technology was imported from Russia meaning that their craft are technically capable of docking with the Russian segments of the ISS. That’s also good news for Russia as well as their Soyuz craft could provide transport services to Tiangong in the future.

Private space companies are also changing the space ecosystem significantly, both in regards to transport costs and providing services in space. SpaceX has just been approved to roll up two of its demonstration missions to the ISS which means that the next Dragon capsule will actually end up docking with the ISS. Should this prove successful SpaceX would then begin flying routine cargo missions to the ISS and man rating of their capsule would begin in earnest. Couple this with Bigelow Aerospace gearing up to launch their next inflatable space habitat in 2014~2015 the possibility of the ISS being re-purposed by private industry becomes a possible (if slightly far fetched) idea.

The next decade is definitely going to be one of the most fascinating ones for space technologies. The power international power dynamic is shifting considerably with super powers giving way to private industry and new players wowing the world stage with the capabilities. We may not have a definitive future for the ISS but its creation and continued use has provided much of the ground work necessary to flag in the next era of space.

The current way of accessing space isn’t sustainable if we want to make it as a space fairing species. Whilst the methods we use today are proven and extremely reliable they are amongst the most inefficient ways of lifting payload into orbit around our planet, requiring craft that are orders of magnitude larger than the precious cargo they carry. Unfortunately the alternatives haven’t been too forthcoming, due in part to nuclear technologies being extremely taboo and the others still being highly theoretical. Still even highly theoretical ideas can have a lot of merit especially if they have smaller aspects that can be tested and verified independently, giving the overall theory some legs to stand on.

I’ve talked before about the idea of creating a craft that uses only a single stage to orbit (SSTO), in essence a craft that has only one complete stage and conceivably makes extensive use of traditional aerodynamic principles to do away with a lot of the weight that conventional rockets have. My proposal relied on two tested technologies, the scramjet and aerospike engine, that would form the basis of a craft that would be the Model T equivalent for space travel; in essence opening up space access to anyone who wanted it. In all honesty such a craft seeing reality is a long way off but that doesn’t mean people aren’t investigating the idea of building a SSTO craft using different technologies.

One such company is Reaction Engines, a name that I was only marginally familiar with before. They’ve got a proposal for a SSTO craft called Skylon that uses a very interesting engine design that combines both an air breathing jet engine as well as a traditional rocket motors. The design recently passed its first technical review with flying colours and could see prototypes built within the decade:

They want the next phase of development to include a ground demonstration of its key innovation – its Sabre engine.

This power unit is designed to breathe oxygen from the air in the early phases of flight – just like jet engines – before switching to full rocket mode as the Skylon vehicle climbs out of the atmosphere.

It is the spaceplane’s “single-stage-to-orbit” operation and its re-usability that makes Skylon such an enticing prospect and one that could substantially reduce the cost of space activity, say its proponents.

The engine they’re proposing, called Sabre, has an extremely interesting design. At lower speeds it functions much like a normal jet engine however as speeds approach Mach 5, the point at which my hand waving design would switch to a scramjet, it continues to operate in much the same fashion. They do however employ a very exotic cooling system so that the engine doesn’t melt in the 1000+ degree heat that would be blasting the components and once Skylon is out of the atmosphere it switches to a normal rocket engine to finish off the job.

The issues I see, that face nearly all SSTO designs, is the rule of 6 for getting to orbit. The rule simply states that at Mach 6 at 60,000 feet you have approximately 6% of the total energy required to make it successfully to orbit. Skylon’s engines operate in the jet mode all the way up to Mach 5 to an altitude of 85,000 feet which is no small feet in itself, but it’s still a far cry from the total energy required. It is true though that the first stages of any rocket are the most inefficient and eliminating them by using the atmosphere for both oxidiser and thrust could prove to be a real boon for delivering payloads into orbit. Still whether this will be practical with Skylon and the Sabre engine remains to be seen but there are tests scheduled for the not too distant future.

Walking through unknown territory like this is always fraught with unknowns so it’s no wonder that the team at Reaction Engines has been met with such skepticism over their idea. Personally I’m still on the fence as their technology stack is still mostly unproven but I applaud their vision for wanting to build the first SSTO craft. I’d love to see the Skylon making trips to the International Space Station, effectively replacing the shuttle and extending the ISS’ lifetime but until we see some more proof that their concept works I’m going to be skeptical, but it won’t take much to make into a believer