On paper the Space Shuttle was the signal of the new space age where access to the final frontier would be cheap and reliable, ushering in the next wave of human prosperity. It would do this through two innovative (at the time) ideas: make the craft reusable and reduce the turn around time on launches to a mere 2 weeks, enabling 26 flights per year at a drastically lower cost than any other launch system. Unfortunately due to the requirements placed on it by the numerous different agencies that had their hand in designing it the final incarnation could not meet the latter goal and thus failed to provide the cheap access to space that it dreamed of. Of course it also taught us a lot about spacecraft design most notably that giant space planes aren’t particularly efficient ways of getting payloads into orbit.
That doesn’t seem to stop people from designing more of them, however.
DARPA recently announced that it was seeking designs for a revolutionary space vehicle, dubbed the XS-1, with the intention of drastically lowering the cost per kg to orbit for small sized payloads (up to about 2,000KG). The design requirements are fairly open with the only stipulations being that the main craft is a reusable, hypersonic vehicle with the payload achieving the desired orbit using a traditional rocket. This means that whilst the potential craft detailed in the artist’s impression above is a good indicator of what the XS-1 hopes to achieve the actual craft could end up being radically different, especially if any of the other companies currently playing in this field having anything to do with it.
The main goal of this program is to drastically reduce the cost to orbit for smaller payloads, almost by an order of magnitude if you compare it to traditional launch systems. This, in turn, would lead to a lot of missions that were otherwise infeasible to become a reality and whilst the initial applications are more than likely to be military in nature I’m sure any private contractor would ensure a dual use agreement for the bulk of the technology. The crux of the XS-1, at least in my opinion, is whether or not this is achievable in the time frames that have set out for the project, considering that the first launch is scheduled for 2017.
Taking the rule of 6 into account (Mach 6 at 60,000 feet is 6% of the energy required for orbital velocity) a craft with such a flight profile would need to make several strong technological advances in order to be able to fly. The only engines capable of achieving speeds above that (at the required price) are scramjets and the fastest we’ve ever managed to get one to fly was Mach 5.1 last year. That means there’s still a long way to go to get sustained flight out of a hypersonic, air-breathing engine and it’s questionable that anyone would be able to achieve it in that time frame. Indeed even Lockheed Martin, who recently announced the hypersonic SR-72, doesn’t believe they’ll get a prototype flying before 2023.
I’m a fan of the idea, and indeed if anyone can pull it off I’ll be wildly impressed, however the technology to support it is still in its infancy with the cutting edge being far away from viability. There are other ways of tackling it of course but I can’t really see any of them being done for the price that DARPA is asking. Indeed the cheapest fully rocket solution goes to SpaceX but it’s still double the asking price for less payload than what DARPA requires. In any case the designs will hopefully show some ingenuity and, if we’re lucky, 2017 will bring us another baby brother to the retired Space Shuttle.
Debris in orbit are becoming one of the greatest challenges that we face as we become a space fairing species. You see by the simple fact that something is in orbit means that it has an incredible amount of potential energy, zipping around the earth at Mach 25 ready to wreck anything that might cross its path. Thankfully there’s quite a lot of empty space up there and we’re really good at tracking the larger bits so it’s usually not much of an issue. However as time goes by and more things are launched into orbit this problem isn’t going to get any better, so we need to start thinking of a solution.
Problem is that recovery of space junk is an inherently costly exercise with little to no benefits to be had. A mission to recover a non-responsive satellite or other spacecraft is almost as complex as the mission that launched said object in the first place, even more so if you include humans in the equation. Additionally you can’t send up a single mission to recover multiple other missions as typically satellites are on very different orbits, done so that they won’t collide with each other (although that has happened before). Changing orbits, known as a plane change, is extremely expensive energy wise and as such most craft aren’t capable of changing more than a couple degrees before their entire fuel supply is exhausted. The simple solution is to deorbit any spacecraft after its useful life but unfortunately that’s not the current norm and there’s no laws governing that practice yet.
It’s even worse for geostationary satellites as in that particular orbit things don’t tend to naturally deorbit over time. Instead anything in a geostationary orbit is pretty much going to be there forever unless some outside force acts on them. Geostationary orbits are also particularly valuable due to their advantageous properties for things like communication and location so the problem of space debris up there is of a much bigger concern. Thankfully most geostationary satellites have the decency to move themselves into a graveyard orbit (one just outside geostationary which will eventually see them flung from earth orbit) but this method isn’t guaranteed. Mass that’s already in orbit is incredibly valuable however and DARPA has been working on a potential solution to debris in geostationary orbit.
The DARPA Phoenix program is an interesting idea, in essence a in orbit salvager that cannibalizes other satellites’ parts in order to create new “satlets”. These new satlets won’t be anywhere near as capable as their now defunct donors were but they do have the potential to breathe a whole lot of life back into the hardware that’s just sitting there idle otherwise. Compared to a regular geosynchronous mission something like Phoenix would be quite cheap since a good chunk of the mass is already up in orbit. Such a mission can really only be done in geostationary orbit since all the satellites are in the same plane and the energy required to move between them is minimal. That is our most valuable orbit however so such a mission could prove to be quite fruitful.
Dealing with the ever growing amount of space debris that we have orbiting us is a challenge that we’ve still yet to answer. Programs like DARPA’s Phoenix though are the kinds of projects we’ll need to both reduce the amount of orbital junk we have as well as making the most out of the stuff we’ve already put up there. I’m really keen to see how the Phoenix project goes as it’d would be quite a step forward for on orbit maintenance and construction as well as being just plain awesome.
With the retirement of the Shuttle looming over our heads, even though it’s been moved back a couple months (ARGH!), organisations with an interest in space have been looking for alternatives to ensure they still have access once the iconic crafts roll back into their hangars for the last time. Whilst supply missions are more than aptly handled by the European ATV, Japanese HTV or Russian Progress and the ferrying of people handled by the Russian Soyuz it seems that military, who really didn’t get as much of the face time they wanted when it came to the Shuttle, have gone ahead and developed their own purpose built craft and boy does it ever look familiar:
That my friends is the X-37B, an orbital test prototype of the X-37 series of spacecraft. Don’t let the NASA badging on that plane fool you though as whilst the project was initially started in the hands of NASA it is now completely in the hands of the Department of Defense with NASA only having a small informal involvement in the project. Last week saw this craft successfully make its maiden flight into orbit but not to the usual fanfare that a new craft attracts and for good reason, everything about it is super secret.
About 10 years ago NASA began the X-37 project and invested quite a bit of cash into the development of the vehicle. Even back then the purpose of the craft was somewhat of a mystery as the primary function of this craft would be the launch and retrieval of payloads into space. Realistically this capability was already covered off by the space Shuttle (and indeed this craft was going to be launched in the Shuttle’s payload bay until they figured out that would be a waste of money) and even that had been usurped by the fact that it’s cheaper to deorbit and launch a new satellite than it is to bring an old one down for repairs and send it back up again. In 2004 the X-37 project was transferred to DARPA and the project became classified.
Usually that would mean the project would forever be surrounded in the mystery that accompanied its birth but the acquisition by the Department of Defense clarified its purpose. The Shuttle owes its current massive girth and plane like design due to the military’s involvement. Back then satellites were still expensive and the idea was that the Shuttle should be able to capture and retrieve broken military satellites (hence the large payload bay). Additionally there were some mission profiles which required the shuttle to launch into polar orbits, complete one orbit and then return to where it had launched from. Because of this the Shuttle had to have very large wings in order to be able to glide back to its original position, as the earth would have moved about 2000KM in the time it took them to complete such a maneuver.
Looking at this diminutive cousin of the Shuttle you can see such the characteristics of such missions profiles are very prevalent, such as the large wings and payload bay. The differences begin when you look under the hood and find that it’s fully robotic, capable of completing almost every task without human intervention. Additionally it carries with it a large solar array which allows it to stay in orbit for 270 days which is an eternity when compared to the Shuttle’s measly 2 weeks. Additionally unlike the Shuttle which is in essence its own rocket (those 2 SRBs strapped to the side of it are just to get it started, most of the work is done by the main 3 engine cluster on the back) the X-37 craft launches atop an ATLAS V rocket. The engine you see on the back is used for maneuvering on orbit and nothing else.
Overall its a pretty nifty little ship and really it should’ve been designed at the same time as the Shuttle. This craft serves the purpose of being a reusable transport to space that’s design to deliver and retrieve cargo and the lack of a crew makes it that much more efficient at doing its job. Had such a craft been designed around then you can bet that the Shuttle would look nothing like it does today and, more importantly, it wouldn’t be the huge cash drain that it has been for NASA over the past decade. Still there’s not much reason to dwell on that fact since it will soon be replaced by those upstarts in the private space sector which, in my opinion, can’t come any sooner. Hopefully since the military now has its own craft for performing its super secret missions they’ll keep their noses out of NASA’s business and we’ll avoid the whole design by committee debacle that was the Shuttle’s design process with future craft.