As instruments such as image sensors get smaller, cheaper, and yet improve in performance, they open up possibilities for very small satellites. Of particular interest to me are nanosatellites (under 10 kg) and microsatellites (under 100 kg). To date, these have been launched as secondary payloads on rockets carrying extremely expensive primary payloads.
To simplify the integration of low-cost small satellites, Prof. Jordi Puig-Suari of Cal Poly Luis Obispo and Prof. Bob Twiggs of Stanford University came up with a standard framework known as a CubeSat. It is no understatement to say that it has revolutionized the design and deployment of low-cost small satellites.
Standard 1U CubeSat nanosatellites are exactly 1 liter in volume, 10 cm on a side, and have mass of up to 1.33 kg. A 2U CubeSat is 20x10x10 cubic cm, and up to 2.66 kg. A 3U is 30x10x10 and up to 4.0 kg. They typically fly in very low orbits, and may re-enter and burn up in a matter of weeks or a few years. Thus, their design life-times are adjusted accordingly.
Because they fly as secondary payloads, they are subject to the rules of the typically very expensive primaries. Launches can be anywhere from months to years away. But increasingly, they are first flown to the International Space Station, and then released into a trailing orbit behind it.
The case for nanosat launchers
I have previously posted my thoughts about the business case for a nanosat launcher. I believe the premises for a business case still hold. In fact, I am beginning to see increasing evidence of interest.
The purported benefits of a nanosat launcher include: better control over launch window, selection of orbital plane/trajectory, no risk to a more expensive primary payload, no risk to humans on the ISS, option to test exotic propulsion systems.
Current launch costs of payloads are fairly high. But in my view, the greater impediment to broader access to space is schedule. If launches can be arranged weeks or days in advance (instead of months or years), it then becomes possible to build an iterative research and development cycle where payloads are designed for a month or two, launched and monitored for a month, and then a new experiment is developed in another month or two while continuing to digest results from the current one in orbit. Researchers do not go off to another two or three projects while waiting for this one to launch again, and then come back and have to restart their research efforts. A company can conceivable fly 4-6 times a year, and dramatically shorten their research efforts.
(Who would do this? There are a variety of effects in microgravity or vacuum conditions which can be utilized. Going through these is a separate subject, and is more suited to those researchers who might benefit from them. So I won’t belabor those here.)
Why do we not hear more about these? The major media will not be reporting on nanosat launchers because the big space issue is how the US will launch its own people into space.
Among the trends quietly emerging is the use of the International Space Station as a launch platform for nanosatellites. All the requisite safety checks apply. But there is a regular schedule of launches to the ISS every two months, bringing food and other supplies. Payload integrator NanoRacks has effectively gotten the checks and procedures into a reliable business cycle. There are limits on what can be flown to the ISS. Even though a CubeSat is intended for launch from the station, it still needs to be handled by the crew, and there has to be iron-clad assurances that no small incident would precipitate a major emergency on the station. NanoRacks has been so successful at this that they have received an ISS Innovation Award from the American Astronautical Society. (The major innovation is really in bringing small experiments into the ISS on a regular basis. Nevertheless, the same principles apply to satellite deployment from the ISS.)
The ISS is not necessarily in the ideal orbit for deploying satellites. It occupies one orbital plane. It cannot handle orbits which are more polar or more equitorial. These still require separate launch vehicles.
A case is arising for asteroid mining, or at this stage, prospecting. The chances of a primary payload being aligned with a passing near-Earth asteroid are extremely slim. Companies like Deep Space Industries would like to fly lots of prospecting CubeSats to lots of asteroids. A launcher on which their probe is the primary payload can greatly simplify the logistics of prospective.
Who is working on nanosat launchers?
NASA released an SBIR Select topic for nano/microsatellite launch vehicles in 2012; these are expected to loft 20 kg into a circular (possibly polar) orbit at 400-450 km altitude. DARPA has selected teams to develop vehicle technology for an microsatellite (up to 45 kg, 100 lb-m) air-launch vehicle (ALASA: Airborne Launch Assist Space Access).
- DARPA ALASA has now funding five companies’ research studies. In addition to them, Virgin Galactic is a non-funded ALASA participant, and is now working on LauncherOne, using the same launch platform as SpaceShipTwo.
- US Army and NASA are working on SWORDS. A tactical nanosatellite launch due for flight test in 2014. Payloads will be up to 25 kg.
- Small satellite company Microcosm spun off Scorpius to solely focus on rocket technology they had developed.
- When XCOR matures the Lynx rocketplane to Mark III, its dorsal pod is intended to house a nanosatellite launcher.
There are also smaller efforts with varying degrees of hardware development. Among the notable is the Microlaunchers effort of Charles Pooley. Charles prefers a grassroots movement that is akin to the PC revolution. He believes in a cadre of people building skills from the ground up. He has at least done a propulsion test.
There’s also me, with no hardware, some conceptual designs, and a bit of simulation. I’ve spent too much time in recent years among pilots and aerodynamicists; they smile when I say air-launch. But then I tell them my design is premature; I am very direct about the holes that need to be filled in before a credible design optimization can be done.
My personal suspicion is that one of the dual-use plans, where the support infrastructure is also used in another business model, will be the one that succeeds. That means possibly XCOR, Virgin, or even my crazy air-launch scheme. However, Charles may win the award for lowest cost, if he can win the grassroots people over.