The increasing popularity of using dedicated miniaturised cubesat-class spacecraft for scientific, commercial and military use has meant that many more “launch opportunities” will be needed. NASA knows this itself as its success in promoting cubesat construction by offering launches via its Cubesat Launch Initiative has left it with the problem of actually finding launch opportunities for them. For while some of these nanosats in the size range of 1-10kg will be accommodated via piggy back rides on large launch vehicles, NASA wants to encourage the development of a dedicated commercial cubesat launch vehicle and has announced its NASA Launch Services Enabling eXploration & Technology (NEXT) programme/competition tor just this purpose.
Cubesats are a pain to launch
While the traditional method for launching such microsatellite and nanosatellite spacecraft is to have them hitch rides as secondary payloads on large launch vehicles, there are downsides to this approach. Apart from launch providers having to incur the cost of designing and operating specialist adaptors, sometimes their core clients (the owners of the main spacecraft payloads) found themselves in the irritating position of being delayed by the smaller (and lower paying) co-payloads. To avoid such instances of the “tail wagging the dog” some launch vehicle providers have decided to disbar secondary payloads from flying altogether.
Meanwhile, even those launch providers which offer mulitiple rides to smaller satellites on launches of their Dnepr 1A, Minotaur 1, Soyuz and Tsyklon 4 rockets, still have the organisational complications in getting so many spacecraft ready on time.
Sometimes, it is actually the late delivery of main heavier payload that can delay the minor spacecraft as recently happened on a Soyuz 2-1B Fregat whose launch has now been held up by Meteor 3M-N2 until next year. With these problems noted, it is no surprise that such hitchhiking opportunities are becoming rarer.
A dedicated small launch vehicle is needed
To find a way around this, some organisations are now working on building very small launch vehicles (VSLVs) and micro-launchers with the potential of launching miniature spacecraft as the main payloads of such a flight. And as it views its own backlog of 50 cubesats and notes the relative low number of co-payload opportunities, NASA realises it needs one itself.
It was, of course, before NASA’s time that the US Navy that fielded the very first very small launch vehicle: the Project Vanguard launch vehicle. While this needle-like rocket was beaten into orbit by Sputnik’s R7 flight, it did eventually make it into orbit successfully with a payload of 9kg. With such a small payload, the three-stage (two liquid/one solid) Vanguard launch vehicle was soon eclipsed by its more powerful brethren and was retired in 1959. However, time has moved on, and now very small launch vehicles with payload capabilities of less than 50kg are become a more attractive proposition to NASA and other organisations – but only if their launch costs can be kept down.
NASA’s NEXT programme for a cubesat launcher
In August, NASA announced its NASA Launch Services Enabling eXploration & Technology (NEXT) programme/competition to accelerate development such Very Small Launch Vehicles (VSLVs). NEXT is actually a successor to NASA’s recently cancelled Nano-Satellite Launch Challenge which was a competition to award a prize of $3 million to the first company to stage two single-unit cubesat launches in two weeks. Realising that there were few genuine runners for this size of space launch vehicle, the new NEXT competition was devised.
The NEXT programme’s defined aim to encourage the development of a launch vehicle capable of putting three 3U (three unit) cubesats with a combined mass of 15kg into polar and sun-synchronous orbits with a minimum orbital altitude of 425km. A one off demonstration NEXT launch demonstration would be made in 2016 with a payment of $300,000 being made per 3U cubesat payload carried. Several potential candidates for the NEXT programme have already become apparent.
First out of the box: OTRAG lives on as Interorbital’s Neptune launch vehicle
The US-firm Interorbital Systems Corporation is offering its Neptune design is based on the OTRAG modular launch vehicle concept which had been planned to be launched out of Africa and which had been developed in the 1970s by rocket designer Lutz Kayser.
The Neptune 7 (N7) rocket consists of three “stages” each carrying Common Propulsion Modules (CPM): four on stage one – two on stage two, and a single one on the final stage. The Common Propulsion module has a single pressure-fed ablatively-cooled GPRE-7.5KNTA rocket engine using the hypergolic propellant combination of White Fuming Nitric Acid and Turpentine as propellants. Steering on the first stage of the N7 is managed by differential throttling while small steerable vernier thrusters would be used for the upper stages.
A smaller 35kg payload version version of the Neptune, dubbed the Neptune 5 (N5), uses only five CPMs: four on the first stage, one for the second stage and a solid rocket motor for the final stage.
The first launch of the N7 is planned to carry up to 24 satellites with a combined payload of 50kg. Its first launch has been reported as being set for November this year. Amusingly it will also carry a model of the science fictional Tardis being built from an Interorbital “Tubesat Kit” by fans of the Dr Who television series.
Differential steering: the military men of US Army have their SWORDS
SWORDS (Soldier-Warfighter Operationally Responsive Deployer for Space) is a cooperative project between Office of theSecretary of Defense, U.S. Army Space and Missile Defense Command/Army Forces Strategic Command and NASA as an attempt provide an “on demand” nanosatellite launcher.
SWORDS consists of three stages, each powered by four Tridyne pressure-fed engines and using liquid methane fuel and liquid oxygen as an oxidizer. Steering will be accomplished by differential throttling of the engines. The aim is to launch a 25kg payload (of one or more spacecraft) to a 750km, 28.5 degree inclination low Earth orbit for less than $1 milliion at less than 24 hours’ notice. Quantum Research International has been selected as the prime contender for the project. An orbital flight test is planned for summer of 2014.
Harnessing suborbital spaceplanes: XCOR’s Lynx craft’s dorsal pod to carry nanosat launch vehicle
While Virgin Galactic has plans for a much larger launch vehicle, its competitor XCOR, has a plan to launch a much smaller two-stage rocket from the dorsal pod of the Mark 3 version of its Lynx suborbital space plane. This launch vehicle should be able to carry a single 20kg microsatellite, or alternatively, a group of nanosatellites of equivalent total mass, into low Earth orbit.
Optimised air-breathing: DARPA/Boeing entry may lead to a larger launcher
The most advanced concept is Boeing’s Small Launch Vehicle design developed under DARPA’s Airborne Launch Assist Space Access (ALASA) programme. While NASA’s failed X-30/NASP project was stymied by the mass growth issues involved in putting several types of air-breathing and rocket engines onto a single-stage-to-orbit launch vehicle, Boeing’s proposed a multi-stage solution takes a different multi-engine tack. Each stage of its three-stage system uses an engine optimised for its flight regime.
The first winged tandem stage of its air-dropped vehicle uses air breathing jet propulsion to reach supersonic velocities, while the second winged stage is accelerated to near orbital velocities using scramjet technology. An expendable solid rocket upper stage is the final stage and is released from Stage 2 to finally push a payload of up to 45kg into orbit. The programme is attempting to drive down launch costs to as low as $300,000 per launch and may be fielded by 2020.
DARPA has been recently reported to be planning to use its ALASA winged research to develop a first stage dubbed XS-1 for a much larger launch vehicle.
Smallest but sweetest players of all: Garvey Spacecraft, Ventions and Tranquillity Aerospace
Other firms developing very small or micro-launch vehicles include Garvey Spacecraft of Long Beach, California which his working on a two -stage pressure-fed LOX-densified propylene vehicle liquid fuel Nanosat launch vehicle which is designed to carry payloads of up to 10kg into orbit. The firm is already in received of NASA funding via a Small Business Innovation Research (SBIR) Phase II award.
Another US contender is Ventions LLC which is planning to build a LOx/kerosene powered two-stage launch vehicle capable of placing upto 15kg payloads into orbit. Similar to Garvey, Ventions is also already in receipt of NASA SBIR money to fund its regeneratively cooled engine development programme.
While UK firms are planning much larger reusable launch vehicles, the Oxfordshire-based outfit of Tranquility Aerospace has revealed that it plans to use its Devon 1 reusable suborbital rocket which is fitted with a hydrogen peroxide/kerosene burning “Cornwall One” rocket engine, as the first stage of a two-stage cubesat launch vehicle dubbed “Devon 2”. However, with a payload of only 2 kg to low Earth orbit, Devon 2 may not be large enough to compete for NASA’s money.
Some of NASA’s field centres are in the hunt themselves. NASA’s Dryden Flight Research Centre is reported to be considering a concept using unmanned automonous glider vehicles to carry air-launched rockets which ignite on release. This avoids the risk of having rocket efflux impingment on a crewed vehicle or having to perform an altitude consuming air drop.