By Brian Dodson
An Interorbital Systems TubeSat in low Earth orbit
Image Gallery (12 images)
Interorbital Systems (IOS), a rocket and spacecraft construction company founded in 1996, is ready to fulfill its 2009 goal of making access to space available to all. Well, at least to anyone who can afford a motorcycle. For US$8K, IOS provides the TubeSat Personal Satellite (PS) Kit, complete with launch to low Earth orbit (LEO).
In the last decade, interest in picosatellites, or satellites weighing less than about a kilogram, has been increasing rapidly. A TubeSat is a (very) low-cost alternative to the CubeSat, which is currently the leading picosatellite standard. Nearly 100 CubeSats have been built and launched. (Not all launches were successful.)
A CubeSat is essentially that – a nearly cube shaped satellite measuring 10x10x10 cm (3.9×3.9×3.9 in), although they are scalable along one axis – with a total mass of less than 1.33 kg (2.9 lb). The basic structure of a CubeSat is about 0.4 kg (0.9 lb), so a 0.9 kg (2 lb) payload can be accommodated. CubeSats have been proposed for everything from simple radio transponders to interplanetary missions. Despite their popularity, CubeSats are not inexpensive – by the time you have assembled a CubeSat and had it placed in orbit, your cost will be well north of US$100K, a fortune compared to IOS’s cost of US$8000.
An Interorbital Systems Tubesat showing its antennas and solar cells next to its ejection chamber
The far more affordable TubeSat, oddly enough, has a hexadecagonal (16-sided) cross-section rather than the circular form one might expect from the name. This allows it flat surfaces on which to mount solar cells. A TubeSat has an outside diameter of 8.94 cm (3.52 inches), an inside diameter of 8.56 cm (3.37 inches), and is 12.7 cm (5 inches) long. The maximum mass of a TubeSat is 0.75 kg (1.65 lb). As the TubeSat with the standard electronics (power, communications, and microcomputer) installed weighs 0.5 kg (1.1 pounds), any additional payload must weigh no more than 0.25 kg (0.55 lb), and must occupy no more than about 5 cm (2 in) of the length of the tube – a payload volume of 288 cc (17.6 cubic inches).
The finished TubeSat is launched to self-decaying orbits roughly 310 kilometers (193 miles) in altitude, where it will remain in orbit for several weeks (the duration depends on the exact orbit and on solar weather conditions). They will not add to the orbital debris problem.
The TubeSat comes in the form of a kit, which includes the satellite’s structural components, printed circuit board (PCB) Gerber Files, electronic components, solar cells, batteries, 0.5 watt UHF transceiver, antennas, microcomputer, and the required programming tools. With these components, the builder can construct a satellite that can be received on the ground by a hand-held amateur radio receiver. Perhaps the simplest mission is to broadcast a repeating message from space, or to program the satellite to act as an amateur radio transponder, allowing ham radio operators to communicate using the TubeSat as a relay.
Other types of payloads and missions that have been suggested as suitable for TubeSats include:
- Earth-from-space video imaging
- Earth magnetic field measurement
- Satellite orientation detection (horizon sensor, gyros, accelerometers, etc.)
- Orbital environment measurements (temperature, pressure, radiation, etc.)
- On-orbit hardware and software component testing (microprocessors, etc.)
- Tracking migratory animals from orbit
- Testing satellite stabilization methods
- Biological experiments
- On-orbit advertising
- Space art
- Space burials
Launches will be carried out by a NEPTUNE series rocket developed and built by IOS at its Mohave manufacturing and test facilities. NEPTUNE Modular Series rocket components have been undergoing ground and flight tests since 1999. Testing includes ongoing static rocket engine firings as well as launches of the IOS Neutrino sounding rocket. IOS is currently developing a spaceport on the island of ‘Eua in the South Pacific Kingdom of Tonga, but will follow U.S. space regulations.
Artist’s conception of the launch of a NEPTUNE30 rocket from the IOS spaceport in Tonga
The Neptune launcher rockets are based on a launch system developed in the 1970’s and 1980’s by the German Orbital Transport und Raketen AG OTRAGproject. Although prematurely terminated due to political pressure, OTRAG provided a platform upon which IOS has based a new generation of low-cost, rapid-response unmanned orbital launch vehicles. As the original OTRAG Common Propulsion Modules (CPM) were rated for manned flight (estimated to have a few failures in every million CPM firings), IOS also has manned orbital missions in their viewscreen.
Interorbital Systems’ Common Propulsion Module, having a thrust of 6000 pounds using storable liquid fuel and oxidizer
Each Common Propulsion Module is composed of four propellant tanks and a single throttleable, ablatively-cooled rocket engine. The rocket engine is a throttleable low-thrust engine burning white fuming nitric acid and “hydrocarbon X,” which is rumored to consist primarily of turpentine. The fuel and oxidizer are storable and hypergolic (self-igniting). Together with the use of ablative cooling, the design greatly reduces the complexity of the CPM, which basically becomes a tube with two integral tanks, two metal hoses, a pair of throttling valves, and the combustion chamber and rocket nozzle. Propellant is fed from the tanks by pressure in an ullage space. Simplicity has safety advantages, but also allows construction costs to be kept low by using off-the-shelf components and state-of-the-art mass production manufacturing techniques.
The movie above shows an excerpt of a static throttling test of a Common Propulsion Module. The test was held at Interorbital’s Alpha Test Site, located at the Mojave Spaceport. Rocket engine ignition is hypergolic, meaning that when the combination of propellants exit the rocket engine’s injector, they ignite on contact. The movie shows the thrust of the CPM is varied during the test.
The IOS Neutrino sounding rocket (test flight video below) is based on a single CPM, and has provided valuable data on rocket engine and hypergolic propellant performance in flight, Inertial Measurement Unit and Guidance Computer operation under high acceleration and vibration conditions, data logging and telemetry systems, and payload recovery systems.
Each member of the NEPTUNE Modular Series of launch vehicles is assembled from multiple Common Propulsion Modules (CPMs). When the CPMs are clustered in multiples of three or four per stage, differential throttling of opposing rocket engines provides pitch, yaw and roll control. Staged rockets are parallel staged, with the first stage consisting of an outer ring of CPMs, the second stage consisting of a smaller ring of CPMs mounted within the outside ring, and a third stage mounted within the smaller second-stage ring. Despite the somewhat cumbersome appearance, the aerodynamic performance of NEPTUNE series rockets is better for orbital insertion flights than that of the Space Shuttle.
Suborbital NEPTUNE1 rocket ready for flight
The modular NEPTUNE 9 (N9) rocket is a three stage (parallel staged) satellite launch vehicle capable of launching 70 kg (154 lb) payloads into polar low-earth orbit. It is composed of nine Common Propulsion Modules. The engine count breaks down to six stage-1 engines, two stage-two engines, and one stage-three engine (a total of nine engines). N9 is designed specifically to support the TubeSat, CubeSat, and general small-sat communities.
The NEPTUNE 36 (N36) is a three-stage (parallel staged), medium-lift launch vehicle capable of placing a 1,000 kg (2,205 lb) payload into polar low-earth orbit or accelerating a 190 kg (419 lb) payload to Earth-escape velocity. The rocket is composed of 36 Common Propulsion Modules. The engine count breaks down to 24 booster engines, eight stage two engines, and four stage three engines. The N36 is slated to launch the Google Lunar X PRIZE SYNERGY MOON lander/rover to the Moon. It will also be utilized to launch a two-person crew module into low earth orbit for short orbital tourism missions. The crew module (CM-2) is presently in development.
IOS engineers examine a prototype of the CM-6, a six passenger crew module for orbital flights up to a week in duration
In expectation of the NEPTUNE series of rockets being certified for manned launches, crew modules are currently being developed. The CM-6 crew module is designed to accommodate five expedition crew members and one command pilot. The six-person crew will be seated radially around a centrally located service compartment access hatch, following the Russian Soyuz pattern. Each crew member has a window providing excellent visibility. The CM-6 will be attached to the forward section of the rocket (planned to be a NEPTUNE4000) and has the following primary components: emergency escape system, life-support system, electric power system, docking collar, retro-rocket de-orbit system, attitude control system (ACS), parachute recovery system, and an aft heat-shield for reentry.
IOS is currently offering 10 “free” promotional deals on a week-long orbital mission. You give them the use of US$250K, which will be refunded two years after your orbital trip. Of course, if it never happens, you don’t get your money back. Still, compared to a price of US$5 million for a regular seat on such a journey, the deal is sufficiently attractive that two passengers have already signed aboard.
Source: Interorbital Systems