NEPTUNE MODULAR SERIES LAUNCH VEHICLES

Interorbital Systems (IOS) is developing a new generation of low-cost, rapid-response manned and unmanned orbital launch vehicles. NEPTUNE Modular Series rockets are designed for minimum cost and maximum reliability. Unnecessary, expensive, complex, failure-prone, and performance-limiting systems such as wings and turbopumps have not been included in their design. Since the NEPTUNE Modular Series launch vehicles are designed to be deployed from a private island launch site or from the Sea, launch costs will be relatively insignificant (compared to standard spaceport fees), and launch scheduling will be based on customer demand (not on placement in a spaceport's launch rotation). The IOS modular rocket system is an evolved version of a similar system developed by OTRAG in the 1970's. Lutz Kayser, the former head of the OTRAG team, is a primary consultant on the IOS project.

MODULAR ROCKET SYSTEMS
Each member of the NEPTUNE Modular Series of launch vehicles is assembled from multiple Common Propulsion Modules (CPMs).  Payload capacity can be varied by increasing or decreasing the number of CPMs.

COMMON PROPULSION MODULE
Each Common Propulsion Module is composed of four propellant tanks and a single throttleable, ablatively-cooled rocket engine.  Depending on the configuration, the modules can operate in either blowdown or pressurant tank-fed modes. The capacity of the propellant tanks is regulated by varying their lengths. Construction costs are kept low by utilizing many off-the-shelf components and state-of-the-art assembly line methods. 

LIQUID ROCKET ENGINES AND PROPELLANTS
A single fixed, throttleable, low-thrust, liquid rocket engine powers each CPM. 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. Stand-alone CPMs will be steered by four small gimbaled vernier rocket engines. Storable, high-density white fuming nitric acid (WFNA) and turpentine/furfuryl alcohol are the CPM’s primary propellants. These low-cost, storable, environmentally friendly propellants provide reliable, efficient, hypergolic ignition.  

Aerodynamics
The aerodynamic properties of the uniquely configured NEPTUNE Modular Series rockets have been extensively analyzed. Data shows the thrust to drag ratio is acceptable with values less that that of the Space Shuttle. In general, the rockets follow a slow build-up of velocity in the region below 10 km (32,800 ft.), reaching Mach 1 at between 25,000 ft. and 35000 ft. with the rocket's velocity just rising above Mach 4 at an altitude of 33 km (110,000 ft). At this altitude, the atmospheric pressure is extremely low (only 0.125 psi) (sea level pressure = 14.7 psi). Since orbital velocity is around Mach 25, the majority of the acceleration (90%) takes place outside of the denser parts of the atmosphere where the drag  is extremely small.

Multiple Engines
Launch vehicles with multiple engines have been in use since the beginning of the space age. The Saturn 1B had 8 booster engines, 6 stage two engines, and 2 stage three engines (a total of 16 engines). The Soyuz three-stage rocket has a total of 34 engines, with the upper stage engines included. When looking at the the engine view of the NEPTUNE Modular series rockets, one sees not only the booster engines, but also all of the upper stage engines. This is due to the parallel staging configuration. With the standard stacked stage configuration, the upper stage engines are not visible. Below is an engine view of the Soyuz launcher with 32 booster and vernier engines. The Soyuz rocket is one of the most reliable rockets in the world.

NEPTUNE 9 (N9)
The modular N9 rocket is a three stage (parallel staged) satellite launch vehicle capable of launching 70-Kg payload into polar low-earth orbit. It is composed of 9 Common Propulsion Modules. The engine count breaks down to 6 stage-1 engines, 2 stage-2 engines, and 1 stage-3 engine (a total of 9 engines). N9 was designed specifically to support the TubeSat, CubeSat,  and general small-sat community.

NEPTUNE 36 (N36)
The N36 is a three-stage (parallel staged), medium-lift launch vehicle capable of placing a 1000-Kg payload into polar low-earth orbit or accelerating a 190-Kg payload to Earth-escape velocity. The rocket is composed of 36 Common Propulsion Modules. The engine count breaks down to 24 booster engines, 8 stage two engines, and 4 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.

Crew Module 6 (CM-6)
The CM is designed to accommodate five expedition crew members and one command pilot. The 6-person crew will be seated radially around a centrally located service compartment access hatch. Each crew member has a window providing excellent visibility. The CM is attached to the forward section of the rocket 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.

Common Propulsion Module STATIC Engine Test
Click on the image below to see an excerpt of a static throttling test of a Common Propulsion Module altitude liquid rocket engine. The test was made at Interorbital's Alpha Test Site, located at the Mojave Spaceport. Rocket engine ignition is hypergolic. When the propellants exit the rocket engine's injector, they ignite on contact. Nozzle expansion ratio is ambient.

NEPTUNE MODULAR SERIES TEST PROGRAM
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. The IOS Neutrino sounding rocket (see photo below) 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. It will provide on-orbit start/stop capability for interorbital transfer operations.

Interorbital Systems will be carrying out further static rocket engine testing as well as at least three low-altitude (50,000 ft) flight tests of a single Common Propulsion Module. A photograph of a Common Propulsion Module Test Vehicle (CPM TV) on its Mobile Launch Trailer (MTA) is shown below.  A multiple CPM flight test will complete the flight test program before the first orbital launch from Tonga or the Pacific Ocean in 2012.

Payload space is currently available on these pre-orbital test flights at a cost of $500.00 per kilogram ($227.00 per pound). Payloads can include TubeSats, CubeSats, or single payloads weighing up to 30 kg. Universities, companies, or individuals are encouraged to contact Interorbital if they would like to fly a test payload.

Interorbital Systems P.O. Box 662 Mojave, CA 93502-0662
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