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Neptune (CPM-2 based)

Neptune-1-GTV [InterOrbital]



InterOrbital Systems plans a series of small modular launch vehicles called Neptune consisting of clusters of simple pressure-fed rocket modules.

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.

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.

Each Common Propulsion Module 2.0 is composed of four parallel propellant tanks - two tanks for the oxidizer (WFNA), one for the fuel (turpentine), and one for the pressurant (helium).

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 CPMs primary propellants. These low-cost, storable, environmentally friendly propellants provide reliable, efficient, hypergolic ignition.

The Neptune-1-GTV is a single stage guidance test vehicle capable to be launched on a low-altitude atmospheric flight in 2017.

The Neptune-1 is a three stage nano-satellite launch vehicle capable of launching 6 kg payload into polar low-earth orbit. It is composed of one Common Propulsion Module and two liquid fueled upper stages.

The Neptune-3 is a three stage (parallel staged) micro-satellite launch vehicle. It is composed of 3 Common Propulsion Modules and liquid fueled satellite kick-stage. The engine count breaks down to 2 booster engines, 1 stage two engine, and 1 stage three motor or engine (a total of 4 engines).

Flights of the Neptune series have been announced for several years to be imminent, with little visible progress happening. The GPRE-7.5KNTA main engine of the CPM was first test fired in October 2012. IOS currently claims to be able to launch an orbital mission in th 4th quarter of 2017.

Version Stage 1 Stage 2 Stage 3 Stage 4
Neptune-1-GTV (N1-GTV) CPM 2.0 / GPRE-7.5KNTA - - -
Neptune-1 US2 (N1 US2) CPM 2.0 / GPRE-7.5KNTA US US -
Neptune-3 US2 (N3 US2) 2 × CPM 2.0 / GPRE-7.5KNTA CPM 2.0 / GPRE-7.5KNTA US US
Neptune-5 US2 (N5 US2) 4 × CPM 2.0 / GPRE-7.5KNTA CPM 2.0 / GPRE-7.5KNTA US -US
Neptune-8-Long (N8-Long) 6 × long CPM 2.0 / GPRE-7.5KNTA 2 × long CPM 2.0 / GPRE-7.5KNTA Kick stage -
Performance (kg) LEO LPEO SSO GTO GEO MolO IP
Neptune-1 US2 (N1 US2) 6 - - - - -
Neptune-3 US2 (N3 US2) 20 - - - - - -
Neptune-5 US2 (N5 US2) 30 - - - - - -
Neptune-8-Long (N8-Long) 500 100
No:   TNo: Serial    Type              Date          LS            Payload


* = suborbital