Final Report

Faculty of Engineering and Physical Sciences Final Report Project Aether – Supergun “Ad infinitum et ultra” Multi-Disciplinary Design Project ENGM001 Prepared by: Michael Brasted Aerospace Engineer Toby Chipperfield Electronic Engineer Matthew Evans Aerospace Engineer Ben Jarman Aerospace Engineer Robert Lloyd Medical Engineer Marcus McCarthy Electronic Engineer Jamie Osei Mechanical Engineer Supervisors: Professor. Neil Downie, Dr. Ignazio Cavarretta and Dr. Chris Bridges Submitted: 19th January 2015 Executive Summary The proposed supergun could provide an excellent new opportunity to parties wishing to launch nano/micro-satellites into orbit. Most small payloads rideshare as an auxiliary payload and thus concede control of launch date and orbital trajectory. Presently, dedicated launch of small payloads such as through “LauncherOne” or “Pegasus” launch vehicles comes at a price premium. The supergun could provide independence to companies wishing to launch small scale payloads into space at a price competitive with larger launch systems. A detailed project plan with a supporting business case and financial analysis is presented. The project is split into three main stages; prototype conventional light gas gun (LGG) design and testing, operational full scale LGG and finally a LGG injected RAM accelerator. Each stage has a series of objectives, which are set to prove project feasibility and help secure funding. Initially an electrothermal light gas gun (ELGG) with further hydrogen injections throughout the barrel was the intended firing mechanism that would provide the projectile with the required muzzle velocity. It was assumed to be capable of producing a more constant acceleration than conventional LGGs. A Matlab model of the ELGG was made to verify this, however it revealed that the ELGG cannot be scaled for this application. Focus returned to the LGG. The model was updated to account for pressure losses due to the difference in the gas and projectile speed. By increasing the pre-fill pressure of the hydrogen and lowering the burst threshold, a “bleed” effect was achieved resulting in a lower peak pressure, sustained for a longer period. This resulted in the projectile experiencing an acceleration of 7000 g and exiting the muzzle at 5.5 km/s. The supergun’s main components will be constructed from 4140 steel, giving a safety factor of 1.4. Additionally the gun can handle in excess of 10,000 cycles before fatigue failure would occur. During launch, the supergun will experience a peak recoil velocity of 14 cm/s. The LGG uses the recoil generated by the oscillating piston to provide soft recoil, reducing the required performance of the recoil system. The recoil system transfers momentum from the gun to a wheeled 10 tonne mass accelerating it along a track. This mass is then slowed down using a magnetic brake, reducing its velocity such that the mass’s kinetic energy can be safely absorbed by a buffer stop. The foundations and supporting structures will provide a safety factor of 5.9 and 3.0 respectively. The flight path model was improved to three DoF to more accurately simulate the trajectory of the projectile. A launch variable solver was then written to calculate the optimal launch angle, propellant mass and rocket ignition time given a set of launch conditions and target orbital i parameters. This was used to assess the viability of the design options, giving the project team the information required to make informed decisions on project decisions. The final parameters chosen were a launch angle of 26.7° firing a 150 kg dry mass and 185 kg of propellant. Liquid H2/O2 was chosen as the rocket propellant for the high specific impulse of 455 seconds. The simulator was also used to assess the methods deorbiting of the projectile. This indicated that the projectile would experience sufficient atmospheric drag to bring it out of orbit within the 25 year requirement. The projectile was designed to be similar to the final stage of a conventional rocket launcher. Sensors provide orientation and location data to a state feedback controller which controls the thrust level duration and amplitude of the thrusters in response to disturbances. A Thermal Protection System was designed in order to protect the payload and internal structure of the projectile. CFD analysis was performed in order to predict temperatures in the highest temperature regime of launch and suitable materials were selected. These included common materials such as an ablative heat shield and a state of the art self-transpiring hot skin. The payload is ejected in the radial direction from the projectile. To avoid setting the payload in an eccentric orbit the projectile will rotate 90º before ejection of the projectile. Initially the LGG based orbital launch system seemed to be a promising proposal. However the G- forces that 7000 g would lead to unsurmountable challenges in the projectile design. To reduce the acceleration either the muzzle velocity or the projectile mass would have to be decreased. The LGG would no longer be capable of meeting the project objectives with these alterations. Therefore it is proposed that the LGG should be redesigned as an injection system for a ram accelerator with the G-force limited to 1500 G. The final aim of the project would be to design an operational LGG injected RAM accelerator, capable of performing two launches per day, two hundred times a year at cost of £1600 per kg of payload. The project requires an investment of £2.4 billion in the first 5 years, taking 18 years to break even and would produce a total profit of £5.4 billion over 32 years, with an internal rate of return of 7.25%. Government investment in this project would provide a relatively cheap route for parties to launch small payloads to space, encouraging growth in the space sector. ii Contents Nomenclature ................................................................................................................. viii List of Symbols .................................................................................................................. ix List of Acronyms ................................................................................................................ x Design Specifications ........................................................................................................ xi 1 Introduction ................................................................................................................ 1 1.1 Objective and Scope ....................................................................................................... 1 1.2 Project Background ........................................................................................................ 2 1.3 Idea Selection .................................................................................................................. 3 1.4 Alterations from inception report ................................................................................. 3 2 Project Plan ................................................................................................................. 4 2.1 Stage 1: Prototype LGG Design and Testing ............................................................... 4 2.2 Stage 2: Supergun Fired Rocket-Boosted Projectile into Orbit ................................. 5 2.3 Stage 3: LGG Injected RAM Accelerator with Projectile Recovery ......................... 6 2.4 Project Plan Summary ................................................................................................... 7 3 Project Financials and Business Case ....................................................................... 8 4 Sustainability ............................................................................................................. 14 4.1 Threat to the Landscape .............................................................................................. 14 4.2 Emissions ....................................................................................................................... 14 4.3 Reusable Components .................................................................................................. 14 4.4 Noise ............................................................................................................................... 15 5 Project Management ................................................................................................ 16 6 Electrothermal Light Gas Gun ................................................................................ 18 6.1 Assumption and Equations for ELGG ....................................................................... 19 iii 6.2 Gun Model ..................................................................................................................... 19 7 Two-Stage Light Gas Gun ....................................................................................... 23 7.1 Breech Propellant ......................................................................................................... 23 7.2 General Gun Design ..................................................................................................... 25 7.3 Gun Tube Design .......................................................................................................... 33 7.4 Piston Control ............................................................................................................... 36 7.5 Experimental Testing ..................................................................................................

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