Rocket Science And Satellites PDF

Rocket Science And Satellites Ae111 – Introduction to Aeronautics...

Rocket Science And Satellites Ae111 – Introduction to Aeronautics E.Boniol 1 Fun learning Kerbal Space Program  Enables you to build your own  Rocket & Sattelite  Airplane  Pretty fair simulation of the basic physics principles (astronautics, fuel management, aerodynamics, etc.) E.Boniol 2 Slides named NOTE are bonus information, not to be learnt. 1  Cosmos : no friction at all  With no external force, each object shall keep its initial speed and direction forever ! Alone in the cosmos, with no external force  how can spacecraft operate and manoeuver ? E.Boniol 3 Cosmos : no friction at all  How can spacecraft operate and manoeuver ?  In space, a constant mass object follows a free fall trajectory (conic)  This trajectory cannot be altered without changing the mass « To go somewhere, you have to give something » Using Newton’s Third Law E.Boniol 4 Slides named NOTE are bonus information, not to be learnt. 2  Constantin Tsiolkowski (1857 – 1935) Russian scientist, considered as the Father of modern astronautics “Earth is the cradle of mankind, but you cannot live forever in the cradle.” (« Планета есть колыбель разума, но нельзя вечно жить в колыбели. ») First one to conceive multi-stage rocket, propelled by burning fuel and ejecting it in the opposite direction  Derived the fundamental Rocket equation (proven in the next lecture) E.Boniol 5 Deriving Tsiolkowski Equation So that the mass of is constant E.Boniol 6 Slides named NOTE are bonus information, not to be learnt. 3  Deriving Tsiolkowski Equation Inside : Masses Inside : Velocities  At time t, we consider being in the reference frame of the rocket, thus, its speed is initially considered zero E.Boniol 7 Deriving Tsiolkowski Equation Mass of is constant We consider no external force is applied on (no gravity nor air resistance) Thus, its momentum is conserved over time E.Boniol 8 Slides named NOTE are bonus information, not to be learnt. 4  Deriving Tsiolkowski Equation E.Boniol 9 Deriving Tsiolkowski Equation Differential form of the Tsiolkowski Equation E.Boniol 10 Slides named NOTE are bonus information, not to be learnt. 5  Deriving Tsiolkowski Equation Integration : ∆𝑉 : Difference in velocity of the rocket (‘acceleration’) 𝑣 : Gas exhaust speed 𝑚 : Initial mass of the rocket (with the yet unused propellant) 𝑚 : Final mass of the rocket (without the yet burnt propellant) E.Boniol 11 Application Sending a 2 Tons payload to Space  Without taking benefit of Earth rotation (average exhaust speed with nowadays technologies) Need for 82 tons of propellant ! E.Boniol 12 Slides named NOTE are bonus information, not to be learnt. 6  Application Sending a 2 Tons payload to Space  By taking benefit of Earth rotation (Launching Eastward from the Equator) Need for 69 tons of propellant ! E.Boniol 13 How to mitigate this issue ? By using series design :  The ∆𝑽 add up By using parallel design :  The thrust forces 𝐹 add up E.Boniol 14 Slides named NOTE are bonus information, not to be learnt. 7  Serial design : Separation Masses on…  Stage 2 : Payload mass Propellant mass Structural mass  Stage 1 : Propellant mass Structural mass E.Boniol 15 Serial design : Separation i.e when all the propellant has been burnt in stage 1 E.Boniol 16 Slides named NOTE are bonus information, not to be learnt. 8  Serial design : Separation E.Boniol 17 How to mitigate this issue ? By using series design :  The ∆𝑽 add up Having : Enables a greater E.Boniol 18 Slides named NOTE are bonus information, not to be learnt. 9  Rocket architecture  Payload  Structure : Frame Aerodynamic devices : Nose cone & Fins  Propulsion system : Tanks Engines E.Boniol 19 Expelling propellant Accelerating gas  Use of a Pressure gradient force along the nozzle Need to have an enormous initial pressure Need to greatly increase gas temperature (burning it) Same principle for an airplane turbojet / turbofan engine (using fuel burn)… BUT…What about rockets ? Because of absence of oxygen in Space, need to use fuel and oxydizer ! E.Boniol 20 Slides named NOTE are bonus information, not to be learnt. 10  Rocket engine principle (Chemical propulsion) Gas burn Pressure & Temperature increase Gas is accelerated Velocity (Momentum) increase E.Boniol 21 Rocket engine architectures Solid rocket engine Principle : ignite a solid propellant grain (fuel + oxydizer), hot gas being ejected through a central canal High thrust (up to 10 MN) Storable for long times (5 to 20 years) Few sub-systems No movable parts Low throttleable Not reignitable Not reusable Dangerous Very polluting  Used for the lower stage, in parallel design E.Boniol 22 Slides named NOTE are bonus information, not to be learnt. 11  Rocket engine architectures Liquid rocket engine Principle : ignite a liquid fuel and oxydizer, brought through pumps into the combustion chamber High 𝐼 (see after) Complexity Throttleable Highly energetic propellant Reusable are not storeable Reignitable So Propellant management is needed for Cryogenics E.Boniol 23 Rocket engine architectures Hybrid rocket engine Principle : ignite a liquid or gaseous oxydizer, brought through pumps into the combustion chamber, with a solid fuel grain Simple (no moving part) Poor performance Storeable Cheap E.Boniol 24 Slides named NOTE are bonus information, not to be learnt. 12  Nozzle Converging-Diverging (de Laval) Nozzle  Enable gas to reach supersonic speeds Liquid fuel can be set to travel around the nozzle to reduce the nozzle core temperature Converging section  Subsonic flow (Mach < 1) accelerates (see lecture on Aerodynamics) Nozzle throat  Flow set to reach Mach 1 here (sonic flow) Diverging section  Supersonic flow (Mach > 1) accelerates  Inverted tendancy when supersonic E.Boniol 25 Nozzle efficiency Depending on the exhaust gas pressure 𝑷𝒆 , compared to the ambient atmospheric pressure 𝑷𝒂 , several cases are possible : Adapted nozzle 𝑃 =𝑃  Maximum efficiency Under-expanded nozzle 𝑃 >𝑃  Reduced efficiency  Added stress on the nozzle structure Over-expanded nozzle 𝑃