lecture4 - MECH 6521/498D Space Flight Performance Basic...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
MECH 6521/498D Space Flight Performance Gemini 3 - Titan II • Basic relations of motion • Multistage rocket • Space flight (orbital mechanics) Reading: Sutton and Biblarz Chapter 4 and Chapter 3
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Rocket Fundamentals - Summary Revisit Newton’s third law and conservation of momentum - Rocket thrust model - Rocket equation for an ideal rocket engine Define different performance parameters - Effective exhaust velocity - Specific impulse - Energy efficiencies - Impulse or thrust to weight ratio Define different masses and their ratios = Δ MR I g V sp 1 ln 0 F = m e V e + p e A e p A e () Ties mission requirements and system requirements together to accomplish a particular mission (given by Δ v), the system has to deliver specific characteristics.
Background image of page 2
2. Rocket Fundamentals 1. Rocket technology 3. Space Flight Trajectories
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Space Flight Performance So far, we only look at the ideal rocket equation i.e. Gravity-free, drag-free space flight - drag, gravity, and burn time effects Applications of the rocket equation to: To model launch trajectories Multi-staging concept Understanding different factors involved in designing launch trajectories Space flight - orbital transfers, and other maneuvers = Δ MR I g V sp 1 ln 0 F = m e V e + p e A e p A e ()
Background image of page 4
Space Flight Trajectory The rate of acceleration of the vehicle is: dt g dt M D M dM c dV e θ cos = C e is the effective exhaust velocity of the vehicle or the thrust divided by the exhaust mass flow rate Look at forces on rocket in flight again: V For example, another simple particular case: - flight direction and thrust are co-linear - life forces are negligible for wingless vehicle with zero angle of attack α - constant thrust, stationary earth, no wind
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Space Flight Trajectory D f C A V D 2 5 . 0 ρ = where atmospheric density above earth varies roughly as: ( ) 5 . 1 exp ) ( bh a h = With density in kg/m 3 and h is meters, a = 1.2 and b =2.9x10 -5 Roughly, density at 30,000 meters is about 1% of its sea-level value Aerodynamic force or drag D Equivalently you can write down similar expression for the lift L, dynamic force acting in a direction normal to the flight path.
Background image of page 6
Lift and Drag Variation of lift and drag coefficient with Mach number of the German V-2 missile based on cross-sectional area with jet off and without exhaust plume effects at several angle of attack α .
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Space Flight Trajectory 2 + = h R R g g e e e At 100 miles above the surface the change from the surface is still only about 5%. To calculate velocity increment for acceleration near the earth (or any other large mass), we will generally assume g to be constant. But be sure to state it as an approximation!!! Gravitational force
Background image of page 8
Space Flight Trajectory The rate of acceleration of the vehicle is: dt g dt M D M dM c dV e θ cos = Neglecting the air drag and gravity terms, we get the ideal rocket equation M dM c dV e = For space launch vehicles, the drag loss is typically 5% to 10% of the final vehicle velocity increment Δ v. Very
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/12/2010 for the course MECH 351 taught by Professor Chekhov during the Fall '10 term at Concordia Canada.

Page1 / 46

lecture4 - MECH 6521/498D Space Flight Performance Basic...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online