Seminar 8 Building Spacecraft & Launch Vehicles Space Vehicle Design FRS 112, Princeton University Robert Stengel Copyright 2015 by Robert Stengel. All rights reserved. For educational use only. http://www.princeton.edu/~stengel/FRS.html Building Spacecraft & Launch Vehicles Chariots for Apollo, NASA-SP-4205, Ch 3 to 7 Stages to Saturn, NASA-SP-4206, Parts & IV Space Vehicle Design Understanding Space, Ch 11, Sec 13.3, 13.4 1 • Defining a mode for the mission, who would execute it • What was the goal? • First LOR proposals; Tom Dolan, Vought Astronautics, 1958 • Energy budgets • MALLAR, MORAD, ARP, MALLIR • Safety and reliability of LOR • Number of launches, complexity of systems • Evolution: Mercury, Mercury II (Gemini) • Dynamics of lunar touchdown Contending Modes 2
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Seminar 8!Building Spacecraft & Launch Vehicles!
Space Vehicle Design!FRS 112, Princeton University!
Robert Stengel"
Copyright 2015 by Robert Stengel. All rights reserved. For educational use only.!http://www.princeton.edu/~stengel/FRS.html!
Building Spacecraft & Launch Vehicles !Chariots for Apollo, NASA-SP-4205, Ch 3 to 7 !
•# Defining a mode for the mission, who would execute it"
•# What was the goal?"•# First LOR proposals; Tom Dolan, Vought
Astronautics, 1958"•# Energy budgets"•# MALLAR, MORAD, ARP, MALLIR"•# Safety and reliability of LOR"•# Number of launches, complexity of systems"•# Evolution: Mercury, Mercury II (Gemini)"•# Dynamics of lunar touchdown"
Contending Modes"
2!
•# Reaching consensus"•# Centralizing decision processes at
NASA HQ"•# Lunar crasher"•# Chance Vought study"•# Weight-lifting capability of Saturn C-5"•# Von Braun’s acquiescence for LOR"
Joe Shea"
3!
•# Evolution of Saturn launch vehicles"•# Development of rocket motors with greater thrust than ICBMs’"•# F-1 and J-2"•# Evaporation of C-1 and Dyna-Soar (X-20)"•# Von Braun group used to developing integrated vehicle and
payload; now different design teams would be involved"•# Contending styles and approaches: MSFC, MSC. STG,
companies"•# Grumman: prime contractor for LEM"•# Expansion of MSFC facilities"
Missions, Modes, and Manufacturing"
4!
•# MSFC’s “factory look” inherited from former Army arsenal"•# Chrysler, Boeing, North American: Saturn contractors"•# Description of extensive facilities for production"•# Flight worthiness certificates"•# GE: facilities management"•# Rocketdyne: F-1 engine contractor; thrust vectoring
requirement"•# Separate tanks, fuel slosh baffles"•# Study of 1st stage recovery"
5!
•# Improbable estimate of Saturn launch rates (100/year)"•# Block I and Block II concept"•# Loads and stiffness of structure"•# Spider beams"•# Thrust structure, cross beams, holddown points, stabilizing fins"•# Flight stability, low natural frequency, advanced control
procedures"•# Base heating, shock waves, turbulent mixing, hot spot, turbopump
exhaust, no dead air"•# Acoustic vibration and impact"•# Douglas: S-IV engine contractor"
6!
•# NASA-North American relationship, defending LOR, finding LEM contractor"
•# Harrison Storms, et al, at NAA"•# Design and testing facilities"•# Briefings, agendas, subcontractors, mockups,
boilerplates"•# Test launches, landing systems, cabin layout"•# Involvement of NASA centers, MIT
Instrumentation Lab"•# GM/AC Spark Plug Division"•# Interface control documents"
Matching Modules and Missions"
Harrison Storms"7!
•# Lunar landing vehicle, mysterious nature of the surface"•# PSAC pressures, reliability estimates, success-failure probabilities"•# JFK’s opinion of landing mode, preoccupation with the Cuban
missile crisis"•# Wiesner’s opposition, Webb’s commitment to LOR"•# Responsibility for CSM-LEM rested with MSC"•# NAA suggested that LEM builder be sub-contractor to NAA"•# Grumman vs. McDonnell, other programs in progress (primarily
aircraft), contract negotiations"•# Integrated Mission Control Center at MSC"•# Selection of Gemini for critical rendezvous and docking tests"
Jerome Wiesner"
8!
•# Selection of CSM-LEM docking configuration"•# Block I and Block II CM configurations (before AS-204 fire)"•# Mercury, Gemini, and Apollo programs all in motion at same time"•# GE role in ground support"•# Interjecting Bellcomm (NASA HQ support contractor) into the mix"•# Apollo Systems Specification manual "•# Countless systems review meetings [Critical Design Review (CDR),
Performance Development Review (PDR), Panel Review Board]"•# Competition, lack of cooperation among NASA centers, a
consequence of overlapping responsibilities; HQ as arbitrator"•# Telecommunications and Tracking Stations, GSFC"•# 9-, 26-, and 64-m diameter antenna dishes"
Command Module and Program Changes"
9!
•# Selection of landing sites, 5 types:"•# High latitudes"•# Maria"•# Inside craters"•# Near rilles or “wrinkles”"•# In mountainous areas"
•# General objectives for lunar science:"•# Lithosphere"•# Gravitational and magnetic fields"•# Solar protons and cosmic radiation"•# Astronomical observatories"•# Studies of proto-organic material" 10!
•# “The Apollo project is primarily a ‘glorious adventure’”"•# Technical/financial problems in Gemini program;
removal of Holmes, Mueller replacement"•# USAF experience in configuration and logistics
management, Gen’l. Sam Phillips"•# Request for long-range plans for program management"•# Associate administrators"•# Termination of Saturn I after 10 flights"•# JFK assassination, criticism of NASA’s priorities"
11!
•# Block I (Earth orbital) and Block II (lunar) versions of the CM"
•# Stabilizing the CM during launch abort"•# Land or water touchdown"•# Design Reference Mission; division of
responsibilities between NAA and Grumman"•# Probe-and-drogue docking adapter"•# Mockup Review Board"•# Parachute failure in Little Joe II test"•# From fixed to controlled fins on LJII"
12!
13!
Lunar Module Cabin!(in construction)"
14!
Lunar Landing Flight Simulators"Lunar Landing Research Facility" Lunar Landing Research Vehicle"
Lunar Landing Training Vehicle Cockpit"
15!
Ground-Based Lunar Landing Simulators, NASA JSC/KFC"
16!
•# A truly unique vehicle; means of transportation and a shelter"
•# Tom Kelly, Grumman, “Father of the LEM”"•# Increased lift capability of Saturn V allowed
LEM mass to be increased"•# Placement and shape of components,
systems, window, and hatches"•# Ingress and egress"•# Concern about ascent stage rocket firing “in
the hole”"•# CM and LEM instruments as similar as
possible"
Tom Kelly"
17!
•# Astronauts played a critical role in the design of the CM and LM"
•# Electroluminescence, Conrad"•# Standing allowed crew to be closer to the
•# Early testing at Aerojet General, NASA Lewis Research Center"
•# Centaur upper stage"•# 6-RL-10 engines
used on Saturn 1 S-IV stage"
•# Succeeded by one J-2 engine on SIVB"
Unconventional Cryogenics: RL-10 and J-2"
28!
29!
S-IVB with single J-2 engine""
30!
•# 1st stage of the Saturn V to be designed"•# Started before von Braun group transferred from ABMA to NASA"•# Rationale for choosing Douglas to build the S-IV and S-IVB"
From the S-IV to the S-IVB"
31!
•# Coasting orbit, restart capability"
•# Expansion of launch window"
•# Volumetric considerations for hydrogen and oxygen tank positions"
•# Fabrication and manufacturing"•# “Waffle-shaped” integral stiffening of the skin"•# Reliance on aviation production technology"•# Ullage rockets? Retro-rockets?"•# Domes and hemispheric common bulkhead"•# Thin aluminum shells"•# Self-supporting structures rather than reliance on internal
pressure (Atlas, Centaur)" 32!
•# Proportions of the stages"•# Both used brand new technology
extensively"•# Welding, forging, materials"
•# S-IC off to a better start"•# S-II left to make up for end-game
problems, as S-IC and S-IVB were further along in development "
Lower Stages:S-IC and S-II"
33!
34!
•# S-IC and the Huntsville connection"•# Tools and tankage"•# Few but cumbersome components"•# Fabrication and manufacture"
35!
36!
37!
•# S-II Concepts"•# Configuration"•# Systems"•# Trial and error: the welding problem"•# Management difficulties at NAA"•# Importance of NASA HQ intervention"
38!
Space Vehicle Design!
39!
Launch Vehicle Configuration Design Goals "•# Minimum weight -> sphere"•# Minimum drag -> slender body"•# Minimum axial load -> low thrust"•# Minimum gravity loss -> high thrust"•# Maximum payload -> lightweight structure, high
mass ratio, multiple stages, high specific impulse"•# Perceived simplicity, improved range safety ->
single stage"•# Minimum cost -> low-cost materials, economies of
•# Dynamic loads"–# Bending and torsion"–# Pogo oscillations"–# Fuel sloshing"–# Aerodynamics and thrust
vectoring"•# Acoustic and mechanical vibration
loads"–# Rocket engine"–# Aerodynamic noise"
42!
Structural Material Properties"•# Stress, !!: Force per unit area"•# Strain, "": Elongation per unit length"
! = E "•# Proportionality factor, E: Modulus of elasticity, or Young s modulus"•# Strain deformation is reversible below the elastic limit"•# Elastic limit = yield strength"•# Proportional limit ill-defined for many materials"•# Ultimate stress: Material breaks"
Poisson s ratio, #:"
! = "lateral"axial
,
typically 0.1 to 0.35Thickening under compression"
Thinning under tension"
43!
Structural Material Properties"
Material Properties (Wikipedia)Young's Modulus, GPa
Structural Stiffness"•# Geometric stiffness of a structure that bends about
its x axis is portrayed by its area moment of inertia"
Ix = x z( )z2 dzzmin
zmax
!•# Area moment of inertia for simple cross-sectional
shapes"•# Solid rectangle of height, h,
and width, w:"•# Solid circle of radius, r:"•# Circular cylindrical tube with
inner radius, ri, and outer radius, ro:"
Ix = wh3 /12
Ix = !r4 / 4
Ix = ! ro4 " ri
4( ) / 4
45!
Structural Stiffeners"•# Axial stiffeners provide high
Ix per unit of cross-sectional area"
•# Circular stiffeners increase resistance to buckling"
•# Honeycomb and waffled surfaces remove weight while retaining Ix"
46!
Propellant Tank Configurations!for Launch Vehicles"
Serial tanks with common bulkhead"
Separate serial tanks" Parallel tanks"
47!
Mercury-Redstone Structure"
Semi-monocoque structure (load-bearing skin stiffened by internal components)"
External skin, internal tanks separated by longerons and circular stiffeners"
Aerodynamic and exhaust vanes for thrust vectoring "
48!
Hoop, Axial, and Radial Stresses in Pressurized, Thin-Walled Cylindrical Tanks"
For the cylinder"R : radiusT : wall thicknessp : pressure! : stress
! hoop = pR /T! axial = pR / 2T
! radial " negligible
For the spherical end cap"! hoop =! axial = pR / 2T! radial " negligible
Cylinder hoop stress is limiting factor, $hoop > $axial" 49!
Weight Comparison of Thin-Walled Spherical and Cylindrical Tanks
(Sechler, in Space Technology, 1959)"
•# Pressure vessels have same volume and same maximum shell stresses due to internal pressure; hydraulic head* neglected"•# Rc = cylindrical radius"•# Rs = spherical radius"
•# Weight increases as L/D increases"* Hydraulic head = Liquid pressure per unit of weight x load factor" 50!
Staged Spherical vs. Cylindrical Tanks !(Sechler, in Space Technology, 1959)"
51!
Comparison: pressure vessels have same volume and same maximum shell stresses due to internal pressure with and
without hydraulic head (with full tanks)"
Numerical example for load factor of 2.5"Cylindrical tanks lighter than comparable spherical tanks"
Common bulkead even lighter"
Critical Axial Stress in Thin-Walled Cylinders!(Sechler, in Space Technology, 1959)"
•# Compressive axial stress can lead to buckling failure"
•# Critical stress, !!c, can be increased by"
–# Increasing E"–# Increasing wall thickness, t"
•# solid material"•# honeycomb"
–# Adding rings to decrease effective length"
–# Adding longitudinal stringers"
–# Fixing axial boundary conditions"
–# Pressurizing the cylinder"
52!
SM-65/Mercury Atlas"•# Launch vehicle originally designed with
“balloon” propellant tanks to save weight"–# Monocoque design (no internal bracing or
stiffening)"–# Stainless steel skin 0.1- to 0.4-in thick"–# Vehicle would collapse without internal
pressurization"–# Filled with nitrogen at 5 psi when not fuelled"
•# Pressure stiffening effect"–# No internal pressure"
! c
E= 9 t
R"#$
%&'1.6
+ 0.16 tL
"#$
%&'1.3
–# With internal pressure"
! c
E= Ko + Kp( ) tR
where
Ko = 9tR
"#$
%&'0.6
+ 0.16 RL
"#$
%&'1.3 t
R"#$
%&'0.3
Kp = 0.191pE
"#$
%&'
Rt
"#$
%&'2
53!
Force and Moments on a Slender Cantilever (Fixed-Free) Beam"
•# Idealization of "–# Launch vehicle tied-down to a
launch pad"–# Structural member of a payload"
•# For a point force"–# Force and moment must be
opposed at the base"–# Shear distribution is constant"–# Bending moment increases as
moment arm increases"–# Torsional moment and moment
arm are fixed"
54!
Bending Stiffness"•# Neutral axis neither shrinks nor stretches in bending"•# For small deflections, the bending radius of curvature of
the neutral axis is"
r = EIM
Deflection at a point characterized by displacement and angle:"
55!
Bending Deflection"
Second derivative of z and first derivative of ! are inversely proportional to the bending radius:"
d2zdx 2
= d!dx
=My
EIy
56!
Buckling"
•# Predominant steady stress during launch is compression"
•# Thin columns, plates, and shells are subject to elastic instability in compression"
•# Buckling can occur below the material s elastic limit"
! cr =C" 2EL / #( )2
= PA
Critical buckling stress of a column (Euler equation)"
C = function of end " fixity"E = modulus of elasticityL = column length
! = I A = radius of gyrationPcr = critical buckling loadA = cross sectional area 57!
Effect of Fixity on Critical Loads for Beam Buckling"
Crippling vs. Buckling"
58!
•# Euler equation"–# Slender columns"–# Critical stress below the
elastic limit"–# Relatively thick column
walls"•# Local collapse due to thin
walls is called crippling"
Quasi-Static Loads!(Spacecraft Systems Engineering, 2003)"
59!
Springs and Dampers"
fx = !ks"x = !ks x ! xo( ) ; k = springconstant
fx = !kd"!x = !kd"v = !kd v ! vo( ) ; k = dampingconstant
Force due to linear spring"
Force due to linear damper"
60!
Mass, Spring, and Damper"
!!!x = fx m = "kd!!x " ks!x + forcing function( ) m
!!!x + kd
m!!x + ks
m!x = forcing function
m
!!!x + 2"# n!!x +# n2!x =# n
2!u
!n = natural frequency, rad /s" = damping ratio#x = displacement#u = disturbance or control
Newton s second law leads to a second-order dynamic system"
61!
Response to Initial Condition"
•# Lightly damped system has a decaying, oscillatory transient response"
•# Forcing by step or impulse produces a similar transient response"
! n = 6.28 rad / sec" = 0.05
62!
Oscillations"
!x = Asin "t( )
!!x = A" cos "t( )= A" sin "t +# 2( )
!!!x = "A# 2 sin #t( )= A# 2 sin #t +$( )
•# Phase angle of velocity (wrt displacement) is $$/2 rad (or 90°)"•# Phase angle of acceleration is % rad (or 180°)"•# As oscillation frequency, & varies"
–# Velocity amplitude is proportional to &%%–# Acceleration amplitude is proportional to &2"
63!
Frequency Response of the 2nd-Order System"
•# Bode plot"–# 20 log(Amplitude Ratio) [dB] vs. log &%%–# Phase angle (deg) vs. log &%%
•# Natural frequency characterized by"–# Peak (resonance) in amplitude
response"–# Sharp drop in phase angle"
•# Acceleration frequency response peak occurs at natural frequency!!
•# Convenient to plot response on logarithmic scale"
ln A(!)e j" (! )[ ] = lnA(!) + j"(!)
64!
Acceleration Response of the 2nd-Order System"
•# Important points:"–# Low-frequency acceleration
response is attenuated"–# Sinusoidal inputs at natural
frequency resonate, I.e., they are amplified"
–# Component natural frequencies should be high enough to minimize likelihood of resonant response at input frequencies experienced in flight"
65!
Pogo Oscillation "!# Longitudinal resonance of the launch vehicle structure "
!# flexing of the propellant-feed pipes induces thrust variation"!# Gas-filled cavities added to the pipes, damping oscillation"!# Problem experienced on Saturn 5, Titan 2, (±2.5 g), other vehicles"!# Pogo oscillation http://history.nasa.gov/SP-4205/ch10-6.html"
66!
Pogo Oscillation Mitigation for Ares I Launch Vehicle "
67!“This concept is expected to reduce the G-forces on the
•# Margin of Safety"–# the amount of margin that exists above the
material allowables for the applied loading condition (with the factor of safety included) , Skullney, Ch. 8, Pisacane, 2005"
Load (stress) that causes yield or failureExpected service load
79!
Bending Moment due to a Distributed Normal Force"
Flight through varying winds produces vibratory bending input"
N y(xs)!
80!
Bending Vibrations of a Free-Free Uniform Beam"
Mode shapes of bending vibrations"
81!
82!
Vibrational Mode
Shapes for Saturn 5"
Fundamental Vibrational Frequencies of Circular Plates"
f = natural frequency of first mode, Hz"
83!
Finite-Element Structural Model"TIMED Spacecraft" •# Grid of elements, each with "
–# mass, damping, and elastic properties"
–# 6 degrees of freedom"
84!
Next Time:!
85!
Early Robotic Lunar Spacecraft: Ranger, Surveyor, and Lunar Orbiter"
Lunar Impact: A History of Project Ranger, NASA-SP-4210!
Unmanned Space Craft Management: Surveyor and Lunar Orbiter, NASA-SP-4901"
"Spacecraft Attitude Dynamics and Control:"!
Understanding Space, Sec 12.1, 12.2!
Supplemental Material!
86!
Heritage in Building High-Performance Aircraft"North American" Grumman"
87!
•# Automatic checkout"•# Launch sequencing and control"•# Launch vehicle guidance and
control"
The Quintessential Computer"
88!
Apollo Launch Vehicles"Saturn IB" Saturn V"
89!
Command Module"Service Module"
Lunar Module"
90!
Apollo"Command Module"
Service Module"
Lunar Module"
91!
Apollo Command and Service Modules (CSM)"!# 3-person crew"!# Autonomous
guidance and control capability"
92!
Apollo !Lunar Module (LM)"
93!
Saturn Checkout – Control Center "
94!
Saturn Checkout - Vehicle "
95!
96!
F-1 Engine Start from Command Module"
97!
Saturn ST-124 Inertial Measurement Unit "
98!
Specific Impulse of Launch Vehicle Powerplants"
99!
Vertical Takeoff, Horizontal Landing Vehicles"
•# Martin Astro-Rocket" •# General Dynamics Triamese"
•# Heat shield-to-heat shield" •# Three identical parallel stages"
100!
Horizontal vs. Vertical Launch"•# Feasibility of airline-like operations?"•# Use of high Isp air-breathing engines"•# Rocket stages lifted above the sensible atmosphere"•# Flexible launch location, direction, and time"
101!
Specific Energy Contributed in Boost Phase"
•# Total Energy = Kinetic plus Potential Energy (relative to flat earth)"
•# Specific Total Energy = Energy per unit weight = Energy Height (km)"
E = mV2
2+mgh
E ' = V2
2g+ h
102!
Specific Energy Contributed in Boost Phase"
•# Specific Energy contributed by 1st stage of launch vehicle"–# Less remaining drag loss (typical)"–# Plus Earth s rotation speed (typical)"