ROCKET LAUNCH TRAJECTORY SIMULATION MECHANISM

https://ntrs.nasa.gov/search.jsp?R=20020052379 2017-09-02T11:30:24+00:00Z 0

Ravi Margasahayam 1

ROCKET

LAUNCH

TRAJECTORY

SIMULATION

MECHANISM

Ravi Margasahayam Dynacs John F. Kennedy Raoul National

address:

Center,

FL, USA

and Sharon

and Space

John F. Kennedy E-mail

Space

E. Caimi

Aeronautics

Inc.

Hauss

Administration

Space

Center,

(NASA)

FL, USA

Ravi. Margasahayam-1

@ksc.nasa.gov

Abstract The design Systems

and development

Testbed

(LST)

is outlined.

TSM serves

as a platform

subsequent

dynamic

launch

pad.

of a Trajectory

effects

tests in a laboratory

In addition

on the equipment researchers

environment rocket

scenario

Mechanism

to being

to study the interaction

For the first time,

tures in a moving

Simulation

one-of-a-kind

and assess

facility

of rocket launch-induced and structures

the impact equipment,

alike

in the world, vicinity

and of the

will be able to perform

of vibroacoustic launch

for the Launch

environments

in the close

and academicians

on ground

(TSM)

vehicle,

behavior

of struc-

and its valuable

pay-

load or spacecraft: INTRODUCTION A successful Historical

space data

mission

[1-3],

scaled and full-scale

analytical models

10] are all used in the design pad.

requires

Cost considerations

thorough

predictions

consideration [4,5],

ground

[3], engineering

judgment

cycle phases

of the launch

have placed

significant

of sound acoustic

and vibration and

vibration

[5,6], and test-analysis

emphasis

vehicle,

spacecraft,

effects. tests

correlation

on [7-

and the launch

on the use of analytical

methods

e

Ravi Margasahayam 2

and test techniques

that lead to overdesign.

are force-limited sound

vibration,

and vibration

uniform

Examples

of the results

test standards,

analytical

predictions.

of critical

structures

payload

of cost reduction

fill factors,

efforts

and more

accurate

Background There

are a number

engines,

and launch

Architects

and designers

quakes,

water

waves,

the discussion acoustic

must

loads

(e.g., bridges,

for which structural

consider

aerodynamic

of this paper

pressure

behavior

loads,

is limited

(Figure

the effect

The design

of launch

dynamic

pad structures,

by launch-induced activities,

exhibiting

dynamic

(e.g.,

earth-

cycle.

Since

loads

in the design accurate

supersonic

ground

reflections,

atmospheric

conditions,

duration,

vibroacoustic

coupling,

exposure material

or forcing mixing

characterization of structural

and geometrical

influence

their dynamic

comprehensive Because

and accurate

of

dynamic

with launch

novative

exhaust

definitely

prior

Acoustic

to fabrication

that seldom

but require impact

Over the last several

decades,

spacecraft, structures

launch types

aspects

[10].

acoustic

effi-

trajectory,

of deflectors, shielding,

of pad structures

the above factors

is especially

the design

also in any

However,

tests in the structural

response

and survivable

suppression

significant qualified Space

cost

to sys-

launch

water

early in the design

John F. Kennedy

acoustic

knowledge

of structural

of reusable

must be incorporated

NASA's

is incomplete

acute for new launch

like sound

fully and accurately

since full-scale

there

and in-

cycle and

overruns

have

prior to launch. Center

(KSC)

has led

analytical tools for accurate predicdynamic response of structures [6-9]. and vibration

testing of launch

and launch pad is often difficult and measurement of vibration is often cost prohibitive. Space Shuttle launches provide a unique

dynamic

laboratory

important

acoustic

the pad placement,

on the prediction

the way in the development of field-measurement-based tion of rocket launch-induced noise and subsequent This is especially

engines,

to include

environment,

features

and installation.

are all components

thrust,

patterns,

Moreover,

The problem

environment-mitigating

ducts.

directivity

The factors influencing

(rocket

clustered

ra-

(< 20 sec-

treatment.

or the Government

environment.

behavior.

and operational

of launch

tems that have never been launched facilities

sound etc.).

mounting,

nature

industry

acoustic

from

a large area-to-mass

are long-duration

are numerous

Thus, it is impossible

analytical

of the unique

the aerospace

launch-induced

attributes, behavior.

plumes

having

which

random

on any pad structure of exhaust

those

pressures,

nonstationary

ciency,

tegrate

rocket

importance.

to the understanding

particularly

acoustic

excitation

meant

aircraft,

is of the utmost

pressures)

pad structures

1) is paramount

acoustic

within

platforms,

of random

or acoustic

to launch

offshore integrity

[1 ].

tio, is governed onds)

pad structures)

design

analysis

process,

vehicles,

on launch pad platform to in-

not possible

in the

RaviMargasahayam 3

LAUNCH NASA

has designated

systems.

Under

sound,

this mandate,

(2) increase

new vehicles; continually above

the operational

increase

goals.

to meet varying

Simulation

LST is an avenue

overall

mission

structures

of design Mechanism

customer

costs

and mechanisms

(TSM),

for future

through

is to reduce

and infrastructure

four important

processing

goals:

in the design/development

core capabilities

of launch

aspects

knowledge

and payload

(1) ensure

are in place for private/commercial

new technologies

implemented

for launch

to address

techniques

to develop

LST's

availability

TESTBED

for Excellence

KSC is required

vibroacoustic

(3) partner

The newly

Brief

KSC as the Center

safe, and efficient

essing;

SYSTEMS

space needs

which

exposed

development

to rocket

are the focus

and

and (4)

will accomplish

the

safety,

reliability,

launch

environments.

of the Rocket

key LST components,

of payloads initiatives; and demands.

KSC

and increase

proc-

Launch

and

Trajectory

of this paper.

LST projects will focus on the following technical areas: • Predict, measure, and validate acoustic excitation models •

Enhance

structural

•

Develop

and evaluate

•

Analyze

exhaust

•

Optimize

•

Institute

rocket

•

personnel

data analysis, •

A unique

launch

•

result

of launch

pad designs

at launch,induced

response

significant

under

the Verification

mist's

dream

be generated

liftoff

test, launch

environment

experience

vibration,

strain,

etc.) database

for over

reservoir)

and structural

analysis

test facility

of LST is to simulate

estimates

acoustic

methodologies

to simulate

effort

for future provided

moving

to assess

rocket

in the lab; take the entire

behind testing

project. VETA

space

environments

vehicles

scenar-

for use in

for NASA.

The end

that yield more realistic

by the methods

currently

struc-

available.

MECHANISM

to measure

(VETA)

The premise

launch

models

SIMULATION

was undertaken

Test Article

come true.

small-scale

excitation

than those

TRAJECTORY At KSC,

dynamics,

in the real world

and evaluation

tural vibration

structural

(acoustics,

rocket

is to arrive

methodologies

fluid dynamics

as a knowledge

A unique,

One key objective testing

with acoustics,

prediction data

small-scale

scaling

vehicles

include:

Launch environments nonstationary random ios required

fluid dynamics

for new

and vibration

environment

(serving

systems

using computational

and computational

100 launches •

noise

methods

suppression

duct configurations

LST capabilities

Specialized

response

acoustic

plume

exhaust

The current

vibration

acoustic VETA testing

operation

loads proved

and vibration

response

to be a structural

[ 10] was if acoustic

to the field (Figure

dyna-

loads cannot

2). This totally

Ravi Margasahayam 4

eliminatedthe ambiguityof simulatingthelaunchenvironment.Despitethis,VETA series of testspavedthe way for validatingthevibrationresponsemethodologydevelopedovera decadeat KSC [7-9]. As outlinedearlier,launch-inducedacousticexcitationis anonstationaryandrandom andexhibitsnon-Gaussian behavior.Unlikevehiclesandpayloads,launchsupportstructures cannotbe testedandverified prior to launch.Fully valid acousticloadscanonly begeneratedby the launchof a full-scalevehiclein the strictestsense.Laboratoryacoustictests comecloseto applyingveryhigh acousticloads.However,theselackthetruesimulationof thedynamicnatureof thelaunchenvironment.Evena limited simulationof nonstationary randomenvironmentdisplayingcharacteristics of true acousticshasbeenlacking to date. A surveyof the literatureonsmall-scaletestingof rocketsdidnotrevealanypasteffort to simulatea testfacility thatcouldhandleamovingrocketscenarioto assess the impactof launch-inducedenvironmentson groundequipmentandstructureswithin the vicinity of the launchpad.Most studieshavereliedonstaticfiring of scaledor full-scaleengines.Someof theearlytestsincludedhorizontalfirings,yetsomeotherresearchers haveattemptedtotake acousticdataby moving therocket nozzlevertically or horizontallyin a stepwisemanner. Thesestaticor quasi-statictestsdo not simulatethelaunchenvironmentin a true sense. Lessonslearnedfrom literaturesurvey,enhancements to othertestfacilities,andthe experiencefromVETA werecarefullyincorporatedin thedevelopmentstageof TSM. One drawbackof VETA testingwasthe timefactor. To collectstatisticallysignificantdatanecessitatedyearsof testing. Designanddevelopmentof TSM capabilityaddressed theproblemof acquiringacousticalandvibrationdatafrom multiplelaunchesin a shorttime. Moreover,theTSM is usedtogenerateanonstationary, scaledacousticload. Ourprimarygoalin thedesignanddevelopmentof theTSM wasto eliminatethemostimportantdrawback- the ability to simulatethe launchtrajectoryin a dynamicsense,hithertonot attemptedby researchers.Thus,it wasplannedto designandconstructatestfacility thatis capableof being configuredto scaledlaunchenvironmentsof future vehicles. The scaledlaunchenvironmentswill be usedto predictthe full-scalelaunchenvironments. Performance TSM

Parameters

is a one-of-a-kind,

supersonic

scaled,

jet plume

trajectories

similar

to those generated

scaling trapment,

1 outlines

The overall

inducing

laboratory.

random

of a rocket.

exhaust

plume

of composite

combusting,

TSM

nonstationary

by the launch systems

assessment

and related

Table TSM.

while

suppression

methods,

single/multiple,

test and research

launch

tics, acoustic

moving,

is capable acoustic

LST projects

flow modeling,

structures,

fatigue

and noncombusting of simulating

loads

varied

on pad structures

will focus on vibroacousexhaust

duct optimization,

life prediction,

hydrogen

en-

areas. the general

project

requirements

plan, encompassing

that were developed cold jet tests followed

prior to the design by hot and combusting

of

RaviMargasahayam 5

jets,primarily drovetherequirements.Issuespertainingtothe useof liquid andsolid fuels andtheir impacton theTSM wereconsidered.Basedon theseneeds,the operablelife of TSM wasdeterminedto bearound10years.Thisis alleviatedby TSM's usagerateof 1500 rocketlaunchesper year,comparedto the SpaceShuttle'srateof 7 to 8 launchesperyear. Thedesignanddevelopmentof TSM capabilitieswerelargelybasedon U.S. launch industryrequirements.Table2 documentsperformancerequirementsof the TSM. The SpaceShuttlewill mostlikely bethemainstayof NASA's avenuefor theimmediatefuture. TheInternationalSpaceStation(ISS)goalsandobjectivesdrivethis use. Therefore,it was decidedto scaleverticalandhorizontaltravelbasedontheSpaceShuttlelaunchscenario.In addition,requirementsfor TSM verticalspeedsandhorizontalspeedsweredrivenby Space Shuttletrajectory. The travel speedscanbe preciselycontrolledin fractionalincrements. Thus,basedon theabove;theTSM wasdesignedtobe a 1/10-scale model.Literaturereview identifiedscalemodelsthatrangefrom 1/5to 1/12scale.Optimalvaluesfor thescaledtest facilities arein the 1/7-to-i/10range. TSM featuresa planarmotioncapabilitywith programmable trajectory.In anutshell,it is giantX-Y tablemountedvertically(Figure3). In additionto thesimulationoflinear (vertical) trajectory,anyparabolic(similartoShuttle)or othergenericprofilecanbeincorporated in thetestsequence.Thiswasdeemednecessary tosupporttheliftoff sequence of Delta,Titan,Atlas,andanyotherU.S.rockets.TSM will permitthesimulation(increase or decrease) of liftoff ratesandhandleany drift duringthe ascentstagesof the rocket as the tower is cleared.TSM canalsohandlenozzletilt requirements.Besidesprovidingthecapabilityto operateremotelyfrom over200meters,carewastakento minimizeflat reflectingsurfaces andincludeweatherprotectionfeaturesfor outdooruse. CONCLUSIONS A test capability acoustic namic

to simulate of acoustic

by the launch

induced

acoustic

mission

success.

the payload,

noise

TSM,

for the first time, will enable

launch

loads

vehicle,

and to generate

and help them on the design

LST research

and ground represents

trajectories

on pad equipment

and its influence

and development, systems.

accurately

of rockets

Immediate

LST therefore

tic research rocket

launch

loads is presented.. effects

generated

tems.

rocket

systems,

will focus

of ground on reducing new launch innovation to architects,

support

Impact equipment

acoustic exhaust

scaled

to study the dy-

the vibration

and structures.

to develop

not available

researchers

to assess

a leap in technological hitherto

nonstationary,

responses of launchis vital to

environments management

at sys-

in the area of vibroacousengineers

and designers

of

d,

Ravi

Margasahayam 6

REFERENCES

1.

"Acoustical Considerations in Planning and Operation of Launching and Static Test Facilities For Large Space Vehicles," Report No. 884, NAS8-2403 (December 1961) 2. "Acoustic and Vibration Environments and Test Specification Levels Ground Support Equipment Launch Complex 39," Document SP-4-38-D, NASA (July 1964) 3. "Sonic and Vibration Environments for Ground Facilities - A Design Manual," NAS-11217, Wyle Laboratories (March 1968) 4. R. Caimi, R. Margasahayam, and J. Nayfeh, "Rocket Launch-Induced Vibration And Ignition Overpressure Response," ICSV8, Hong Kong, China (July 2001) 5. "Acoustics Loads Generated by the Propulsion Systems," NASA-SP-8072 (1971) 6. "Environment and Test Specification Levels Ground Support Equipment for Space Shuttle System Launch Complex 39," Kennedy Space Center: NASA (1976) 7. "Procedure and Criteria for Conducting Dynamic Analysis of the Orbiter Weather Protection Structure," KSC-DM-3147 (September 1987) 8. "Computation of Generalized Modal Loads in an Acoustic Field Defined by a Distribution of Correlated Pressures," KSC-DM-3265 (August 1989) 9. "Validation of a Deterministic Vibroacoustic Response Prediction Model," NASA-TM-112649 (April 1997) 10. R. Margasahayam and R. Caimi, "Random Vibration Response of a Cantilever Beam to Acoustic Forcing by Supersonic Rocket Exhausts During a Space Shuttle Launch," ICSVS, Australia (December 1997)

Table

1.

TSM

General

Features

Feature Minimum Minimum

Lifecycle

Operable

Usage

Up to 1500 times

Payload

Weight

Exhaust

Duct

Launch Flex,

Rate

Envelope

lines

Remote

Control

Operation

Tilt

Axis

Protection Protection

per year;

(lb)(90.72

5 to 6 launches

kilograms

[kg]);

× 30 feet

per day

rocket

and flex

long

10 feet high x 30 feet wide × 30 feet long To be able to traverse in vertical and horizontal

direc-

freely

Operable

from

Ability

Reflecting Surfaces Weather Protection Lightening Malfunction

and pho-

tions

Transportable

of 10 years

10 feet high × 10 feet wide

Envelope

instrumentation,

tography

for minimum

200 pounds lines

Structure

Adjustable

Qualification

Mount

rocket

Minimize

operation

nozzles

in excess and move

of 700 feet to a different

up to 10 degrees

fiat and reflecting

Weatherproof Consideration Multiple

a distance

to disassemble

surfaces

from

for acoustics

paint and material selection due to location of TSM

redundant

safety

features

location vertical

built

in design in for fail-safe

axis

Ravi Margasahayam 7

Table

2. TSM Performance

Parameters

Parameter

Quantification

Rocket Vertical Thrust Rocket Vertical Motion

5 to 100 lbs.(2.27 kg to 45.36 kg) 30 ft maximum (9.14 m) and selectable

Rocket Horizontal

12 ft maximum

Rocket Vertical Rocket Horizontal Programmable

Motion Speed Speed

Trajectory

(3.66 m) and selectable

0-5 ft/s in 0.1 ft/s increments 0.031 rn/s)

(0.61 m/s in

0 to 2 ft/s in 0.1 ft/s increments 0.031 m/s) Motion

(0.24 m/s in

Planar motion with programmable trajectory option (linear, parabolic, or any generic profile)

KEY: VIBRATION RESPONSE GROUND VIBRATION

EXCITATION ACOUSTIC

@

TRANSMITTED

VIBRATION

ACOUSTICS

OF EQUIPMENT

AND LIGHT PANELS

@

,/_

FAR-FIELD

PAYLOAD

ACOUSTICS

VIBRATION

AIR AND STRUCTURE BORNE SOUND AND VIBRATION VIBRATION AND INTERIOR EQUIPMENT/FLOOR

TRANSMITTED ACOUSTICS

SOURCE ACOUSTIC

BUILDING GROUND VIBRATIONS

Figure

1. Effects

of Acoustics

on Pad Structures

AND

Ravi Margasahayam 8

Figure

Figure

2. Verification

3. Trajectory

Test Article

Simulation

Mechanism