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Parametric DesignPrinciples of Space Systems Design

Parametric Design

• The Design Process• Example: Project Diana

© 2001 David L. Akin - All rights reservedhttp://spacecraft.ssl.umd.edu

Parametric DesignPrinciples of Space Systems Design

Akin’s Laws of Spacecraft Design - #3

Design is an iterative process. Thenecessary number of iterations is onemore than the number you havecurrently done. This is true at anypoint in time.

Parametric DesignPrinciples of Space Systems Design

Overview of the Design Process

System-level Design(based on discipline-

oriented analysis)

Vehicle-level Estimation(based on a few

parameters from prior art)

System-level Estimation(system parameters based

on prior experience)

Program Objectives ✑System Requirements

Increasing complexity

Increasing accuracy

Decreasing abilityto comprehend the “bigpicture”

Basic Axiom:

Relative rankings betweencompeting systems willremain consistent fromlevel to level

Parametric DesignPrinciples of Space Systems Design

Regression Analysis of Existing Vehicles

Veh/Stage prop mass gross mass Type Propel lants Isp vac isp sl sigma eps delta( l b s ) ( l b s ) ( s e c ) ( s e c )

Delta 6925 Stage 2 13 ,367 15 ,394 Storab N2O4-A50 319.4 0.152 0.132 0.070Delta 7925 Stage 2 13 ,367 15 ,394 Storab N2O4-A50 319.4 0.152 0.132 0.065Titan II Stage 2 59 ,000 65 ,000 Storab N2O4-A50 316.0 0.102 0.092 0.087Titan III Stage 2 77 ,200 83 ,600 Storab N2O4-A50 316.0 0.083 0.077 0.055Titan IV Stage 2 77 ,200 87 ,000 Storab N2O4-A50 316.0 0.127 0.113 0.078Proton Stage 3 110 ,000 123 ,000 Storab N2O4-A50 315.0 0.118 0.106 0.078Titan II Stage 1 260 ,000 269 ,000 Storab N2O4-A50 296.0 0.035 0.033 0.027Titan III Stage 1 294 ,000 310 ,000 Storab N2O4-A50 302.0 0.054 0.052 0.038Titan IV Stage 1 340 ,000 359 ,000 Storab N2O4-A50 302.0 0.056 0.053 0.039Proton Stage 2 330 ,000 365 ,000 Storab N2O4-A50 316.0 0.106 0.096 0.066Proton Stage 1 904 ,000 1 ,004 ,000 Storab N2O4-A50 316.0 285.0 0.111 0.100 0.065

average 3 1 2 . 2 2 8 5 . 0 0 . 1 0 0 0 . 0 8 9 0 . 0 6 1standard deviation 8 . 1 0 . 0 3 9 0 . 0 3 3 0 . 0 1 9

Parametric DesignPrinciples of Space Systems Design

Regression Analysis

• Given a set of N data points (xi,yi)• Linear curve fit: y=Ax+B

– find A and B to minimize sum squared error

– Analytical solutions exist, or use Solver in Excel

• Power law fit: y=AxB

• Polynomial, exponential, many other fits possible

error Ax B yi ii

N= + −( )∑

=

2

1

error A x B yi ii

N= + −[ ]∑

=log( ) log( )

2

1

Parametric DesignPrinciples of Space Systems Design

Regression Analysis of Inert Mass Fraction

Hypergolic stages

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0.080

0.090

0.100

1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07

Hypergolic stages

Stage Gross Mass (lbs)

Inert MassFraction

Parametric DesignPrinciples of Space Systems Design

Regression Values for Design Parameters

Isp (vac) delta Max DV( s e c ) ( m / s e c

LOX/LH2 4 3 3 0.078 1 0 8 2 5L O X / R P - 1 3 2 0 0.063 8 6 7 0Storables 3 1 2 0.061 8 5 5 2Solids 2 8 3 0.087 6 7 7 2

Parametric DesignPrinciples of Space Systems Design

Project Diana - Mission Statement

Design a system to return humans tothe moon within the shortest feasibletime span for the minimum achievablecost.

Parametric DesignPrinciples of Space Systems Design

Project Diana - Requirements Document

• System must be based on the use ofAmerican launch vehicles in operationalstatus as of 2005

• System shall be at least as capable forlunar exploration as the J-mission Apollosystem– Two landed crew– 72 hour stay time, 3 x 6 hour EVAs– 300 kg of science payload (each way)

Parametric DesignPrinciples of Space Systems Design

American Heavy-Lift Vehicles (2005)

• Space Shuttle -27K kg to LEO

• Delta IV Heavy -23K kg to LEO

Parametric DesignPrinciples of Space Systems Design

∆∆∆∆V Requirements for Lunar MissionsTo:

From:

Low EarthOrbit

LunarTransferOrbit

Low LunarOrbit

LunarDescentOrbit

LunarLanding

Low EarthOrbit

3.107km/sec

LunarTransferOrbit

3.107km/sec

0.837km/sec

3.140km/sec

Low LunarOrbit

0.837km/sec

0.022km/sec

LunarDescentOrbit

0.022km/sec

2.684km/sec

LunarLanding

2.890km/sec

2.312km/sec

Parametric DesignPrinciples of Space Systems Design

Mission Scenario 1

• What can be accomplished with a single shuttlepayload (27K kg)?

• Assume δ=0.1, Isp=320 sec• Direct landing

– LEO-lunar transfer orbit ∆V=3.107 km/sec– Lunar transfer orbit-lunar landing ∆V=3.140 km/sec– Lunar surface-earth return orbit ∆V=2.890 km/sec– Direct atmospheric entry to landing

Parametric DesignPrinciples of Space Systems Design

Scenario 1 Analysis• Trans-lunar injection

• Lunar landing– r=0.3674– mLS=1958 kg

• Earth return– r=0.3978– mER=583 kg

r eTLI

V

gITLI

sp= =−

0 3713.

m m r kgTLI o TLI= −( ) =δ 7325

This scenario would work for amoderate robotic sample returnmission, but is inadequate for ahuman program.

Parametric DesignPrinciples of Space Systems Design

Mission Scenario 2

• Assume a single shuttle payload is used to sizethe lunar descent and ascent elements

• Assume δ=0.1, Isp=320 sec• Direct landing

– LEO-lunar transfer orbit ∆V=3.107 km/sec– Lunar transfer orbit-lunar landing ∆V=3.140 km/sec– Lunar surface-earth return orbit ∆V=2.890 km/sec– Direct atmospheric entry to landing

Parametric DesignPrinciples of Space Systems Design

Scenario 2 Analysis• Lunar landing

– r=0.3674– mLS=7219 kg

• Earth return– r=0.3978– mER=2150 kg

• Trans-lunar injection– r=0.3713

Payload mass still too low forhuman spacecraft. TLI stagemass of 72,520 kg is too largefor any existing launch vehicle.(Ideal situation is to ensure 100%load factors on all launches.)

mm

rkgLEO

TLI

TLI

=−( )

99 520,

Parametric DesignPrinciples of Space Systems Design

Mission Scenario 3

• Assume three Delta-IV Heavy missions carryidentical boost stages which perform TLI andpart of descent burn

• Space shuttle payload completes descent andperforms ascent and earth return

• All other factors as in previous scenarios

Parametric DesignPrinciples of Space Systems Design

Scenario 3 Standard Boost Stage

• mo=23,000 kg• mi =2300 kg• mp =20,700 kg• LEO departure configuration is three boost

stages with 27,000 kg descent/ascentstage as payload

• mLEO =96,000 kg

Parametric DesignPrinciples of Space Systems Design

Scenario 3 TLI Performance• Boost stage 1

– VTLI remaining=2345 m/sec• Boost stage 2

– r=0.7; ∆V2=1046 m/sec– VTLI remaining=1300 m/sec

• Boost stage 3– r=0.55; ∆V3=1300 m/sec– Residual ∆V after TLI=376 m/sec

∆V gIm m

mm

spLEO prop

LEO1 762= −

=ln sec

Parametric DesignPrinciples of Space Systems Design

Alternate Staging Possibilities

• Three identical stages• Serial staging (previous chart) ∆V=3483 m/sec• Parallel staging (all three) ∆V=3264 m/sec• Parallel/serial staging (2/1) ∆V=3446 m/sec• Pure serial staging is preferred

Parametric DesignPrinciples of Space Systems Design

Scenario 3 Ascent/Descent Performance

• 376 m/sec of lunar descent maneuver performedby boost stage 3

• Remaining descent requires 2764 m/sec– r=0.4143– mi=2700 kg– mLS=8485 kg

• Earth return– r=0.3978– mi=849 kg– mER=2528 kg

Return vehicle mass is stillsignificantly below that of theGemini spacecraft - need toexamine other numbers of boostvehicles

Parametric DesignPrinciples of Space Systems Design

Effect of Number of Boost Stages

0

500

1000

1500

2000

2500

3000

3500

Number of Boost Modules

Ear

th R

etu

rn P

aylo

ad (

kg)

Payload 583 1068 1809 2528 32290 1 2 3 4

Parametric DesignPrinciples of Space Systems Design

Baseline System Schematic - Project Diana

Boost Stage 123,000 kg

Boost Stage 223,000 kg

Boost Stage 423,000 kg

Boost Stage 323,000 kg

Descent/Landing Stage

16,160 kg

Ascent Stage7611 kg

Crew Cabin3299 kg

Parametric DesignPrinciples of Space Systems Design

Alternate Lunar Transport Architectures

• Transportation node at intermediate point (low lunarorbit, Earth-Moon L1)

• Leave systems at node if not needed on the lunarsurface, e.g.:– TransEarth injection stage– Orbital life support module– Entry, descent, and landing systems

• Will increase payload capacities at the expense ofadditional operational complexity, potential for safetycritical failures

Parametric DesignPrinciples of Space Systems Design

Mass Breakdown of Payload Systems• 27,000 kg assembly delivered to LEO by space shuttle• mi,orbit = orbital maneuvering module inert mass• mp,node = propellants for arrival at transport node• mp,TEI = trans Earth injection propellants• mi,asc = inert mass of lunar ascent vehicle• mp,asc = propellant mass of lunar ascent vehicle• mi,des = inert mass of lunar descent vehicle• mp,des = propellant mass of lunar descent vehicle• mL,node = payload transported to node and back• mL,LS = payload transported to/from lunar surface only• mL,thru = payload transported to/from lunar surface and

returned to Earth (assumed to be ≥500 kg)

Parametric DesignPrinciples of Space Systems Design

Variation 1: Lunar Orbit Staging• Assume same process as baseline, but use lunar

parking orbit before/after landing• Additional DV’s required for LLO stops

– Lunar landing additional ∆V=+31 m/sec– Lunar take-off additional ∆V=+53 m/sec

• Low lunar orbit waypoint changes baseline payloadto 3118 kg (-3.5%)

• Not useful without taking advantage of node tolimit lunar landing mass

Parametric DesignPrinciples of Space Systems Design

Variation 2: Lunar Orbit Rendezvous• Use specialized vehicle for descent/ascent• Use four boost stages as per baseline• Boost stage 4 residual propellants

– 10,680 kg following trans lunar insertion– 1315 kg following lunar orbit insertion– Use remaining stage 4 capacity to aid descent stage

• Leave TEI stage in lunar orbit during ascent/descent– Descent ∆V=2334 m/sec– Ascent ∆V=2084 m/sec– TEI ∆V=837 m/sec

Parametric DesignPrinciples of Space Systems Design

Baseline System Schematic - Project Diana

Boost Stage 123,000 kg

Boost Stage 223,000 kg

Boost Stage 423,000 kg

Boost Stage 323,000 kg

Descent/Landing Stage

16,160 kg

Ascent Stage7611 kg

Crew Cabin3299 kg

Parametric DesignPrinciples of Space Systems Design

LOR System Schematic - Project Diana

Boost Stage 123,000 kg

Boost Stage 223,000 kg

Boost Stage 423,000 kg

Boost Stage 323,000 kg

Descent/Landing Stage

15,010 kg

TEI Stage

Ascent Stage5811 kg

Crew Cabin4114 kg

2066 kg

Parametric DesignPrinciples of Space Systems Design

The Next Steps From Here

• Perform parametric sensitivity analyses– Inert mass fractions– Specific impulse– Size of entry package left in orbit

• Investigate reduction from 4 to 3 boost stagesfor minimal system

• Examine growth options allowed by system– One-way cargo variants– Larger module with more boost modules

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