Meeting

1
Engineering 176
(Space) Machine DesignMeeting 2 January 30,
2003
Dr. Rick Fleeterrfleeter_at_mindspring.comcell
703 599.5885 http//www.rickfleeter.com
2
Review of Last time

• Why space
• Scaling
• Wilderness ( arbitary)
• Large v. Small
• Democratization
• Efficiency
• Course Overview
• Teams
• Design build
• Books
• Mission Samples
• Design Process
• Assignment

• On Design
• Complexity strata
• Linear design roadmap

3
(Re) Orientation

• 1 - Introduction
• 2 - Propulsion ?V
• Rockets the Rocket Equation
• Rocket applications
• Thermochemistry- The Space Environment
• Vacuum / Thermal
• Radiation / Chemical / Debris
• 5 - Navigation Control Instruments (Rogers)
• 4 - Orbits Orbit Determination GPS
• 3 - Launch Vehicles (Pedlikin)
• 6 - Power Mechanisms

• 7 - Radio Comms
• 8 - Thermal / Mechanical Design. FEA
• 9 - Reliability
• 10 - Digital Software
• 11 - Project Management Cost / Schedule
• 12 - Getting Designs Done
• 13 - Design Presentations

4
Homework Questions Review

• Your missions for January 30
• Come up with 3 mission suggestions prepare to
  present 1
• Read SMAD Chapter 1 (pp. 1 - 18) look at
  Chapter 17 (pp. 685-718)
• Read TLOM Chapter 1 (pp. 3 - 6) Read Chapter 2
  (pp. 7 - 34) (note the Roman numeral pages are
  painless)

5
Homework Questions Preview

• 1 - Propulsion system for Phobos Landing
• Requirements
• Electricity (100W)
• 1 km/s ?V
• Small bursts for ACS soft landing
• 100N deceleration burns (pulse or vernier)
• Pick a Propulsion System
• Justify via (1 or more of these)
• Calcs
• Tradeoffs vs. alternatives
• Qualitative (bullets?) advantages
• Sketch major elements of system
• Tanks, pressurization, fluid mgt.
• Valves, nozzles, electrical
• Thrust Vector Control

• 2 - Trip to Phobos Space Environment
• Assume cubic spacecraft of 2m characteristic
  length
• What is P(impact) with object of dimension 1 mm3
  or larger during 4 year interplanetary cruise?
• What is Total Ionizing Dose (TID) for the cruise?
• What is largest disturbance torque during cruise?
  What might be 2 and 3?
• Design Milestones
• Form teams (3 - 4 members)
• Mission Statement
• Requirements Definition

6
Propulsion Requirements
Conundrum Propulsion, ?V or orbits first?
Application ?V Requirement (meters /
sec) (note m/s x 2 mi/hr) Transfers
from Piggyback Orbits 100 to 2000 GTO to
Interplanetary transfer 1000 to 2000 Leaving
the solar system gt10,000 Orbit
installation constellation setup 10 -
100 Geosynch setup 10 - 100 Orbit
Maintenance constellation position
(3years) 100 - 500 geosynch position (10
years) 1000 - 2000 sun synchronicity (3
years) 100 - 300 (insertion dependent)
 Orbit Trim docking 100
harmonic 100 to 300 per site
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Other Propulsion Applications
Application Special Requirement Attitude
control Small impulse bit Plume
Studies Multiple propellants Chemical
Lasers Homogenous combustion Gas
Generation Low exit plume temperature Note
2C12H26 37O2 -gt 24CO2 26H2O and tailored
burn time But 3N2H4 -gt 4NH3 1N2
Thrust Thrust Isp  Thermal
Batteries Burn time Bootstrap
pumps Simplicity, benign plume
Manufacturing Controlled heat release
8
Propulsion considerations for ACS
For bang-bang - propellant efficiency not as
important as minimum impulse bit For
momentum wheel - wheel is impulse capacitor -
makes min impulse bit less critical -
propellant efficiency counts Valve / Thruster
hardware mass is more important (lots of
axes) Duty cycle may be very low
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Propulsion Fundamentals - 1
Impulse Mass x Velocity I kg x m /
s If you weigh 100 kg and throw 1 kg _at_ 100
m/s... I 1 x 100 100 kg m/s ?V I/M 100
kg x m/s ? 100 kg 1 m/s
Specific Impulse Impulse per unit mass of
propellant SI I / M m / s kg x m/s ? kg
m/s Isp SIm/s/ gm/s2 Isp seconds
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Propulsion Fundamentals - 2
Impulse Mass x Velocity I kg x m /
s If you weigh 100 kg and throw 1 kg _at_ 100
m/s... I 1 x 100 100 kg m/s ?Vi I/M
100 kg x m/s 100 kg 1 m/s
?V ?i Vi?mpi/(M(p)) gt V?dm/M (from MMo to
MMbo) Vln(Mo/Mbo) gIspln(Mo/Mbo)
gIspln(R) Where gIsp includes pressure effects R
is the mass ratio mass(start) / mass (burnout)
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Rocket Impulse Momentum Pressure
Isp (Velocity x (kg/s) Pressure x Area) ?
mass flow rate (momentum flux pressure
force) per mass flux (kg m/s2 kg m2 /m s2)
? (kg / s) m/s ! (?g)
Sample calculation 3000 m/s exit velocity
(300 s Isp) 1500 psi chamber (100 atm) gt
momentum flux ? mass flow 3000 m/s Pressure
force ? mass flow P x A / r x A x V P / r x
Ve P 107 kg/ms2 (Pascal) r 20 kg/m3
(perfect gas state equation) Ve 1000 m/s
(sonic velocity throat condx) r (30 g/22.4)
litre_at_STP 1.3kg/m3 x 100atm ? 2000 x 300 gt
Pressure ? mass flow P/r x Ve 107/20x103)
500 m/s (about 17 of total Isp contribution)
12
P vs. V back of envelope check
13
Choosing Your Molecule
Isp a exit velocity a sonic velocity g R T /
M1/2 gt Maximize g (Cp / Cv) (minimum
of molecules, tight bonds, low mass) (g Helium
1.667, g Nitrogen 1.4, g large molecules
_at_1.1) (when you add heat energy to large
molecules, little of it goes to V, hence P) gt
Maximize T (highly energetic reactions, light,
small products) (some electric propulsion
systems are essentially heaters) gt Minimize M
(low molecular mass products - like
H2O)(Question of dissociation - helps lower M,
reduces T, increases reactivity)
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Power of Propulsion - example 1
Thrust ve (dm/dt) gt 1 Newton 1 kgm/s2 ve
gIsp 3000 m/s (for typical chemical reactive
propellants) gt (dm/dt) 1/3000 3.3x10-4 kg/s
(for 1 N) Energy 1/2 mV2 and Power dE/dt
1/2 (dm/dt) V2 P(1N) 1/2 x 3.3x10-4 kg/s x
(3000 m/s)2 1.5x103 kgm2/s3 Note that F(dm/dt)
x Ve kgm/s2 1.5 kW (per Newton) gt per
Newton of force (constant) dm/dt 1/Ve and P
1/2 dm/dt x Ve2 1/2 x (1/Ve) x Ve2 So power per
Newton 1/2 Ve (propellant efficiency _at_
T(fixed) a power available) Check units P
kgm2/s3 F kgm/s2 gt P/F m/s v
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Power of Propulsion - Example 1
Thrust ve (dm/dt) gt 1 Newton 1 kgm/s2 ve
gIsp 3000 m/s (for typical chemical reactive
propellants) gt (dm/dt) 1/3000 3.3x10-4 kg/s
(for 1 N) ?h ?cpdT cp(avg)x ?T (2500j/kg
K) x 1500K 3.8x106 j / kg Power dH/dt
(dm/dt) ?h 3.3x10-4 kg/s x 3.8x106 j / kg
1.3x103 watt (i.e. j/s) 1.3 kW per Newton
16
Power of Propulsion - Examples 2 3
2 For 100,000 lbf thrust 445000 N, (1 lb x
9.8 / 2.2 ) P _at_ 1.5kW/N 670 MW (rule of
thumb 1 kW 1 household gt 100klb 1
city) 3 For high Isp (2000 s) P/N 1/2Ve
10,000 m/s 10 kW/N Typical EP h 50 gt
20 kW/N gt 100W yields about 5 x10-3N Acc
Thrust / Mass 5 x10-3N / 100 kg 5
x10-5m/s2 To achieve 10 km/s is 104m/s / 5
x10-5m/s2 2 x108s 2300 days 6 years (But with
1 MW, acc 5 x10-1m/s2 gt t 0.2 days)
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Solar Sailing
Solar Thrust Approximation Ts(per unit area)
Cs / c 1340 W/m2 / 3 x 108 m/s(force x
distance / time) ? (distance / time) 1.34 x
103 kgm2/s3m2 / 3x108 m/s 4.5x10-6kg / m s2
kg m / s2 x 1/m2 N / m2 Thus even at 104 m2, Ts
4.5x10-2 N For m 10 kg (including sail), acc
4.5x10-3 m/s2 gt to reach 10 km/s 104 m/s
takes 2.2x106 sec 25 days But can you build a
10,000 m 2 controllable sail plus payload for 10
kg? if density is (SOA) 10g/m2 gt 250
days (Note solar sail h much lower than EP)
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Rocket Catalogue
Compounds  nitrogen (simple, safe Isp around
45s)  helium (ditto, ,Isp around 60s)  ammonia
(denser storage but phase separation, Isp
50s)  hydrazine (monopropellant, highly toxic,
Isp 220s), N2O4 / MMH (highly toxic
corrosive but stores at room temp, hypergolic,
Isp low 300s range, 100s/lb)  LOX / Kerosene
(LOX must be loaded just before launch, cheap,
clean, Isp up to low 300s)  LOX / hydrogen
(low density, expensive, hard to produce store
but very high Isp - over 400s) Isp upper
200s to 300s, prepackage solution, long term
storage, very high thrust possible, short burn
times Pulsed Plasma (teflon propellant Isp
1000 to 2000s) Ion thrusters (xenon Isp around
1500s) Arc jets (many propellants Isp 500s
range) LOX / rubber, LOX / Kerosene (safety
comparable with LOX / kerosene, now in RD).
Lower performance compounds in use by amateurs
with Isp appx. 150s)
Categories Inert Gas Liquids Solids Elect
ric Hybrids
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Liquid Propulsion off-the-shelf
Class Propellant Application Advantages Isp
products Cold Gas Nitrogen ACS,
Astronauts Safe, storable, 40 _at_ room
temp Helium ACS, pressurize Safe, low mass, 65
_at_ room temp tanks Controllable V
ap. Ammonia ACS, Station Keep High Density 50
_at_ room temp Liquid like cold
gas Monoprop Hydrazine ACS, Station
Monoprop, 220 NH3, N2 N2H4 keeping
good Isp Biprop N2O4 / MMH Station keep,
Storable, high Isp 3l0 N2, H2O, NH3 ?
Orbit LOX / Kerosene Primary Propulsion Dense,
high Isp, 300 H2O CO2 C LOX /
Hydrogen Primary Propulsion High Isp 425 H2O
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Liquid Propulsion Custom
Propellant Pros Cons Readiness Hydrogen
Peroxide Dense Propellant Flew in 60s
Kerosene Storable Oxidizer / Engines in
dvt Impulse density low ? Oxidizer may
be unstable HAN-TEAN High density,
high Pressure range? Used in military guns Isp
Monoprop In test _at_ Allied/Signal, Hybrids
Safety, Control Low efficiency Prototypes built
and run LOX / Rubber Complex Used in amateur
rockets / High NRE Solar
Thermal Integrate Prop Needs hydrogen for high
Isp Current RD power high Isp System
efficiency low for flight demo Sun point
constraint Plasma Ion Huge Isp
(gt2000s) Huge Electric power (kw) Flying _at_
geo Solar Sail Infinite Isp - but at
Infinitesimal thrust Ground tests Large
deployable array Inner Solar System Only
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Rocket Buyers Guide
Safety Carcinogens caustics acids
explosives cryogenics suffocation
hazards  Isp performance (and do you
care?)  Mass fraction  Cost supplier
population - size and makeup safety integration
test maturity team familiarity flight
spares availability scalability multiple
uses  Reliability / Test-ability / hypergolic
or inert?  Applicability (control vs. total
impulse vs. thrust) min impulse bit duty cycle
range restart thermal requirements
storage leaks TVC throttling synergies
(electric power, heating, gas generation,
cooling, thermal battery...)  Ecology
Regulations transportation range and range
radius community applicable regulations Note
Huge criteria list means every candidate has
some advantages
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Rocket Engine Component Suppliers
Solids
Liquids
Components
TRW, Redondo Beach, CA - Big Dumb
Booster  Rocketdyne, Canoga Park - SSME
Aerojet, Sacramento, CA - Delta 2nd stage
Energia, Russia - 11D58M Energomash,
Russia - RD120, l80 Long March, China
- storable liquids AeroAstro - low cost
LOX/Kerosene
Allied/Signal - Fluid Handling
TVC  Kaiser Marquart, LA - Overwrap tanks
- Propellant valves Primex - low
thrust engines - propellants Pratt
Whitney - RL-l0 Upper Stage Janes -
Industry listing in print
Thiokol, Ogden Utah - Star,
Castor  United Technologies, San Jose, CA
- Orbus Hercules - Pegasus Israeli
Aircraft - Shavit launcher Fiat -
Ariane strapons Atlantic Research
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From Isp to ?V
For the 1 kg rock ?V -g Isp x ?M / M g
9.8 m/s Isp 10 s ?M 1 kg M 100 kg
?V _at_ 10x10x1/100 -1 m/s but M Mo - ?M
SV ?dV ?gIspdM/M gIsp?dM/M
gIspln(Mo/Mf)
?V Performance dry mass 50 kg
Isp 300 seconds
Isp 60 seconds
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Thoughts on ?V, Isp, Mass Fraction

• Typical large rockets put lt1 of their mass into
  orbit as payload, 9 of their mass is rocket, 90
  is propellant gt Mi - Mbo / Mi _at_ 0.9
• Typical jet transports are 1/3 fuel, 1/3
  structure, 1/3 payloadgt Mi - Mbo / Mi _at_ 0.33

15,000
5,000
Rocketry as proof of existence of...
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Generic Hydrazine System