Propulsion Systems Design • Lecture #23 - November 12, 2019 • Rocket Engine Basics • Survey of the Technologies • Propellant Feed Systems • Propulsion Systems Design

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Propulsion Systems Design • Lecture #23 - November 12, 2019 • Rocket engine basics • Survey of the technologies • Propellant feed systems • Propulsion systems design

© 2019 David L. Akin - All rights reserved http://spacecraft.ssl.umd.edu U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 1 Team Project #2 - Due 12/5/19 • Based on ENAE 484 teams • Requirements document draft – Level 1 requirements – Start of flow-down to levels 2, 3, 4… • Concept of operations • Prioritized list of trade studies • Analysis results to date on top-priority studies • Conceptual/“strawman” design (CAD, mass est.) • Plans for Spring term (notional schedule)

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 2 Propulsion Taxonomy

Mass Expulsion Non-Mass Expulsion

Thermal Non-Thermal

Ion Chemical Non-Chemical Solar Sail

MPD Laser Sail Nuclear Monopropellants Bipropellants Beamed Electrical Microwave Sail Cold Gas Solar MagnetoPlasma

Solids Hybrids Liquids Air-Breathing ED Tether

Pressure-Fed Pump-Fed

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 3 Thermal Rocket Exhaust Velocity • Exhaust velocity is

γ − 1 γ 2γ ℜTo pe ve = 1 − γ − 1 M¯ ( po ) where M¯ ≡ average molecular weight of exhaust Joules ℜ ≡ universal gas constant = 8314.3 moleoK γ ≡ ratio of specific heats ≈ 1.2

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 4 Ideal Thermal Rocket Exhaust Velocity • Ideal exhaust velocity is

2γ ℜTo ve,ideal = γ − 1 M¯ • This corresponds to an ideally expanded nozzle • All thermal energy converted to kinetic energy of exhaust • Only a function of temperature and molecular weight!

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 5 Thermal Rocket Performance • Thrust is · T = mve + (pe − pamb)Ae • Effective exhaust velocity · Ae c T = mc ⟹ c = ve + (pe − pamb) Isp = m· ( go ) • Expansion ratio

1 γ − 1 1 γ γ A γ + 1 γ − 1 p γ + 1 p t = e 1 − e Ae ( 2 ) ( po ) γ − 1 ( po )

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 6 Nozzle Design

• Pressure ratio p0/pe=100 (1470 psi-->14.7 psi) Ae/At=11.9

• Pressure ratio p0/pe=1000 (1470 psi-->1.47 psi) Ae/At=71.6

• Difference between sea level and vacuum Ve γ − 1 γ − 1 γ γ ve1 po − pe1 = γ − 1 γ − 1 ve2 γ γ po − pe2 • Isp,vacuum=455 sec --> Isp,sl=397 sec

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 7 Solid Rocket Motor

From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 11 Advanced Grain Configurations

From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 12 Liquid Rocket Engine

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 13 Liquid Propellant Feed Systems

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 14 Space Shuttle OMS Engine

From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 2001 U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 15 Turbopump Fed Liquid Rocket Engine

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 18 SpaceX Merlin 1D Engines

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 19 Falcon 9 Octoweb Engine Mount

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 20 Staged-Combustion Engine Schematic

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 21 RD-180 Engine(s) (Atlas V)

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 22 SSME Powerhead Configuration

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 23 SSME Engine Cycle

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 26 Injector Concepts

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 28 Solid Rocket Nozzle (Heat-Sink)

From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 30 Active Chamber Cooling Schematic

From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 33 Hybrid Rocket Combustion

From G. P. Sutton, Rocket Propulsion Elements (5th ed.) John Wiley and Sons, 1986 U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 35 Reaction Control Systems • Thruster control of vehicle attitude and translation • “Bang-bang” control algorithms • Design goals: – Minimize coupling (pure forces for translation; pure moments for rotation)except for pure entry vehicles – Minimize duty cycle (use propellant as sparingly as possible) – Meet requirements for maximum rotational and linear accelerations

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 36 Single-Axis Equations of Motion ⌧ = I✓¨ ⌧ t = ✓˙ + C I 1 ⌧ at t = 0, ✓˙ = ✓˙ = t = ✓˙ ✓˙ o ) I o 1 ⌧ t2 + ✓˙ t = ✓ + C 2 I o 2 1 ⌧ at t = 0, ✓ = ✓ = t2 + ✓˙ t = ✓ ✓ o ) 2 I o o 1 2 ⌧ ✓˙2 ✓˙ = (✓ ✓ ) 2 o I o U N I V E R S I T Y O⇣ F ⌘ Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 37 Attitude Trajectories in the Phase Plane

3.00%

2.00%

1.00%

0.00% !20.00% !10.00% 0.00% 10.00% 20.00% 30.00% 40.00%

!1.00% tau/I=0% !0.001% !0.002% !2.00% !0.003% !0.004%

!3.00% U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 38 Gemini Entry Reaction Control System

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 39 Apollo Reaction Control System

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 40 RCS Quad

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 41 Apollo CSM RCS Assembly

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 42 Lunar Module Reaction Control System

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 43 LM RCS Quad

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 44 Viking Aeroshell RCS Thruster

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 45 Viking RCS Thruster Schematic

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 46 Space Shuttle Primary RCS Engine

1 2 T p V = < 0 1 e e v ¯ u 1 M " po # u ✓ ◆ t M¯ = 28 p0 = 300 psi

T0 = 300 K pe =2psi = 8314.3 =1.4 < 1.4 1 2(1.4) 8314.3(300) 2 1.4 m V = 1 = 689 e v u1.4 1 28 " 300 # sec u ✓ ◆ t U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 49 Cold-gas Propellant Performance

• Total impulse It is the total thrust-time product for the propulsion system, with units

It = Tt =˙mvet ⇢V t = m˙

It = ⇢V ve • To assess cold-gas systems, we can examine total impulse per unit volume of propellant storage I t = ⇢v V e U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 51 Performance of Cold-Gas Systems

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 52 Self-Pressurizing Propellants (CO2)

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 53 Self-Pressurizing Propellants (N2O)

Density 625 kg/m3 Density 1300 kg/m3

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 54 N2O Performance Augmentation • Nominal cold-gas exhaust velocity ~600 m/sec

• N2O dissociates in the presence of a heated catalyst 2N2O 2N2 + O2 engine temperature ~1300°C! exhaust velocity ~1800 m/sec • NOFB (Nitrous Oxide Fuel Blend) - store premixed N2O/hydrocarbon mixture exhaust velocity >3000 m/sec

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 55 Pressurization System Analysis Adiabatic Expansion of Pressurizing Gas γ γ γ pg,0Vg = pg, f Vg + pl Vl Pg0, Vg Pgf, Vg Known quantities:

Pg,0=Initial gas pressure

P , V P , V L L L L Pg,f=Final gas pressure

PL=Operating pressure of propellant Initial Final tank(s)

VL=Volume of propellant tank(s)

Solve for gas volume Vg U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 56

€ Boost Module Propellant Tanks • Gross mass 23,000 kg – Inert mass 2300 kg – Propellant mass 20,700 kg – Mixture ratio N2O4/A50 = 1.8 (by mass) • N2O4 tank – Mass = 13,310 kg – Density = 1450 kg/m3 3 – Volume = 9.177 m --> rsphere=1.299 m • Aerozine 50 tank – Mass = 7390 kg – Density = 900 kg/m3 3 – Volume = 8.214 m --> rsphere=1.252 m U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 57 Boost Module Main Propulsion

3 • Total propellant volume VL = 17.39 m • Assume engine pressure p0 = 250 psi • Tank pressure pL = 1.25*p0 = 312 psi • Final GHe pressure pg,f = 75 psi + pL = 388 psi • Initial GHe pressure pg,0 = 4500 psi • Conversion factor 1 psi = 6892 Pa • Ratio of specific heats for He = 1.67 1.67 1.67 3 1.67 (4500 psi)Vg = (388 psi)Vg + (312 psi)(17.39 m ) 3 • Vg = 3.713 m p M ρ = g,0 • Ideal gas: T=300°K --> He ℜT 3 0 ρ=49.7 kg/m (4500 psi = 31.04 MPa) MHe=185.1 kg U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 58

€ € Autogenous Pressurization • Use gaseous propellants to pressurize tanks with liquid propellants • Heat exchanger to gasify and warm propellants, then route back into ullage volume • Eliminates need for pressurized gases for ullage and high-pressure storage bottles (e.g., Falcon 9 failures) • Issue: start-up transient

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 59 Nuclear Thermal Rockets • Heat propellants by passing through nuclear reactor • Isp limited by temperature limits on reactor elements (~900 sec for H2 propellant) • Mass impacts of reactor, shielding • High thrust system

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 60 Electrostatic Ion Thruster

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 61 Hall-Effect Thruster

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 62 Ion Engine Schematic

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 63 Ion Engines Existing/In Development • NSTAR (NASA Solar Technology Application Readiness) – DS1 and Dawn – 30 cm, 2.3 kW, 92 mN, 3120 sec • NEXT (NASA Evolutionary Xenon Thruster) – Available 2019 – 6.9 kW power, 236 mN thrust, Isp 4190 sec • HiPEP (High Power Electric Propulsion) – TRL 3 – 670 mN, 39.3 kW, 7 mg/sec prop, Isp 9620 sec

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 64 Variable Specific Impulse Magnetoplasma

By Source (WP:NFCC#4), Fair use, https://en.wikipedia.org/w/index.php?curid=35831241 U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 65 VASIMR Engine Concept

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 66 VASIMR Operating Specifications • Optimum operating point – Isp 5000 sec – Thrust 5.7 N – Power 200 kW • Can be derated for higher thrust at lower Isp • Compare to ion engines at equivalent power – 87 NSTAR thrusters: 8 N, 3120 sec Isp – 29 NEXT thrusters: 6.8 N, 4190 sec Isp – 5 HiPEP thrusters: 3.4 N, 9620 sec Isp

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 67 Solar Sails • Sunlight reflecting off sail produces momentum transfer T = 2m˙ V = 2m˙ c E E 1 P E = mc 2 ⇒ m = ⇒ m˙ = = c 2 t c2 c 2 • At 1 AU, P=1394 W/m2 • c=3x108 m/sec • T=9x10-6 N/m2

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 68

€

€ Propulsion Taxonomy

Mass Expulsion Non-Mass Expulsion

Thermal Non-Thermal

Ion Chemical Non-Chemical Solar Sail

MPD Laser Sail Nuclear Monopropellants Bipropellants Beamed Electrical Microwave Sail Cold Gas Solar MagnetoPlasma

Solids Hybrids Liquids Air-Breathing ED Tether

Pressure-Fed Pump-Fed

U N I V E R S I T Y O F Propulsion Systems Design ENAE 483/788D - Principles of Space Systems Design MARYLAND 69