Niklas Wingborg FOI, Energetic materials

1. Chemical Rockets Performance and propellants Niklas Wingborg FOI, Energetic materials

2. Principle of rocket engines Combustion chamber Nozzle Throat Exit

3. Principle of rocket engines De Laval nozzle M<1 M=1 M>1 Tc Tt<Tc Te<Tt

4. Gustav de Laval, 1845-1913 1883 AB Separator → Alfa Laval 1893 AB de Lavals Ångturbin → Stal-Laval AB →ALSTOM Sverige AB

5. Rocket propellant classification Fuel + oxidizer  gas + energy • Propellant = fuel + oxidizer • Liquid propellants • Bipropellant (storable, non-storable, hypergol) • Monopropellant • Solid propellants

6. Propulsion systems in the Ariane 5 Upper stage with storable propellants and Aestus engine Solid propellant booster Cryogenic main core stage Vulcain engine

7. Propellant performnace • Propellant content: up to 90% • Not unusual with 50% • The performance of the propellant very important • Propellant figure of merit: Specific impulse, Isp • Isp unit: Ns/kg, m/s or s

8. Specific impulse, Isp • Optimum mixture oxidizer/fuel  high Tc • High heat of formation, ΔHf  high Tc • High hydrogen content  low M CO2 44 g/mol CO 28 g/mol N2 28 g/mol H2O 18 g/mol H2 2 g/mol

9. Calculation of specific impulse • Nozzle/chamber • Pressure in combustion chamber, pc • Nozzle expansion • Pressure ratio: pc/pe • Area ratio: Ae/At • Chemical equilibrium or frozen equilibrium • Propellant • Chemical composition of fuel and oxidizer • Heat of formation of fuel and oxidizer • Mixing ratio fuel/oxidizer

10. Thermochemical computation • Computer programs for calculation of thermochemical equilibrium and Isp • NASA CEA (chemical equilibrium with applications) • NASA Reference Publication 1311 (June 1996) • Equation of state: ideal • Chemical equilibrium  minimizing ΔG = ΔH-TΔS • CEA can be obtained for free • http://www.grc.nasa.gov/WWW/CEAWeb/ • http://www.openchannelsoftware.com/projects/CEA

12. Liquid rocket propellants

13. Common liquid rocket propellants • Oxidizers • Liquid oxygen, O2 • Dinitrogen tetroxide, N2O4 • Nitric acid, HNO3 • Hydrogen Peroxide, H2O2 • Fuels • Liquid hydrogen, H2 • Hydrazine, N2H4 • Monomethylhydrazine • Methane • Unsymetrical dimethylhydrazine • Kerosene • Ethanol

14. Liquid oxygen (LOX), O2 • Non storable oxidizer • Nontoxic • Mp= -219oC, Bp = -183oC • Used in combination with H2, kerosene, ethanol • Density = 1.14 g/cm3

15. Dinitrogen tetroxide (NTO), N2O4 • Widely used storable oxidizer • Different percentages (1-3%) of nitric oxide, NO, added as stress corrosion inhibitor (MON-1 and MON-3) • MON-1 and MON-3 are used more often than pure NTO • Bp= 21°C, Mp=-11°C, dens=1.43 g/cm3

16. Dinitrogen tetroxide (NTO), N2O4 • Safety concerns • Concern about reactivity of MON with titanium alloys, ignition by friction on freshly formed surfaces (e.g., pyrovalves). • History of accidents • Toxicity of vapor clouds in case of launch mishaps • State governments impose restrictions on transportation of NTO/MON • Space agencies have considered manufacturing NTO (and other toxic fuels) at the launch site to alleviate transportation restrictions

17. Liquid hydrogen, H2 • Non storable cryogenic fuel, Mp= -259oC, Bp = -253oC • Used in combination with LOX • Density = 0.07 g/cm3 bulky fuel tank • Material problems  brittle at low temperature • Air / H2 explosive

18. Hydrazine, N2H4 • Can be used as a bipropellant fuel and as a monopropellant • Thermally unstable and cannot be used as a regenerative coolant in bipropellant engines • As a fuel, it is hypergolic with many oxidizers • Positive enthalpy of formation (+50.434 kJ/mol =+12.05 kcal/mol, liquid at 298 K) • Bp= 114°C, Mp=+2°C, dens= 1.00 g/cm3

19. Hydrazine, N2H4 • Hydrazine toxicity concerns • Acute toxicity: short-term exposure • Chronic toxicity: long-term exposure • Volatile • Carcinogen

20. Monomethylhydrazine (MMH), H3C-NH-NH2 • Frequently used storable, hypergolic bipropellant fuel for satellites and upper stages • Can be used as a regenerative coolant in bipropellant engines • Low freezing point (-52°C) • Density = 0.87 • Concern about toxicity of vapors (more volatile than hydrazine itself), Bp= +88°C

21. AMSAT P3-D Launch Campaign Kourou MMH filling operation N2O4 filling operation http://www.amsat-dl.org/launch

22. Aestus: Ariane 5 upper stage engine • Fuel: MMH • Oxidizer: N2O4 • MMH regenerative cooling • Multiple re-ignition capability • Thrust: 3 tons • Engine mass: 120 kg • Length: 2183 mm

23. Rocket engine design Injector Chamber At Lc Ae

24. Injector face Mass flow and mixing  diameter of chamber

25. Characteristic velocity, c* • Depends on the properties of the propellant • Unit: m/s (but it is not a velocity) • Independent of pressure (as long the reactions don't change) • CEA  c* • c*-efficency; ratio between calc. and measured c*

26. Characteristic velocity, c* UDMH / HNO3

27. Rocket engine design: summary • Propellant • Thrust, pressure and Ae/At • CEA  Isp, c* • Massflow • c* and massflow  At Ae • Injector and massflow  Ac • Propellant  Lc

28. Solid rocket motors

29. Solid rocket motors Igniter Nozzle Case with propellant

30. Solid propellants • Solid mixture of oxidizer and fuel • Oxidizer: Ammonium perchlorate (AP), NH4ClO4 • Rubber binder matrix: HTPB • Fuel: Aluminium powder • Burns on the surface • Burn time determined by the smallest dimension

31. Solid propellant geometry • The case is protected by the propellant • Shape of combustion channel  pre-programmed pressure and thrust profile

32. VEGA

33. Combustion of solid propellants Piece of solid propellant: 10x20x50 mm

34. Combustion of solid propellants Small pices of propellants

35. Combustion of solid propellants • Small pieces burn fast • The combustion proceeds perpendicular to the surface • Gas generation proportional to burning surface and burning rate, r

36. Combustion of solid propellants • r measured at different pressures • a and n calculated In this case at atmospheric pressure

37. Combustion of solid propellants n must be < 1, preferably 0.5 or lower

38. Combustion of solid propellants • r is altered by the initial temperature. A warm propellant burn faster T2 > T1 T2 T1 pressure time

39. Solid propellant mechanical properties • Cracks in the propellant  > Ab > pc • Might lead to failure • Good mechanical properties is important • Must be elastic • Tg < minimum service temperature • Good bonding to case important • Debonding  > Ab > pc

40. Manufacturing composite solid propellants • Liquid rubber (HTPB), AP and Al are mixed under vacuum • When properly mixed a curing agent is added • Continued mixing • Cast in mould to obtain desired shape • Cured at elevated temperatures • Mould = rocket motor • Machining • Final charge X-rayed to detect cracks, voids etc

41. ~80% Isp (Ns/kg) % AP Manufacturing composite solid propellants • Not possible to obtain maximum theoretical Isp • Isp limited by viscosity • AP particle size: bimodal or trimodal

42. Composite solid propellants • Large amount of smoke is formed • AP  HCL  hydrochloric acid • Shuttle  ~600 tons conc. hydrochloric acid • Ariane-5  ~300 tons conc. hydrochloric acid

43. Current trends

44. Current trends • Green solid propellants to replace AP (ADN, AN, HNF) • Green cryogenic solid propellants • Green oxidizers (N2O, H2O2) • Hypergolic rocket fuels to replace hydrazine and MMH • Green monopropellants to replace hydrazine • Exotic molecules, HEDM (N4, N8)

45. Minimum smoke propellants

46. Why is smoke a concern? NC-baserat AP/Al/HTPB

47. Ammonium dinitramide, ADN • Solid white salt • Intended for solid propellants • No chlorine content • Minimum smoke • High performance • Very soluble in water (80% at RT) • Synthesis developed at FOI • Produced on license by EURENCO Bofors in Sweden NH4·N(NO2)2

48. ADN-based solid propellants

49. Solid propellant testing at FOI Testing of missiles for the Swedish defense