# Presentation: 576420

## Pressure Vessel Technology Developments 4th International Planetary Probe WorkshopPasadena, CA

- Mike Pauken, PI
- Elizabeth Kolawa, Ram Manvi, Witold Sokolowski, Joseph Lewis
- June 29, 2006

## Outline

- Why Pressure Vessels Need Development
- Historical Perspective
- Design Guidelines
- Some Candidate Materials
- Material Down-Selection
- Various Manufacturing Methods
- Moving Forward

## Why Pressure Vessels Need Development

- Decadal Survey identifies Venus Lander, Jupiter Deep Probes as 2 of 6 highest priority missions
- Present state-of-the-art pressure vessel technologies are not adequate for the mass requirements of these missions
- The pressure vessel represents one of the single largest mass elements in a Venus Lander or Deep Atmospheric probe
- It appears that pressure vessel mass could be reduced by up to 50% of a Titanium shell

## Historical Perspective

- Soviets began Venus exploration program with launch of Venera 1 in 1961.  Program ended in 1984 with VEGA 1 and 2.
- NASA launched Pioneer Venus Probes in 1978

| Mission | Launch Year | Pressure Rating |
| --- | --- | --- |
| Venera 3 | 1965 | 5 bar |
| Venera 4 | 1967 | 20 bar |
| Venera 5,6 | 1969 | 25 bar |
| Venera 7 | 1970 | 150 bar Titanium |
| Venera 8-14 | 1972-1981 | 100 bar Titanium |
| Pioneer Large Probe | 1978 | 100 bar Titanium |
| Pioneer Small Probe | 1978 | 100 bar Titanium |

## Venera 5 Descent Module

**The layout of the Venera-5 descent vehicle**:
-    1. drogue parachute
-    2. main parachute
-    3. explosive bolts of cover
-    4. transmitter antenna
-    5. gas density gauge
-    6. grooving charge valve
-    7. dehumidifier
-    8. circulation fan
-    9. electrical umbilical
-   10. commutation unit
-   11. accelerometer
-   12. transmitters
-   13. anti-vibration damper
-   14. power unit
-   15. onboard transmitter
-   16. accelerometer
-   17. program timing unit
-   18. heat shielding
-   19. heat shielding
-   20. external insulation
-   21. internal insulation
-   22. temperature control system
-   23. lid of instrument compartment
-   24. explosive bolt
-   25. cover of parachute compartment
-   26. radio altimeter antenna
-   27. gas analyzer

**All systems, including instruments, were protected by pressure vessel and passive thermal control**

## Venera 8 Descent Module

-    **Venera 8 descent module:**
-    1. cover of parachute housing
-    2. drogue parachute
-    3. main parachute
-    4. altimeter antenna
-    5. heat exchanger
-    6. heat accumulator
-    7. internal thermal insulation
-    8. program timing unit
-    9. heat accumulator
-   10. shock absorbing damper
-   11. external thermal insulation
-   12. radio transmitter
-   13. spherical instrument compartment
-    14. commutation unit
-   15. circulation fan
-   16. cooling conduit from bus
-   17. ejectable secondary antenna
-   18. parachute housing
-   19. primary antenna
-   20. electrical umbilical
-   21. antenna feeder system
-   22. explosive bolts of cover
-   23. telemetry unit
-   24. stabilized quartz oscillator
-   25. commutation unit

## Venera Instruments

**Venera 13. A number of instruments were placed outside the pressure vessel.**

## Pioneer Venus Probe

**Pioneer Venus Large Probe inside view of pressure vessel.**

## Pressure Vessel Design Guidelines

- Buckling @ ultimate load of 150 atm pressure and 500oC
- use standard NASA specified knockdown factor of 0.14 for pressure vessels (0.3 is commonly used in industry).
- Yielding @ proof load of 125 atm pressure at 500oC.
- Creep at 500oC limit allowable total strain at 10 hours to 0.5%.
- Impermeable to gases
- Low thermal conductivity at 500oC
- Compatible with Venus environment

## Required Material Properties at Temperature

- Tensile/compressive yield strength
- Tensile elongation
- Shear strength
- Tension/compression modulus
- Fracture toughness
- Thermal conductivity
- Specific heat capacity
- Thermal expansion
- Creep rupture time
- Creep rate (in compression/bending)

## Some Candidate Materials

- Metallic materials:
- Titanium: Ti-6Al-4V alloy  and Beta S
- Nickel-chromium alloys: Inconel 718, Inconel X or Haynes 230
- Nickel-chromium-cobalt alloys: Haynes 188
- PH stainless steels: 17-7 PH or 15-5 PH
- Beryllium I-220H
- Advanced composite materials:
- SiC reinforced titanium matrix composites
- B fiber reinforced titanium matrix composites
- Inorganic Sialyte based composite
- Aluminum/Sapphire and aluminum/silicon carbide metal matrix composites
- Polymer Matrix Composite

## Material Down-Selects

- Inconel 718: best performance in both creep and tensile property comparisons
-  primary metallic candidate for the pressure shell using honeycomb structure.
- Ti-6Al-4V: second best performer in creep and tensile comparisons also has low thermal conductivity.
- State-of-the-art material on previous missions with monolithic shell.
- Haynes 188 has superior creep properties at high temperature.  Performs best in 900C to 1100C range. At 500C it is no better than Inconel 718.  Haynes 188 was not retained for further consideration.

## Material Down-Selects

- 15-5 PH showed reasonable creep properties at 500C, but creep resistance falls very rapidly above 500C leaving little margin.  15-5 PH was not retained for further consideration.
- Creep data was not available for 17-7 PH.  However it is not expected to perform significantly better than 15-5 PH and was not retained for further consideration.
- SiC/Ti matrix composite has superior strength/density performance compared to other materials. Creep resistant at 500C.
- Beryllium is lightweight and has high elastic modulus, high thermal conductivity and high specific heat and low creep resistance in tension.

## Material Down-Selects

- Young’s Modulus against density for various materials at room temperature.  At 500C the Magnesium and Aluminum alloys drop out.

## Various Manufacturing Methods TYPICAL HONEYCOMB FABRICATION

- Facesheets
- Bulge-form Beta S titanium or Inconel 718 sheet to hemispherical shape.
- Honeycomb
- Corrugate Beta S titanium or Inconel 718 sheet.
- Diffusion bond corrugated sheet to form honeycomb block.
- Slice honeycomb to desired thickness.
- Bulge-form honeycomb to hemispherical shape.
- Assembly
- Assemble facesheets, TICUNI braze alloy or BNi-8 alloy, and honeycomb in hemispherical braze fixture
- Vacuum furnace braze assembly.

- Bulge Form Tooling

- Vacuum Braze Furnace

## Various Manufacturing MethodsComposite Wrapped Tanks

- Composite tanks using Aluminum/Sapphire or aluminum/silicon carbide  or Polymer Matrix Composite
- Wrap matrix runs through wet adhesive such as molten aluminum or epoxy.
- Wetted matrix is wrapped around mandrel.
- Composite wound tank is cured at elevated temperature.
- Need to work out details of adding flanges, view ports, feed-throughs etc.

- Linerless Composite Tanks by Composite Technology Development Inc.

## Various Manufacturing MethodsMonolithic Shells

- Titanium or Beryllium can be fabricated into monolithic shells.
- Titanium hemispheres can be shaped using spin forming.
- Flanges, windows, feed throughs, brackets etc can be welded onto the shell.
- Beryllium hemispheres must be machined from billets.
- Flanges, windows etc must be machined into parent shell out of the original billet

- Cut-Away sectional view of 3 piece monolithic shell

## Moving Forward

- Develop more detailed manufacturing engineering plans for leading candidate materials.
- Estimate comparative fabrication costs for the different manufacturing technologies.
- Obtain samples/prototypes of shells from leading candidate materials.
- Perform testing on prototypes under Venus-like environmental conditions for temperature and pressure for survivability.