The document describes a proposed Custom Crew Exploration Vehicle (CEV) spacecraft design. It has almost three times the internal volume of the Apollo Command Module at 30.6 m^3, providing 29.4 m^3 of pressurizable volume for crew during transits. The CEV structure would use an Al-Li 2195 alloy with Kapton thermal protection. Kapton could provide meteoroid shielding due to its layered insulation design. Flammability testing of materials like Kapton was important to ensure safety for spacecraft operating with pure oxygen atmospheres.

2. Custom Crew Exploration Vehicle
• CONCEPT
• Custom Crew Exploration Vehicle spacecraft
structure idea based on Apollo Command
Module and Orion Crew Exploration Vehicle.

3. Custom Crew Exploration Vehicle
32.5 deg
5.5m
Image Source: NASA’s Exploration Systems Architecture Study
(ESAS) Final Report documents

4. Advantages
• The CEV pressurized volume is 30.6 m^3 .It has almost three times the internal
volume as compared to the Apollo Command Module(10.4 m^3).
• The CEV was designed for the EOR–LOR (Earth Orbit Rendezvous- Lunar Orbit
Rendezvous ), and volume reduction helps to reduce mass to that required for the
mission.
• This configuration provides 29.4 m^3 of pressurized volume and 12–15 m^3 of
habitable volume for the crew during transits between Earth and the Moon.
• The CEV operates at a nominal internal pressure of 65.5 kPa with 30 percent
oxygen composition for lunar missions, although the pressure vessel structure is
designed for a maximum pressure of 101.3 kPa. Operating at this higher pressure
allows the CEV to transport crew to the ISS without the use of an intermediate
airlock.
NOTE: The above mentioned advantages are based on “CEV Overview and
Recommendations” by NASA (SOURCE).

5. Subsystem Structure
• Structure Material: Al-Li 2195
• Patch Material: Kapton

6. Al-Li 2195
ADVANCED MATERIALS & PROCESSES/OCTOBER 2005

7. Spacecraft charging(Structural Element-Al)
• Atomic number: 13.0
• Photoelectric current: 4.000E-05 A m-2
• Secondary yield for 1 keV protons: 0.244
• Energy for maximum yield: 230.000 keV
• Maximum secondary yield for electrons: 0.970
• Energy for maximum yield: 0.300 keV
• SEE formula: Katz
• R1: 154.0 Å
• n1: 0.800
• R2: 220.0 Å
• n2: 1.760

8. EQUIPOT Environment parameter as a function of energy
(For structure material Aluminium)

9. EQUIPOT current as a function of time
(For structure material Aluminium)

10. EQUIPOT Electron emission yields
(For structure material Aluminium)

11. Patch Material (Kapton)
• Relative permittivity: 3.000
• Thickness: 2.500E-05 m
• Conductivity: 1.000E-15 ohm-1 m-1
• Atomic number: 5.0
• Photoelectric current: 2.000E-05 A m-2
• Secondary yield for 1 keV protons: 0.455
• Energy for maximum yield: 140.000 keV
• Maximum secondary yield for electrons: 1.900
• Energy for maximum yield: 0.200 keV
• SEE formula: Katz
• R1: 70.0 Å
• n1: 0.600
• R2: 300.0 Å
• n2: 1.750

12. EQUIPOT Environment parameter as a function of energy
(For Patch Material Kapton)

13. EQUIPOT current as a function of time
(For Patch Material Kapton)

14. EQUIPOT Electron emission yields.
(For Patch Material Kapton)

15. Thermal Conductivity vs Temperature

16. Specific Heat vs Temperature

17. Kapton can be used as Protective Shielding
• The primary technique for meteoroid protection is placement of
multi-layer insulation (MLI) blankets on critical areas of the
spacecraft, such as propellant and helium tanks. MLI blankets are
composed of layers of a Kapton polyamide .
• MLI effectiveness in preventing damage to critical spacecraft
subsystems depends on the:
• Blanket material, location, and number of layers.
• Meteoroid mass, impact velocity, density, and angle of impact.
• Impacted structure material, thickness, temperature, stress level,
and the number and spacing of the plates composing the structure
and the subsystem package.

18. Critical mass (mc) for a double-wall structure
• Critical mass (mc) for a double-wall structure where a blanket
shields the exterior of a spacecraft structure (such as a
propellant tank) or component (such as a cable along a
spacecraft boom).

19. Critical mass (mc) for a double-wall structure
• Where:
• S = spacing between blanket and tank wall (cm)
• tb = thickness of tank wall (cm)
• sy = yield stress for the tank wall (47,000 lb/in2)
• rm = meteoroid mass density (2.5 g/cm3)
• rt = blanket mass density (0.3 g/cm3)
• V = impact velocity (km/s)
NOTE:Equation demonstrates that the critical penetration
mass will increase and the probability of failure will
decrease with increased spacing between the blanket and
the shielded surface.

20. One of several tears in the outer layer of Hubble's multi-layer insulation
blanket along the direct Sun-exposed side of the telescope.
Credit: NASA

21. Hubble's multi-layer insulation blanket
• Sixteen thin layers of dimpled aluminized
Kapton material are covered by an outer
aluminized Teflon shell , all together measure
less than one-tenth of an inch thick.

22. Flammability Testing
• Mercury and Gemini spacecraft operated with pure oxygen
atmospheres at all times.
• Flammability testing consists of purposely short-circuiting or
overloading wires at strategic points throughout the spacecraft to
start fires.
• Once the fires are started, engineers study their self-extinguishing
characteristics.
• The spacecraft is normally tested prior to launch at a positive
internal pressure of about 16 pounds to assure spacecraft sealing
integrity. That is to overcome the 14.7 pounds of normal sea level
atmosphere pressing on the spacecraft at launch.
• In orbit , a cabin pressure of from five to six pounds is maintained
in contrast to the zero pressure of outer space.

23. Conclusion
• Crew Exploration Vehicle(CEV) should light
weight.
• To increase the volume of CEV , the outer
diameter of CEV may be increased.
• Sidewall angles can be decreased further to
increase the volume of CEV, but it should
increase the weight of CEV.
• It can accommodate 4 to 6 crew to ISS or
MOON.(as CEV volume increased due to
increase in diameter and decreases the sidewall
angle.