SR02 Planetary environment I Flashcards
Planetary environment I
List the main environmental factors
- Vacuum
- Gravity
- Illumination
- Temperature
- Radiation
- Impacts
- Dust
What is the average orbit distance from the Sun for Earth, Moon, and Mars?
Earth: 1.4959789 x 10^8 km (1 AU)
Moon: 3.84400 x 10^5 km (0.00257 AU)
Mars: 2.2793664 x 10^8 km (1.523662 AU)
What is the equatorial radius for Earth, Moon, and Mars?
Earth: 6.37814 x 10^3 km
Moon: 1.734 x 10^3 km
Mars: 3.397 x 10^3 km
What is the escape velocity on Earth, Moon, and Mars?
Earth: 11.180 km/s
Moon: 2.380 km/s
Mars: 5.020 km/s
What is the surface gravity on Earth, Moon, and Mars?
Earth: 9.78033 m/s²
Moon: 1.622 m/s²
Mars: 3.711 m/s²
What is the orbital eccentricity of Earth, Moon, and Mars?
Earth: 0.01671022
Moon: 0.05490
Mars: 0.0934
Why is a life support system necessary on the Moon and Mars?
Due to lack of atmospheric pressure and oxygen (Earth: 1013 mbar, Mars: 6 mbar, Moon: ultra-high vacuum), humans need a life support system for survival.
What are the main environmental challenges of vacuum in space?
-Lack of oxygen, requiring life support.
-Pressure difference leading to need for pressure suits.
-No convection, causing thermal stress.
-No atmospheric drag, increasing risk of meteoroid impacts.
What happens to a human exposed to vacuum in space?
Air is sucked from the lungs, blood and bodily fluids boil, oxygen transport to the brain stops, leading to unconsciousness and suffocation within seconds.
Low Gravity consequences
Reduced contact to ground –> reduced traction and control, risk of bouncing off
Increased dust aggregation –> compromised vision, increased contamination
Varied fluid behavior –> bubble growth/detachment and reduced convection (for reactors)
How does gravity vary on Earth, Moon, and Mars, and what are its effects?
-Earth: 9.8 m/s²
-Moon: 1.6 m/s²
-Mars: 3.7 m/s² Effects: Reduced ground contact (bouncing risk), increased dust aggregation, and altered fluid behavior.
Moon: 14 days illumination vs. 14 days dark
Causes and consequences:
Limited power supply –> energy storage, other power sources
Reduced radiation intensity –> other power sources
Extreme temperature gradients –> thermal stress, damage, wide design envelope
Psychological effects –> psychological stress, mood
Solar irradiance on moon
Solar irradiance is
𝐼_solar =1361 W/m²
What is the inverse square law of illumination in space?
The intensity of solar radiation is inversely proportional to the square of the distance from the Sun:
𝐼=1/𝑑^2
What are Peaks of Eternal Light (PEL) and Permanently Shadowed Regions (PSR)?
PEL refers to regions (like on the Moon) that receive illumination >80% of the time, useful for continuous power. e.g. Moon, Mercury, Ceres
* Benefit: continuous power close to potential resource deposits
PSR refers to areas in permanent darkness, the coldest places in the solar system.
How does temperature differ between Earth, Moon, Mars, and Mercury?
-Earth: -88°C to +58°C
-Moon: -247°C to +123°C
-Mars: -128°C to +21°C
-Mercury: -180°C to +430°C
Temperature
Causes and consequences:
Temporal/spatial gradients –> thermal stress (dynamic/static), thermal expansion
Extreme values –> enhanced outgassing, increased power demand
What are the major sources of space radiation
Galactic cosmic rays (GCR), mainly protons and alpha particles.
Solar particle events (SPE), including x-rays, gamma rays, and protons.
What are the risks of space radiation to humans and electronics?
For humans: DNA and cell damage, gene mutations, cancer risk.
For electronics: Jamming, glitches, and damage from high-energy particles.
Earth‘s magnetic field
Earth‘s magnetic field shields radiation
But: the magnetic field also traps highly energetic particles in the Van-Allen Belts
* Inner belt: ~0.2 to 2 Earth radii (mainly protons)
* Outer belt: ~3 to 10 Earth radii (protons and electrons, highest intensity around 4 to 5 Earth radii)
* Between both main belts: safe zone
Effects of radiation on CMOS (Complementary metal–oxide–semiconductor)
Total Ionising Dose: Ionisation process causes energy to be trapped in the materials (dose), leading to:
* Oxide doping (fixed charge, leading to lower barrier, threshold shifts)
* Leakage current (device stays „on“ even with no gate voltage)
Single Event Effects:
* Single Event Transients (heavy ion creates voltage pulse along its path)
* Single Event Upsets (device changes its logical state, e.g. bitflip)
* Single Event Latch Up (low impedance, electric short, loss of device functionality)
The luck of Apollo (or: the solar cycle)
No major solar-particle events occurred during Apollo
* Individual solar eruptions are impossible to forecast
* Time between observation of an eruption and arrival in
the Earth-Moon system is <1 h up to 4 h
* Only ~20% of the flares result in particle events
* The maximum operational dose (MOD) limit for each of
the Apollo missions was set to 400 rads (X-ray
equivalent) for skin and 50 rads for the blood-forming
organs
* The average for all Apollo missions was 0.38 rad,
equivalent to 2 CT scans of the head
* Shielding level differed between command module, lunar
module less, and EVA
Radiation counter measures
- Radiation avoidance:
- Timing of a mission (during lower solar activity)
- Careful planning of orbital trajectory
- Shielding: Aluminium provides limited shielding, propellant tanks are much more effcient
- Risk of secondary radiation depending on material and thickness
- Different materials are suitable for different types of radiation
Radiation hardening by architecture - Redundancy è increases overhead in voting logic, power consumption, mass
- Multiple levels of redundancy (i.e. component, board, system, spacecraft level)
- Radiation hardening by design
- Triple Modular Redundancy (TMR) strategies within the chip layout
- Dopant wells and isolation trenches in the chip layout
- Error detecting and correction circuits
- Device spacing and decoupling
- Radiation hardening by process,
- Employ specific materials, processing techniques
- Usually performed on dedicated rad-hard foundry fabrication lines
