Environment

Question 1

Describe the environment factors acting on a satellite during the launch. Which of them are
the most severe for the satellite?

Answer 1

The challenging environment when putting the satellite into orbit is:
1. Acceleration: increases to the end of working of every stage
2. Severe acoustic/vibration environment.
3. Mechanical shocks (explosive bolts, latches)
4. Thermal environment: aerodynamic frictional force heats the shroud.
5. Ambient atmospheric pressure (permanently declines ~4-5 kPa/s)
6. Electromagnetic interference: can activate payload, severe if the ignition of in-board propulsion system.

vibrations and shock most severe

Question 2

The space environment is a challenging environment for a satellite to operate in. What are the principal effects of the space environment on a satellite?

Answer 2

Environment factors affected the satellite in space during its mission are:
1. Vacuum
2. Atmosphere (atmosphere drag, atomic oxygen erosion) (LEO or elliptic orbit with low
perigee altitude)
3. Meteoroids/micrometeoroids
4. Man-made debris
5. Gravitational fields
6. Magnetic fields
7. EM Radiation: visible light/IR/UV (solar), radio waves, X-rays (solar flare, primary cosmic rays)
8. Plasma (solar wind, solar flare, atmospheric plasma (LEO))
9. High energy particles/ions (cosmic rays, Van Allen radiation belts)

Question 3

Describe the environment factors acting on a satellite at LEO. Which of these factors are not
essential at GEO?

Answer 3

Atmosphere drag, atomic oxygen erosion( LEO or elliptic orbit with low perigee altitude)

Question 4

Describe the effect of a vacuum on satellite materials and systems. Outline negative and
positive effects.

Answer 4

Negative factors:
Materials sublime and outgas
The possibility of the condensation of gases on cold surfaces is more serious
Traditional lubrications do not work: they are evaporated very soon.
Contact surfaces have a tendency to diffuse into each other that causes the cold welding process; the result is a large frictional force on bearings and moving mechanisms

Positive factors:
In vacuum is that metals do not corrode.
Some fatigue life of materials is improved.

Question 5

Explain effect of “self-healing” of some metals in vacuum leading to improving material
strength and fatigue life.

Answer 5

Microscopic cracks appear in a metal near its surface when a material is stretched or bended. In the atmosphere surface of the crack is covered by oxides very fast because of atmosphere oxygen. In vacuum, the oxides are not formed. Therefore, after the load has been released and crack’s opposite surfaces contact each other again and because of cold welding become connected restoring the material integrity.

Question 6

Describe the sources of high energy particles and describe the effect of ionizing radiation on
satellite systems.

Answer 6

Cosmic Rays, solar flares and the Van Allen radiation belts. Those can damage spacecraft electronics, Human beings and biological subjects.

Question 7

Describe the solar radiation mentioning all component of this radiation.

Answer 7

EM Radiation + plasma flux(Solar wind + solar flares)

Question 8

Describe the structure of terrestrial magnetic field. How the solar wind affects its structure?

Answer 8

Terrestrial Magnetic Field (Magnetosphere).

Earth’s magnetic field has two primary sources:
(i) current in the Earth’s core,
(ii) currents caused by different motions of ions and electrons in the magnetosphere.

The solar wind plasma carrying its own magnetic field, distorts the Earth’s simple dipole field into shape:

Question 9

What hazard do meteoroids and material particles present to a satellite in orbit? What
design is used to decrease the effect of meteoroid impact?

Answer 9

small particles can cause damage to satellite components

Multilayer insulation (MLI) can protect from small debris and meteoroids

Question 10

Describe solar flares and their effect on a satellite/spacecraft.

Answer 10

Sudden (1- 10 min) release of magnetic energy stored in the corona.

Sun flare causes damage to:
1. spacecraft electronics
2. human being
3. biological objects

Question 11

Which of the environment factors are the most dangerous for the crew travelling to Mars?

Answer 11

X-Rays radiation is the main risk in manned mission to Mars, the moon or other planets.

Question 12

describe van allen belt effect on satellites

Answer 12

The radiation belt is the most damaging for a MEO
(middle earth orbiting).

High energy particles result in degradation of the
spacecraft surface, the solar array, dielectric charging.

failure of electronic equipment.

Energetic protons can pass through the human body, causing biochemical damage

Question 13

describe van allen belt method to decrease effect

Answer 13

to avoid orbits most essential of which is located in the Van Allen belt. Additional
shielding of equipment and crew. Habitable spacecrafts and stations are orbiting below
the radiation belt.

Question 14

Describe Van Allen belt nature

Answer 14

layer of energetic charged particles trapped by the terrestrial magnetic field.
The belts contain energetic electrons that form the outer belt and a combination of protons and electrons that form the inner belt.

Question 15

Describe the physical phenomenon lying in base of van Allen belt formation.

Answer 15

Most of the particles that form the belts are thought to come from solar wind and other particles by cosmic rays.

By trapping the solar wind, the magnetic field deflects those energetic particles and protects the atmosphere from destruction.

Question 16

Explain the South-Atlantic Anomaly.

Answer 16

The South Atlantic Anomaly is an area where the inner Van Allen radiation belt comes closest to the Earth’s surface dipping down to an altitude of 200 km. This is because of the local weakening of the terrestrial magnetic field.

Question 17

Describe origin of atomic oxygen

Answer 17

Atomic oxygen is formed when ionization due to UV radiation from the sun leads to the dissociation of O2 into O + O.

Question 18

describe the effect of atomic oxygen

Answer 18

Atomic oxygen provides an aggressive environment for materials used on space vehicles in LEO: erosion, formation of stable oxide, chemoluminiscent glow.
The net effect is degradation of material properties (optical, thermal, mechanical, electrical).

Question 19

Describe the evolution of an elliptic orbit effected by atmospheric drag at its perigee.

Answer 19

elliptic orbit → circular → spiral → burned.

Question 20

Describe the problem with lubrication in space.

Answer 20

Usual lubrication doesn’t work. liquid substances usually evaporate fast in
vacuum. Also the great and fast change of temperatures as well as action of radiation can essentially change the properties of standard lubricants.

Question 21

Expected time to collide the satellite of 5 m diameter

Answer 21

Step 1: Calculate surface area of the satellite assuming is a sphere.

Step 2: Find the flux of the particles using formula Log10(N) = -14.37 -1.21Log10(m), where m is the mass of the particles. (Most likely 2 different masses).

Step 3: Find delta N, and the expected number of particles passing through the surface area A in time t is n =DeltaN * A * t.

Step 4: Substitute n = 1, and rearrange to find t.

Question 22

Describe the problem of zero weight in a spacecraft and methods of its solution

Answer 22

Without the proper diet and exercise routine, astronauts also lose muscle mass in microgravity faster than they would on Earth. Moreover, the fluids in the body shift upward to the head in microgravity, which may put pressure on the eyes and cause vision problems