Lecture 3

Question 1

What are some causes and consequences of impacts and why are they relevant?

Answer 1

• Relevant because of lacking atmosphere on most celestial bodies, so no protection
• Particle impact –> Mechanical damage, rupture, electrical failure
• Secondary impacts –> Dust accumulation

Question 2

How can some mechanical damages on the JWST be corrected and how can it be protected from them?

Answer 2

• Some deformations are correctable through mirror realignments
• Meteor-shower forecasts generated, allowing reorientation

Question 3

Where and how often are impacts on the Moon visible from Earth?

Answer 3

• Impact flashes on the dark portions of the Moon, sometimes visible with the naked eye
• Hundreds of detectable impacts per year

Question 4

What is LUMIO and what is its purpose?

Answer 4

• Newly approved CubeSat mission to observe meteoroid impacts on the lunar farside
• Conduct observations of the lunar surface to detect impacts and characterise flux, magnitudes, luminous energies, sizes and locations

Question 5

How dangerous are sporadic meteoroid showers and how does the impact frequency relate to the diameter of the impactor?

Answer 5

• More dangerous than regular showers, as they have more smaller particles
• Impact frequency decreases inversely to the diameter of the impactor

Question 6

How do secondary ejecta and particle size relate and how much does a single impact with 20 km/s eject in secondary particles?

Answer 6

• The smaller the particles, the more secondary ejecta are produced
• May eject 100 to 1000 time the impactors mass in secondary particles

Question 7

How often do impacts on Jupiter happen per year with impactor diameter of 5-20m, 300m and 1600m?

Answer 7

5-20m: 10-65 per year
300m: 1/500 per year
1600m: 1/6000 per year

Question 8

What are 8 shielding concepts from impacts and how do they work?

Answer 8

• Monolithic (simple and heavy)
• Whipple (thin bumper shocks the projectile, debris cloud less harmful)
• Stuffed Whipple (variation of Whipple with layers of Nextel and Kevlar, further impact energy reduction)
• Multi-Shock (staggered layers of Nextel)
• Mesh Double Bumper (double layer bumper of aluminum mesh, aluminum rear wall)
• Honeycomb Panel (light and rigid)
• Foam Panel (light and rigid, better shielding than honeycomb)
• Transhab (layers of Mylar, Nextel, Kevlar and foam, compressible for launch, prototype for Mars habitat)