Self-Assessment Quiz: Space Debris, Space Law, and Sustainability

Twenty questions on the Kessler syndrome, the debris environment, mitigation and disposal, active removal, space law, and traffic management. Answer each before opening the key. Aim for 16 or more. Use $\mu = 3.986\times10^{5}\ \text{km}^3/\text{s}^2$ where needed.

Question 1

The Kessler syndrome is best described as:

A) a dense wall of debris that instantly traps humanity on Earth B) a self-sustaining collision cascade in which debris breeds more debris C) the gradual re-entry of all low-orbit satellites D) the loss of a satellite to a single micrometeoroid

Question 2

A $1\ \text{cm}$ aluminum sphere ($\sim 1.4\ \text{g}$) at a $10\ \text{km/s}$ closing speed carries roughly the kinetic energy of:

A) a falling raindrop B) a rifle bullet C) a small car in a low-speed crash D) a tonne of TNT

Question 3

The orbital-collision rate scales with the number of objects $N$ as:

A) $N$ B) $\sqrt{N}$ C) $N^2$ D) $\ln N$

Question 4

The "lethal non-trackable" debris population is dangerous mainly because objects $1$–$10\ \text{cm}$ are:

A) too slow to cause damage B) too small to shield against yet too small to track and dodge C) already all de-orbited D) only found above GEO

Question 5

Roughly how many objects larger than $10\ \text{cm}$ are currently tracked? (Tier 2)

A) ~360 B) ~3,600 C) ~36,000 D) ~36,000,000

Question 6

Passivation at end of mission means:

A) turning the satellite so its solar panels face the Sun B) removing all stored energy (venting propellant, safing tanks and batteries) so it cannot later explode C) painting the satellite to reduce radiation pressure D) transferring control to another operator

Question 7

Historically, the single largest source of orbital debris (before the 2007/2009 events) was:

A) micrometeoroids B) astronaut tools lost on spacewalks C) explosions of abandoned, un-passivated rocket stages D) paint flecks

Question 8

A geostationary satellite disposes of itself by:

A) de-orbiting into the atmosphere B) boosting a few hundred km up to a graveyard orbit C) drifting east until it leaves the belt D) waiting for drag to bring it down

Question 9

The delta-v to raise a GEO satellite $\sim 300\ \text{km}$ to a graveyard orbit is closest to:

A) $\sim 11\ \text{m/s}$ B) $\sim 190\ \text{m/s}$ C) $\sim 1{,}500\ \text{m/s}$ D) $\sim 3{,}000\ \text{m/s}$

Question 10

Natural atmospheric decay is a "free" disposal method only:

A) at all altitudes equally B) below roughly $600\ \text{km}$, where lifetimes are short enough to meet the rules C) above $1{,}000\ \text{km}$ D) in geostationary orbit

Question 11

A drag sail shortens a derelict's orbital lifetime because it:

A) raises the ballistic coefficient $\beta$ B) lowers the ballistic coefficient $\beta = m/(C_D A)$, and $\tau \propto \beta$ C) adds thrust D) changes the orbital period

Question 12

The modeling result behind active debris removal is that, to stabilize the crowded shells, we must remove roughly:

A) all debris within one year B) 5–10 large derelicts per year C) one satellite per decade D) nothing — mitigation alone suffices

Question 13

The foundational treaty of international space law, and its year, is:

A) the Registration Convention, 1976 B) the Moon Agreement, 1979 C) the Outer Space Treaty, 1967 D) the Artemis Accords, 2020

Question 14

Under the Outer Space Treaty, a nation's ownership and jurisdiction over a space object it registered:

A) ends the moment the object is abandoned B) is retained indefinitely, even after the object becomes debris C) transfers automatically to the UN D) applies only while the object is operational

Question 15 (True/False, justify)

"Because no nation may own outer space, orbit is effectively a lawless free-for-all." True or false? Justify.

Question 16 (True/False, justify)

"Doubling the number of satellites in a shell roughly doubles the collision risk." True or false? Explain.

Question 17 (True/False, justify)

"A satellite at $800\ \text{km}$ will re-enter on its own soon enough to satisfy the 25-year disposal rule." True or false? Say roughly how long it actually takes and why.

Question 18 (Short answer)

Distinguish mitigation from active debris removal, and explain why models say mitigation alone cannot stabilize the most crowded orbital shells.

Question 19 (Short answer)

A satellite with area $A = 10\ \text{m}^2$ flies $t = 5$ years through a flux $\Phi = 1\times10^{-5}\ \text{m}^{-2}\text{yr}^{-1}$ of $>1\ \text{cm}$ debris. Compute the expected number of impacts and the approximate probability of at least one.

Question 20 (Short answer)

Explain in two or three sentences why orbital sustainability is a "tragedy of the commons," and name one policy idea meant to fix it.

Answer Key

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