So, imagine a 22th-23th century human space-faring civilization which has settled several colonies on asteroids and moons (not too different from our own Moon, for the sake of comparison).
Suppose that there is the need to define the position for a "last line of defense" around the colony itself, in case of enemy starship attack / bombing (let's say, internal rebellions, conflicts between colonies, conflicts between colonies and Mother Earth).
My idea was to define the Bell-Kann Edge (from the fictional two guys who theorised it in my story):
The Bell-Kann Edge is defined as the distance from the colony which prevents spacecrafts deployed from surface from intercepting incoming enemies before they can gain air (space) supremacy. The enemy ships are considered moving at full velocity, while the defending ships are considered unmanned and parked at the instant the Edge is reached by the invading force.
I'll try to explain it better:
when a number of enemy starships overcome the Bell-Kann edge, they are actually able to destroy spaceports and landed starships before they could effectively take off to retaliate.
Provided that colonies like that would have not a thick atmosphere, we can think about it like everything is in vacuum (so, no atmospheric friction and so on). Also, consider that AA defenses are not taken into account since the Bell-Kann Edge is considered to be a worst-case-scenario definition.
Obviously, there are several hypothesis this definition is based on (knowledge of the maximum velocity of the enemy spacecrafts, minimum time needed to deploy a spacecraft from land, efficiency of enemy weapons, and so on), leading to an evolving definition of the Edge during the war...
So, it comes the question:
- Is there a way to smoothly define this concept in order to rely on a smaller number of parameters?
- If not, how could it be improved?
- Considering this definition reliable, it would make sense to locate a permanent line of defense in proximity of the Bell-Kann Edge, so that landed spacecrafts could have time to take off while the preliminary troops try to contain the enemy?
I am looking for scientific / pseudo-scientific answers with some touches of military strategy :)
- How can this definition be extended to planets with Earth-like atmosphere?
I hope this is not too broad or off-topic :D If so, I will try to squeeze it to the bones ;)
Edit: the definition has been updated following @Mike Nichols's comment, in order to be more precise. As regards @Frostfyre's comment, if expanded in a complete answer I could think about accepting it :D
The Bell-Kann Edge is defined as the distance from the colony which prevents spacecrafts deployed from surface from intercepting incoming enemies before they can gain air (space) supremacy. The enemy ships are considered moving at full velocity, while the defending ships are considered unmanned and parked at the instant the Edge is reached by the invading force. This definition can be applied only in case of direct spacecraft attack from an enemy and doesn't take into account long-range bombing.
So, with this adjustment the definition becomes valid only in case of direct engagement (that is, scenario number 3 in @Mike Nichols's answer), since - as @Kolaru stated - space bombing would have no actual limitation (safe for "damage control"). And, yes, it would have some political/military implications as @Cort Ammon stated.