Orbital Defenses [Space/Spaceships]

AlexanderHowl · 01-24-2020, 08:09 PM

One of the often neglected aspects of space defense in fiction is the orbital defense platform, which can range from a SM+4 AKV with 16cm missiles to a SM+16 orbital platform with 3 TJ major batteries. Depending of the technological assumptions of the settings, orbital defenses may range from useless to essential, or anything in between. In general though, orbital defenses should have some utility, as planets would otherwise be oceans of magma.

Imagine a TL10^ setting with the following technological constraints. First, FTL travel exists, but FTL spacecraft are incapable of exiting closer to an object than (10 × square root of object mass in Sol's mass) AU. Second, reactionless drives exist, but they have a maximum velocity of (square root of number of drives × .01)c. Third, FTL communications and sensors do not exist, though the speed of FTL is (square root of number of drives parses per day), allowing for a rapid postal system.

How important would orbital defenses be in such a setting? Would you imagine that worlds would heavily invest in orbital defenses? How much do you think they would invest per year dueing peacetime as a percentage of their GDP to maintain orbital defense readiness?

Humabout · 01-25-2020, 01:27 PM

I assume you have already read Rocketpunk Manifesto's series of articles on space warfare?

AlexanderHowl · 01-25-2020, 02:24 PM

Yes. The problem with ground defenses is that they are have limited arcs of engagement compared to orbital defenses, and they are not that much cheaper than orbital defenses (the main costs are associated with armor, energy, and weaponry). Now, you could have ground defenses sell off their excess energy when they are not being used, but you could do something similar with orbital defenses as well (or orbital defenses could be supplied by planetary energy systems).

The real advantage of orbital defenses though is that they would not preclude the existence of planetary defenses. For example, a developed Earth-Luna planetary system could have a network of defensive systems on the surface of the Earth and Luna, as well as orbital defensive systems in GSO and the Lagrange Points. The orbital defenses would be the first line of defense while the planetary defenses would be the second line of defense.

Another thing to consider is that the majority of the population of a developed system may be in orbit, requiring orbital defenses, while the minority would be on a planet. It would be relatively easy at TL10 to construct massive space colonies, since the only expense is the Open Spaces and the Spin Gravity, and SM+20 space colonies would only cost $13B to contruct (12 Open Spaces, 6 Rock Armor, 2 Cargo Holds, and Spin Gravity) though they would require 1.2 million people to maintain. With 120,000 areas though, they could easily hold 12 million people, meaning that only 10% of the population would be required to maintain the space colony.

Since it would only cost around $1,111 per person to house people in orbit, it would make sense to construct massive numbers of such space colonies, since it would be cheaper to house them in space than on the Earth. Twenty thousand of them could be build in an orbital ring around the Earth for $260T, which would not even be the GDP of a TL10 society with 24 billion people (around 17%). Such a society could easily afford such a thing over the course of a decade, and they would need defending.

Agemegos · 01-25-2020, 04:16 PM

Quote:

Originally Posted by AlexanderHowl

Yes. The problem with ground defenses is that they are have limited arcs of engagement compared to orbital defenses

On the other hand, they are easy to cool and don't need huge radiators, a vulnerability for spacecraft and space stations. Also it is possible to hide or camouflage them.

Aldric · 01-25-2020, 05:05 PM

What would these defenses be used for? Rogue asteroids, or raids from other groups/races or an all out war of annihilation?
Because the setup and the effort to maintain it would be quite different

The Colonel · 01-25-2020, 05:13 PM

Surely the main problem with surface based defences is that they have to fire through the planet's atmosphere and gravity well … and that if they hit anything in orbit it will probably land on the planet. Against that they have the advantages of being a lot cheaper to build, being able to be hidden and/or better protected and that the enemy have to fire through the atmosphere at them...
Orbital defences can potentially fire over a much longer distance and don't have the barrier of the atmosphere to cope with, but against that are sitting targets and a lot more expensive to construct. Stuff they hit may still collide with the planet, but should be coming from a lot further away and so disperse better.

AlexanderHowl · 01-25-2020, 05:19 PM

Well, a TL10 society is going to probably have everything larger than a meter diameter plotted in any developed system, so they would likely exist to protect a planetary system from attack. While a SM+16 defense platform would probably cost $1T (+$1T for secondary craft), twenty-four of them would provide multiple overlapping arcs of fire that would make life quite uncomfortable for any invading force (with ~1,200 dDR on their front hulls, they would be able to shrug off proximity blasts from 100 kiloton nuclear weapons and ignore 1TJ beam weapons). The assembly would cost $48T to set up, but that would be cheap compared to the $1600 T economy that it would be protecting.

01-24-2020, 08:09 PM	#1
AlexanderHowl Join Date: Feb 2016	Orbital Defenses [Space/Spaceships] One of the often neglected aspects of space defense in fiction is the orbital defense platform, which can range from a SM+4 AKV with 16cm missiles to a SM+16 orbital platform with 3 TJ major batteries. Depending of the technological assumptions of the settings, orbital defenses may range from useless to essential, or anything in between. In general though, orbital defenses should have some utility, as planets would otherwise be oceans of magma. Imagine a TL10^ setting with the following technological constraints. First, FTL travel exists, but FTL spacecraft are incapable of exiting closer to an object than (10 × square root of object mass in Sol's mass) AU. Second, reactionless drives exist, but they have a maximum velocity of (square root of number of drives × .01)c. Third, FTL communications and sensors do not exist, though the speed of FTL is (square root of number of drives parses per day), allowing for a rapid postal system. How important would orbital defenses be in such a setting? Would you imagine that worlds would heavily invest in orbital defenses? How much do you think they would invest per year dueing peacetime as a percentage of their GDP to maintain orbital defense readiness?

01-25-2020, 01:27 PM	#2
Humabout Join Date: Aug 2008	Re: Orbital Defenses [Space/Spaceships] I assume you have already read Rocketpunk Manifesto's series of articles on space warfare? __________________ Buy My Stuff! *Free Stuff:* Dungeon Action! Totem Spirits My Blog: Above the Flatline.

01-25-2020, 02:24 PM	#3
AlexanderHowl Join Date: Feb 2016	Re: Orbital Defenses [Space/Spaceships] Yes. The problem with ground defenses is that they are have limited arcs of engagement compared to orbital defenses, and they are not that much cheaper than orbital defenses (the main costs are associated with armor, energy, and weaponry). Now, you could have ground defenses sell off their excess energy when they are not being used, but you could do something similar with orbital defenses as well (or orbital defenses could be supplied by planetary energy systems). The real advantage of orbital defenses though is that they would not preclude the existence of planetary defenses. For example, a developed Earth-Luna planetary system could have a network of defensive systems on the surface of the Earth and Luna, as well as orbital defensive systems in GSO and the Lagrange Points. The orbital defenses would be the first line of defense while the planetary defenses would be the second line of defense. Another thing to consider is that the majority of the population of a developed system may be in orbit, requiring orbital defenses, while the minority would be on a planet. It would be relatively easy at TL10 to construct massive space colonies, since the only expense is the Open Spaces and the Spin Gravity, and SM+20 space colonies would only cost $13B to contruct (12 Open Spaces, 6 Rock Armor, 2 Cargo Holds, and Spin Gravity) though they would require 1.2 million people to maintain. With 120,000 areas though, they could easily hold 12 million people, meaning that only 10% of the population would be required to maintain the space colony. Since it would only cost around $1,111 per person to house people in orbit, it would make sense to construct massive numbers of such space colonies, since it would be cheaper to house them in space than on the Earth. Twenty thousand of them could be build in an orbital ring around the Earth for $260T, which would not even be the GDP of a TL10 society with 24 billion people (around 17%). Such a society could easily afford such a thing over the course of a decade, and they would need defending.

01-25-2020, 05:05 PM	#5
Aldric Join Date: Nov 2015	Re: Orbital Defenses [Space/Spaceships] What would these defenses be used for? Rogue asteroids, or raids from other groups/races or an all out war of annihilation? Because the setup and the effort to maintain it would be quite different

01-25-2020, 05:13 PM	#6
The Colonel Join Date: Jul 2006	Re: Orbital Defenses [Space/Spaceships] Surely the main problem with surface based defences is that they have to fire through the planet's atmosphere and gravity well … and that if they hit anything in orbit it will probably land on the planet. Against that they have the advantages of being a lot cheaper to build, being able to be hidden and/or better protected and that the enemy have to fire through the atmosphere at them... Orbital defences can potentially fire over a much longer distance and don't have the barrier of the atmosphere to cope with, but against that are sitting targets and a lot more expensive to construct. Stuff they hit may still collide with the planet, but should be coming from a lot further away and so disperse better.

01-25-2020, 05:19 PM	#7
AlexanderHowl Join Date: Feb 2016	Re: Orbital Defenses [Space/Spaceships] Well, a TL10 society is going to probably have everything larger than a meter diameter plotted in any developed system, so they would likely exist to protect a planetary system from attack. While a SM+16 defense platform would probably cost $1T (+$1T for secondary craft), twenty-four of them would provide multiple overlapping arcs of fire that would make life quite uncomfortable for any invading force (with ~1,200 dDR on their front hulls, they would be able to shrug off proximity blasts from 100 kiloton nuclear weapons and ignore 1TJ beam weapons). The assembly would cost $48T to set up, but that would be cheap compared to the $1600 T economy that it would be protecting.