On June 18 2018 U.S. President Donald Trump signed into existence the US Space Force which will be a new arm of the American military separate from the Air Force, Army, Marines, Coast Guard and Navy.

This got me thinking more seriously about this topic and this post is Part 3 of a short series on space warfare.

My first one was on stealth in space (hint: there isn't any). My second post on this topic was about space weapons systems and the targets.

In this post I am going to speculate about how a poor and less developed country can fight in space against a larger, richer and better equipped Space Force.

Very Low Earth Orbit (VLEO) Artificial Debris Fields

Without a doubt, there is currently a lot of debris in orbit around the Earth. So much in fact that rocket launches need to pay attention to predicted debris tracks whenever they launch and delay or scrub the launch if the risk is calculated to be too high.

If you are a nation of modest means and find yourself in conflict with a richer nation with a well-equipped Space Force then deliberately generating a debris field in orbit may just be a feasible space war tactic.

Such a debris field, if sufficiently dense would deny space to your enemy and everybody else on Earth.

If the debris field were generated in very low Earth Orbit (VLEO) it would have the following advantages:

• Rapidly decaying orbits: VLEO orbits decay relatively quickly, due to the tiny residual atmospheric pressure, from a metres per day up to a few hundred metres per day (depending on the altitude). A debris field inserted into VLEO would have the advantage of denying access to space for your enemy but it would also be a temporary phenomenon. The combatant could chose the orbital altitude to determine the duration of effectiveness from months to years.
• Smaller area/volume to cover: The lower one goes in orbital altitude the lower the surface area of the sphere that one needs to cover. The average density of the debris would therefore increase as the altitude dropped. A higher debris density would mean more effective area denial.

GPS Orbit Debris Fields

GPS capabilities are critical to both civilian operations as well as military operations. The US GPS satellites are at 20,180 km, the European GPS satellites are at 23,222 km, the Indian satellites are at 36,000 km and the Russian satellites are at 19,130 km. The Chinese satellites are also up there but data is hard to come by.

These altitudes are significant and would be harder orbits to achieve for a country with a moderate space budget. Also at these altitudes the surface area of the sphere is incredibly large and it would be less likely for a debris field to be able to eliminate the entire constellation of GPS satellites.

It may therefore be an infeasible target for this tactic for countries with modest space budgets.

Geostationary Orbit Debris Fields

Geostationary satellites orbit at 35,786 km in the same direction as the Earth's rotation (west-to-east). At this altitude the time to complete one orbit is 23 hours 56 minutes and 4 seconds (one sidereal day) so they keep an apparent stationary spot in the sky and are therefore very useful for communications.

These satellites are all strung out in a line along the circumference of this circle and are therefore sitting ducks for any intentional debris field.

The altitude is very high and might be harder to reach for a nation of modest means but you only have to get a single killer satellite into orbit to be effective. It would also be useful if that debris field could be in a retrograde orbit but this would require more fuel to counter the speed of rotation of the Earth at launch.

This would be a difficult and expensive launch for sure but if successful it could wipe out the majority of space communications for the entire planet.

Retrograde Orbits

The Earth rotates west to east at a velocity of about 1650 km/h at the equator. This gives satellites 'free' orbital energy if the rocket rolls over towards the east at launch.

This free lunch also means that most satellites ever launched by humanity are orbiting west-to-east (prograde, or counter-clockwise if you are looking down on the north pole).

The most effective debris fields would therefore be retrograde orbits. This would give the debris a significant additional velocity during any collision.

If a satellite is moving prograde at about 8 km/s in LEO and a piece of debris is moving retrograde at 8 km/s then the subsequent collision will be at 14 km/s.

A 1 gram piece of debris would have a relative energy of E = 1/2 mv² = 0.5 x 0.010 kg x 14,000 m/s x 14,000 m/s = 980,000 J.

The energy in a gram of TNT is 4,184 J so the above collision would be like 230 g of TNT (half a pound of TNT) going off either in rocket that is launching or in a satellite that is already in orbit.

More than enough to destroy it.

Closing Words

Space warfare is a no-win scenario for everybody. Going in this direction is not advisable but we will see what transpires over the next few months and years.

The likelihood of generating massive debris fields during a space battle is very high and every asset up there is extremely vulnerable.

Having said that, any smaller nation with a modest space budget (ahem, North Korea, ahem, Iran) might feel threatened enough to simply deny space to every nation on Earth by creating a massive VLEO debris field.

That would not be a good day at all.

Post Sources

My own thoughts plus the following:
[1] Wikipedia - Space warfare
[2] GPS satellite system
[3] Wikipedia - Kessler Syndrome
[4] YouTube - Space Warfare - Isaac Arthur
[5] Project Rho - Space Warfare
[6] ARES - Orbital debris research
[7] Wikipedia - Space debris
[8] Galileio satellite navigation
[9] Indian Regional Navigation Satellite System
[10] GLONASS
[11] Geostationary orbits
[12] Sidereal time
[13] Retrograde and prograde motion
[14] TNT equivalent