Wednesday, September 21, 2011

The ultimate shoot down : anti-satellite warfare

As with any advance in military technology as soon as the Cold War rivals were able to put up spy satellites then the capability to destroy these satellites was also sought. In this blog article we will look at the various attempts and systems developed to attack satellites, in what must be the ultimate shoot down.

Manned interception

As the Soviets were developing their Soyuz space capsule in the early 1960s (which is easily the most successful space ship to date considering it is still in use) one of the planned variants was the Soyuz P (Perekhvatchik or Interceptor).

Modern day Soyuz spacecraft - NASA photograph

This military subtype was intended to allow manned inspection and destruction of enemy satellites. Once the Soyuz has got up to the enemy satellite's orbit the cosmonaut was then intended to leave the Soyuz and then either destroy (either totally or just put out of action) or capture the satellite. In the end the idea of a "space interceptor" like this was abandoned because of the technical challenges and also the danger to the cosmonauts. The Soviets had started to booby trap their satellites to destroy them if the ground base lost contact and the Soviets expected the U.S. had done the same.

A later manned system was experimented with the Almaz manned spy satellites (which are probably better known as Salyut). Salyut 3 was fitted with an aircraft cannon which was test fired at a target satellite while the station was unmanned. The cannon was also intended as a self-defence measure. A later Salyut was to have tested rocket armament but was never launched. One problem with firing the cannon of course was the recoil effect could modify the Salyut's orbit. Considerable shaking of the space station was also caused.

Anti-satellite missiles & unmanned "satellite killers"

The way forward was in unmanned anti-satellite weapons and both superpowers began to develop missile based systems. The problem with this of course is that hitting a small object in orbit is not easy. An early U.S. missile that was tested was based on the Martin Bold Orion air-launched ballistic missile. In a test it passed within 4 miles of the target satellite. To kill the satellite a nuclear warhead would be needed for that range but of course detonating a nuclear warhead in orbit would also wipe out many other satellites nearby, including your own! Indeed high atmospheric nuclear weapon tests knocked out satellites over the Pacific with their EMP (Electromagnetic Pulse).

However nuclear warhead based ASAT systems are not really an option for the superpowers because increasingly their infrastructure and that of their allies is dependent on satellites for communication, imagery et cetera and their militaries also rely on satellites for targeting and weapon guidance (such as GPS guided bombs). A nation like North Korea who arn't so dependent on satellites, however, could strike quite a blow in a wartime situation by detonating a nuclear weapon in low Earth Orbit (LEO).

Moving forward to the 1980s the U.S. tried out the Vought ASM-135 ASAT which could be launched by fighters like the F-15. Although in tests the system was said to be successful the project was canceled at the end of the 1980s. The Vought ASAT employed a kinetic warhead guided to collide with the target using a sophisticated interceptor vehicle which had a ring of 56 motors to enable exact control.

Vought ASAT test launch - Public domain image

The Soviet Union worked on a number of satellite interceptors or Istrebitel Sputnikovs (IS), as well as the Soyuz-P. The IS system was intended to enter an orbit very close to the target satellite and when it got within range the warhead of the IS would explode in the same manner as a shaped charge mine and destroy the target satellite with directed shrapnel. In tests in the late 1960s some shrapnel hits were recorded on a special target satellite. The IS system was considered operational but was not used and was finally canceled in the early 1980s.

Laser based weapons

As well as missiles both superpowers developed ground based lasers (also known as Directed Energy Weapons or DEWs) to attack enemy satellites. The Soviet Union launched a series of "attacks" on U.S. satellites from the late 1970s intended to "blind" the satellites or cause system malfunctions. Things came to a head in the early 1980s when the Space Shuttle mission STS-41-G was affected by a Soviet laser strike. On 10th October 1984 the Shuttle Challenger was hit by an ion laser (Terra-3) as part of a protest by the Soviet Union at the U.S. plans for space-based ballistic missile defence and because of fears by some in the Soviet government that the Shuttle was being used for spying. The laser caused some system malfunctions and temporary blindness of the crew. The U.S. also worked on ground based laser weapons, in one test a laser managed to destroy a missile fuselage being held in a stressed condition on a ground test rig.

Current developments : FY-1C and USA 193

Anti-satellite weapons, and related technologies, were of course part of the "Star Wars" ballistic missile defence systems that generated many column inches (and cost a lot of money) on both sides in the last decade of the Cold War but after the end of the Cold War most projects were either canceled or cut back to a lower level. Anti-satellite warfare remained very much a thing of history books until January 2007 when the Chinese announced they had joined the ASAT club. A ballistic missile (a DF-21) launched from Xichang fitted with a kinetic warhead was able to successfully hit a weather satellite (FY-1C) and spread debris across space. NASA said that 35,000 pieces of debris over 1cm2 had been spread and 2,317 pieces were big enough to track. China are also said to be working on laser weapons and may have "blinded" some U.S. satellites.
Debris field from Chinese ASAT test
STK-generated image courtesy of CSSI (

But then it was the U.S.' turn to try and shoot down a satellite. A U.S. satellite, USA-193, was coming down out of control and the problem was no one is quite sure where the 2 and a quarter ton satellite would land. The US Navy managed to shoot down the satellite using Aegis guided missile destroyers that had already been modified for ballistic missile defence so the satellite could be directed to land safely in water. The attempt took place earlier in the year and was successful and used a modified RIM-161 Standard Missile 3.

References :

"Defending Space : US Anti-Satellite Warfare & Space Weaponry" by Clayton K S Chun (Osprey 2006)
"Modern Airborne Missiles" by Bill Gunston (Salamander 1983)
"Soyuz P" - Encylopedia Astronautica website
"OPS-2 (Salyut-3)" - Russian Space Web
"The F-15 ASAT story" - Space History Notes website
"STS-41-G" - Encylopedia Astronautica website
"Red Star Wars" by Steven J Zaloga (Jane's Intelligence Review May 1997)
"Blunt arrows: the limited utility of ASATs" - The Space Review June 2005
"Chinese ASAT Test" - Centre for Space Standards & Innovation
"Navy tasked with destroying satellite" - Navy Times website

Republished from my general tech site

Thursday, June 2, 2011

My latest electronic toy, a HP-12C

What is it with me and electronic gizmos this year, first the iPad then the Kindle and then the calculator but this is no normal calculator. This calculator is a Hewlett Packard HP-12C, an icon of calculator design. A calculator that first went on sale in 1981 and continues in production to the present day, to put that in context i was about half-way through my time at primary school the year HP began making this.

Looks wise its just... fantastic. Classic tech retroism i'd call it and i love it. Its not cheap though but i don't mind because i needed a decent calculator anyway (can't stand using software calculators on the computer, its all wrong keying in numbers with a mouse, like making coffee in a microwave). It looks and feels... quality. It has that old skool solidity about it (i hope it doesn't break tomorrow now i've said that!)

Although the HP-12C looks the same as it always has internally it has changed completely and now has an ARM microprocessor. It uses Reverse Polish Notation which i've never used before but i've done some basic calculations with it and all seems fine. The keys are lovely and clicky by the way. I wonder what i'll get next, i did plan to get an iPhone but i think i'll just wait to see what happens with that as a new version is apparently due soon...