With Black Powder into Space
from Gerhard Holtkamp, 05. April 2010, 00:23
Although modern rockets use advanced fuels to send satellites into space an upcoming launch will resort to something that goes back to the dawn of rocketry in ancient China: Black Powder...
(I took care not to post this blog on April 1st!)
This upcoming Thursday (8-APR-2010) the European Cryosat 2 spacecraft is scheduled to be launched from the Baikonur Cosmodrome at 13:57 UTC. The launch had been postponed from an original date in February due to problems with the Dnepr rocket but those problems seem to have been fixed.
Cryosat 2 is an ESA Earth Explorer mission with the task to accurately survey the ice on our planet. Although the area of glaciers in Antarctica and Greenland as well as the extend of sea ice already has been mapped by other satellites Cryosat will be able to add the third dimension to it by also determining the thickness of the ice. It is thus a mission of fundamental importance to find out about the effects of global climate changes.
To launch the 700 kg satellite ESA selected the Russian Dnepr rocket. This rocket started out as an SS-18 ICBM (InterContinental Ballistic Missile). Those missiles had been deployed during the Cold War as a carrier of thermo-nuclear weapons which would annihilate whole areas.
Lucky for all of us the Superpowers eventually realized that a themo-nuclear war would destroy not only enemy territory but the planet as a whole. After lengthy negotiations they agreed to reduce the number of offensive missiles.
Rather than destroying the former ICBMs outright a share of those missiles has been refurbished and is now offered as a (comparatively cheap) means to launch smaller satellites. Among the changes an extra stage is typically being added for insertion of the satellite into orbit. What has stayed the same is the way in which these former ICBMs were supposed to be launched.
This has let to some curious launches. Some satellites using submarine-based missiles were actually launched from submerged nuclear submarines. The Dnepr rocket used by Cryosat will be launched out of a silo.
Igniting the main rocket engine right inside the silo would probably cause the immediate destruction of the whole rocket together with its payload. Instead the rocket is ejected from the silo by means of hot gases via a gas generator powered by - would you believe it - black powder! So the whole thing is kind of an oversized muzzle loader the Three Musketeers would have been proud of.
Why black powder was chosen for the gas generator I don't know. But as this has been used for centuries we can look at it as a time-proven reliable technology.
Once out of the silo the actual rocket engine will be ignited (this time using modern fuel) and the following part of the launch proceeds as with other satellite launches. Well not quite. Once the first two stages have done their job it's time for the third stage to inject the satellite into its proper orbit. Normally the upper stage will push the satellite forward meaning that the satellite is at the front while the rocket engine is at the rear.
But again Dnepr launches are different. After separation from the second stage the third stage turns around by 180 degrees and then pulls rather than pushes the satellite! The small thrusters used by the Dnepr third stage are mounted sideways to make this possible (see the picture of the Cryosat - Dnepr separation). Kosmotras - the company operating Dnepr - claims that this will result in a more accurate insertion.
Cryosat together with other specialized Earth observing missions will help us understand and mitigate global environmental changes. And a rocket which was originally developed to bring death and destruction now plays its part to help us save our planet.
I'm sure that none will be more happy about this than the very engineers that designed these systems.
To learn more about Cryosat check the ESA website.
And here you will find more about Kosmotras and Dnepr.
(I took care not to post this blog on April 1st!)
This upcoming Thursday (8-APR-2010) the European Cryosat 2 spacecraft is scheduled to be launched from the Baikonur Cosmodrome at 13:57 UTC. The launch had been postponed from an original date in February due to problems with the Dnepr rocket but those problems seem to have been fixed.
Cryosat 2 is an ESA Earth Explorer mission with the task to accurately survey the ice on our planet. Although the area of glaciers in Antarctica and Greenland as well as the extend of sea ice already has been mapped by other satellites Cryosat will be able to add the third dimension to it by also determining the thickness of the ice. It is thus a mission of fundamental importance to find out about the effects of global climate changes.To launch the 700 kg satellite ESA selected the Russian Dnepr rocket. This rocket started out as an SS-18 ICBM (InterContinental Ballistic Missile). Those missiles had been deployed during the Cold War as a carrier of thermo-nuclear weapons which would annihilate whole areas.
Lucky for all of us the Superpowers eventually realized that a themo-nuclear war would destroy not only enemy territory but the planet as a whole. After lengthy negotiations they agreed to reduce the number of offensive missiles.
Rather than destroying the former ICBMs outright a share of those missiles has been refurbished and is now offered as a (comparatively cheap) means to launch smaller satellites. Among the changes an extra stage is typically being added for insertion of the satellite into orbit. What has stayed the same is the way in which these former ICBMs were supposed to be launched.
This has let to some curious launches. Some satellites using submarine-based missiles were actually launched from submerged nuclear submarines. The Dnepr rocket used by Cryosat will be launched out of a silo.
Igniting the main rocket engine right inside the silo would probably cause the immediate destruction of the whole rocket together with its payload. Instead the rocket is ejected from the silo by means of hot gases via a gas generator powered by - would you believe it - black powder! So the whole thing is kind of an oversized muzzle loader the Three Musketeers would have been proud of.Why black powder was chosen for the gas generator I don't know. But as this has been used for centuries we can look at it as a time-proven reliable technology.
Once out of the silo the actual rocket engine will be ignited (this time using modern fuel) and the following part of the launch proceeds as with other satellite launches. Well not quite. Once the first two stages have done their job it's time for the third stage to inject the satellite into its proper orbit. Normally the upper stage will push the satellite forward meaning that the satellite is at the front while the rocket engine is at the rear.
But again Dnepr launches are different. After separation from the second stage the third stage turns around by 180 degrees and then pulls rather than pushes the satellite! The small thrusters used by the Dnepr third stage are mounted sideways to make this possible (see the picture of the Cryosat - Dnepr separation). Kosmotras - the company operating Dnepr - claims that this will result in a more accurate insertion.Cryosat together with other specialized Earth observing missions will help us understand and mitigate global environmental changes. And a rocket which was originally developed to bring death and destruction now plays its part to help us save our planet.
I'm sure that none will be more happy about this than the very engineers that designed these systems.
To learn more about Cryosat check the ESA website.
And here you will find more about Kosmotras and Dnepr.
