You may know James Oberg as NBC News' space analyst using his 22 years experience in NASA mission control to add context to technical issues. In another of his frequent contributions to the IEEE Spectrum blog he puts some perspective on China's anti-satellite technology.
The missile used to destroy the satellite was a 'kinetic kill' device - it had no explosives. The satellite was destroyed by the force of the collision.
Oberg points out that the head-on collision between the missile and its target sums the velocity of the two objects. The satellite's LEO orbit speed is around 28 000 km/hr, adding the missile's speed "creates a hypersonic shock wave that propagates from the inside of the target outward and, at the outer edge, shreds the target into metallic confetti that moves away at up to hundreds of meters per second."
He goes on to say the satellite was an easy target whose position, orbit and velocity were known in advance.
"The Chinese targeted a low-orbiting, obsolete, weather satellite, where the kinetic kill energy was very great. However, the really strategic satellites fly much higher—the navigation network is 20 000 km up, and the communications constellations are in a geosynchronous arc at 40 000 km. At geosynchronous altitudes, the orbital velocities are so much lower that the impact energy would be only about a tenth as high as in last week's test.
Distance introduces a second burden: terminal navigation. When a target satellite is close to the Earth, ground radars can track it and relay final course corrections, both to the rocket during its ascent and to the kill vehicle, once it has been deployed on its hoped-for collision course. Radar operates at an inverse fourth power law, which means that for the Chinese system to aim many times farther than low Earth orbit—as it would have to do to track objects geosyncronously—the demands on a ground-based radar would be simply impossible."Labels: China Satellite, Space debris, Space Militarisation
Washington, DC -- On January 11, 2007 China destroyed one of its old weather satellites by launching a kinetic energy device from a ballistic missile fired from the ground leaving hundreds of pieces of debris orbiting the earth in the path of existing satellites and, potentially, the space elevator (SE).
The Space Elevator Journal was conceived to cover not only the technical aspects of the SE but the issues that affect it and near-Earth real estate. Watching how the various governments and agencies react gives us an idea of how they will work for/against each other in the future. An area that is sure to heat up as space becomes more valuable in the years to come.
In this excerpt of a January 19, 2007 US State Department daily press briefing Deputy Spokesman Tom Casey outlines the US governments policies on the issue and response to date in response to questions from various reporters.
"U.S. policy is that all countries should have a right to peaceful access to space ... simply because so much of the world we live in today is dependant on space-based technology, communications in particular. We certainly are concerned by any effort, by any nation, that would be geared towards developing weapons or other military activities in space. That's absolutely contrary [to our policies]. So we have raised our concerns with the Chinese Government ... both here in Washington and in Beijing. I think you've seen comments from the Japanese Government as well as from Australian Prime Minister Downer and I think several other governments as well raising these same issues.
We don't want to see a situation where there is any militarization of space. We certainly don't want to see a situation in which even tests of this kind that produce extensive amounts of space debris have the potential for disturbing or accidentally disrupting communications satellites or other kinds of space vehicles that are out there. So certainly this is an issue that I think is of general concern not only to us but to the broader international community and we'll be looking to get some more information from the Chinese about it.
"We've been on record previously I think as saying that there are concerns about the level of transparency in China's military and [the satellite kill ] fits in with this pattern. We would like to see and understand and know more about what they're really trying to accomplish here.
The US conducted similar tests in the 1980's and Casey was questioned as to why the US can do it and the Chinese can't. His response portends the potential for conflict caused by the growing importance of space.
"I think there's two factors you might want to take a look at. The first is the fact that 22 years ago, there was a Cold War ... between the United States and the Soviet Union ... [which] dictated. I think, quite a different policy on the part of the U.S. that exists now.
"More importantly, though, I think you need to look at the development of space in those past 22 years. The extent to which countries not only the United States, but countries throughout the world are dependent on space-based technologies, weather satellites, communications satellites and other devices to conduct modern life as we know it. And so the consequences of any kind of activity like this are significantly greater now than they were at that time.
Reporter: "Since you don't think anybody should be engaged in such kind of activities, will the United States foreswear or say it won't do this, or do you wish to reserve the right to do so?"
MR. CASEY: "Arshad, my understanding is there are no plans or intentions on the part of the United States to engage in such activities." ... there's always concern whenever there's debris in space, regardless of the cause, for the potential impact it might have on commercial satellites on manned space missions like the space shuttle, on the international space station, on anything that's potentially up there. You've certainly seen, given the history of some of the events of manned space flight, that small things can cause very big problems."
It'll be interesting to watch this unfold. As space activities increase and their relative importance to those back on Earth grows, will we simply extend territorial thinking into space? I'm hoping the SE is too big and important a project to be left to any one country or vested interest and we set aside our terrestrial differences and humanity climbs up the gravity together.
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Labels: China Satellite, Space debris, Space Militarisation
Space debris already causes major problems in space elevator design and space operations and the situation just got worse.
Aviation Week & Space Technology reporter Craig Covault says the January 22 issue will carry an article detailing reports of a "a major new Chinese military capability" in the form of an Anti-Satellite (ASAT) weapon.
Covault's report explains as-yet unconfirmed intelligence agency reports indicate China performed a successful ASAT weapons test at more than 500 mi. altitude destroying an aging Chinese weather satellite target with a kinetic kill vehicle launched on board a ballistic missile.the attack is believed to have occurred at about 5:28 p.m. EST Jan. 11.
"Details emerging from space sources indicate that the Chinese Feng Yun 1C (FY-1C) polar orbit weather satellite launched in 1999 was attacked by an ASAT system launched from or near the Xichang Space Center ...as the weather satellite flew at 530 mi. altitude 4 deg. west of Xichang located in Sichuan province ... a major Chinese space launch center.
The test, if it occurred as envisioned by intelligence source, could also have left considerable space debris in an orbit used by many different satellites."
Labels: Space debris, Space elevator
Some people like art or cars. Techno-journalists are info-geeks who get excited about well-designed web sites engorged with hard information. Couple that with the desire to write about things that will happen after the space elevator is built like space tourism and solar-power satellites and the Space Future (SF) site is pure info-porn.
In a kind of logical mobius strip SF credits its own commercial consulting arm, Space Future Consulting with its genesis. In any case, it is the work of some well-ordered minds who have laid out a smörgåsbord of articles and studies about space habitat and tourism, space vehicles and space power generation.
Among those is the article mentioned in title from Spaceport Associates' Derek Webber laying out the principal parameters of a successful space tourism venture.
Webber posits that "the average potential orbital space tourist is probably male, aged mid fifties, and works full time even though being worth at least $200M" who will book his trip with a specialist space agency on a polar orbit that will provide the most diverse view of terrestrial features.
The article covers the potential medical, technical and human aspects of pre-flight, on-orbit and return phases of the journey.
Webber assumes orbit will be achieved by conventional rockets or space planes with no consideration given to a space elevator.
--PB--
Labels: Private space travel, space colonisation, Space commerce, space commercialisation, Space elevator, space habitat, space tourism
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