Space junk faces a dust-up

25 June 2012

It has been a while since I last visited the subject of 'space junk' but an item posted on the US Naval Research Laboratory website caught my attention last week. Physicists and engineers at the Laboratory's Plasma Physics Division and Naval Center for Space Technology are researching a technique to 'sweep' low earth orbit debris from space using an 'Active Debris Removal' (ADR) system comprising nothing more than micron-scale dust.

NASA's Orbital Debris Program Office estimates there are more than 21,000 orbital debris objects larger than 100mm in diameter within low earth orbit (LEO), and approximately 500,000 object particles between 10 and 100mm, with the number of debris particles smaller than 10mm in excess of 100 million. Last year, a report concluded that LEO orbital debris is at the 'tipping point'- the threshold for a collision cascade - the so-called Kessler Effect - posing a huge risk to valuable space assets such as communication satellites and the Space Station.

"Hundreds of near-misses occur each year between orbital debris and operational satellites," says NRL's Gurudas Ganguli, who believes dust, similar to that which naturally fills the near-Earth environment, can be deployed artificially in a narrow altitude band to enhance drag on debris, forcing its re-entry into the Earth's atmosphere and subsequent incineration.

About 100 tons of cosmic dust is introduced daily into the Earth's environment in the form of micrometeorites. In addition to this natural source, human space activity also regularly introduces large quantities of dust in space, but it is distributed over a very large volume, making it too widely dispersed to affect orbital debris.

According to Ganguli, if dust is artificially deployed, in orbit, in opposite direction to the debris trajectory, it can induce an enhanced drag on the debris. The novelty is that by choosing the dust characteristics - density, particle size and so on, it is possible to synchronize the rate of dust and debris descent. This offers the possibility to clear a very large volume of small debris by deploying a modest amount of dust, say 20 to 40 tons, in a narrow layer.

"It is well known that the natural drag due to neutral atmosphere decays satellite orbits," Ganguli explains. "We use the natural atmospheric drag to decay the deployed dust orbits and simultaneously use the dust to induce enhanced drag on the orbital debris. Like the natural dust, most of the deployed dust as well as the small orbital debris will incinerate while re-entering the Earth's dense atmosphere. So the environmental effect of releasing the dust is expected to be benign."

The researchers believe a dust based ADR system can be developed with off-the-shelf type technologies in the near term and present manageable risks to existing space assets. Their preliminary analysis suggests tungsten to be a prime candidate for the dust because of its high density, relative abundance, availability in powder form and modest cost - all of which contributes to the efficiency and economy of the system.

Social networking's gender divide
While we might expect men and women to use the Internet in different ways, a new study by psychologists at the University of Bath has found that this gender gap in Internet use is actually widening. The researchers found that differences in the Internet experience of men and women was more apparent than ten years ago, following the introduction of sites such as Facebook and microblogging sites such as Twitter.

Nearly 500 first year undergraduate students from six universities took part in the study, split between 389 women and 100 men with a mean age of 20. The exercise was a repeat of an original study the researchers undertook ten years ago and aimed to analyse changes in Internet use and whether the gender differences they found in 2002 remained in 2012. What the researchers found was that the difference between men and women is now more distinct than it was ten years ago since the advent of social networking sites.

Richard Joiner, lead author of the paper - Gender, Internet Experience, Internet Identification and Internet Anxiety: a ten year follow up - said the findings indicate that, rather than transcending or overcoming gender differences in wider society, Internet use by males and females seems to reflect - and in some instances even exacerbate - these broader trends. “In previous research we found no gender differences in the use of the Internet for communication, whereas in the current study we found gender differences in communication and that females were using social network sites more than males,” he says.

The research found that the mean age students started using the Internet was 11 years old and they spend approximately 3.4 hours a day online. Men were more likely to use the Internet for games and entertainment, online betting and news sites. As well as social networking, women were also more likely to make travel reservations online.

Dr Joiner believes gender differences in the use of the Internet are more a reflection of gender differences in wider society. "It is important to continue to investigate these differences because of the importance of the Internet in virtually every aspect of our lives and the erroneous assumption that all young people have similar and high level of technology ability and experience.”

Free BBQ for hybrid drives developers
HBM is hosting a free drop-in event for automotive design and test engineers tasked with improving the efficiency of hybrid drives. The event will be held at The Heritage Motor Centre in Warwickshire on Wednesday, 18th July from 9.00am through to 3.00pm. The lure is a free barbecue but the technological centrepiece will be HBM’s ‘My Car’, a vehicle packed with instrumentation to whet the appetite of any automotive systems test engineer.

A mini-exhibition will explore a variety of techniques for capturing data from the mechanical and electrical systems of a variety of hybrid drives, and a number of HBM test system end-users will also be on hand to share their experiences.

If you’d like to join the party, click here.

Les Hunt
Editor