A model of space debris populations around Earth.

What kinds of problems could debris in space cause? They travel at speeds on the order of tens of thousands of miles per hour, which means that debris of any shape, size, and form will be destructive if it collides with a satellite or space shuttle. Collisions with space debris isn’t unheard of. Also, they could delay space launches if it is known that a large cloud of debris is hovering directly over the launch pad.

Space debris comes from a variety of sources. Nuts and bolts could become loose and float away from spacecraft during normal operation. When rocket stages (or segments) separate in space, they release debris. Also, in-space collisions between satellites, while rare, will create large-sized debris – the same goes for intentional spacecraft destruction, such as the Chinese anti-satellite test that was conducted a few years ago. Some of these events unleashes several thousand pieces of debris, most of which are tiny (less than an inch in size) and are much more difficult to track than larger-sized debris.

Over the past few decades, scientists and engineers have brainstormed possible solutions to decreasing space litter. However, all of the ideas have been technologically and/or economically infeasible. This could change as time goes on, especially as technology advances and/or the cost of launching a vehicle into space decreases. One possible solution is launching a garbage-collecting spacecraft to do just that, but what to do with the collected garbage is a problem. Another solution is somehow colliding objects with the orbiting debris in an effort to reduce their energy enough so that they fall into the Earth’s atmosphere (due to gravity) and burn up, but no one has thought of a feasible means to do that.

(Image from Wikipedia)

Refineries can use large quantities of water that need to be purified for the next process.

An interesting article from ScienceDaily reports that techniques being researched for an upcoming European mission to Mars could be directly applied to help address the energy crisis here on Earth. Basically, the process of separating organic material from space rock could be applied to purifying the large quantities of water required to refine unconventional fossil fuels. Unconventional fossil fuels are of interest in times like these, when conventional crude oil is in short supply. From the article:

Professor Mark Sephton from Imperial’s Department of Earth Science and Engineering, said: “The research involves using extraction-helping materials, called surfactants, to liberate organic matter from rock in space to gain a deeper understanding into the biological environment on Mars. We aim to show that the same technique could also be used to recycle the prodigious amounts of water necessary to process tar sand deposits and turn them into conventional petroleum.”

Usable energy resources are essential to the global economy.  Conventional crude oil is a staple energy resource and accounts for over 35% of the world’s energy consumption.  As the demand for oil exceeds supply, focus has now turned to trying to tap unconventional fossil fuels, such as tar sands. However, these unconventional fossil fuels must be extracted and upgraded to match the characteristics of more conventional oil deposits and make them commercially viable. The extraction process requires substantial amounts of water which is then left contaminated for extended periods of time. In just hours, the new technology can strip this water of its oily contaminants, removing a bottleneck in the refining process.

By removing this “bottleneck” in the process, more oil can be extracted from these unconventional fossil fuels, which reduces reliance on crude oil in short supply.

It is interesting to see how research and development in one area can be directly applied in another. The article has a conclusion that also expresses interest in the versatility of this research:

Dr Liz Towns-Andrews, Director of Knowledge Exchange at STFC, which is funding the study through its Knowledge Exchange Follow on Fund award scheme, added, “This is a truly valuable study which will not only reveal more about our neighbour Mars, but could also deliver enormous benefits here on Earth. The new research is a direct solution to our worsening energy supply crisis and is a great example of the seamless interaction of pure and applied science with engineering to solve real world environmental and commercial issues.  Professor Sephton’s work is well aligned with the current needs of industry and we believe that this ambitious project could be of great benefit to the UK economy.”

(Image from Wikipedia.)

The U.S. government has announced increasing concern over the quality of its Global Positioning System (GPS), which could begin to deteriorate as early as next year, resulting in regular blackouts and failures – or even dishing out inaccurate directions to millions of people worldwide [The Guardian]. The possibility that new satellites would not be launched in time was announced in late April, but the warning was stepped up this week in a government statement that recognized cost over-runs of defence department space programmes [Nature] as part of the problem.

Basically, the article explains that the existing GPS system could deteriorate in the near future if old functioning GPS satellites in space go out of commission without fresh replacements. So, with this buzz about the GPS system which many people in the world today use in their everyday activities (sometimes without knowing it too), how does GPS work anyway? Here is a very high-level basic concept of how GPS works.

Artist's rendition of a GPS satellite in orbit.

There are currently 31 functional GPS satellites orbiting the Earth (although 24 satellites is the bare minimum for GPS to work at any location on Earth). Each GPS satellite periodically broadcasts “messages,” which GPS receivers read and interpret. These messages that GPS satellites broadcast contain three pieces of information:

• Time: the (standardized) time that the message was sent from the GPS satellite
• Ephemeris: the orbital information of the GPS satellite (position, etc.)
• Almanac: general information about all functional GPS satellites in orbit

The time and ephemeris are key pieces of information that GPS receivers use in order to determine precise location of the receiver. A GPS receiver can calculate its distance to a GPS satellite by figuring out how long it took the message to travel from satellite to receiver (transit time), then using that with the known speed of light to calculate distance. Theoretically, a receiver is able to calculate its precise location if it knows the distance to three different GPS satellites, since there are three dimensions to a position in space. However, in practice four GPS satellites are used to calculate the precise location of a receiver, because a fourth satellite can be used to correct potential errors in the GPS receiver’s clock. There are economic reasons for this necessary correction. In order to make GPS devices affordable to the general public, GPS receivers are equipped with less-expensive adequately-functioning clocks (that are used to calculate transit time of the broadcasted messages) rather than super-expensive uber-accurate clocks. These less-than-perfect receiver clocks can cause large errors in calculating distances to GPS satellites if there is even a small error in the transit time of the GPS message due to the large magnitude of the speed of light.

Now, the number of GPS satellites in space affects the speed and accuracy of GPS algorithms. If a GPS receiver can track more GPS satellites than the minimum four satellites, then it can calculate its position faster and more accurately. There is a higher probability of tracking more satellites if there are more satellites in orbit. If there are fewer satellites in orbit (like if old satellites are put out of commission without a new replacement), then that can lead to less accurate GPS calculations from receivers. Don’t panic yet! It does not mean that the GPS system will suddenly stop working – rather, it will lose its robustness if the number of functioning GPS satellites in space were to decrease, which the article in Discovery Magazine explains.

[Image from Wikipedia]

Carbon nanotubes are made of hexagonal lattices.

A recent article published by MIT’s Technology Review describes the uniquely resilient properties of carbon nanotubes and some of their applications. Carbon nanotubes is one of the main areas of today’s nanotechnology research. The structures are tube-shaped with walls made of hexagonal lattices, and can be a few nanometers in diameter, which is a miniscule fraction of the width of a single human hair.

Despite their tiny dimensions, carbon nanotubes have significant mechanical and electrical properties that dwarf common macroscopic engineering materials such as copper and steel. While carbon nanotubes are extremely flexible and lightweight, their tensile strength is unparalleled, which means they are very difficult to break. The article provides a testament to how strong carbon nanotubes are:

These materials change shape and size in response to electrical or chemical signals; some expand by up to 1 percent and exert 100 times more force than natural human muscle over the same area.

Also, they can thrive in extreme temperature environments. According to the article:

They can expand and contract thousands of times and withstand temperatures ranging from -190 to over 1,600 °C.

Carbon nanotubes are also modern-day champions in conducting electric current. Their conducting ability can be thousands of times greater than that of copper, which is a common material for today’s wires for electricity. This makes carbon nanotubes potentially very useful in electrical circuits, because they can conduct current very well for their miniscule size. This can aid in the development of even smaller electronic gadgets than what we have today. Also due to their electrical properties, carbon nanotubes have potential for use in solar cells to increase their energy output.

The article also mentions some other applications of carbon nanotubes that researchers are looking into today. Researchers are looking into using carbon nanotubes for artificial muscles in robotics because of their unparalleled material strength. Researchers at NASA are looking into utilizing carbon nanotubes in developing “shape-shifting spacecraft parts” due to their light weight, flexibility, and ability to operate in a wide range of temperatures. The article points out that extreme temparatures are commonplace in space, such as the extreme cold on Mars and the extreme heat on Venus. Spacecraft that can handle these extreme temperatures can help us better analyze and understand these planets by traveling deep inside them.

Because carbon nanotubes are still in the development stages, the general public has not heard a whole lot about them. However, research with these materials have been advancing well, and it could be not too long in the future that we see carbon nanotubes in everyday devices.

(Image from Wikipedia.)