Archive for the ‘Space’ Category

Titan LNG

Photo by Wikimedia Commons. Some rights reserved.

You may have seen the recent news coverage of a Nature article describing the discovery of a large lake of liquid hydrocarbon (presumably methane) in the equatorial regions of Titan, one of Saturn’s moons. Science fiction writers like Robert Heinlein and Isaac Asimov helped create visions of human colonies on Titan, and its complex atmosphere suggested to scientists that it bore some key resemblances to Earth. While exciting from a scientific standpoint because previous models of methane behavior on Titan suggested that lakes could not form outside its polar regions, the discovery also has energy-related implications.

The liquified natural gas in today’s energy market is primarily liquid methane, which has been artificially cooled and maintained in that state for transport before being converted back to a usable form when it reaches its destination. The associated costs for the vessels and terminals involved in LNG conversion and transport run into the hundreds of millions of dollars, but the technology is established and widespread.

Could NASA someday achieve the dream of a Titan colony using LNG? On Titan, transport costs could be minimalized by locating near the lakes, requiring only regasification and storage technology. NASA has tested methane-powered rocket engines, but most of its current habitation technology, such as that used on the ISS, is built around solar sources. However, it’s not always convenient to lug around a 73-meter solar array. At a distance from the sun of 9.0-10.1 AU (an average distance of around 891 million miles) depending on its position in its elliptical orbit, Saturn and its satellites aren’t exactly local. And Titan’s atmosphere might affect the viability of solar-based technology on the surface. The presence of an abundant surface energy source, however, could have a game-changing effect on the chances of a colony’s survival – if we can get there.

Loch NPOESS Monster: The Environmental Satellite Rarely Spotted

Image from unukorno. Some rights reserved.

On Friday, the GAO released written testimony before the Subcommittees on Oversight and Investigations and Energy and Environment, Committee on Science, Space, and Technology on the topic of polar satellites. The testimony reviewed and summarized work that National Oceanic and Atmospheric Administration (NOAA) and the Department of Defense (DOD) have been doing to develop individual environmental satellite programs that are replacing the recently disbanded joint-agency National Polar-orbiting Operational Environmental Satellite System (NPOESS). The main area of concern? Whether agency slowness could lead to gaps in weather and climate data coverage.

But first, let’s step back a few years.

NPOESS was planned to be a “next generation” environment-monitoring satellite system – circling the earth once every 100 minutes – that would have replaced some clunkier existing satellite systems. The data it would have collected was considered critical for long-term weather and climate forecasting. A contract for the project was awarded in 2002.

In February of 2010, however, the President cut the plug – before the first demonstration satellite was even launched. The program had been plagued with problems. The cost estimates for NPOESSie, our proverbial beast, grew more than 100% (from $6.5B in 2002 to $13.9B at the time of its demise). The program had also suffered significant delays (the planned launch date for a the test satellite was pushed back by over 5 years), as well as technical and management “challenges,” as a White House Fact Sheet put it bluntly.

More accurately, the program was “restructured.” The joint agency project was re-worked as separate satellite programs to be established by NOAA and DOD. A few months after the restructuring was announced, GAO published an initial report assessing the agencies’ efforts, and – surprise, surprise! – found a few areas of concern relating to delays (“the two agencies are scrambling to develop plans for their respective programs”), loss of staff, and insufficient oversight of new program management. The report included recommendations for both agencies to address the key risks.

Last week’s testimony checked back in on NOAA and DOD. According to the GAO, in the year since their first report on the satellite systems, both agencies have made progress in developing their programs and implementing GAO’s recommendations, though not everything has been addressed. The key concern here is that failure to get things up and running quickly – in other words, launching new satellites before the old ones fail – could lead to gaps in satellite data. (There are several figures in both the GAO testimony and report that detail potential gaps.)

And what exactly is the problem with gaps in satellite data? The GAO testimony says it best:

 “According to NOAA, a data gap would lead to less accurate and timely weather prediction models used to support weather forecasting, and advanced warning of extreme events—such as hurricanes, storm surges, and floods—would be diminished. The agency reported that this could place lives, property, and critical infrastructure in danger. In addition, NOAA estimated that the time it takes to respond to emergency search and rescue beacons could double.”

Let’s hope we get a glimpse of NPOESSie (or her spawn) soon.

2011: A Garbage Odyssey?

Though global warming may have eclipsed litter as the environmental issue vying for our attention (when’s the last time you saw a public service announcement from Keeping America Beautiful?), there’s still one place where the (potentially lethal) effects of garbage are a pressing matter: space.

Recent NASA estimates show tens of millions of pieces of debris floating through space as we speak. Of those, 500,000 are between 1 and 10 cm in diameter, and 19,000 are larger than 10 cm. The remainder are all less than 1 cm. Sound harmless? Consider that the average impact speed of orbital debris with another object in space will be about 10 km/s (that’s about 22,000 miles/hour). These speeds render even the smallest detritus a threat – a fleck of paint caused this 1 mm pit on the Space Shuttle Challenger’s front window.

If flecks of paint fall on one end of the continuum of space debris, the larger end can see anything from defunct satellites to spent stages used to launch vehicles. Generally, and by NASA’s definition, orbital debris is “any man-made object in orbit about the Earth which no longer serves a useful purpose.”

Computer generated image of objects in space within 2,000 km of the Earth's surfaces. 95% of the objects in this illustration are orbital debris. Dots are not to scale. Image courtesy of NASA.

Most orbital debris resides within 2,000 km of the Earth’s surface. Around this altitude, the density of objects is such that, if the growth of space debris isn’t put in check, it is thought that collisions between objects could cause subsequent debris and subsequent collisions, eventually resulting in an exponential cascade of debris that could render space travel in that area impossible. This scenario is referred to as the “Kessler syndrome.”

Currently, however, NASA claims that, while operational spacecraft is routinely struck by small objects with little or no effect, “the probability of two large objects (> 10 cm in diameter) accidentally colliding is very low.” While certain technological and structural precautions can be taken to prevent damage to spacecraft from orbital debris, and there are certain proposals (though many are impractical) for the physical removal of debris from space, most space debris mitigation measures are focused on prevention.

Though there is no international treaty requiring such measures, the UN has published guidelines for curtailing “the generation of potentially harmful space debris.” These guidelines are supposedly based on an earlier set of recommendations from the Inter-Agency Debris Coordination Committee.

In the US, NASA has published Procedural Requirements, a Technical Standard, and a companion Handbook on the topic of limiting orbital debris. NASA also worked with the Department of Defense to develop the U.S. Government Orbital Debris Mitigation Standard Practices.

Generally, all of these guidelines include at least one or more of the following mitigation measures: (1) limiting release of debris during normal operations; (2) preventing accidental explosions or break-ups, during or after operations; (3) minimizing collisions; and (4) planning for postmission disposal of space structures.

Perhaps a public space announcement is in order.

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