Over the past few years we have endured idea after idea on how to remove space debris. The list is almost endless. There is the ground-based high energy laser that will zap trash right out of space. Tethers can do it better, faster and cheaper. Water sprays are simple and effective. Orbiting trash cans make all kinds of sense. Air bursts are very clean and simple. Nets can collect lots of debris quickly. And, the list goes on and on.

Our all-time favorite idea is "Space Balls" that can passively collect trash and naturally dispose of themselves by reentry into the atmosphere.

Let's do a simple reality check. Every one of the proposed ideas has at least one major flaw. Some violate the laws of physics. Some are too technologically complex to effectively implement. Some violate existing space treaties. Some present serious safety issues.

But, all violate the most important law: affordability. To date, there are no known solutions to the space debris collisions-with-satellites threat that can be justified on a cost basis. Satellites placed in orbits between about 700 and 1100 km are exposed to an increasing collision threat from the growing density of debris objects in that zone.

The issue to date has been one of finding a remediation solution: How do we remove enough debris to stabilize debris proliferation? Recent studies indicate that removing a few key large debris items each year may arrest the debris growth rate. However, these studies make several assumptions which are questionable in view of recent events such as the Iridium-Cosmos collision and the continued addition of new satellites to the high-debris zone.

Let's hypothetically assume that the removal of 10 large expired satellites per year will stabilize debris growth. Each object removal flight will likely cost about as much as placing a new satellite in orbit, say $200 million. Ten of these per year would then cost a total of about $2 billion annually.

Once we have a cost number, several other issues become important. Who will pay for the missions? The Russians (and former USSR) are the known worst offenders. Then there are the US, Europe and China. Are there any volunteers to spend this kind of money just to take out a small amount of space trash? We don't hear any enthusiastic outcries of "I will."

Remember, the $2 billion annual expenditure does not clean up space, but only removes a few large objects. There remain at least hundreds of thousands of other objects ranging in size from several meters to a few millimeters that can damage or destroy a spacecraft in the danger zone of debris.

Many of you will immediately point out that we should carry out dual-purpose missions in which a removal is possible each time we launch a new satellite. This would be very nice, but not practical due to several factors.

First, new satellites like to go to specific orbits, while dangerous debris objects are generally not easily reachable as secondary mission objectives. Second, each basic launch mission would likely be much more complicated if a secondary mission were added, e.g., additional hardware and fuel would be required. Larger launch vehicles would be needed and reliability might be compromised.

So, is there a practical and affordable solution to the debris issue? Yes, but we have not yet found it. Keep looking.