When We’ll Really Nuke The Moon

October 14, 2009

The dust is still settling from the public blowup over NASA’s LCROSS experiment to go prospecting for water on the moon by crashing a rocket booster into it last Friday. The impact was a PR flub. There were no dramatic images for any evidence of the smashup.

Nevertheless, I have subsequently received a few angry e-mails from people who are incensed that we would harm Earth’s only natural satellite.

The tersest note was from a retired Marine:

“Stop bombing the fu*king moon.”

In a following e-mail he was more philosophical: 

“Yes, worlds are being destroyed every second in our timeless universe, but through natural processes of creation and recreation . . .”  

If I apply that logic, then we should do nothing in the future to deflect or destroy any Earth-bound asteroid, but instead let nature take its, er, natural course  in “recreating” life on the surface of an incinerated Earth.

Space Trekkers Live in Binary Planetary Systems

July 05, 2009

For years I’ve hypothesized that binary planetary systems exist, and that these are the places to go looking for space-faring civilizations.  By binary planetary system I mean a pair of gravitationally bound stars, each with its own independent family of worlds.

There could be habitable planets around each star in the binary system, if the stars are far enough apart. If technological civilizations independently evolve around both stars, they could actually travel across space and visit each other. This would be a powerful motivation to build the fusion-powered rockets needed to travel back and forth within a reasonable amount of time.

Astronomers have now found such as system, but we’ll have to wait another 4 billion years before an alien civilization manifests itself. Why? Because the double star is just a few millions of years old, and if Earth is any example, it takes a long time to evolve intelligent beings.

The Meaning of Spacetime, Relatively Speaking

June 17, 2009

Space and time are something we deal with every waking moment of the day. We need to navigate space (at least between home and office) and are subservient to time from cradle to grave. But there are inherent puzzles that stumped history’s top scientists. And, these puzzles can frustrate science fiction writers who want to find shortcuts though space and time to get from one side for the galaxy to the other within the lifetime of their characters.

Would there be space if there weren’t matter around to define a volume, like the walls of a room, or periphery of the solar system? How could we ever know that space in the universe is expanding, without galaxies flowing along with the expansion and sending us signals from the remote past? Would there be time if we never saw anything changing?

Are We Ready to Live on Other Planets?

June 08, 2009

The  International Space Station has a beefed up crew that has gone from three to six astronauts, now that the construction of the $100 billion space laboratory is nearly complete. We are told that the station crew will be able to spend more time doing medical and biological experiments in the station's microgravity environment to prepare humans for journeys to the moon and Mars.

We are “learning to live in space” is the shorthand justification for why we have a space station. But are the right questions behind the ISS experiments being asked? Exactly how salient is the research on the ISS when applied to human interplanetary travel?

Going Up! Next Stop, Earth Orbit

September 23, 2008

One of my favorite fairy tales from childhood is Jack and the Beanstalk, where the untouchable clouds can be reached by shimmying up an oversized vine.

The Arthur C. Clarke 1979 novel The Fountains of Paradise, describes the space age incarnation of this fairy tale: the construction of a space elevator that whisks people up to Earth orbit without the need of rocket ships.

This idea goes as far back as the Russian physicist and theoretical father of rocketry, Konstantin Tsiolkovsky, of a century ago.

When I mention this concept among friends they give me a quizzical look as if I was really talking about something as absurd as climbing a beanstalk.

A space elevator is essentially a very long super strong cable extending from Earth’s surface high into space.  The elevator capsule would carry cargo and passengers to a tethered space station in geostationary Earth orbit (GEO), at 22,300 miles altitude.

To keep the cable taunt, it would be attached to a large counterbalance mass beyond geostationary orbit, perhaps a captured near Earth asteroid. The GEO gateway station would be at the center of balance of the cable.

Yes, The concept of a space elevator sounds utterly fantastic. You can just imagine the buttons: “9 millionth floor please.” Kids would be banned. They’d push all the buttons!

Nevertheless the promise of a space elevator is every bit as tantalizing as it is seemingly improbable. I do believe it will be a matter of when not if, when this daunting super-engineering dream is finally realized.

Why? Because from a vantage point only three miles from the launch pad, I’ve watched several NASA space shuttles roar skyward atop Promethean flames. The raw power of the 7 million pounds thrust is as terrifying as it is awesome to behold. 

In that back of your mind you think there must be a more civilized way to get into space instead of strapping yourself to two oversized skyrockets that are nearly one-third the height of the Washington Monument.

Just as terrifying is the though of screaming back into Earth’s atmosphere at 25 times the speed of sound. Your vehicle glows red hot, as it has to bleed off as much energy as it used to get into space.

Two fatal space shuttle accidents – one while going up and one while coming down – underscore the extreme aerodynamics and extreme physics in operating such a space transportation system.

In recent years NASA has offered a $400,000 prize for teams that can build an energy beam-powered space elevator model that can ride 200 feet up a ribbon of material. In a second competition NASA offered a prize for the team that could come up with their best formulation for an ultra-light, ultra-strong ribbon material that survives grueling tug-of-war stresses. So far there have been no winners.

Last week Japan announced that a consortium of scientists and industrial firms has formulated a plan to build a space elevator for $9 billion.

At the heart of concept is a three-foot wide carbon nanotube ribbon. IN the coming years nanotube technology is expected to reach the tensile strength required to fabricate a 75,000 mile-long ribbon. The strength of nanotubes materials has increased a hundredfold in just the last five years.

Elevators attached to the ribbon would crawl up and down powered by electricity, a laser beam, or electromagnetic propulsion. The elevator would drastically reduce the cost of moving people and cargo into orbit. Rocket payloads can cost $10,000 per pound.  The space elevator could drop costs to $100 per pound say some experts. Orbital transportation vehicles like the space shuttle would be remembered as the Hindenburg of the space age.

It’s easy to imagine a sort of second-generation space race where the world’s major powers compete to see who can be the first to establish a permanent space presence by constructing a space elevator.
It would be a resource of national pride and a status symbol of technological prowess. You could imagine a string of international space elevators stretching out from the equator like spokes radiating from the hub of a bicycle wheel.

However, the elevator would be as "choke point", as characterized in military language. Destroy the slender ribbon and you cut off a nation’s access to space.

The Earth platform for the elevator would be a prized target for enemy nations as well as terrorists. What’s more, it would have to be located outside a country’s boundaries and near the equator. One prime anchor location is in the Pacific Ocean, roughly 1000 miles west of the Galapagos Islands where interference by lightning, hurricanes, strong winds, and clouds is minimal.  But It would have to be surrounded by several concentric defense perimeters to ward off attacks.

The space elevator would not only make sense on Earth but on Mars too. Colonists would reach Mars’ surface by docking with the elevator’s orbiting station node and pressing the down button. I described in an earlier blog that Mars is very problematic for making safe rocket landings. The thin atmosphere makes it much more treacherous than landing on the moon or Earth.

Advanced space faring civilizations elsewhere in the galaxy may have already reached the space elevator era. Regrettably even this sort of macro engineering around a star is not detectable from Earth. A circumequtorial ring of space colonies might give a terrestrial planet a slightly anomalous infrared excess. But this would easily be explained as a dusty slender ring system rather than the handiwork of an advanced intelligence.

artwork credit: Pat Rawling/NASA

An Interstellar GPS System

August 01, 2008

When we jump into the car we are accustomed to using a Global Positioning System (GPS) mapping device to find our way around town. 

What’s easy to forget is that a mega-technology is behind this small dashboard mounted accessory. It's a constellation of two dozen satellites. They transmit precise microwave signals that enable a GPS receiver to determine its location, speed, direction. It’s $750 million per year operation.

The galaxy provides its equivalent of a GPS system on a vastly grander scale, and for free.  This celestial "GPS" (Galactic Positioning System) could conceivably be used for tooling around our solar system as well as for interstellar travel.

Called XNAV (X-ray Navigation) it is based on the fact that astronomers have mapped a substantial number of X-ray pulsars whose machine gun like bursts of energy are as reliable as signals from our GPS satellites.

Pulsars are rapidly rotating neutron stars with powerful magnetic fields. A neutron star is the crushed core of a super massive star that has exploded. A spinning pulsar paints the sky with a flickering beam, just likes a lighthouse beacon.  The pulse signals, which can arrive as quickly as 1000 time a second, are so regularly that the fastest pulsars are as accurate as an atomic clock.

When pulsars were first discovered in 1967 astronomers half-jokingly imagined that these bizarre objects were some kind of artificially produced interstellar beacon. The incredible regularity of the signal pulsation seemed at first to have no natural explanation.

An X-ray pulsar is a particularly high-energy class of neutron star that generates temperature of millions of degrees at its surface, allowing it to blast out an X-ray beam more energetic than even “Star Wars’” Death Star battle station. These pulsars feed off a steady stream of fuel falling onto them from a normal stellar companion they are devouring.

Powered by the raw forces of gravity and magnetism, pulsar “clocks” are reliable and for all practical purposes fixed on the sky. Measurements of these sources can be used to establish the location of a spacecraft anywhere in this region of the galaxy.

Not surprisingly, science fiction writers thought about a Galactic Positioning System half a century ago. In his 1952 story Troubled Star, writer and engineer George O. Smith wrote about space beacons that were created to facilitate interstellar travel.

This is one of the few astronomical phenomena we would share a common interest in with alien technological civilizations. A nearby civilization might use the same constellation of X-ray pulsars for interstellar travel.

Besides a navigational aid the pulsars are absolute chronometers as well. As their spinning slows down the time between pulses lengthens. So if your starship had a record of pulsar rates at the start of the voyage, a measurement of the rates at the end of the voyage would yield travel time (assuming you had confidence you knew the spin-down rate).

In fact, our first physical message to extraterrestrials includes normal pulsars in its content. The postcard-sized aluminum plaque, bolted to the Pioneer 10 and Pioneer 11 spacecraft that are now barreling into interstellar space, has etched symbols for any alien to decipher.  In addition to a sketch of the solar system, hydrogen atom, and two naked humans, there is a schematic of Earth’s location relative to 14 pulsars.

In the unlikely event any extraterrestrial find this interstellar note-in-bottle, they will be able to pinpoint our location in the galaxy as well as calculate the epoch the spacecraft was launched

Photos: NASA