“Where is everybody?” The Fermi Paradox

September 7th, 2014

A paradox has been puzzling astronomers for decades.

In 1961 Frank Drake proposed his now famous Drake Equation, which is a thought experiment to simulate calculating the expected number of intelligent civilizations in the galaxy. It uses estimated values for things like the average number of planets around a star and how often life will form on a habitable planet. Though most of these values were complete guesses (some still are), we’re getting better at estimating the likelihood of extraterrestrial intelligence in our cosmic neighborhood.

As it turns out, we expect there to be thousands of civilizations on various planets throughout the Milky Way. Many of whom should have the ability to communicate and possibly even travel through the immense distances between solar systems. And yet, despite the Search for Extraterrestrial Intelligence (SETI) searching for signs of this life for many decades, we have no evidence of life anywhere else in the Galaxy. This is known as the Fermi Paradox after Enrico Fermi, the physicist who first proposed it.

Dozens of explanations for this paradox have been proposed over the years, but the true answer still eludes scientists. Let’s take a look at some of the common thoughts, as well as a few of the more curious solutions.

We are essentially alone

The most obvious explanation of this paradox is that the assumption of extraterrestrial intelligence currently existing in the galaxy is incorrect. This could be the case with a few different explanations:

  • Life is extremely rare to begin in the first place. Earth was a rare case where the necessary ingredients for life was a fluke, and is not a common occurrence on other planets.
  • Simple life is common on habitable planets, but rarely does it evolve into complex organisms, much less sentient, intelligent life that attempts communication.
  • Intelligent life does arise fairly often, however it destroys itself shortly after becoming spacefaring, thus the likelihood of another intelligent species currently able to communicate with us is low.

In any of these scenarios, the likelihood of finding evidence for complex life on other planets is extremely low. We may very well be the only sentient creatures in the galaxy.

We can’t find them

The Aricebo observatory in Peurto Rico

Alternative to the fact that we may be alone, is the idea that although intelligent life is relatively common in the universe, it difficult (or impossible) to find evidence of this. This assumes life, given the chance, will almost always evolve into more intelligent beings, eventually reaching a point where communication or space travel becomes possible. A number of explanations to this scenario have been proposed:

  • The distance between Earth and the nearest intelligent life is so far that communication is essentially impossible.
  • Even if a species possesses the technology to spread throughout the galaxy, it may not find it economical. Thus they remain in their local celestial neighborhood.
  • We have not been searching long enough, or looking for the right clues. Humans have been listening to only certain radio waves, and only for about 60 years. It is possible extraterrestrials are using something other than radio frequencies to communicate, such as gamma rays , or we do not understand how the information is formatted in their signals.
  • Earth is not as ideal for life as “superhabitable” planets, thus the effort of another species trying to communicate with us isn’t worthwhile.
  • Extra Terrestrials may not have any incentive to reach out to other species. This could be because they are solely interested in themselves, or perhaps because they don’t want to be found. In this scenario, a species may actually avoid detection for fear of a hostile engagement with another species.
  • Everybody is listening, and nobody is talking. SETI primarily focuses on listening to the airwaves for indications of intelligence, but does not actively transmit its own intelligent transmissions. The same could be happening for a majority of other beings.
  • Earth could be some sort of experiment, either by an extremely intelligent alien species, or entirely a computer simulation. This is known as the Planetarium Hypothesis.
  • Perhaps we have already been visited by aliens, and are either A) unknown to us, or B) occurred in the distant past, so we have no evidence.

Deflecting Disaster – Can we Prevent Armageddon via Asteroid?

August 31st, 2014

The threat of a large asteroid collision with the earth is not just the basis of a good movie plot, but an actual concern that scientists are monitoring daily.

Scientists use the Torino Scale to determine the level of concern for discovered Near Earth Asteroids (NEOs). As discussed in a previous article, the Torino scale ranks NEOs on a zero to ten scale based on both the probability of impact, as well as the potential devastation due to size. An asteroid greater than about one mile in diameter would impact the earth with more than one million times the energy of the nuclear bomb dropped on Hiroshima. This would not only wipe out anything within a 200 mile radius of the impact point, but due to dust and debris thrown into the atmosphere, would cause worldwide devastation.

Avoidance Techniques

There are essentially two frames of thought when considering asteroid deflection – direct and indirect intervention. Direct intervention send some sort of explosive device directly at the asteroid to obliterate it into fragments small enough to burn up in Earth’s atmosphere. Indirect intervention exploits the fact that with adequate warning, an asteroid’s trajectory need only be modified by a fraction of a degree over time to miss an Earth impact. Thus, slow and consistent techniques of trajectory modification are employed.

asteroidDirect Intervention

This is pretty straight forward. We would send a rocket directly at the asteroid to impact its surface, modifying the trajectory or reducing it to acceptably small fragments. This could either be a high-mass spacecraft, or a nuclear weapon detonating upon collision. This is currently the best option for asteroid deflection, as it requires the least amount of lead time, and is the simplest (and therefore cheapest) spacecraft necessary.

In 2005 the Deep Impact spacecraft successfully collided with the nucleus of comet Tempel 1. This was the first time a spacecraft has impacted a comet or asteroid. The comet’s trajectory was modified by about four inches. Knowledge gained from this impact is vital for understanding the effects of spacecraft collisions with celestial bodies.

Indirect Intervention

Example Gravity Tractor spacecraft

As opposed to a quick solution such as a nuclear strike, the indirect redirection of an asteroid has the likelihood of a higher success rate due to its slow trajectory modification approach. In the gravity tractor technique, a relatively large spacecraft would hover next to an asteroid, using its mass to gravitationally pull the asteroid towards it. With adequate lead time, a trajectory modification of a fraction of a degree is all that is necessary to deter an impact event. This also is an effective strategy if the asteroid is actually made up of a collection of asteroids, known as a “rubble pile”, which direct intervention is ineffective against.

In the Event of an Impact Detection

Tomorrow if astronomers discovered an asteroid on a collision course with Earth, would we have the capability of deflecting it? The answer depends on both the size of the asteroid and the time until impact.

Currently there is no known spacecraft equipped to handle an immediate launch to an asteroid. Thus, in the event of impact detection, developing this rocket or retrofitting an existing rocket with asteroid deflection technology would take significant time.

Dr. Edward Lu, physicist, former astronaut, and head of the private NEO detecting program B612 Foundation, made the following comments when asked in a senate hearing about the duration of time needed to develop and execute an impact asteroid: “I think with 10 years you can do this in a controlled manner with backups and so on. Certainly, with 20 years you could do that. It gets much more difficult the closer in it is, and that is, again, the importance of getting early warning, because the closer it is to you, the more you need to deflect it by to get it to miss… Five years or less, it is really hard unless you have thought the problem through and design things, maybe have components built, maybe have a full system”

If something like a city killing asteroid is discovered to impact the Earth in the next five years, the most likely course of action would be a repeated bombardment of direct impacts. While a single spacecraft may not transfer enough energy to push the asteroid off course, a dozen or more may have the necessary combined effect to avert disaster.

Are Plasma Rockets the Future of Space Travel?

August 25th, 2014

VASIMR stands for Variable Specific Impulse Magnetoplasma Rocket. It is a rocket technology currently in development by Ad Astra in conjunction with NASA that has the potential to take spacecraft – and ultimately humans – to deep space significantly faster and more efficiently than today’s technology.

Chemical Rockets

The four states of matter based on the atomic bonds

Today’s spacecraft primarily use chemical rockets as their propulsion system. This is used both to launch the vehicle into orbit, as well as propel it to deep space. Sometimes gravitational acceleration is used around the moon or nearby planets to “slingshot” the vehicle, but the primary acquisition of velocity comes from chemical rockets.

These rockets usually consist of multiple chemicals that mix together and combust, forming an expansion of gas that accelerates out the back of the rocket, providing thrust. The biggest disadvantage to chemical rockets is how heavy the fuel is compared to the energy provided. In order to provide adequate thrust to propel a spacecraft to high speeds, a rocket must carry a significant amount of fuel. But in order to get that fuel to space, it must burn more fuel to launch the additional weight. This make today’s chemical rockets quite inefficient.

Plasma

Before discussing how the VASIMR rocket works, we must understand what exactly plasma is. Plasma is the fourth state of matter along with solid, liquid, and gas. Plasma is generated when a gas is ionized: changing the number of electrons in the fundamental structure of the gas. Because of this ionization, plasma is extremely susceptible to electromagnetic fields. This is fundamentally different than the other three states of matter. Plasma is produced by natural high energy phenomenon in the sun and lightning strikes, but can also be artificially produced.

Five steps for thrust in VASIMR

Plasma propulsion

Plasma propulsion is founded in the fact that plasma responds to electromagnetic fields. Because of this, its direction and velocity can be manipulated by strong electromagnets. In VASIMR, a gas such as argon is ionized with radio waves. This argon plasma is then propelled down a tube of electromagnets to create thrust. The electromagnets excite the plasma particles, and can heat the plasma up to more than 1,000,000 degrees Kelvin. This superheated is then forced out the end of the rocket engine, providing the thrust to the spacecraft.

Benefits

The largest benefit of the VASIMR rocket is the reduction in propellant mass. Although it does not possess the high thrust capabilities of a chemical rocket, it is much more suitable for long-duration spaceflight to achieve much faster speeds than current technology. Thus, current plans are to launch spacecraft with traditional chemical rockets, then once in Low Earth Orbit, enable the plasma rockets to propel the craft to its destination. With this process, journeys from Earth to Mars would reduce from seven months with current technology to as little as 40 days.

The Future of Human Spaceflight – Part 2: Mars

August 24th, 2014

NASA’s SLS rocket carrying the Orion spacecraft

In the previous article we discussed the transitioning burden of human spaceflight to low Earth orbit (LEO) from NASA’s dependency on the Russians to private industry such as SpaceX and Boeing. In doing so, NASA set its sights on manned deep space missions, that will take place over the next few decades.

In the 1960s NASA pioneered human spaceflight with a series of manned spaceflight programs known as Mercury, Gemini and Apollo. Each program was divided into a series of missions building upon each other as stepping stones to reach the ultimate goal of putting humans on the moon. Apollo 11 was the first to achieve this goal, occurring in July 1969. On December 14, 1972 Apollo 17 left the moon, marking the last time humans traveled beyond LEO.

The Path to Mars

In the same way as the manned spaceflight programs from the 1960s and 1970s, NASA has ostensibly laid out a series of potential mission objectives that ultimately culminate in landing humans on Mars in the 2030s. Though these missions are far from guaranteed (and subject to budget cuts), the Space Launch System (SLS) and Orion spacecraft are taking these milestone missions into account during their design phases.

Canadian Astronaut Chris Hadfield monitoring a plant experiment on the International Space Station

The International Space Station

The first step in our journey to Mars is underway right now. Astronauts on the ISS are performing experiments to better our understanding of long term space exposure to the human body. In a document issued by NASA on May 29th, 2014 entitled “Pioneering Space: NASA’s Next Steps on the Path to Mars”, NASA indicated their research specifically targets “decreased gravity affecting bone, muscle, cardiovascular and sensorimotor systems, nutrition, behavior/performance, immunology and the ability to provide remote medical care via telemedic” It also provides us with a test bed for developing better technologies in areas such as spacecraft docking, life support, and extravehicular activity.

The Moon

While NASA may not be landing humans on the Moon anymore, it still provides an excellent place to test long duration, self sustaining systems in a low-risk environment. The first manned missions of the Orion and SLS, slated for 2021-2022, will send humans into an extended lunar orbit to prove the capabilities and habitability of the spacecraft.

Lunar orbit also is valuable for future missions in that the Moon’s gravity is one-sixth of Earth’s. Conceivably, a long duration mission to Mars could be staged and launched from lunar orbit, reducing the fuel requirements to reach cruising velocity to Mars. In this scenario, a manned rocket could be refueled in lunar orbit, increasing the potential payload launched from Earth and decreasing the cost of the mission.

Asteroid Redirect Mission (ARM)

Artist rendition of a potential asteroid redirect mission spacecraft

In addition to human spaceflight, NASA also has projects involving deep space missions to near Earth asteroids (NEAs). To leverage this technology, NASA has decided to attempt a NEA capture and transfer into lunar orbit using robotic spacecraft powered by a solar electric propulsion (SEP) rocket in 2019. Once placed in lunar orbit, astronauts will take Orion to the asteroid, and attempt Extra Vehicular Activity (EVA). This will be the first time a human has set foot on an asteroid, slated for 2025.

The purpose of this mission is complex. From a scientific standpoint, asteroids are extremely old remnants of the early solar system, thus scientists want a closer look at their chemical makeup to help us understand how the solar system was formed. In terms of technology, it will be an impressive feat to both capture and relocate an asteroid, and SEP technology can later be used to transfer cargo to Mars in anticipation of a manned mission, effectively creating a Martian space station before humans ever arrive. Additionally, it will provide an excellent test of Orion’s ability to rendezvous with robotic spacecraft, and give astronauts a chance to test EVA in a low-gravity environment.

Phobos and Deimos

Before landing humans on Mars, NASA may launch a mission to one of Mars’s moons, Phobos or Deimos. Though scientists currently believe they are captured asteroids rather than pieces of Mars broken off, they could provide access to Martian material accrued from millions of years of meteor strikes to the martian surface. The also provide a test environment for landing men in a deep space environment, as Phobos’s gravity is 650 times weaker than Mars’s.

Artist rendition of the first humans on Mars

Mars Landing

Sometime in the 2030s, NASA plans to attempt the first landing of humans on another planet. This will be a culmination of the aforementioned programs, as well as countless hours of development and testing by NASA, partner space programs, and commercial space companies. As of now a mission to Mars will take a minimum 550 days, with more than 95 percent of that time spent in deep space between Earth and Mars. A Martian lander has yet to be developed, but will come to fruition as scientists and engineers learn more about Mars, and human sustainability in deep space.