Archive for the ‘Space Travel’ Category

Is Time Travel Possible?

Monday, December 29th, 2014

The ability to manipulate one’s place in time has often been embraced as a key plot element in science fiction. But how realistic is traveling forward or backward in time? The answer might surprise you.

Traveling back in Time

Artist rendition of a wormhole traversing a curved spacetime.

Unfortunately for Marty McFly and Doc Brown, traveling back in time is not as simple as strapping a flux capacitor onto a Delorean. In fact, there are a number of physics laws that prevent traveling against the arrow of time entirely. Theoretically, the only way one could travel to an earlier point in time would be to utilize a wormhole. A wormhole is a cosmic “shortcut” between two points in spacetime. Entering on one end would result in exiting the other end faster

than light could get to that point on it’s own, effectively getting to the destination before time does. Unfortunately, the likelihood of finding a stable wormhole capable of allowing anything to pass through it is almost zero, so traveling to the past may never be a possibility.

Traveling into the Future

This is where things get interesting. Scientifically, it is quite possible to time travel to the future. This is done utilizing Einstein’s Theory of Relativity, which allows for time to pass at different rates depending upon the environment the observers exist in. This concept is referred to as Time Dilation.

 

Photon clock on a rocket ship as viewed from the rocket and from an outside observer.

Relative Velocity Time Dilation

One postulate of the Theory of Special Relativity states that light will always travel at the same velocity in a vacuum, regardless of the velocity and direction of the source. While on the surface this doesn’t seem particularly interesting, it actually has unexpected consequences on the passage of time.

Imagine two mirrors facing each other, one meter apart. Now imagine a photon of light bouncing back and forth between those two mirrors. At rest, the photon will bounce off each mirror approximately three hundred million times per second, as this is the speed of light.

Now imagine that device on a rocket ship traveling close to the speed of light. Just like throwing a ball up and down on a train, to observer A on the rocket ship, the light looks like it’s bouncing up and down, just like it was at rest. However, to an observer B outside of the ship watching it rocket past, the path of the photon looks like it is traveling on an angled trajectory.

Because the observer B sees the photon travel at a non-vertical trajectory, it actually appears to travel slightly more than one meter between each mirror. But since light MUST always at the speed of light, that extra distance means it takes slightly longer to bounce between the mirrors, according to the observer B. Therefore, the clock looks to be moving at a slower rate than what the observer A sees, as it is bouncing at less than three hundred million times a second.

In essence, the time that passes “feels” the same to both observers, but the one on the rocket ship will actually experience a shorter duration of time relative to the outside observer. This phenomenon can then be used to manipulate time in such a way that a short period of time can pass for someone traveling at an extremely fast rate of speed relative to the Earth. For example, people on a rocket traveling at 87% the speed of light could travel for two year’s worth of Earth time, and only have aged one year.

Gravitational Time Dilation

The Theory of General Relativity adds the element of gravity to Einstein’s equations. In Newtonian Physics, gravity and acceleration are essentially analogous when it comes to calculations. Therefore, an observer close to a source of high gravity such as a black hole, will experience time travel at a slower rate relative to an observer further away from the gravitational source.

For instance, if you could shrink all of Jupiter’s mass down to a 5 meter wide sphere and stand next to it, time would travel four times slower for you than an observer in empty space.=

A Relativistic Tug of War

One interesting consequence of these two time dilation methodologies is their apparent cancellation in regards to Earth’s satellites. Satellites travel much more quickly around the planet than we do on the surface, which should slow their time relative to ours. However they also are further from Earth’s gravity, which means the surface’s time should be slower. So which wins out?

In fact, it depends upon the distance of the orbiting satellite. At around 3166 km above Earth’s surface, the effects of motion and gravitational time dilation cancels out. Below this distance, such as where the ISS orbits, the relative motion governs the time change. Further out, such as where GPS satellites exist, the difference in gravity is a more significant contributor to the time dilation. In fact, GPS satellites have to be programmed to account for this small but significant difference in time.

Past, Present, and Future – Current Events in Space

Monday, December 8th, 2014

2014 was a big year for space science and exploration, and 2015 is poised to be just as exciting. Lets take a look back at some of the year’s biggest stories from NASA, ESA, other government agencies, and the private space industry, and look forward to what is coming in 2015.

Rosetta’s orbit of 67P

Rosetta and Philae

Arguably the most widely covered space mission of the year was the European Space Agency’s Rosetta mission to Comet 67P/Churyumov-Gerasimenko. The Rosetta spacecraft was launched in 2004 and arrived at the comet on August 6, 2014. Rosetta used four different slingshots around both Earth and Mars to build enough speed to catch up to 67P, which is traveling at about 84,000mph. In total, the spacecraft has traveled more than four billion miles in it’s ten year journey.

Philae Lander

On November 12, 2014, the lander portion of the Rosetta mission, known as Philae, landed on the surface of Comet 67P. Because the comet is relatively small (only about 2.5 miles in diameter), the gravity is not strong enough to hold objects to it. Philae was designed to use both harpoons in its feet, as well as a top-down thruster to hold it to the surface. Unfortunately, both devices failed, and Philae went skipping across the surface of the comet. This resulted in a landing location with little sunlight, rendering the craft unable to continue operating due to power shortages after about three days. 

Despite the landing troubles of Philae, the mission has been considered a monumental success, and significant scientific research is being accomplished because of the information Rosetta and Philae have gathered. Rosetta will continue to orbit Comet 67P until December 2015. During this time, the comet will make a closer approach to the Sun, which has the chance to increase the power received by Philae, to the point where it could be awoken again.

 

Orion Capsule and Delta IV Second Stage

Orion Exploration Flight Test

Another heavily covered space event occurred just a few days ago. The Orion spacecraft, NASA’s first spacecraft since Apollo designed to take humans beyond low Earth Orbit, was launched on it’s very first flight on December 5th. Orion was elevated to a distance of 3,600 miles above the Earth’s surface, and returned through the atmosphere at 20,000 miles an hour. This velocity was necessary to test Orion’s heat shield, which will protect astronauts on their return trip from deep space.

Orion was launched atop a United Launch Alliance Delta IV rocket. Orion is ultimately destined to ride atop the Space Launch System (SLS), which will be tested for the first time in 2018. Orion’s ultimate goal is to transport humans to and from Mars, which NASA has projected for a mid 2030 timeframe.

Boeing’s CST-100 (left) and SpaceX’s Dragon

 

Commercial Crew Transportation Program

In September of 2014 NASA announced partnerships with two companies, SpaceX and Boeing, for manned transportation to the International Space Station. Since the end of the Shuttle program in 2011, NASA has been contracting rides to the ISS for its astronauts on the Russian Soyuz spacecraft. in 2017, the United States will return to the business of human space travel with the Boeing CST-100 and SpaceX Dragon spacecraft.

 

New Horizons Spacecraft

New Horizons

NASA’s New Horizons mission is currently en route to Pluto. Launched in 2006, New Horizons plans on being the first spacecraft to visit the solar system’s former ninth planet. This will give us the best pictures ever of Pluto and it’s moon, Charon. New Horizons just woke up from it’s most recent slumber, and plans on arriving at Pluto On July 14, 2015. Because of the velocity needed to get to Pluto’s orbit, New Horizons will not stop at Pluto, but instead perform a flyby on it’s way into the Kuiper belt, to study other Trans-Neptunian objects.

 

Dawn Spacecraft

Dawn

Dawn is an unmanned spacecraft currently approaching Ceres, the only dwarf planet in the inner solar system, and just over one third the diameter of our Moon. Dawn was launched in September 2007, and is set to arrive in orbit around Ceres in April 2015. In 2011 Dawn also visited Vesta, a large asteroid in the asteroid belt, and will become the first spacecraft to orbit two different celestial bodies. Dawn uses a unique and experimental Ion Thruster propulsion system to allow it to enter and exit orbits efficiently. It is one of the first missions to utilize this technology, which accelerates charged particles with electromagnetic fields.

Are Plasma Rockets the Future of Space Travel?

Monday, 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

Sunday, 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.