Stellar Aperture

Hawking’s Starshot, Relatavistic iPhones, and Planetary Protection

This week on Yuri’s Night (April 12th), Stephen Hawking (who needs no introduction) and Yuri Milner (Russian entrepreneur and physicist) announced a truly remarkable and inspiring project. They announced a bold plan to send a swarm of small iPhone sized spacecraft to the nearest star system, Alpha Centauri, at one-fifth of the speed of light. This would mark humanity’s first ever spacecraft sent to another star beyond our own solar system, and could lay the ground work for other robotic missions to nearby stars, and perhaps even one day sending the first human settlers out into Cosmos. I wholeheartedly support this project, and I hope they can pull it off.  However, that said, there is one thing that they did not address that I think should be taken into account for a mission such as this, namely, Planetary Protection.

Planetary Protection is a policy that NASA has established to prevent us from contaminating another planetary body, such as a planet or moon, which may harbor life.  For example next year, in 2017, the Cassini spacecraft will be directed to burn up in Saturn’s atmosphere so that it can never accidentally crash on either Titan or Enceladus (moons of Saturn) because of the possibility that life may be present in their subsurface oceans. If Alpha Centauri has planets, as most star systems do, then we must take precautions to ensure that we do not contaminate or damage them.

The first such danger comes from the (albeit remote) possibility that microbes from Earth may hitch a ride on the spacecraft. If the spacecraft encounters a planetary body (i.e. crashes into it), we may be contaminating that body with our microbes, thus disrupting the natural processes there. We now know, from our own solar system, that liquid water seems to be quite prevalent. And anywhere on Earth where there is water, we find life. This doesn’t mean it’s a sure thing that life would be present there. But if it is, our microbes (bacteria, viruses, etc.) that hitched along for the ride, could be harmful or even catastrophic to that alien ecosystem.

The second danger is the impact itself, should one of our probes accidentally collide with a planet or moon in the Alpha Centauri system. Which brings me to the fun part of the article. Physics! Below we’ll calculate exactly how much energy an impact from one of these spacecraft will produce.  Don’t worry, I’ll explain the ideas presented, so don’t be intimated by the math.  There won’t be a test or anything at the end. 🙂

For this exercise, let’s make a comparison to meteorite strikes on the earth. For example, the famous meteor explosion over Chelyabinsk Russia in 2013. You might recall seeing on the news that this meteor exploded over Chelyabinsk and damaged thousands of buildings and blew out countless windows. According to NASA, the asteroid was about 11,000 metric-tons, and was moving about 18 kilo-meters per second (or about 2236 miles per hour), and released about 440 kilo-tons of energy as it impacted the Earth’s atmosphere (or about 20 times the amount of energy released in the atomic bomb exploded over Hiroshima in 1945). The first question in your mind is likely, “But Josh, why are we comparing this massive asteroid strike to these small iPhone sized spacecraft? Surely this tiny spacecraft wouldn’t pose any real danger to any planet that it could hit”. But the thing to remember here, is that it’s not about the size of the object, it’s about the kinetic energy of the object. This “starshot” spacecraft will be moving at one-fifth the speed of light! That’s well over 3,000 times faster. And kinetic energy scales by the square of the velocity. All that means is, that if you double the velocity, you quadruple your energy. So 3,000 times faster, means your energy is 9,000,000 times greater! Now, lets see the math.

Here I’ll use what’s known as scientific-notation.  Meaning that we will express large numbers by powers of 10.  For example:


The equation for kinetic energy is given by:


Notice that it depends greatly on the velocity. However, at higher velocities, namely close to the speed of light, you need to take into account relativistic effects. This means applying Einstein’s theory of special-relativity. The kinetic energy then becomes:


If we assume that the spacecraft has the mass of an iPhone 6s Plus, then we can calculate the energy of the spacecraft moving at one-fifth the speed of light.

iPhone\\m=0.192kg\\v=6\times10^7m/s\\c:Light-Speed\\E_k=\frac{mc^2}{\sqrt{1-(\frac{v}{c})^2}}-mc^2=3.456\times10^{14} Joules

A Joule is a unit of energy. From here we can compare with the energy of the Chelyabinsk meteor explosion:

Chelyabinsk-Meteor\\m=11,000,000kg\\v=18295m/s\\c:Light-Speed\\E_k=\frac{mc^2}{\sqrt{1-(\frac{v}{c})^2}}-mc^2=1.84\times10^{15} Joules

This means that the spacecraft would have roughly 20%, or one-fifth, the energy of a Chelyabinsk sized impact! That’s pretty huge really when you think about it, but again, it’s the total kinetic-energy that matters. The velocity is one-fifth the speed of light after all. If this hit a planet like Earth, it would most likely burn up in the atmosphere without too much damage to any potential lifeforms below. But imagine if it hit a moon like Europa which has a subsurface ocean, with no atmosphere. Then it could cause a lot of damage to the surface of the moon, and perhaps wind up infecting the subsurface ocean with our nasty Earth microbes. This is something to consider when sending probes to other destinations in the galaxy, or even in our own solar system. Especially in the off-chance that an intelligent civilization inhabits that star system. If our probe hit something else, perhaps an orbiting space station of some kind, it would completely destroy said station. Again, this would be an extremely unlikely event.

All that said, I’m not overly worried about hitting a planet in the Alpha Centauri system. The probability of hitting a planet or moon, is vanishingly small. However, care should be taken to ensure that the spacecraft have some ability to maneuver so that they can avoid any planetary objects. It’s the right thing to do. After all, we wouldn’t want to get a bad reputation around the Cosmos would we? 🙂


Posted in Physics, Space Flight

State of NASA: A visit to Goddard Spaceflight Center

Thermal Vacuum Test Chamber for JWST

“The state of our NASA, is strong” NASA Administrator Charlie Bolden emphatically stated.  This was the mantra of the press conference on February 9th, broadcast to all NASA centers as well as to NASA TV at 1:30pm eastern time.  The State of NASA event was a powerful event to attend, and I feel truly honored to have been present at Goddard Spaceflight center for this historic occasion.  This event was focused on the present and future of our space program.  With a special emphasis on the importance and necessity of exploration and scientific understanding of our solar system and of our home world, Earth.

The passion in Bolden’s voice was clearly audible as he outlined the importance of this great organization, as well as the future plans for the exploration of our solar system, as well as our home planet.  But perhaps his most moving moment was his recollection of the past.  He recalled growing up as a young african american in the segregated south and the struggles that he faced.  He never imagined that today, he would be leading our nation’s space program.  We truly have come a long way as a country, and our space program is better for it, both in terms of diversity and gender equality.  As Bolden pointed out, our latest class of astronauts is 50% female and 50% male for the first time in history.

NASA has contributed to our overall quality of live in ways that most people don’t realize.  In fact by some estimates, for every $1 we put into NASA, we get nearly 7$-14$ return.  There was an excellent article in Forbes with an interview with Neil deGrasse Tyson about this.  As we look forward to future human crewed missions to Mars, we need to keep these benefits in mind.  The technology and innovation that are created out of necessity for these upcoming missions will be invaluable to industry and indeed our civilization as a whole.  Bolden made the claim that “every american will benefit from our journey to Mars.”  I wholeheartedly agree.  He also underscored the importance of our Earth science program, to understand our home planet, as he put it, “the most important planet.”  NASA has a huge role to play in our understanding of our climate and our planet as a whole.


JWST Mirror assembly at NASA Goddard.

In addition to the State Of NASA press conference, this event was also a NASA Social, where members of the public, particularly those with blogs and/or social media presence, can apply to attend and document the event.  I attended the event hosted at Goddard Spaceflight Center and was treated, along with the other attendees, to a tour of the facility, including a visit to the clean room where the James Webb Space Telescope is currently being assembled!  This, for me, was by far the highlight of the day.  As we ascended the staircase to the glass wall overlooking the clean room, I became very excited.  I could hardly breath as I looked out onto the massive structure that holds the segmented primary mirror assembly, as well as the arm which holds the secondary mirror.

JWST Secondary Mirror arm.

JWST Secondary Mirror arm.

Seeing this monument to our collective intelligence as a species in person, was an indescribable experience.  This artifact of our technological civilization will help us to understand our universe by looking deeper into the observable universe than the Hubble Space Telescope is capable of doing, and will also help us understand the atmospheres of nearby planets, among many other scientific objectives.  This massive telescope will be sent to our Earth-Sun Lagrange point L2, roughly 1.5-million kilometers away from Earth.  Someday soon in the near future, we will be able to look back at this telescope and point to our new understandings that were made possible by this great instrument, just as we have (and continue to have) with Hubble and other great space missions.

We also toured the area which housed their enormous vacuum chambers for testing spacecraft.  Below is one image of the chamber which will be used to test the JWST.

Thermal Vacuum Test Chamber for JWST

Thermal Vacuum Test Chamber for JWST




We also got a personal briefing on another space telescope currently planned for 2018, called TESS, the Transiting Exoplanet Survey Satellite, which will study the whole sky over a period of two years during its primary mission looking for exoplanets orbiting nearby star systems.  If Kepler is any indication, this will prove to change our understanding once again about the amazing number of planets out there in our galaxy.  I’m extremely excited about this mission in particular, because it will show us exoplanetary systems which are much closer to us than those discovered by Kepler.  This will allow us to better characterize their atmospheres (with the JWST and other observatories) which may ultimately help us to find planets with conditions that are potentially favorable to life.  Such planets would also make excellent targets for SETI search operations.  It was a privilege to hear about this mission from some of the scientists that work directly on this mission.

It was my great honor and pleasure to be invited to attend the NASA Social at Goddard Spaceflight Center on February 9th.  I want to thank those that organized this event, which was truly a one of a kind experience.


Posted in News, Space Flight

NASA’s Rich History: A visit to the Smithsonian Air and Space Museum


Next week, I will be at NASA Goddard Space Flight Center, on Tuesday February 9th, for the State Of NASA event, held simultaneously across all NASA centers. I will be live tweeting the event, and posting an article later that evening. Use the Links on the side-bar to follow Stellar Aperture on your favorite social media platform, and follow the #StateofNASA hashtag for more information. This event will focus on the future of our remarkable space program.

But for this week’s post, I would like to focus on where we have been. Or more specifically, on the rich inspirational history of spaceflight that has advanced our culture in so many ways.

Last November, I attended the American Astronomical Society Division For Planetary Sciences annual meeting in DC. While I was there, I was able to carve out a little time to visit the Smithsonian National Air and Space Museum to see first hand some of the most amazing artifacts that our civilization has ever produced. My sense of awe was completely overloaded. A feeling of hope and optimism towards humanity’s future was impossible to ignore as I walked among these inspiring expressions of our collective intelligence. I was able to make time to visit both the museum in DC, as well as the Steven F. Udvar-Hazy Center in Virginia where the Space Shuttle Discovery is housed. It is truly awesome feeling to walk beneath the wings of a Space Shuttle.


Mercury-Atlas 10 / Freedom 7 – II

Let’s start at the beginning of human spaceflight in the US, with the Mercury program. These small capsules had only room for a single spacefaring occupant, and tightly at that. The Mercury capsule design, first flown by Alan Shepard (the first US astronaut in space) on the historic Freedom 7 mission on May 5th 1961, was very similar to the capsule shown on the left. This particular capsule, which was intended to be the Mercury-Atlas 10 mission, nicknamed the Freedom 7 – II, sadly never actually flew. For museum goers this is actually quite fortunate however, because it affords an opportunity to see a near pristine Mercury capsule in its complete orbital configuration. You can literally peek into the window on the side, which was an absolute thrill for me, to see what Alan Shepard would have seen back when it all started. Truly remarkable.



Next up are the Gemini. A two astronaut space capsule, which allowed for greater capability, including the first US space walk performed by Ed White aboard the Gemini 4 mission. It is important to note, that the first space walk was actually performed by Soviet cosmonaut Alexei Leonov, about 4 months prior. That said, this was a stepping stone which allowed US astronauts to learn to operate outside their spacecraft, which would later lead to the eventual moon landing.


Apollo 11 Command Module

The biggest thrill for me, by far, was seeing the actual Apollo 11 Command Module! I literally almost walked right past it, and then turned around to look at something, and it was right in front of me. The feeling I experienced is difficult to describe. I found simultaneously with a huge smile along with tears welling up in my eyes. I almost couldn’t breath. It was as if I had been looking for it my whole life, and there it was right in front of me. Neil Armstrong, Edwin “Buzz” Aldrin and Michael Collins rode in that very spacecraft on the way to the moon that summer in 1969. The Command Module was one of three components of the Apollo 11 mission, and was the only one returned to Earth. It was quite literally breathtaking to see. I stood there for quite a while just enjoying every rivet, every panel, and indeed every scorch mark on it’s surface.


Buzz Aldrin Apollo 11


David Scott Apollo 15

Also breathtaking were some of the actual space suits worn by the Apollo astronauts, with lunar dust still visible on surface of the space suits! This was a real treat to see, and was absolutely wonderful to examine with my own eyes. The image on the left is one from Apollo 15, worn by David Scott. The image on the right, was worn by none other than Buzz Aldrin himself on Apollo 11. Outstanding.


Lunar Lander Replica

The full scale replica of the Apollo Lunar Lander was awe inspiring. I had no idea how large it really was until I stood next to its feet. It was a giant insect like monster that frankly I’m amazed anyone could pilot down to the surface of the moon. It is a testament to the engineering ingenuity and the unparalleled piloting skills that NASA somehow coordinates in concert.


Space Shuttle Discovery

And of course, the Space Shuttle Discovery! The size of this spacecraft makes one feel quite minuscule standing underneath it. I spent nearly an hour walking around the Shuttle, taking pictures of nearly every square centimeter of its surface. That morning, I arrived at the Steven F. Udvar-Hazy Center just as they opened, and I practically ran in when they opened up the little gate at the top of the staircase that led down to the hangar floor. I went straight for the shuttle, and started taking pictures.

There were of course many other artifacts, from a full scale replicas of Skylab, the Viking Mars landers, and a variety of equipment, space suits, helmets, and gloves. I could go on for hours. This Included a display of one of the most inspiring missions of our space program, the Apollo–Soyuz spacecrafts docked together. This mission is particularly inspiring to me because it represents scientific and cultural cooperation at a time when our two nations were locked in bitter cold-war. At a time when suspicions were high, and the dangers of war presented an ever present tension, we somehow found a way, through space travel, to come together in a grand gesture of peace. And indeed, this tradition holds true even today on the International Space Station, where many nations come together in scientific collaboration, regardless of our differences. This to me is a symbol of hope, and a foundation for our future. Space offers us a way to heal our divisive wounds that we have inflicted upon one another throughout the ages. We can come together as a species, one whole planet Earth, and venture out into the cosmos. Space seems to bring this out in us and we should embrace it. It is truly our only chance to evolve past our technological adolescence to become a long lived peaceful civilization. We can get there if we will it to be so.



Stay tuned space fans.  Tuesday promises to be a very exciting day, be sure to follow on Twitter, Facebook and Google+ for all the details as they happen.


Posted in Space Flight

Upcoming NASA Social: State Of NASA

Greetings space fans!  Quick post today.  I am pleased to announce that I will be attending the upcoming NASA Social event on February 9th, the “State of NASA”.  I was scheduled to attend the previous NASA Social event, on January 25th at Goddard Spaceflight Center, but it was canceled due to the blizzard, and so they moved me to the February 9th event.  I am extremely excited and honored to take part in this event, and will post more details as they are available.

On February 9th, I will live-tweet the event at @StellarAperture, topped off with a blog post at the end of the day detailing the days events.  Stay tuned!


Posted in Uncategorized

DPS 2015 Days 3 and 4: Venusian Aircraft, Pale Orange Dots, and Magma Oceans!

Yesterday on the third day of DPS, Dr. Yuk Yung of Caltech, towards the end of his acceptance speech after having been awarded the Gerard P. Kuiper Prize at this year’s DPS meeting, stated the following:

“Life is the ultimate poetry of the universe, written with the alphabet of molecules.” – Yuk Yung

This one sentence sums up the beautiful truth that Life is an emergent property of the universe.  It is a beautiful consequence of the four fundamental forces that govern our universe.  This one statement seems to embody the spirit of the DPS and its members.  By studying the planets, both inside and outside our solar system, we gain understanding about ourselves and where we come from.

The past two days have been a whirlwind.  I was very tired last night, so I didn’t post an article.  So tonight I plan to give a smattering of some of the more interesting talks I attended.

Venus Atmospheric Maneuverable Platform (VAMP)

At the poster session yesterday, I came across a particularly interesting mission concept, presented by Northrup Grumman.  This mission would involve a buoyant winged aircraft that would be powered by solar panels and would be able to glide through the Venusian atmosphere, taking samples and reporting back to an orbiting spacecraft.  This is a beautiful idea, and could well be used on other planets as well.

Pale Orange Dot

Giada Arney of the University of Washington gave a talk today about Exoplanets. She pointed out that when we look for habitable exoplanets, we typically look for planets that we consider Earth-like, or having liquid water and oxygen, etc., on their surface.  However, in the early archeo-Earth environment, as Arney points out, the world looked much different than it does today.  Early in the Earth’s history, the skies were filled with an orange hydro-carbon haze, similar to that of Titan.  This atmosphere would kill a human, but would be the perfect environment for early life on the earth, and would shield them from nearly all of the UV radiation that might otherwise harm them, just as the Oxygen and Ozone in our atmosphere do for us today.  This is an intriguing idea, one that will broaden the possible search criteria for identifying Earth-like exoplanets.

Magma Ocean Dynamo!

Alexander Bourzutschky of the California Institute of Technology gave a fascinating talk today about exoplanets with global oceans of magma on their surface.  These oceans, Bourzutschky says, could sustain their own magnetic field, acting much the same way that our iron-core dynamo works on Earth.  These global magnetic fields could potentially be detected by radio telescopes here on Earth.

Using Cassini VIMS to view Earth, Exoplanet Analog

It’s important to know what the limits of our current instrumentation are, and how to best utilize them.  Roger Clark at the Planetary Science Institute spoke today about using the VIMS instrument (infra-red spectrometer) on board Cassini to look back at the Earth to determine what kind of information we might expect to glean from an extra-solar planet using similar instrumentation.  This is an excellent test case, because Clark et al. can compare their findings to what we know to be present on the Earth.  This can help to design future missions and observations of other planets outside our solar system.

Well, it’s getting late, and I need to get some sleep.  Tomorrow will be the last day of DPS 2015, sadly.  I will report back tomorrow with and end-of-DPS wrap up.



Posted in News, Planetary Science Tagged with:

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© Josh Elliott and Stellar Aperture, 2016. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Josh Elliott and Stellar Aperture with appropriate and specific direction to the original content.