In The Life of The ISS

In In The Life of The ISS – Question Time

This post is dedicated to our friend Mihaela from Facebook that recently asked us a question that is partially related to the International Space Station (ISS). The Question was…

How many sunrises can an astronaut see from an orbiting space station, if it orbits the Earth in 90 minutes, and why?

This is a brilliant question and thank you Mihaela for asking us to look into it for you. I will be going through two parts to answering this. The first part is the straight forward answer, we will then go through a little more information about the ISS with some visulisations, that will help see why the aforementioned occurs. I have also used the ISS as an example as this is the most commonly known space station (seriously, isn’t it pretty cool we have space stations just whipping above us as we speak), plus there are some great apps available that allow you to track the ISS.

The Short Answer…

The ISS takes 92 minutes to orbit the earth once. Where as somewhere on Earth takes 24 hours to complete a full rotation and we see one sun rise and one sunset.

As it takes approximately 92 minutes for the ISS to complete and orbit, this means that every 45 minutes or so they will witness a sunrise or a sunset as they effectively pass over the point that Earth would be having a sun rise or a sun set at that particular time.

This means, over the course of 24 hours (Earth’s full rotation) the ISS will observe between 15 and 16 sun rises and sunsets.

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Now a little more information on the ISS

The space station is made of many pieces. The pieces were put together in space by astronauts. The space station’s orbit is about 220 miles above Earth. NASA uses the station to learn about living and working in space. These lessons will help NASA explore space.

Questions and Facts

How Old Is the Space Station?

The first piece of the International Space Station was launched in 1998. A Russian rocket launched that piece. After that, more pieces were added. Two years later, the station was ready for people. The first crew arrived on November 2, 2000. People have lived on the space station ever since. Over time more pieces have been added. NASA and its partners around the world finished the space station in 2011.

How Big Is the Space Station?

The space station is as big inside as a house with five bedrooms. It has two bathrooms, a gymnasium and a big bay window. Six people are able to live there. It weighs almost a million pounds. It is big enough to cover a football field including the end zones. It has science labs from the United States, Russia, Japan and Europe.

What Are the Parts of the Space Station?

The space station has many parts. The parts are called modules. The first modules had parts needed to make the space station work. Astronauts also lived in those modules. Modules called “nodes” connect parts of the station to each other. Labs on the space station let astronauts do research.

On the sides of the space station are solar arrays. These arrays collect energy from the sun. They turn sunlight into electricity. Robot arms are attached outside. The robot arms helped to build the space station. They also can move astronauts around outside and control science experiments.

Airlocks on the space station are like doors. Astronauts use them to go outside on spacewalks.

Docking ports are like doors, too. The ports allow visiting spacecraft to connect to the space station. New crews and visitors enter the station through the docking ports. Astronauts fly to the space station on the Russian Soyuz. The crew members use the ports to move supplies onto the station.

Why Is the Space Station Important?

The space station is a home in orbit. People have lived in space every day since the year 2000. The space station’s labs are where crew members do research. This research could not be done on Earth.

Scientists study what happens to people when they live in space. NASA has learned how to keep a spacecraft working for a long time. These lessons will be important in the future.

NASA has a plan to send humans deeper into space than ever before. The space station is one of the first steps. NASA will use lessons from the space station to get astronauts ready for the journey ahead.

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Some Quick Facts about the ISS

• 1. It took an astounding 136 space flights on seven different types of launch vehicles to build it.


• 2. It flies at 4.791 miles per second (7.71 km/s). That’s fast enough to go to the Moon and back in about a day.


• 3. It weighs almost 1 million pounds including visiting spacecraft. Picture 120,000 gallons of milk in supermarket cartons in your mind.


• 4. It has 8 miles of wire just to connect the electrical power system. That will be enough to connect a hair dryer in Newark, New Jersey, to a power plug in New York City.


• 5. It has a complete surface area the size of a US football field, which actually makes it almost as large as the Tantive IV, the Corellian Corvette that carried Princess Leia.


• 6. It has more livable space than a 6-bedroom house.


• 7. It has two bathrooms, a gymnasium and a 360-degree bay window.


• 8. It’s been the spaceport for 89 Russian Soyuz spacecraft, 37 Space Shuttle missions, three SpaceX Dragons, four Japanese HTV cargo spacecraft, and four European ATV cargo spacecraft.


• 9. All its research experiments and spacecraft systems are housed in a bit more than one hundred telephone-booth sized racks.


• 10. The US solar array surface area on the is 38,400 sq. feet (.88 acre), which is large enough to cover 8 basketball courts


• 11. According to NASA, “there are 52 computers controlling the ISS.” Just for the US segment, there are “1.5 million lines of flight software code run on 44 computers communicating via 100 data networks transferring 400,000 signals.”


• 12. Its internal pressurized volume is 32,333 cubic feet, which is about the same of a Jumbo Boeing 747.


• 13. The ISS crews have eaten about 25,000 meals since 2000. That’s a staggering “seven tons of supplies per three astronauts for six months.” That’s 32,558 Big Macs.


• 14. 211 people from 15 countries have visited the ISS so far.


• 15. When it reaches the end of its life, some of the most modern Russian modules—like Nauka—will be reused to make a third space station to support interplanetary mission to Mars, the Moon and Saturn, serving as a launching and return point.

Some Questions Answered by the NASA Team

Do you believe in that the design of the ISS will cause a problem in case of a meteor shower? Why?

That’s a really good question. The space environment is a very harsh environment: there’s radiation and micrometeorite strikes, and other things in the environment that cause it to be very hazardous. So, one of the things that we’ve designed the space station for is to protect the astronauts against micrometeorite striking the outer shell of the space station. Now, in doing so, the basic design philosophy of the pressurized modules has been to develop an inner shell, which contains the pressurized interior of the space station, and then a layer of insulation around that inner shell, and then an outer armor plating, if you will, to the exterior. And what that does is protects against small pieces of debris that strike the station and can cause leaks. Now, for larger pieces of debris: they actually track them and have to actually move the space station out of the way of the larger pieces that could cause serious damage to the station.

What kind of contingency plan does the ISS have in case of an emergency? How long do life support systems on board last for the stranded astronauts? Is there such a thing as an emergency launch to the ISS using the current space shuttles?

Well, there are several redundant systems on the space station, which really enable the astronauts to survive for long periods of time without a space shuttle or a Russian re-supply ship coming to bring additional supplies. Now, in the event of an outright emergency, where the lives of the astronauts were threatened, they would have to evacuate the space station using the Soyuz module, but the life support systems themselves are designed to last for months at a time without a re-supply ship.

What would you say to date has been the greatest benefit to mankind from the space station, and what is its predicted benefits?

Well, I think it’s all a matter of judgment, but to me the greatest benefit of the space station is the international cooperation to date that we’ve had with over 16 different countries contributing to the International Space Station; countries that were at one time, enemies of each other, have now come together to do something that will benefit mankind. I think down the road the space station will bring great leaps in science, in medical fields, in the materials manufacturing fields, and it will also teach us a lot about long duration human space flight so that we can expand our civilization beyond Earth.

Why is the center truss section called S-Zero?

That’s actually a really good question, because the trusses are named for whether they’re on the starboard side or the port side; so you have S-Zero, S-One, P-One, S-Three, P-Three, P-Four, S-Four, P-Five, S-Five. Well, S-Zero being in the middle, I guess they couldn’t decide whether to call it S-Zero or P-Zero, and maybe they flipped a coin or whatever else and decided to call it S-Zero, but it’s actually in the center, it’s not on the starboard side or the port side, so it could have just as easily been named P-Zero.

Does the International Space Station have any hardware or machines that were specifically invented for it and cannot be found anywhere else? What are they?

Well, the International Space Station has lots of unique hardware elements that were designed specifically for the International Space Station. They also use off-the-shelf technology when possible; one instance of that is the cameras that they use on the space station for the interior of the space station are actually just off-the-shelf camcorders. But, some, there’s certainly a great amount of technology that was developed specifically for the International Space Station to function specifically in the space environment. I think one of the best examples of that is the Canadian robotic arm. The Canadian robotic arm was developed specifically for the International Space Station and fills the task of actually constructing the International Space Station, and it doesn’t even function in the Earth environment in the one-G conditions that we have here on Earth.

When will the International Space Station be completed?

Well also that’s a very interesting question. The core complete milestone that we are reaching for right now is due in the mid-2004 timeframe. Now, after we finish building what’s essentially the core of the International Space Station then we have a lot of additional options to add elements developed by international partners, and other additional features that we might want to add. The fact that the space station was designed the way it was allows us to once we get to the core complete milestone to expand it to provide lots of additional capabilities.

Which ISS docking port is being used by the Soyuz TM-34 spacecraft? Also, where on the station will Endeavour and Leonardo dock?

Well, the Soyuz module is nominally docked to the end of the Russian service module. Now, there are additional docking ports on the Russian functional cargo block, I’m sorry, on the bottom of the service module, where the Soyuz modules can be docked. And when they bring a second one up onto orbit in order to switch out the first one when they have to replace them, they actually have to move one of the Soyuz modules from the end of the service module to the bottom of the service module, and the second service module goes on to the end. The space shuttle, on the other hand, docks to the American side of the space station, to the Destiny laboratory. And the MPLM, Leonardo, in this case, is docked to Node-1, which was also built by an American company, Boeing.

Is it possible to give the times and locations of when the ISS passes over Central California?

Well, it’s actually possible to find out when the space station will be passing over your head no matter where you live, and there’s a website, it’s http://spaceflight.nasa.gov, and if you go that website, you can follow links and actually no matter what city you are in the country, you can find out when the space station will be traveling overhead.

With respect to the space station, why can’t we just shoot the trash off towards the sun instead of bringing it back to Earth?

Well, that’s actually a question that I used to wonder about when I was growing up, why didn’t we just put all the trash into the sun to save our garbage problems here on Earth. Unfortunately, it would take a lot of rocket power to get anything to the Sun, and so it’s sort of a limiting factor to be able to launch something out the sphere of influence of the Earth. Now, the trash on the International Space Station, not all of it is brought back to Earth. Some of it is placed in the Russian Progress modules, which are sent on a trajectory into the Earth’s atmosphere that burns it back up. So it’s not all brought back to Earth, just some of it in the MPLM modules.

After the completion of the ISS, how much will it contribute to the flight of humans to Mars, and return trips to the Moon?

Well, this kind of goes with the earlier question, about what the benefits of the International Space Station are. If we’re going to go to Mars, or spend long periods of time on the Moon, we have to learn what the effects of long term space flight is going to be on our astronauts. We don’t have a lot of information about what the space environment does to our astronauts, beyond, say six months. There are astronauts, particularly from Russia, who have spend more time than that in space, but very few, so we don’t have a large amount of data, and it’d be very risky to send astronauts to Mars, to spend say, a year and a half outside of the Earth environment, or more, without knowing exactly what the effects of the long term exposure to space would be. So, the International Space Station in addition to us just developing the technology to live in space for large amounts of time, it gives us the information that we need about how long astronauts can safely stay in space.

Is it possible to use a flywheel mechanism to produce power for the space station? Have there been any experiments using this technology to produce power in space?

Well, it’s actually not possible to use flywheels to generate power in the classical sense, but you can use flywheels to store power. So, you would have to use some other source to generate the power, but then to store it you could spin up flywheels and then use the kinetic energy from the flywheels to actually store energy. But because the power requirements of the space station are so large, it’s a lot more practical for us to use batteries to store power on the station. So, the answer to the question is no, we don’t use flywheels to store power.

How many different civilian contracting companies, on average, participate in the building of one of our space station modules?

Well, most of the American space station modules were developed and built by the prime contractor for the space station, which is Boeing. Now, Boeing has dozens, if not hundreds of subcontractors that it uses to build everything from the smallest screw used on the space station to a complex computer, or a solar array. So, there’s one prime contractor, but dozens, if not hundreds of subcontractors.

When the space station needs to make an orbital adjustment, do the occupants of the space station feel the movement of the adjustment?

Well, the reason why I think that’s such a good question is because it really highlights one of the most fundamental laws of physics we have, and there are basically three laws of physics that Isaac Newton postulated hundreds of years ago, and one of those laws it that force equals mass times acceleration. Now, the key thing about these laws is that no matter where you are in the universe, they are true. So whether you’re on Earth or whether you’re in space, these laws are true. Now, this particular law, force equals mass plus acceleration, when you press the gas pedal in your car, your car accelerates, you go from say, 55 miles an hour to 60 miles an hour. That acceleration is what causes you to feel that force. Now, in space, when they fire the thrusters on the space station, the space station also accelerates. But the acceleration is generally very, very small. So sometimes the astronauts might not notice the space station is accelerating. But that also brings in another interesting point, in what they might see, since the astronauts are floating free with respect to the space station, that when the space station fires it thrusters, the space station would move, and the astronauts, not touching one of the surfaces, would not move, so they would see the space station actually moving around them.

During a 24 hour period, how many times does the ISS orbit the Earth?

Well, the space station orbits Earth about every 90 minutes, so that means in a 24 hour day, the space station orbits approximately 16 times.

In operating, maintaining, and troubleshooting problems on the ISS, how involved does the ISS crew get versus the control center team?

Well, that’s a very good question. NASA has an entire army of people supporting the operations of the International Space Station. Of course, the astronauts are often the first line of defense, and especially in emergency situations, they have to make quick, critical decisions that will allow everybody to be safe. Now, the mission control people are a huge part of supporting that and laying out those plans for the emergency situations. But, in the event that something goes wrong on the station, NASA has the ability to go back to the people who actually designed the hardware and ask them what they think about the problem, and if it’s something they might have seen before in ground testing. So it’s a collaborative effort across all of the different countries that make up the hardware that we use on the International Space Station.

On certain days we are able to visualize the space station as it seems to streak across the sky. How fast is the ISS traveling?

Well, in order for the space station to stay in orbit, it has to travel at seven kilometers per second, which the equivalent in miles per hour, is around 15,500 miles per hour. So that’s pretty fast!

I hope you enjoyed this post and Mihaela, I hope this answered your question and then some more 🙂 thank you so so much for the question. If you or anyone else has any more questions please let us know on our Scientia facebook page or use the forums on Scientia to start your own thread.

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– Credit and Resource –

NASA

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In The Life of The ISS

Stealth Dark Matter Explains Universe"s Missing Mass

This 3D map illustrates the large-scale distribution of dark matter, reconstructed from measurements of weak gravitational lensing by using the Hubble Space Telescope.

Scientia — Lawrence Livermore scientists have come up with a new theory that may identify why dark matter has evaded direct detection in Earth-based experiments.

A group of national particle physicists known as the Lattice Strong Dynamics Collaboration, led by a Lawrence Livermore National Laboratory team, has combined theoretical and computational physics techniques and used the Laboratory’s massively parallel 2-petaflop Vulcan supercomputer to devise a new model of dark matter. It identifies it as naturally “stealthy” (i.e. like its namesake aircraft, difficult to detect) today, but would have been easy to see via interactions with ordinary matter in the extremely high-temperature plasma conditions that pervaded the early universe.

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“These interactions in the early universe are important because ordinary and dark matter abundances today are strikingly similar in size, suggesting this occurred because of a balancing act performed between the two before the universe cooled,” said Pavlos Vranas of LLNL, and one of the authors of the paper, “Direct Detection of Stealth Dark Matter through Electromagnetic Polarizability”. The paper appears in an upcoming edition of the journal Physical Review Letters and is an “Editor’s Choice.”

Dark matter makes up 83 percent of all matter in the universe and does not interact directly with electromagnetic or strong and weak nuclear forces. Light does not bounce off of it, and ordinary matter goes through it with only the feeblest of interactions. Essentially invisible, it has been termed dark matter, yet its interactions with gravity produce striking effects on the movement of galaxies and galactic clusters, leaving little doubt of its existence.

Lawrence Livermore scientists have devised a new model of dark matter. It identifies it as naturally “stealthy” today, but would have been easy to see via interactions with ordinary matter in the extremely high-temperature plasma conditions that pervaded the early universe.

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The key to stealth dark matter’s split personality is its compositeness and the miracle of confinement. Like quarks in a neutron, at high temperatures, these electrically charged constituents interact with nearly everything. But at lower temperatures they bind together to form an electrically neutral composite particle. Unlike a neutron, which is bound by the ordinary strong interaction of quantum chromodynamics (QCD), the stealthy neutron would have to be bound by a new and yet-unobserved strong interaction, a dark form of QCD.

“It is remarkable that a dark matter candidate just several hundred times heavier than the proton could be a composite of electrically charged constituents and yet have evaded direct detection so far,” Vranas said.

Similar to protons, stealth dark matter is stable and does not decay over cosmic times. However, like QCD, it produces a large number of other nuclear particles that decay shortly after their creation. These particles can have net electric charge but would have decayed away a long time ago. In a particle collider with sufficiently high energy (such as the Large Hadron Collider in Switzerland), these particles can be produced again for the first time since the early universe. They could generate unique signatures in the particle detectors because they could be electrically charged.

“Underground direct detection experiments or experiments at the Large Hadron Collider may soon find evidence of (or rule out) this new stealth dark matter theory,” Vranas said.

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– Credit and Resource –

More information: Paper: arxiv.org/abs/1503.04205

Journal reference: Physical Review Letters

Provided by: Lawrence Livermore National Laboratory

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Stealth Dark Matter Explains Universe"s Missing Mass

Volcanic Siberian Traps likely culprit for end-Permian extinction

New study finds massive Volcanic eruptions in the Siberian Traps, likely triggered mass extinction.

Scientia — Around 252 million years ago, life on Earth collapsed in spectacular and unprecedented fashion, as more than 96 percent of marine species and 70 percent of land species disappeared in a geological instant. The so-called end-Permian mass extinction ­— or more commonly, the “Great Dying” — remains the most severe extinction event in Earth’s history.

Scientists suspect that massive volcanic activity, in a large igneous province called the Siberian Traps, may have had a role in the global die-off, raising air and sea temperatures and releasing toxic amounts of greenhouse gases into the atmosphere over a very short period of time. However, it’s unclear whether magmatism was the main culprit, or simply an accessory to the mass extinction.

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MIT researchers have now pinned down the timing of the magmatism, and determined that the Siberian Traps erupted at the right time, and for the right duration, to have been a likely trigger for the end-Permian extinction.

According to the group’s timeline, explosive eruptions began around 300,000 years before the start of the end-Permian extinction. Enormous amounts of lava both erupted over land and flowed beneath the surface, creating immense sheets of igneous rock in the shallow crust. The total volume of eruptions and intrusions was enough to cover a region the size of the United States in kilometer-deep magma. About two-thirds of this magma likely erupted prior to and during the period of mass extinction; the last third erupted in the 500,000 years following the end of the extinction event. This new timeline, the researchers say, establishes the Siberian Traps as the main suspect in killing off a majority of the planet’s species.

“We now can say it’s plausible,” says Seth Burgess, who received his PhD last year from MIT’s Department of Earth, Atmospheric, and Planetary Sciences and is now a postdoc at the U.S. Geological Survey. “The connection is unavoidable, because it’s clear these two things were happening at the same time.”

Burgess and Sam Bowring, the Robert R. Shrock Professor of Earth and Planetary Science at MIT, have published their results in the journal Science Advances.

Learn how MIT researchers determined that volcanic eruptions from Siberian Traps are likely triggers for the end-Permian mass extinction. Video: Melanie Gonick/MIT

A singular event

Around the time of the end-Permian extinction, scientists have found that the Earth was likely experiencing a sudden and massive disruption to the carbon cycle, abnormally high air and sea temperatures, and an increasingly acidic ocean — all signs of a huge and rapid addition of greenhouse gases to the atmosphere. Whatever triggered the mass extinction, scientists reasoned, must have been powerful enough to generate enormous amounts of greenhouse gases in a short period of time.

The Siberian Traps have long been a likely contender: The large igneous province bears the remains of the largest continental volcanic event in Earth’s history.

“It’s literally a singular event in Earth history — it’s a monster,” Burgess says. “It makes Yellowstone … look like the head of a pin.”

It’s thought that as the region erupted, magma rose up through the Earth’s crust, essentially cooking sediments along the way and releasing enormous amounts of greenhouse gases like carbon dioxide and methane into the atmosphere.

“The question we tried to answer is, ‘Which came first, mass extinction or the Siberian Traps? What is their overall tempo, and does the timing permit magmatism to be a trigger for mass extinction?’” Burgess says.

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Dates pinned

For the answer, Burgess, Bowring, and colleagues traveled to Siberia on multiple occasions, beginning in 2008, to sample rocks from the Siberian Traps. For each expedition, the team traveled by boat or plane to a small Siberian village, then boarded a helicopter to the Siberian Traps. From there, they paddled on inflatable boats down a wide river, chiseling out samples of volcanic rock along the way.

“We’d have a couple of hundred kilos of rocks, and would go to the market in Moscow and buy 15 sport duffle bags, and in each we’d put 10 kilos of rocks … and hope we could get them all on the plane and back to the lab,” Burgess recalls.

Back at MIT, Burgess and Bowring dated select samples using uranium/lead geochronology, in which Bowring’s lab specializes. The team looked for tiny crystals of either zircon or perovskite, each of which contain uranium and lead, the ratios of which they can measure to calculate the rock’s age. The team dated various layers of rock to determine the beginning and end of the eruptions.

They then compared the timing of the Siberian Traps to that of the end-Permian extinction, which they had previously determined using identical techniques.

“That’s important, because we can compare green apples to green apples. If everything is done the same, there’s no bias,” Burgess says. “Now we’re able to say magmatism definitely preceded mass extinction, and we can resolve those two things outside of uncertainty.”

Richard Ernst, a scientist-in-residence at Carleton University in Ottawa, Ontario, says the new timeline establishes a definitive, causal link between the Siberian Traps and the end-Permian extinction.

“This paper nails it,” says Ernst, who was not involved in the study. “Given that they have dated a portion of the Siberian Traps occurring just before, during, and only for a short time after the extinction, this is the ‘smoking gun’ for this large igneous province being fully correlated with the extinction. At this point, additional dating and other studies will simply provide more details on the link.”

Now that the team has resolved the beginning and end of the Siberian Traps eruptions, Burgess hopes others will take an even finer lens to the event, to determine the tempo of magmatism in the 300,000 years prior to the mass extinction.

“We don’t know if a little erupted for 250,000 years, and right before the extinction, boom, a vast amount did, or if it was more slow and steady, where the atmosphere reaches a tipping point, and across that point you have mass extinction, but before that you just have critically stressed biospheres,” Burgess says. “Now we’ve pinned it down in time, and others can go in with other techniques to get a more fully fleshed out timeline. But we need it to start someplace, and that’s what we’ve got.”

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– Credit and Resource –

Jennifer Chu | MIT News Office

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Volcanic Siberian Traps likely culprit for end-Permian extinction

New Green Propellants Complete Milestones

Scientia — To stay in the proper orbit, many satellites have thrusters–small rocket engines–that fire to change altitude or orientation in space. On Earth where gravity dominates, 5 pounds of thrust, equivalent to 22 Newtons of force, may seem small, but in space, it doesn’t take much thrust to move a large spacecraft.

Currently, most satellite thrusters are powered by hydrazine, a toxic and corrosive fuel that is dangerous to handle and store. In a quest to replace hydrazine with a more environmentally friendly fuel, NASA is testing thrusters propelled by green propellants that can provide better performance than hydrazine without the toxicity. These propellants could help lower costs by eliminating infrastructure needed for handling toxic fuels and reducing processing time–making it less expensive and safer and easier to launch both commercial and NASA spacecraft.

This image reveals a temperature profile of a 22 Newton thruster using the green propellant LMP-103S during a 10-second pulsing test that ratchets the temperature upward. Using this data, engineers can determine how chemical reactions cause heat to flow around to the thruster over time.
Credits: NASA/MSFC/Christopher Burnside

“When you consider all of the satellites in orbit today that do everything from observing Earth and monitoring weather to peering deep into our universe to answer questions about its origins, it’s easy to see that using green propellants will make a big difference in increased mission performance at a reduced cost while keeping both the environment and our workforce safe from contamination,” said Steve Jurczyk, NASA’s associate administrator for the Space Technology Mission Directorate (STMD) at NASA Headquarters in Washington. “NASA has a rich history of ensuring our technology and scientific prowess has a benefit to life on Earth, and green propellant will help ensure that NASA continues to be a steward of this planet.”

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NASA recently completed several hot-fire tests with thrusters powered by two different green propellants with the potential to replace hydrazine. Both are ionic liquid-based blends that are less toxic and less flammable than hydrazine, which makes them easier and less costly to store, to handle and to fuel up spacecraft before launch. Additionally, the new propellants offer higher performance, delivering more thrust for a given quantity of propellant than hydrazine.

NASA engineers monitor temperature data on the left computer screen as a thruster fueled with the green propellant LMP-103S viewed on the right computer screen is fired at NASA’s Marshall Space Flight Center in Huntsville, Alabama.
Credits: NASA/MSFC/Fred Deaton

One of the green propellants is a hydroxylammonium nitrate-based propellant known as AF-M315E. It was developed by the Air Force Research Laboratory at Edwards Air Force Base in California. This propellant will be demonstrated on a small satellite on NASA’s Green Propellant Infusion Mission (GPIM). During the GPIM flight, the smallsat will fire thrusters powered by AF-M315E to conduct maneuvers to change the satellite’s altitude and orientation. GPIM recently passed a major milestone with the delivery of the propellant’s propulsion subsystem built by Aerojet Rocketdyne in Redmond, Washington, to the mission’s prime contractor, Ball Aerospace & Technologies Corp. in Boulder, Colorado, for integration into the spacecraft. For this project, the GPIM team tested two different sized thrusters (1 and 22 Newton) with AF-M315E. Five of the 1-Newton thrusters will fly on GPIM.

“With GPIM’s flight scheduled to launch next year, NASA and the aerospace industry have taken positive steps to demonstrate use of a propellant that will reduce satellite fueling hazards and save time and money during launch campaigns,” said Tim Smith, GPIM mission manager for NASA’s Technology Demonstration Missions at Marshall. GPIM is managed by STMD’s Technology Demonstration Missions Program Office at Marshall.

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The other green propellant is a fuel called LMP-103S, which is based on the oxidizer ammonium dinitramide produced by Eurenco Bofors in Karlskoga, Sweden. A team at NASA’s Marshall Space Flight Center in Huntsville, Alabama, recently completed tests with both 5 Newton and 22 Newton thruster built by ECAPS and powered by LMP-103S. Engineers fired the 22 Newton thruster 35 times under varying conditions and monitored results with infrared cameras. Orbital ATK, Inc. assisted NASA with these tests.

Large and small thrusters are used to propel satellites in space. NASA engineers conducted the first tests with a 22 Newton (5-pound) thruster fueled with the green propellant LMP-103S. Engineer Chris Burnside examines a smaller 5 Newton (1-pound) thruster that also was tested at NASA’s Marshall Space Flight Center in Huntsville, Alabama.
Credits: NASA/MSFC/Fred Deaton

“We conducted the first NASA tests with 22 Newton thrusters with this propellant in the United States,” said Christopher Burnside, lead engineer for testing the LMP-103S propellant. “They performed quite well, providing performance at comparable levels to today’s hydrazine thrusters. It’s always great to put thrusters through the paces in an environment that simulates operational conditions.”

To guide future investments, NASA is leading the development of a green propellant roadmap along with other government agencies, industry and academic leaders who recently shared their collective experiences during a technical interchange meeting at Marshall.

“I like the analogy of relating thrusters and propellant systems to aircraft,” said Charles Pierce, manager of Marshall’s Spacecraft Propulsion Systems Branch, which recently completed the tests with LMP-103S. “One aircraft doesn’t meet every need. Some high performance aircraft need to fly fast while other larger aircraft need to conserve fuel and fly slowly. Some carry passengers while others carry only cargo. Likewise, NASA needs to have flexibility in the types of thrusters and propellant systems it has to meet a variety of mission needs. One type of propellant might work best for one type of mission while another is better suited for a different mission. It’s important that we have choices as we go green.”

– Credit and Resource –

Tracy McMahan

NASA Marshall Space Flight Center

256-544-0034

tracy.mcmahan@nasa.gov

Last Updated: Sep. 14, 2015

Editor: Lee Mohon

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New Green Propellants Complete Milestones

Researchers build bacteria"s photosynthetic engine

bacteria’s photosynthetic engine

Scientia — Nearly all life on Earth depends on photosynthesis, the conversion of light energy into chemical energy. Oxygen-producing plants and cyanobacteria perfected this process 2.7 billion years ago. But the first photosynthetic organisms were likely single-celled purple bacteria that began absorbing near-infrared light and converting it to sulfur or sulfates about 3.4 billion years ago.

University of Illinois researchers used the Titan supercomputer at the Oak Ridge Leadership Computing Facility to create a model of a complete 100-million-atom photosynthetic chromatophore. The final chromatophore model contained about 16,000 lipids and 101 proteins, including the five major types of proteins that contribute to the clockwork of processes that result in the conversion of light energy to ATP. Credit: Abhi Singharoy and Melih Sener, UIUC

Found in the bottom of lakes and ponds today, purple bacteria possess simpler photosynthetic organelles—specialized cellular subunits called chromatophores—than plants and algae. For that reason, Klaus Schulten of the University of Illinois at Urbana–Champaign (UIUC) targeted the chromatophore to study photosynthesis at the atomic level.

As a computational biophysicist, Schulten unites biologists’ experimental data with the physical laws that govern the behavior of matter. This combination allows him to simulate biomolecules, atom by atom, using supercomputers. The simulations reveal interactions between molecules that are impossible to observe in the laboratory, providing plausible explanations for how molecules carry out biological functions in nature.

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In 2014, a team led by Schulten used the Titan supercomputer, located at the US Department of Energy’s (DOE’s) Oak Ridge National Laboratory, to construct and simulate a single chromatophore. The soccer ball-shaped chromatophore contained more than 100 million atoms—a significantly larger biomolecular system than any previously modeled. The project’s scale required Titan, the flagship supercomputer at the Oak Ridge Leadership Computing Facility (OLCF), a DOE Office of Science User Facility, to calculate the interaction of millions of atoms in a feasible time frame that would allow for data analysis.

“For years, scientists have seen that cells are made of these machines, but they could only look at part of the machine. It’s like looking at a car engine and saying, ‘Oh, there’s an interesting cable, an interesting screw, an interesting cylinder.’ You look at the parts and describe them with love and care, but you don’t understand how the engine actually works that way,” Schulten said. “Titan gave us the fantastic level of computing we needed to see the whole picture. For the first time, we could go from looking at the cable, the screw, the cylinder to looking at the whole engine.”

Schulten’s chromatophore simulation is being used to understand the fundamental process of photosynthesis, basic research that could one day lead to better solar energy technology. Of particular interest: how hundreds of proteins work together to capture light energy at an estimated 90 percent efficiency.

Furthermore, the chromatophore project marks a shift in computational biophysics from analyzing the individual cell parts (e.g., a single protein) to analyzing the specialized systems of the cell (e.g., hundreds of proteins working together to carry out an autonomous function). This is a significant step toward the long-term goal of simulating an entire living organism.

Reconstructing Photosynthesis

When the purple bacteria Rhodobacter sphaeroides switches into photosynthetic mode, its inner membrane begins to change, bulging out into small, round vesicles that house the light-harvesting machinery.

Five major types of proteins arranged within two layers of lipids, or fats, contribute to the clockwork of processes that result in the conversion of light energy to adenosine triphosphate (ATP), the common fuel for cellular function across all branches of life.

During the initial steps of photosynthesis, two types of light-harvesting proteins absorb wavelengths of light that lift them into an excited state. This electronic excitation travels through the light-harvesting network to the third type of protein, known as the reaction center. Here, electrical energy is converted into an initial form of chemical energy. Molecules called quinols carry this chemical energy across the organelle to the fourth type of protein—the bc1 complex—where a charge separation process strips the quinol of electrons. This process triggers a current of protons in the fifth type of protein, known as ATP synthase, driving the molecule’s paddle wheel-like c-ring to produce ATP. A detailed video of this process narrated by Schulten can be seen below:

Schulten’s team solved the 100-million-atom model under an allocation on Titan, awarded through the Innovative and Novel Computational Impact on Theory and Experiment, or INCITE, program.

The team used experimental data gathered from atomic force microscopy and the molecular dynamics code NAMD to build and calculate the forces exerted by the spherical chromatophore’s millions of atoms. The final chromatophore model measured 70 nanometers across and contained about 16,000 lipids and 101 proteins. To ensure the simulation mirrored nature, the chromatophore was submerged in a virtual 100 nanometer cube of water—equal to the largest particle size that can fit through a surgical mask—at room temperature and pressure.

Titan, a Cray XK7 with a peak performance of 27 petaflops (or 27 quadrillion calculations per second), proved pivotal in the early stages of the project. By offloading computationally demanding calculations to Titan’s GPUs, the team was able to achieve two to three times the performance of a CPU-only simulation. Additionally, NAMD scaled efficiently to more than 8,000 of Titan’s 18,688 nodes. The combination of robust hardware and effective software allowed the team to resolve its model in a few months, a task that would have taken more than a year on a smaller machine.

“Titan helped us immensely because you need to run the simulation for a certain amount of time and on a large number of processors in order to improve the model,” said team member Abhi Singharoy, a postdoctoral fellow at the Beckman Institute at UIUC. “This project would have been impossible to do on another computer. Had we not achieved a stable model within the first few months, all our other aims would have been out of reach.”

Researchers earlier had leveraged Titan to resolve a flat, 20-million atom chromatophore patch as a stepping stone to the larger system. UIUC postdoctoral researchers Melih Sener and Danielle Chandler carried out the bulk of this initial work, arranging the proteins in accordance with atomic force microscopy data. A description of the 20-million-atom system was published in the August 2014 edition of Biophysical Journal.

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Maximizing the Machine

With a stable model, the remarkable processes of the complete chromatophore—how its atoms move and coordinate within an active, energy-conversion system—can be studied in unprecedented detail.

Under a 150-million processor-hour allocation awarded through the 2015 INCITE program, the team is continuing to run its simulation and analyze the chromatophore for notable properties, such as the organelle’s optimum pH and salt concentration levels. Analysis and visualization of the organelle are being conducted using an application called VMD. Both VMD and NAMD originated with and continue to be developed by Schulten’s Theoretical and Computational Biophysics Group at UIUC. The applications support a global community of users.

NAMD calculates the motion of the chromatophore’s atoms in time steps of 2 femtoseconds, or 2,000 trillionths of a second. At this timescale, a 1-day, 4,000-processor run on Titan nets 16 nanoseconds (16 million femtoseconds), or 16 billionths of a second, of simulation time. By continuing to run the simulation—with the goal of capturing a microsecond (1,000 nanoseconds) of simulation time—slower-moving processes of the biomolecular system can be observed.

“With the time we’ve been allotted on Titan, we will actually be able to see a quinol move and the charge being transferred,” Singharoy said.

The OLCF is helping Schulten’s team manage and analyze the terabytes of data produced by the project. Typically, simulation data are transferred to a project’s home institution for analysis. Because of the size of the chromatophore, a transfer job can take days to complete—even using world-class networking resources.

To overcome this bottleneck, the OLCF worked to enable the graphics capabilities of Titan’s GPUs. Opening up Titan for hardware-accelerated graphics makes it possible for users to run VMD’s graphical interfaces in parallel with NAMD from any location, creating a near real-time “window” into calculations being performed on Titan. Such remote visualization would make it easier for researchers to view and manipulate their data while eliminating the file transfer. This VMD capability is expected to be available to users soon.

“We’re making the scientists much more productive,” said John Stone, a senior research programmer at UIUC and VMD’s lead developer. “Essentially, it will be like having a petascale computer on your laptop.”

– Credit and Resource –

More information: D. Chandler, J. Strümpfer, M. Sener, S. Scheuring, and K. Schulten. “Light Harvesting by Lamellar Chromatophores in Rhodospirillum photometricum.” Biophysical Journal 106, no. 11 (2014): 2503–2510. http://dx.doi.org/10.1016/j.bpj.2014.04.030.

Journal reference: Biophysical Journal

Provided by: Oak Ridge National Laboratory

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Researchers build bacteria"s photosynthetic engine

model may explain emergence of self-replication

New model may explain emergence of self-replication on early Earth

A schematic drawing of template-assisted ligation, shown in this model to give rise to autocatalytic systems. Credit: Maslov and Tkachenko

Scientia — When life on Earth began nearly 4 billion years ago, long before humans, dinosaurs or even the earliest single-celled forms of life roamed, it may have started as a hiccup rather than a roar: small, simple molecular building blocks known as “monomers” coming together into longer “polymer” chains and falling apart in the warm pools of primordial ooze over and over again.

Then, somewhere along the line, these growing polymer chains developed the ability to make copies of themselves. Competition between these molecules would allow the ones most efficient at making copies of themselves to do so faster or with greater abundance, a trait that would be shared by the copies they made. These rapid replicators would fill the soup faster than the other polymers, allowing the information they encoded to be passed on from one generation to another and, eventually, giving rise to what we think of today as life.

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Or so the story goes. But with no fossil record to check from those early days, it’s a narrative that still has some chapters missing. One question in particular remains problematic: what enabled the leap from a primordial soup of individual monomers to self-replicating polymer chains?

A new model published this week in The Journal of Chemical Physics, from AIP Publishing, proposes a potential mechanism by which self-replication could have emerged. It posits that template-assisted ligation, the joining of two polymers by using a third, longer one as a template, could have enabled polymers to become self-replicating.

“We tried to fill this gap in understanding between simple physical systems to something that can behave in a life-like manner and transmit information,” said Alexei Tkachenko, a researcher at Brookhaven National Laboratory. Tkachenko carried out the research alongside Sergei Maslov, a professor at the University of Illinois at Urbana-Champaign with joint appointment at Brookhaven.

Origins of Self-Replication

Self-replication is a complicated process—DNA, the basis for life on earth today, requires a coordinated cohort of enzymes and other molecules in order to duplicate itself. Early self-replicating systems were surely more rudimentary, but their existence in the first place is still somewhat baffling.

Tkachenko and Maslov have proposed a new model that shows how the earliest self-replicating molecules could have worked. Their model switches between “day” phases, where individual polymers float freely, and “night” phases, where they join together to form longer chains via template-assisted ligation. The phases are driven by cyclic changes in environmental conditions, such as temperature, pH, or salinity, which throw the system out of equilibrium and induce the polymers to either come together or drift apart.

According to their model, during the night cycles, multiple short polymers bond to longer polymer strands, which act as templates. These longer template strands hold the shorter polymers in close enough proximity to each other that they can ligate to form a longer strand—a complementary copy of at least part of the template. Over time, the newly synthesized polymers come to dominate, giving rise to an autocatalytic and self-sustaining system of molecules large enough to potentially encode blueprints for life, the model predicts.

Polymers can also link together without the aid of a template, but the process is somewhat more random—a chain that forms in one generation will not necessarily be carried over into the next. Template-assisted ligation, on the other hand, is a more faithful means of preserving information, as the polymer chains of one generation are used to build the next. Thus, a model based on template-assisted ligation combines the lengthening of polymer chains with their replication, providing a potential mechanism for heritability.

While some previous studies have argued that a mix of the two is necessary for moving a system from monomers to self-replicating polymers, Maslov and Tkachenko’s model demonstrates that it is physically possible for self-replication to emerge with only template-assisted ligation.

“What we have demonstrated for the first time is that even if all you have is template-assisted ligation, you can still bootstrap the system out of primordial soup,” said Maslov.

The idea of template-assisted ligation driving self-replication was originally proposed in the 1980s, but in a qualitative manner. “Now it’s a real model that you can run through a computer,” said Tkachenko. “It’s a solid piece of science to which you can add other features and study memory effects and inheritance.”

Under Tkachenko and Maslov’s model, the move from monomers to polymers is a very sudden one. It’s also hysteretic—that is, it takes a very certain set of conditions to make the initial leap from monomers to self-replicating polymers, but those stringent requirements are not necessary to maintain a system of self-replicating polymers once one has leapt over the first hurdle.

One limitation of the model that the researchers plan to address in future studies is its assumption that all polymer sequences are equally likely to occur. Transmission of information requires heritable variation in sequence frequencies—certain combinations of bases code for particular proteins, which have different functions. The next step, then, is to consider a scenario in which some sequences become more common than others, allowing the system to transmit meaningful information.

Maslov and Tkachenko’s model fits into the currently favored RNA world hypothesis—the belief that life on earth started with autocatalytic RNA molecules that then lead to the more stable but more complex DNA as a mode of inheritance. But because it is so general, it could be used to test any origins of life hypothesis that relies on the emergence of a simple autocatalytic system.

“The model, by design, is very general,” said Maslov. “We’re not trying to address the question of what this primordial soup of monomers is coming from” or the specific molecules involved. Rather, their model shows a physically plausible path from monomer to self-replicating polymer, inching a step closer to understanding the origins of life.

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Waiter, there’s an RNA in my Primordial Soup—Tracing the Origins of Life, from Darwin to Today

Nearly every culture on earth has an origins story, a legend explaining its existence. We humans seem to have a deep need for an explanation of how we ended up here, on this small planet spinning through a vast universe. Scientists, too, have long searched for our origins story, trying to discern how, on a molecular scale, the earth shifted from a mess of inorganic molecules to an ordered system of life. The question is impossible to answer for certain—there’s no fossil record, and no eyewitnesses. But that hasn’t stopped scientists from trying.

Over the past 150 years, our shifting understanding of the origins of life has mirrored the emergence and development of the fields of organic chemistry and molecular biology. That is, increased understanding of the role that nucleotides, proteins and genes play in shaping our living world today has also gradually improved our ability to peer into their mysterious past.

When Charles Darwin published his seminal On the Origin of the Species in 1859, he said little about the emergence of life itself, possibly because, at the time, there was no way to test such ideas. His only real remarks on the subject come from a later letter to a friend, in which he suggested a that life emerged out of a “warm little pond” with a rich chemical broth of ions. Nevertheless, Darwin’s influence was far-reaching, and his offhand remark formed the basis of many origins of life scenarios in the following years.

In the early 20th century, the idea was popularized and expanded upon by a Russian biochemist named Alexander Oparin. He proposed that the atmosphere on the early earth was reducing, meaning it had an excess of negative charge. This charge imbalance could catalyze existing a prebiotic soup of organic molecules into the earliest forms of life.

Oparin’s writing eventually inspired Harold Urey, who began to champion Oparin’s proposal. Urey then caught the attention of Stanley Miller, who decided to formally test the idea. Miller took a mixture of what he believed the early earth’s oceans may have contained—a reducing mixture of methane, ammonia, hydrogen, and water—and activated it with an electric spark. The jolt of electricity, acting like a strike of lightening, transformed nearly half of the carbon in the methane into organic compounds. One of the compounds he produced was glycine, the simplest amino acid.

The groundbreaking Miller-Urey experiment showed that inorganic matter could give rise to organic structures. And while the idea of a reducing atmosphere gradually fell out of favor, replaced by an environment rich in carbon dioxide, Oparin’s basic framework of a primordial soup rich with organic molecules stuck around.

The identification of DNA as the hereditary material common to all life, and the discovery that DNA coded for RNA, which coded for proteins, provided fresh insight into the molecular basis for life. But it also forced origins of life researchers to answer a challenging question: how could this complicated molecular machinery have started? DNA is a complex molecule, requiring a coordinated team of enzymes and proteins to replicate itself. Its spontaneous emergence seemed improbable.

In the 1960s, three scientists—Leslie Orgel, Francis Crick and Carl Woese—independently suggested that RNA might be the missing link. Because RNA can self-replicate, it could have acted as both the genetic material and the catalyst for early life on earth. DNA, more stable but more complex, would have emerged later.

Today, it is widely believed (though by no means universally accepted) that at some point in history, an RNA-based world dominated the earth. But how it got there—and whether there was a simpler system before it—is still up for debate. Many argue that RNA is too complicated to have been the first self-replicating system on earth, and that something simpler preceded it.

Graham Cairns-Smith, for instance, has argued since the 1960s that the earliest gene-like structures were not based on nucleic acids, but on imperfect crystals that emerged from clay. The defects in the crystals, he believed, stored information that could be replicated and passed from one crystal to another. His idea, while intriguing, is not widely accepted today.

Others, taken more seriously, suspect that RNA may have emerged in concert with peptides—an RNA-peptide world, in which the two worked together to build up complexity. Biochemical studies are also providing insight into simpler nucleic acid analogs that could have preceded the familiar bases that make up RNA today. It’s also possible that the earliest self-replicating systems on earth have left no trace of themselves in our current biochemical systems. We may never know, and yet, the challenge of the search seems to be part of its appeal.

Recent research by Tkachenko and Maslov, published July 28, 2015 in The Journal of Chemical Physics, suggests that self-replicating molecules such as RNA may have arisen through a process called template-assisted ligation. That is, under certain environmental conditions, small polymers could be driven to bond to longer complementary polymer template strands, holding the short strands in close enough proximity to each other that they could fuse into longer strands. Through cyclic changes in environmental conditions that induce complementary strands to come together and then fall apart repeatedly, a self-sustaining collection of hybridized, self-replicating polymers able to encode the blueprints for life could emerge.

– Credit and Resource –

More information: The article, “Spontaneous emergence of autocatalytic information-coding polymers,” by Alexei Tkachenko and Sergei Maslov, The Journal of Chemical Physics on July 28, 2015: http://scitation.aip.org/content/aip/journal/jcp/143/2/10.1063/1.4922545

Journal reference: Journal of Chemical Physics

Provided by: American Institute of Physics

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model may explain emergence of self-replication