Antimatter - Blog Posts

nasa

5 years ago

From Discovering the Secrets of the Universe to In-Space Servicing, We’ve Got The Tools for the Job

If you need to fix something on Earth, you could go to a store, buy the tools you need, and get started. In space, it’s not that easy.

Aside from the obvious challenges associated with space (like it being cold and there being no gravity), developing the right tools requires a great deal of creativity because every task is different, especially when the tools need to be designed from scratch. From the time an engineer dreams up the right tools to the time they are used in space, it can be quite a process.

On Nov. 15, astronauts Luca Parmitano and Drew Morgan began a series of spacewalks to repair an instrument called the Alpha Magnetic Spectrometer (AMS-2) on the exterior of the International Space Station. The first of four spacewalk focused on using specialized tools to remove shields and covers, to gain access to the heart of AMS to perform the repairs, and install a new cooling system.

The debris shield that covered Alpha Magnetic Spectrometer floats away toward Earth as astronaut Drew Morgan successfully releases it.

Once repaired, AMS will continue to help us understand more about the formation of the universe and search for evidence of dark matter and antimatter.

These spacewalks, or extravehicular activities (EVAs), are the most complex of their kind since the servicing of the Hubble Space Telescope. AMS is particularly challenging to repair not only because of the instrument’s complexity and sensitivity, but also because it was never designed to be fixed. Because of this design, it does not have the kinds of interfaces that make spacewalks easier, or the ability to be operated on with traditional multi-purpose tools. These operations are so complex, their design and planning has taken four years. Let’s take a look at how we got ready to repair AMS.

Thinking Outside of the (Tool) Box

When designing the tools, our engineers need to keep in mind various complications that would not come into play when fixing something on Earth. For example, if you put a screw down while you’re on Earth, gravity will keep it there — in space, you have to consistently make sure each part is secure or it will float away. You also have to add a pressurized space suit with limited dexterity to the equation, which further complicates the tool design.

In addition to regular space complications, the AMS instrument itself presents many challenges — with over 300,000 data channels, it was considered too complex to service and therefore was not designed to one day be repaired or updated if needed. Additionally, astronauts have never before cut and reconnected micro-fluid lines (4 millimeters wide, less than the width of the average pencil) during a spacewalk, which is necessary to repair AMS, so our engineers had to develop the tools for this big first.

With all of this necessary out-of-the-box thinking, who better to go to for help than the teams that worked on the most well-known repair missions — the Hubble servicing missions and the space station tool teams? Building on the legacy of these missions, some of our same engineers that developed tools for the Hubble servicing missions and space station maintenance got to work designing the necessary tools for the AMS repair, some reworked from Hubble, and some from scratch. In total, the teams from Goddard Space Flight Center’s Satellite Servicing Projects Division, Johnson Space Center, and AMS Project Office developed 21 tools for the mission.

Designing and Building

Like many great inventions, it all starts with a sketch. Engineers figure out what steps need to be taken to accomplish the task, and imagine the necessary tools to get the job done.

From there, engineers develop a computer-aided design (CAD) model, and get to building a prototype. Tools will then undergo multiple iterations and testing with the AMS repair team and astronauts to get the design just right, until eventually, they are finalized, ready to undergo vibration and thermal vacuum testing to make sure they can withstand the harsh conditions of launch and use in the space environment.

Hex Head Capture Tool Progression:

Hex Head Capture Tool Used in Space:

Practice Makes Perfect

One of the reasons the AMS spacewalks have been four years in the making is because the complexity of the repairs required the astronauts to take extra time to practice. Over many months, astronauts tasked with performing the spacewalks practiced the AMS repair procedures in numerous ways to make sure they were ready for action. They practiced in:

Virtual reality simulations:

The Neutral Buoyancy Laboratory:

The Active Response Gravity Offload System (ARGOS):

Astronauts use this testing to develop and practice procedures in space-like conditions, but also to figure out what works and doesn’t work, and what changes need to be made. A great example is a part of the repair that involves cutting and reconnecting fluid lines. When astronauts practiced cutting the fluid lines during testing here on Earth, they found it was difficult to identify which was the right one to cut based on sight alone.

The tubes on the AMS essentially look the same.

After discussing the concern with the team monitoring the EVAs, the engineers once again got to work to fix the problem.

And thus, the Tube Cutting Guide tool was born! Necessity is the mother of invention and the team could not have anticipated the astronauts would need such a tool until they actually began practicing. The Tube Cutting Guide provides alignment guides, fiducials and visual access to enable astronauts to differentiate between the tubes. After each of eight tubes is cut, a newly designed protective numbered cap is installed to cover the sharp tubing.

Off to Space

With the tools and repair procedures tested and ready to go, they launched to the International Space Station earlier this year. Now they’re in the middle of the main event -- Luca and Drew completed the first spacewalk last Friday, taking things apart to access the interior of the AMS instrument. Currently, there are three other spacewalks scheduled over the course of a month. The next spacewalk will happen on Nov. 22 and will put the Tube Cutting Guide to use when astronauts reconnect the tubes to a new cooling system.

With the ingenuity of our tool designers and engineers, and our astronauts' vigorous practice, AMS will be in good hands.

Check out the full video for the first spacewalk. Below you can check out each of the tools above in action in space!

Debris Shield Worksite: 2:29:16 – Debris Shield Handling Aid 2:35:25 – Hex Head Capture Tool (first) 2:53:31 – #10 Allen Bit 2:54:59 – Capture Cages 3:16:35 – #10 Allen Bit (diagonal side) 3:20:58 – Socket Head Capture Tool 3:33:35 – Hex Head Capture Tool (last) 3:39:35 – Fastener Capture Block 3:40:55 – Debris Shield removal 3:46:46 – Debris Shield jettison

Handrail Installations: 4:00:53 – Diagonal Beam Handrail Install 4:26:09 – Nadir Vacuum Case Handrail Install 4:33:50 – Zenith Vacuum Case Handrail InstallVertical Support Beam (VSB)

Vertical Support Beam (VSB) Worksite: 5:04:21 – Zip Tie Cutter 5:15:27 – VSB Cover Handling Aid 5:18:05 – #10 Allen Bit 5:24:34 – Socket Head Capture Tool 5:41:54 – VSB Cover breaking 5:45:22 – VSB Cover jettison 5:58:20 – Top Spacer Tool & M4 Allen Bit 6:08:25 – Top Spacer removal 7:42:05 - Astronaut shoutout to the tools team

Neutrinos Hint of Matter-Antimatter Rift

the same underground observatory in Japan where, 18 years ago, neutrinos were first seen oscillating from one “flavor” to another — a landmark discovery that earned two physicists the 2015 Nobel Prize — a tiny anomaly has begun to surface in the neutrinos’ oscillations that could herald an answer to one of the biggest mysteries in physics: why matter dominates over antimatter in the universe.

The anomaly, detected by the T2K experiment, is not yet pronounced enough to be sure of, but it and the findings of two related experiments “are all pointing in the same direction,” said Hirohisa Tanaka of the University of Toronto, a member of the T2K team who presented the result to a packed audience in London earlier this month.

“A full proof will take more time,” said Werner Rodejohann, a neutrino specialist at the Max Planck Institute for Nuclear Physics in Heidelberg who was not involved in the experiments, “but my and many others’ feeling is that there is something real here.”

The long-standing puzzle to be solved is why we and everything we see is matter-made. More to the point, why does anything — matter or antimatter — exist at all? The reigning laws of particle physics, known as the Standard Model, treat matter and antimatter nearly equivalently, respecting (with one known exception) so-called charge-parity, or “CP,” symmetry: For every particle decay that produces, say, a negatively charged electron, the mirror-image decay yielding a positively charged antielectron occurs at the same rate. But this cannot be the whole story. If equal amounts of matter and antimatter were produced during the Big Bang, equal amounts should have existed shortly thereafter. And since matter and antimatter annihilate upon contact, such a situation would have led to the wholesale destruction of both, resulting in an empty cosmos.

Somehow, significantly more matter than antimatter must have been created, such that a matter surplus survived the annihilation and now holds sway. The question is, what CP-violating process beyond the Standard Model favored the production of matter over antimatter?

Many physicists suspect that the answer lies with neutrinos — ultra-elusive, omnipresent particles that pass unfelt through your body by the trillions each second.

To that end, starting in 2010, scientists with the T2K experiment generated beams of neutrinos or antineutrinos in Tokai, Japan, and aimed them toward the Super-Kamiokande neutrino observatory, a sensor-lined tank of 50,000 tons of pure water located nearly 200 miles away in Kamioka. Occasionally, these ghostly particles interacted with atoms inside the water tank, generating detectable flashes of radiation. Detecting a difference in the behavior of the neutrinos and antineutrinos would provide an important clue about the preponderance of matter over antimatter, perhaps opening up a route beyond the Standard Model to a more complete theory of nature. Already, the strange properties of neutrinos provide a possible outline of that fuller story.

Kamioka Observatory, ICRR (Institute for Cosmic Ray Research), The University of Tokyo At the Super-Kamiokande observatory in Kamioka, Japan — shown here when it was being filled with water in 2006 — neutrinos interact with atoms inside the water, generating flashes of radiation that are picked up by the surrounding sensors.

Primordial Neutrinos

The 1998 discovery that neutrinos switch flavors on the fly “may change our most fundamental theories,” President Bill Clinton said at the time, “from the nature of the smallest subatomic particles to how the universe itself works.”

Neutrino oscillations defied the Standard Model’s prediction that the particles are massless, like photons. In order for neutrinos to oscillate, each of their three possible flavors (electron, muon and tau) must be a quantum-mechanical mixture, or “superposition,” of three possible masses. Quantum superpositions evolve over time. So a neutrino might start out with its three mass components giving it pure muon flavor, but as the components evolve at different rates, electron flavor gradually enters the mixture, and the neutrino will have some probability of being measured as an electron neutrino.

There’s no mechanism within the Standard Model by which neutrinos might acquire their tiny, nonzero masses. Also unknown is why all neutrinos are observed to be “left-handed,” spinning clockwise with respect to their direction of motion, while all antineutrinos are right-handed, spinning counterclockwise.

Experts overwhelmingly favor a double-duty explanation of neutrino mass and single-handedness called the “seesaw mechanism,” whereby the known, lightweight, left-handed neutrinos have much heavier right-handed counterparts, and the known antineutrinos likewise have superheavy left-handed counterparts (the light and heavy masses are inversely related, like two sides of a seesaw). For this seesaw explanation to work, the neutrinos and antineutrinos on each side of the seesaw must actually be the same particle, except for their opposite handedness. Numerous experiments are now hunting for an extremely rare radioactive decay that would confirm this “Majorana” nature of neutrinos, thereby shoring up the logic of the seesaw mechanism.

If the theory is correct, then the heavy neutrinos and antineutrinos would have populated the hot young universe, when there was enough energy to beget beastly particles. They would have since decayed. Physicists wonder: Might their decays have produced the matter-antimatter asymmetry? This is the question to which an answer may be emerging — and much sooner than expected.

Tilted Seesaw

There’s good reason to think that neutrinos violate CP symmetry. The one established instance of CP violation in the laws of physics arises among the quarks — the building blocks of protons and neutrons — whose flavor mixing is described by a mathematical matrix similar to the one for neutrino mixing. In the quark case, though, the value of a numerical factor in the matrix that creates a disparity between quarks and antiquarks is very small. Quarks and antiquarks behave far too symmetrically to account for the universe’s matter-antimatter imbalance.

Lucy Reading-Ikkanda for Quanta Magazine

But the neutrino mixing matrix comes equipped with its own factor by which neutrinos and antineutrinos can violate CP symmetry. (Paradoxically, they can behave differently from one another even if they are Majorana particles, identical except for their opposite handedness.) If the lightweight neutrinos and antineutrinos violate CP symmetry, then the hypothetical heavy primordial neutrinos and antineutrinos must as well, and their asymmetric decays could easily have produced the universe’s glut of matter. Discovering CP violation among the lightweight neutrinos “will boost that general framework,” said Neal Weiner, a theoretical physicist at New York University.

The question is, how large will the CP-violation factor be? “The fear was that it would be small,” said Patricia Vahle, a physicist at the College of William & Mary — so small that the current generation of experiments wouldn’t detect any difference between neutrinos’ and antineutrinos’ behavior. “But it is starting to look like maybe we will be lucky,” she said.

To search for CP violation, the T2K scientists looked for evidence that neutrinos and antineutrinos oscillated between muon and electron flavors with unequal probabilities as they traveled between Tokai and Kamioka. The amount of CP violation once again works like a seesaw, with the rate of muon-to-electron neutrino conversions on one side, and corresponding antineutrino conversions on the other. The larger the value of the factor in the matrix, the greater the seesaw’s tilt.

If the seesaw is balanced, signifying perfect CP symmetry, then (accounting for differences in the production and detection rates of neutrinos and antineutrinos) the T2K scientists would have expected to detect roughly 23 electron neutrino candidates and seven electron antineutrino candidates in Kamioka, Tanaka said. Meanwhile, if CP symmetry is “maximally” violated — the seesaw tilted fully toward more neutrino oscillations and fewer antineutrino oscillations — then 27 electron neutrinos and six electron antineutrinos should have been detected. The actual numbers were even more skewed. “What we observed are 32 electron neutrino candidates and four electron antineutrino candidates,” Tanaka said.

With so few total events, it’s too soon to know whether the apparent tilt of the seesaw, signifying a large amount of CP violation, is real or a statistical aberration. Two other new hints of CP violation, however, strengthen the case. First, the newly running NOvA experiment, which generates a beam of muon neutrinos in Illinois and measures electron neutrinos in Minnesota, found a large number of these oscillations, again suggesting that the seesaw may be tilted in favor of neutrino oscillations and away from antineutrino oscillations. Second, researchers at the Super-Kamiokande observatory detected a similar enhancement of electron neutrinos coming from Earth’s atmosphere. (T2K and NOvA both plan to submit their findings for publication later this year.)

Vahle, who presented NOvA’s new results this month in London, urged caution; even when the T2K and NOvA results are combined, their statistical significance remains at a low level known as “2 sigma,” where there’s still a 5 percent chance the apparent deviation from CP symmetry is a random fluke. The results “do give me hope that finding CP violation in neutrino oscillations won’t be as hard as many feared it would be,” she said, “but we aren’t there yet.”

If CP violation among neutrinos is real and as large as it currently seems, then the evidence will slowly strengthen in the coming years. T2K’s signal could reach 3-sigma significance by the mid-2020s. “It’s a very exciting time as we look forward to a lot more data from both experiments,” said Peter Shanahan, a NOvA co-spokesperson.

It isn’t yet known exactly how CP violation in the light neutrino oscillations would translate into CP-violating decays of the heavy set. But discovering the former would point physicists in the latter’s general direction. “If we are starting to see [CP violation] in the neutrino sector, it is certainly a critical result,” Weiner said.

Story from Quanta Magazine

Visit Nanotechnology World Association for more articles