SPACE/COSMOS
Trump names billionaire private astronaut as next NASA chief
By AFP
December 4, 2024
US fintech billionaire Jared Isaacman (EV1) peeks out to space from a hatch structure called "Skywalker," during the first private spacewalk performed by the crew of the SpaceX Polaris Dawn mission - Copyright Polaris Program/AFP/File -
US President-elect Donald Trump on Wednesday nominated Jared Isaacman, the online payments billionaire and the first private astronaut to ever perform a spacewalk, as the next head of NASA.
The nod could spark questions about potential conflicts of interest, given Isaacman’s extensive financial ties to Elon Musk, who is set to co-chair a government efficiency commission and is one of Trump’s closest advisors.
Isaacman, 41, the founder and CEO of Shift4 Payments, has emerged as a leading figure in commercial spaceflight through his high-profile collaborations with Musk’s SpaceX.
His achievements include stepping out of a Crew Dragon to gaze at Earth from the void of space, while clutching the spacecraft’s exterior, back in September.
“I am delighted to nominate Jared Isaacman, an accomplished business leader, philanthropist, pilot and astronaut, as Administrator of the National Aeronautics and Space Administration (NASA),” Trump wrote on Truth Social.
“Jared will drive NASA’s mission of discovery and inspiration, paving the way for groundbreaking achievements in Space science, technology, and exploration.”
The historic spacewalk took place under the Polaris program, a collaboration between Isaacman and SpaceX that is set to include three missions in total.
Financial terms of the partnership remain under wraps but Isaacman reportedly poured $200 million of his own money into leading the 2021 all-civilian SpaceX Inspiration4 orbital mission, his first foray into space.
He is also a vocal supporter of SpaceX and Musk, frequently praising the company and its vision on the platform X.
“There will inevitably be a thriving space economy — one that will create opportunities for countless people to live and work in space,” Isaacman said in a post after Trump’s announcement.
“At NASA, we will passionately pursue these possibilities.”
Isaacman, a Pennsylvania native, founded the business that became Shift4 Payments from his family’s basement at just 16.
A skilled aviator, he is qualified to fly military aircraft, has performed in airshows, and set a world record for an around-the-world flight.
A mission design for servicing telescopes in space
University of Illinois Grainger College of Engineering
image:
CAD model of the Gaia spacecraft with service vehicle, post-docking configuration.
view moreCredit: The Grainger College of Engineering at the University of Illinois Urbana-Champaign
The fate of telescopes in space is looking better now that they are being designed to be serviceable. Researchers developed a servicing plan that can be applied to future space observatories based on current missions such as the James Webb Space Telescope and the European Space Agency’s Gaia.
“Although the next generation of large space telescopes are being designed with serviceability in mind, there are enormous challenges with implementation,” said Siegfried Eggl, professor of aerospace engineering in The Grainger College of Engineering, University of Illinois Urbana-Champaign.
One issue is distance. Modern space telescopes are stationed at the Sun-Earth Lagrange Point L2, which is about a million miles away from the Earth. It's moving with the Earth, which makes it easier to reach, but still very far away making the transport time consuming and expensive. The relatively quiet, low interference environment at Lagrange Point L2 means missions like Gaia have an enormous impact on astronomy and planetary science, but according to Eggl, it’s worth the trek.
Eggl said, “Gaia is like a rotating cylinder with a solar panel. it is encapsulated, so it hasn’t been damaged, but after a decade out there it’s running low on fuel. Ruthvik Bommena designed a novel concept to add a sort of spider-looking attachment that can extend its life without impeding its data collection. Gaia will be decommissioned soon, so there isn’t enough time to reach it, but the James Webb might still be a possibility because it will be operating for several more years and they may decide to prolong its mission.”
He explained that the James Webb telescope has unshielded, segmented mirrors, some of which have already been damaged when struck by micrometeorites. The entire mirror surface of JWST is six meters in diameter. The next large telescope will be about twice that size.
“We’re trying to stay a step ahead so there is a plan to replace broken mirrors, for example. If we don’t, it’s like buying an expensive sports car, then like throwing it away when it runs out of gas.”
Another aspect Bommena is working is safe proximity operations.
“A spacecraft sent to repair or refuel a telescope needs to brake when it reaches it,” Bommena said. “Using the thrusters to slow down would be like pointing a blowtorch at the telescope. You don’t want to do that to a delicate structure like a telescopic mirror. How do we get there without torching the whole thing?”
Robyn Woollands, who is also professor of aerospace engineering at U of I said one of the main goals they achieved with this work was finding a trajectory to get there cheaply without reliance on large, cost-prohibitive rockets.
“Fortunately, getting there is doable because of some hidden highways in our solar system. We have a trajectory that is optimal for the size of spacecraft needed to repair the JWST,” she said.
Ph.D. student Alex Pascarella developed a novel technique for quick sampling of the solution space that can shorten the computation time.
“The novelty is in how we brought together two separate approaches to trajectory design: dynamical systems theory and optimal control theory,” Pascarella said.
Pascarella said the traditional approach for trajectory design in multibody systems such as the Sun-Earth system, relies on computing the invariant manifolds of an orbit—manifolds are pathways in space that naturally lead the spacecraft to the given orbit. This is a great approach that has been successfully used for decades, both in academic research and real-life applications.
“It becomes a bit challenging when you are trying to rendezvous with a target spacecraft at a specific location in space/time instead of reaching a target orbit and you are dealing with a low-thrust spacecraft whose engine operates for long stretches of time as opposed to a spacecraft with more powerful thrusters that operate for very shorts bursts.
“Our technique is based on a slightly different idea. We first investigate the solution space by propagating a sample of solutions—either without any thrust or with a very simple thrust control law—and we take note of how close they pass to our desired destination,” Pascarella said.
He added that because the type of orbit they are trying to reach spawns manifolds, they know at least some of their initial guesses will come close to the desired orbit.
“After we create a map of initial solutions, we use optimal control theory to generate optimal end-to-end trajectories,” Pascarella said. “Optimal control allows us to find trajectories that depart near Earth, and rendezvous with our space telescope in the least amount of time. The initial sampling of the solution space is fundamental—optimal control problems are notoriously difficult to solve, so we need a decent initial guess to work with.”
Eggl said the plan to repair/refuel Gaia is a complete design that can be implemented. For the James Webb telescope, more engineering is needed.
The study, “Mission design for space telescope servicing at Sun–Earth L2,” by Alex Pascarella, Ruthvik Bommena, Siegfried Eggl and Robyn Woollands, is published in the journal Acta Astronautica. DOI: 10.1016/j.actaastro.2024.08.031
This work was supported by NASA and the Aerospace Corporation.
Journal
Acta Astronautica
Article Title
Mission design for space telescope servicing at Sun–Earth L2
Seeing deeper into the cosmos with gravitational-wave detectors
With reduced noise, new technique could expand our ability to observe distant cosmic events such as merging black holes
Optica
image:
Thomas Corbitt, Ronald Pagano and Scott Aronson from Louisiana State University (pictured from left) collaborated with researchers from the LIGO Laboratory and Thorlabs Crystalline Solutions.
view moreCredit: Olivia Crowell, Louisiana State University
WASHINGTON — Researchers have shown that optical spring tracking is a promising way to improve the signal clarity of gravitational-wave detectors. The advance could one day allow scientists to see farther into the universe and provide more information about how black holes and neutron stars behave as they merge.
Large-scale interferometers such as the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO) detect subtle distortions in spacetime, known as gravitational waves, generated by distant cosmic events. By allowing scientists to study phenomena that do not emit light, gravitational wave measurements have opened a new window for understanding extreme astrophysical events, the nature of gravity and the origins of the universe.
“Quantum noise has become a limiting noise source when measuring gravitational waves,” said Scott M. Aronson, a member of the research team from Louisiana State University. “By tuning the system to respond at a desired frequency, we show that you can reduce this noise by using an optical spring to track a signal coming from a compact binary system. In the future, this binary system could be two black holes orbiting each other – within our galaxy or beyond.”
In the Optica Publishing Group journal Optics Letters, researchers led by Thomas Corbitt at Louisiana State University in collaboration with the LIGO Laboratory at the California Institute of Technology and Thorlabs Crystalline Solutions report a proof-of-concept experiment showing that dynamic tracking could help reduce noise in a gravitational-wave detector.
“This is the first measurement of an optical spring tracking a target signal over time,” said Aronson, first author of the paper. “This dynamic tracking technique is a strong candidate for quantum noise reduction in the future. Whether in current interferometers such as LIGO, or future detectors such as Cosmic Explorer, optical spring tracking is worth investigating to improve sensitivity and further our ever-growing population of gravitational wave events.”
Creating an optical spring
When two orbiting objects such as black holes emit gravitational waves, their rotational frequency increases creating what is known as a chirp. It has been proposed that matching the frequency of this chirp with a tunable optical spring could reduce noise and improve the signal clarity of a gravitational-wave observatory.
Although this idea is being investigated for future interferometer configurations, Aronson and colleagues decided to carry out a proof-of-concept experiment to demonstrate the potential of dynamic tracking in larger-scale systems, such as a gravitational-wave observatory. The work was conducted as part of the LIGO scientific collaboration and the larger LIGO/Virgo/KAGRA (LVK) collaboration.
To accomplish this, co-author Garrett D. Cole from Thorlabs Crystalline Solutions constructed a cantilever that weighs just 50 nanograms using layers of aluminum gallium arsenide and gallium arsenide. The cantilever acts as a mirror that can “feel” the radiation pressure imparted by a laser beam, creating an optical spring that allows the researchers to investigate the interplay of the radiation pressure from the laser light with the cantilever’s motion.
Tracking the signal
To test the tracking system, the researchers simulated an incoming gravitational wave by embedding a target signal into the phase of a laser beam. They used an alternate signal to control the position of a larger movable mirror within an optical cavity. The optical spring frequency could be tuned by adjusting the distance between the mirror and a cantilever.
During the experiment, the researchers moved the mirror to "track" the target signal as its frequency shifted from 40 kHz to 100 kHz over 10 seconds. Comparing this approach to keeping the mirror stationary, they demonstrated that tracking the signal with the movable mirror increased the signal-to-noise ratio by up to 40 times, producing a clearer measurement.
The researchers note that implementing the dynamic tracking technique in a large-scale interferometer would require highly robust feedback control of all optical components. This can be particularly challenging because as power levels increase, radiation pressure becomes critical in maintaining the precise positioning of mirrors. The technique also requires prior information about an incoming gravitational wave, which could be obtained using proposed space-based detectors like LISA.
“This dynamic tracking technique represents a significant step toward enhancing the sensitivity of gravitational-wave detectors, bringing us closer to unlocking the mysteries of the universe’s earliest moments,” said Aronson. “With future generations of gravitational-wave detectors, we will have the possibility of learning about the merger of compact objects formed by the first generation of stars, or even more exotic objects such as primordial black holes formed shortly after the Big Bang.”
Paper: S. Aronson, R. Pagano, T. Cullen, G. D. Cole, T. Corbitt, “Optical Spring Tracking for Enhancing Quantum-Limited Interferometers,” Opt. Lett., 49, 6980-6983 (2024).
DOI: https://doi.org/10.1364/OL.540195
About Optics Letters
Optics Letters offers rapid dissemination of new results in all areas of optical science with short, original, peer-reviewed communications. Optics Letters accepts papers that are noteworthy to a substantial part of the optics community. Published by Optica Publishing Group and led by Editor-in-Chief Miguel Alonso, Institut Fresnel, École Centrale de Marseille and Aix-Marseille Université, France, University of Rochester, USA. For more information, visit Optics Letters.
About Optica Publishing Group (formerly OSA)
Optica Publishing Group is a division of Optica, the society progressing light science and technology. It publishes the largest collection of peer-reviewed content in optics and photonics, including 18 prestigious journals, the society’s flagship member magazine, and papers from more than 835 conferences, including 6,500+ associated videos. With over 400,000 journal articles, conference papers and videos to search, discover and access, Optica Publishing Group represents the full range of research in the field from around the globe.
The proof-of-concept experiment demonstrates the potential of dynamic tracking in larger-scale systems, such as gravitational-wave observatories.
Researchers showed that optical spring tracking could help enhance the signal clarity of gravitational-wave detectors. First author Scott M. Aronson is shown with the optical setup.
Credit
Olivia Crowell, Louisiana State University
Journal
Optics Letters
Article Title
Optical Spring Tracking for Enhancing Quantum-Limited Interferometers
Article Publication Date
4-Dec-2024
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