SpaceX targets bold new 'catch' strategy for landing Super Heavy rockets
By Mike Wall, Jan. 4, 2021
SpaceX plans to get even more ambitious with its pinpoint rocket landings.
Elon Musk's company routinely recovers and reuses the first stages of its Falcon 9 and Falcon Heavy rockets, bringing the boosters down for soft vertical landings about 9 minutes after liftoff on ground near the launch pad or on autonomous "drone ships" in the ocean.
These touchdowns are impressively precise. But SpaceX aims to achieve something truly mind-blowing with Starship, the next-generation system the company is developing to take people and payloads to the moon, Mars and other distant destinations.
"We’re going to try to catch the Super Heavy booster with the launch tower arm, using the grid fins to take the load," Musk said via Twitter on Dec. 30.
That's right: SpaceX wants to bring Super Heavy, the giant first stage of the two-stage Starship system, down directly on the launch stand.
Musk has voiced this ambition before, but last week's tweet adds new wrinkles — for example, that Super Heavy will ideally be caught by the tower arm, so its touchdowns won't really be landings at all. Unlike Falcon 9 and Falcon Heavy first stages, then, Super Heavy won't need landing legs. (The catch-enabling grid fins, by the way, are waffle-like control surfaces that help returning rockets steer during precise touchdowns.)
The newly announced strategy offers several important benefits, Musk said.
"Saves mass and cost of legs and enables immediate repositioning of booster onto launch mount — ready to refly in under an hour," he said in another Dec. 30 tweet.
Starship's upper stage is a 165-foot-tall (50 meters) spacecraft called (somewhat confusingly) Starship. Both Starship and Super Heavy will be fully and rapidly reusable, Musk has stressed, potentially making Mars colonization and other ambitious exploration feats economically feasible.
SpaceX has already built and flown several Starship prototypes from its South Texas facility, near the Gulf Coast village of Boca Chica. Last month, for example, the SN8 ("Serial No. 8") vehicle soared to an estimated altitude of 7.8 miles (12.5 kilometers) and returned to Earth at the designated spot. Though SN8 came in too fast and exploded in a massive fireball, Musk declared the epic test flight a big success.
Another such leap should be coming soon: SpaceX recently moved SN9 to the launch stand. Like SN8, SN9 sports three powerful Raptor engines, so the maximum altitude of its flight may also be in the 7.8-mile range. (The three prototypes that flew before SN8 were single-engine vehicles that got just 500 feet, or 150 m, off the ground.)
The final Starship vehicle will have six Raptors, making it powerful enough to launch itself off the surface of the moon and Mars (but not Earth). Super Heavy will have about 30 Raptors, Musk has said. Though the Starship program has to date devoted most of its time to building and testing spaceship prototypes, it appears that construction of the first Super Heavy prototype is now underway.
Radio telescopes could give us a new view of gravitational waves
05 Jan 2021
Cosmic time machine: the EDGES radio telescope sheds light on primordial gravitational waves. (Courtesy: Suzyj/CC BY-SA 4.0)
The cosmic microwave background (CMB) is a rich source of information about the early universe, and now physicists in Switzerland and Germany reckon it could also serve as a detector of high-frequency gravitational waves, which are ripples in space–time. Indeed, the researchers have used pre-existing radio observations of the CMB to calculate new upper limits on the size of high-frequency primordial gravitational waves.
The best developed technique for detecting gravitational waves, and the one used to discover them in 2015, relies on interferometry. In LIGO and other observatories, laser beams are deflected between mirrors at the ends of long (several kilometres) evacuated pipes and then interfere with one another. When a gravitational wave travels through the Earth it causes tiny changes in the distance between the mirrors, which is observed as changes in how the light interferes.
The size of interferometers like LIGO makes them most sensitive to gravitational waves within a certain frequency band – from about 10 Hz to 10 kHz – meaning that much of the gravitational-wave spectrum remains unexplored. While the planned space-based LISA observatory will target lower frequencies in the millihertz range to detect waves from supermassive black holes, observations at megahertz, gigahertz or even higher frequencies could provide a window on exotic phenomena in the very young, hot universe. Detecting these high frequencies could also provide new insights into the fundamental constituents of nature, by allowing tests of the Standard Model of particle physics at energies beyond the most powerful particle colliders.
The Gertsenshtein effect
To observe these higher frequencies, physicists have investigated a range of alternative approaches. This latest effort relies on the Gertsenshtein effect, which involves gravitational waves converting into electromagnetic waves (or vice versa) in the presence of a magnetic field.
While other researchers have looked for this effect in the results of pre-existing terrestrial experiments, Valerie Domcke at the CERN laboratory in Geneva and Camilo Garcia Cely at DESY in Hamburg have come up with a way for detecting the effect at cosmic scales. The idea is to scrutinize the spectrum of the all-pervasive CMB, which was produced about 400,000 years after the Big Bang when electrons combined with protons to form neutral hydrogen. Whereas today’s leading cosmological model tells us that this spectrum should be that of a black body, significant cosmic conversion of gravitational to electromagnetic radiation at megahertz to gigahertz frequencies would instead raise the intensity of the CMB’s low frequency “tail”.
The researchers specifically looked for distortions in the CMB spectrum generated before the first stars formed and hydrogen started reionizing, some 150 million years or so after the universe came into being. During these “dark ages” there were few free electrons to scatter photons, so the probability of oscillations occurring between gravitational and electromagnetic waves was higher than it would otherwise have been.
EDGES and ARCADE2
To set new limits on the size of gravitational waves at high frequencies, Domcke and Garcia Cely analysed data from two radio telescopes designed to peer far back in time. One, EDGES, consists of two dipole antennas and a dish located in the desert of Western Australia. The other, ARCADE2, was a balloon experiment flown over Texas.
The researchers found they could indeed use the data to set new limits, although they did have to make an assumption about the strength of cosmic magnetic fields. With the fields set low, their results were less stringent than those from putative terrestrial oscillations – the maximum amplitudes at 78 MHz (EDGES) and 3-30 GHz (ARCADE2) coming in at one part in 1012 and 1014 respectively. But with the fields set high, those limits dropped to one part in 1021 and 1024 respectively, the latter being seven orders of magnitude lower than limits imposed by the most sensitive laboratory experiment.
Domcke and Garcia Cely argue that their new approach to gravitational-wave detection could improve substantially as radio telescopes become more sensitive – particularly as scientists develop new facilities to measure the 21 cm line in neutral hydrogen, which is central to studies of reionization. More sensitive telescopes would set tighter limits on primordial gravitational waves or could even reveal their existence. They say that this radiation could in principle be produced by sources such as merging light black holes or from clouds of dark matter around spinning black holes.
They add that excess photons with frequencies below 10 GHz have been observed by both EDGES and ARCADE2. However, they point out that this excess would imply that gravitational waves have far more energy than that inferred from other cosmological observations. As a result, they say that astrophysical sources, “are a more likely explanation for the excess radiation observed”.
A paper describing the work has been accepted for publication in Physical Review Letters.
Congress asks for report on Arecibo radio telescope collapse
By Doris Elin Urrutia 5 January 2021
The observatory is not closing, according to the National Science Foundation.
Congress wants a report investigating the December collapse of the iconic radio telescope at Arecibo Observatory by late February as the government evaluates what comes next for the facility, located in the mountains of Puerto Rico.
The request comes as the observatory's supporters continue to rally on the facility's behalf, including a successful public petition calling for White House support of rebuilding at the site and a decision by the island's governor to allocate $8 million to the effort.
Arecibo Observatory's 1,000-foot-diameter (305 meters) radio telescope suffered its most recent structural damage on the morning of Dec. 1, when its 900-ton suspended instrument platform came hurtling down onto the dish itself.
The facility has left a 57-year legacy of scientific discovery, in addition to being a mainstay of tourism and education for Puerto Ricans. But the radio dish has been vulnerable for years. In 2017, the National Science Foundation (NSF), which owns Arecibo, evaluated shutting down the radio telescope, then developed partnerships to cover Arecibo's operating costs instead.
But last year was unrelenting for the observatory. In August, a cable that supported the platform slipped out of its socket. And on Nov. 6, just as engineers were preparing to begin repair work, a second supporting cable broke. About two weeks later, on Nov. 19, NSF announced its decision to decommission the radio dish, deeming the platform too dangerous to repair.
Just 12 days later, the platform crashed down.
Determining the radio telescope's future
In the aftermath of the collapse, people want to know precisely what happened to the radio telescope — and how the federal government intends to move forward with science at Arecibo.
Puerto Rican students and other activists have focused on formal petitions to the White House. The White House promises to respond within 60 days to petitions that garner 100,000 signatures within 30 days, a threshold that "Rebuild the Arecibo Observatory" has cleared. (A former campaign called "Save the Arecibo Observatory," relaunched after the Dec. 1 catastrophe).
The petition asks Congress "to allocate funding to build a new Arecibo radio telescope with greater capabilities than the previous telescope."
A drone view of damage to a cable at Arecibo Observatory's radio telescope in Puerto Rico captured after a second cable failed on Nov. 6, 2020. (Image credit: UCF/AO)
Whether Congress will take up the suggestion remains to be seen, but Arecibo did appear in the fiscal year 2021 Consolidated Appropriations Act, released by Congress on Dec. 21, which includes the Commerce-Justice-Science (CJS) appropriations bill that funds the NSF. The act instructs the NSF to update Congress about Arecibo Observatory within 60 days.
"NSF is directed to report … on the causes and extent of the damage, the plan to remove debris in a safe and environmentally sound way, the preservation of the associated AO [Arecibo Observatory] facilities and surrounding areas, and the process for determining whether to establish comparable technology at the site, along with any associated cost estimates," the act states.
An NSF spokesperson told Space.com that the agency had spent about $5 million on Arecibo's engineering evaluation and stabilization efforts between the August cable failure and shortly after the collapse. However, "engineers and environmental experts are still conducting assessments of the site" and the foundation has not yet determined a cost estimate nor timeline to address the damage and clear debris, NSF representative Robert Margetta told Space.com in an email.
What comes next for the site will take even longer to determine. Unrelated to the NSF, on Dec. 28, Puerto Rico Governor Wanda Vázquez ordered that $8 million go toward reconstructing Arecibo. But such a small sum couldn't build a new radio telescope by itself.
The territory's budgetary decision would likely need to be augmented by federal funding, which would presumably be tied to the NSF's oversight of ground-based observatories. NSF needs more time to make a decision on what to do with the site, the agency emphasized.
The platform when it was still suspended above Arecibo's radio dish. (Image credit: University of Central Florida)
"NSF's process for funding and constructing large-scale infrastructure, including telescopes, is a well-established, multi-year procedure that involves assessing the needs of the scientific community, receiving input from researchers and other stakeholders, considering environmental and cultural impacts, and working with Congress," agency representatives told Space.com in an email about the act.
"As the Arecibo Observatory's 305-meter telescope only recently collapsed, NSF cannot comment on any potential future plans at this time," the statement continued. "However, we will continue to work with Congress on the issue, including complying with language accompanying the new omnibus spending package."
The observatory is not closing, the NSF has emphasized. Research using archived data from the massive radio dish telescope, for example, will continue. NSF said it is also looking for ways to restore operations with the observatory's other instruments as soon as possible, including the 12-meter telescope and LIDAR atmospheric-sensing facilities
"NSF will continue the work of clearing and securing the site of the 305-meter telescope and looks forward to working with Puerto Rico to find new ways to support the scientific community and the local community," the agency added.
At 4:34 a Boeing flies past the a Star Trek ship but this give you an understand of the size difference when the Japanese airline UFO encounter in November 17, 1986
We are currently seeing giant spheres large and small regularly next to the sun and it would seem within our own atmosphere similar to Traveller ship from Destiny at 8:23 and lager spheres later on in the clip.
At 8:51 is the fictional space craft from Dune which a similar ship was photographed after the Russian satellite went down in 1989 on the Mars Moon Phobos which was measured at 15km very similar to the Dune craft.
The Moon is 1,737.1 km which is at 12:35 the Alahenena Titan AE
These are real events that can now be measured. Anyone else who can see something similar that was a well documented UFO encounter?