Israeli research showed how a small asteroid was formed, successful solid-fuel launches for China and Korea, and an existential threat to space tourism. This Week In Space

The Family Connection of Asteroids

In September 2022, NASA, the United States space agency, conducted an experiment to deflect an asteroid by colliding a spacecraft with it. The primary objective was to demonstrate the feasibility of deflecting an asteroid heading towards Earth through such a collision or a series of collisions. The spacecraft forcefully collided with a small asteroid named Dimorphos, about 160 meters in diameter, which was chosen for the experiment partly because it orbits a larger asteroid named Didymos. This fact made it easier for researchers to measure the orbital deviation. The successful results of the collision indeed indicated a change in the orbit of the small asteroid. 

In parallel to the main experiment, a research team led by Dr. David Polishuk from the Weizmann Institute of Science tried to seize the opportunity to delve deeper into the structure of asteroids. Among other things, they examined the theory that in such systems, where a small asteroid orbits a larger one, the smaller moonlet is formed from the accumulation of material released from the main asteroid.

Polishuk followed the collision and its aftermath from the Weizmann Institute’s observatory located in Neot Smadar in the Arava region, and simultaneously from a large remotely operated telescope in Hawaii, capable of examining the asteroid's infrared radiation composition. "When it was night here I observed with our telescope, rested briefly, and then operated the telescope in Hawaii when it was night there. It was a pretty exhausting week," he described the experience to the Davidson Institute website.

Since this system was about 11 million kilometers from us at the time of the collision, the resolution of the telescopes in the experiment did not allow distinguishing between the two asteroids. "In our image they appear within the same pixel," explained Polishuk. "Spectrum measurements prior to the collision primarily reflect the composition of Didymos, the larger asteroid, the surface area of which is 20 times that of Dimorphos. However, after the collision, a dust cloud was created, originating from Dimorphos, allowing us to analyze its spectrum and compare its composition to that of Didymos."

The conclusion was not surprising, but it allowed researchers to confirm the theory concerning  the formation of such systems. The findings are in the process of publication  in the Journal of Planetary Sciences. "The measurements show that they are composed of the same material, mainly silicon compounds, and this reinforces the hypothesis that the small Dimorphos was created from material ejected from Didymos," said Polishuk. "Further support for this hypothesis came from the observation that the external color of asteroids of this type changes slightly over time due to radiation and exposure to charged particles. It was expected that the color of the dust cloud, originating from the inner parts of Dimorphos, might match the material less exposed to radiation. However, the color was found to be very similar to the external color of Didymos, supporting the assumption that it was formed from material that had already undergone such wear in the larger asteroid.

According to Polishuk, systems of asteroid pairs of this size are very common, and researchers estimate that at least 15 percent of similar asteroids have a small sattelite. This estimation was reinforced just last month when the American spacecraft "Lucy" discovered a small moonlet near an asteroid it studied. However, investigating these pairs is challenging due to their modest size, making it difficult to confirm the theory regarding their formation. "The asteroid deflection experiment provided us with a unique opportunity to advance our understanding of asteroid physics, and we fully embraced this opportunity.”

ההתנגשות שחשפה את הקשר בין שני האסטרואידים. רגע ההתנגשות של חללית DART באסטרואיד דימורפוס, שתיעדה החללית האיטלקית הזעירה LICIA במסגרת הניסוי | צילום: NASA/ASI
The collision that revealed the connection between the two asteroids. The moment of DART spacecraft's collision with the asteroid Dimorphos, captured by the small Italian spacecraft LICIA, as part of the experiment | Photo: NASA/ASI

Sea-to-Satellite Rockets

Both China and South Korea launched satellites into space this week using solid-fuel rockets, both launched from sea platforms. The Korean missile was launched from a platform located about four kilometers off the coast of Jeju Island in the south of the country. It placed a small radar satellite, weighing about 100 kilograms, into a 650-kilometer orbit, a move that seems largely a response to North Korea's launch of its first reconnaissance satellite about two weeks earlier. The launch followed South Korea's earlier accomplishment of launching its inaugural domestically produced satellite, albeit through SpaceX's Falcon 9 rocket from the United States.

The South Korean missile is a three-stage launcher powered by solid fuel, and a fourth stage powered by liquid fuel, to allow precise placement of the satellite in its orbit. It was designed by the South Korean Ministry of Defense's Development Agency and produced by Hanwha Corporation. This launch was the third of its kind following two previous trials in 2022. The Seoul Ministry of Defense has expressed its intention to develop similar rockets capable of accommodating heavier satellite payloads, ranging from 500 to 700 kilograms.

The Chinese satellite was launched on board a Jielong-3 rocket from a sea platform in the South China Sea, off the coast of Yangjiang, to a 900-kilometer orbit. This four-stage rocket, developed by China Rocket Co. (the commercial arm of the government's aerospace and aviation corporation, CASC), is designed to carry payloads of up to 1,500 kilograms into a 500-kilometer orbit. This week's launch was the second successful launch of such a rocket, indicating that the missile is now operational and adds another component to China's growing space capabilities. The satellite itself represents the third in a series of communication satellites, intended to be part of a massive Chinese network for providing internet services, similar to SpaceX's American Starlink. The complete network is expected to include no fewer than 13,000 satellites.

Both launches also reflect the growing trend of using solid-fuel rockets, not only for military purposes but also for launching small payloads into space. Such missiles are relatively cheap, and easier to produce, maintain, and operate, but they are also considered less efficient and more difficult to control after launch. In recent years, technological improvements have been developed in this field, and solutions such as a fourth liquid-fueled stage, allow for increasing use of such missiles. The fact that both satellites were launched from sea platforms is also interesting. Launching from the sea may introduce unique advantages, such as the possibility to position the launch site closer to the equator, thereby optimizing the Earth's rotational speed to enhance rocket velocity, conserving fuel, and accommodating larger payloads. Additionally, it provides the flexibility to relocate launch sites in case of stormy weather, adapting the site to the launch window, and minimizing the risk to civilians. However, it's important to note that maritime launches also come with their own set of challenges and higher costs, which may not always outweigh the benefits.

עוד נדבך במערך היכולות המרשים של סין בחלל. שיגור טיל ג'ילונג 3 מאסדה בים, השבוע | צילום: Ourspace
Another component in China's impressive space capabilities. Launch of the Jielong 3 missile from a sea platform, last week | Photo: Ourspace

A Setback for Space Tourism

Will Virgin Galactic continue to exist? The company, which operates tourist flights to the edge of space, has recently been facing many financial difficulties, and this week British billionaire Richard Branson, the founder of the company and its majority owner through his various enterprises, announced his decision to cease further investment.

“We don’t have the deepest pockets after Covid, and Virgin Galactic has got $1bn, or nearly”, Branson told the Financial Times, "I believe they have enough of their own money to continue on their own", he said. The announcement caused a sharp drop in Virgin Galactic's stock value last Monday, though it showed some signs of recovery later in the week.

Virgin Galactic recently made a major move by laying off employees to reduce losses, and last month announced that it would soon suspend tourist flights in order to shift its focus towards the development of the next-generation spacecraft, which is supposed to commence commercial flights in 2026.The viability of Virgin Galactic during this revenue-free transition phase, without additional financial support, remains uncertain. Should Virgin Galactic cease operations, the sector of tourist flights to the edge of space would be left exclusively to Blue Origin, owned by Jeff Bezos, who is Virgin's sole current competitor in this market. About six months ago, another space company from the Virgin Group, Virgin Orbit, which was designed to launch small satellites into space using rockets launched from a Boeing 747, filed for bankruptcy a few months after its first launch attempt ended in the crash of the rocket.

הברז נסגר, והמייסד מפסיק להזרים כסף לחברה שהקים. ריצ'רד ברנסון | צילום: Virgin Orbit
The funding tap is closed as the founder, Richard Branson, halts further investment in the company he founded. Richard Branson | Photo: Virgin Orbit

Translated with the assistance of ChatGTP. Revised, expanded and edited by the staff of the Davidson Institute of Science Education