SpaceX zeroes in on the heat shield, a new record is set in the age of space travel, the economics of clearing space debris, and surprising new findings regarding a distant planet. This Week in Space

Atmospheric Re-entry Challenge for Starship

SpaceX announced its intention to conduct the fourth test flight of the Starship system within the week or so. The main challenge this time will be ensuring the spacecraft's successful re-entry into the atmosphere. In the previous March test, the company failed in orienting the spacecraft's heat shield downward during re-entry, resulting in its incineration and disintegration over the Indian Ocean.

Last Monday, the company successfully completed a launch rehearsal, including fueling both the spacecraft and the Super Heavy rocket on the launch pad and performing the countdown stages without an actual launch. Following the test, Elon Musk, CEO of SpaceX, tweeted, "Starship Flight 4 in about 2 weeks. Primary goal is getting through max reentry heating." He added that no one has ever succeeded in creating a fully reusable heat shield for a spacecraft, and that the space shuttles required six months of repairs after each flight.

Starship's heat shield is composed of about 18,000 hexagonal ceramic tiles, covering slightly over half of its cylindrical body. During atmospheric re-entry, friction with the air generates temperatures exceeding 1,400 degrees Celsius. The heat shield side is supposed to face downward, thus preventing the spacecraft itself from overheating.

Facing the re-entry challenge head-on. Will the heat shield stand the test? The Starship system on the launch pad during last week's rehearsal | Photo: Space

The fourth test flight will follow the same outline as the third test, albeit with fewer experiments, focusing on the re-entry phase. The Starship will launch from SpaceX's space base in South Texas, and after separating from the booster rocket, the company will attempt to perform a landing maneuver of the booster over the Gulf of Mexico, a feat not yet achieved in previous tests. Elon Musk recently outlined plans to attempt a soft landing of the booster on land at the launch site following two successful maneuvers. Meanwhile, the spacecraft, powered by its six engines, will ascend to an altitude of over 200 kilometers but will not enter Earth's orbit. Instead, it will re-enter the atmosphere over the Indian Ocean, with hopes of enduring peak heat and potentially executing a vertical landing maneuver over the sea.

SpaceX does not intend to repeat three additional experiments from the third flight for now: fuel transfer between tanks (reportedly successful), in preparation for the possibility of future spacecraft refueling; opening and closing a door intended for future satellite deployment in space (previously unsuccessful); and engine restart in space for precise re-entry maneuvering (also unsuccessful in the previous test). Since the spacecraft will not enter orbit during this test, engine activation for atmospheric re-entry isn't necessary.

For SpaceX, developing the Starship is part of a broader vision of settling on Mars, reducing launch costs to orbit, and gaining almost complete dominance in the satellite launch market. NASA has designated Starship as the crewed lunar landing vehicle for Artemis program’s initial missions, though it is currently facing delays and postponements, partly due to SpaceX's need to fine-tune a unique lunar landing configuration of the Starship, which is still far from the operational stage.

 Focusing on the re-entry challenge. A plasma halo is clearly visible near the heat shield during the spacecraft's re-entry in the previous test, before its incineration and disintegration| Photo: SpaceX

Space Belongs to Seniors

Blue Origin has resumed its space tourism flights to the edge of space after a nearly two-year hiatus, launching six passengers on a suborbital flight reaching an altitude of 105 kilometers. Notably among them was retired U.S. Air Force pilot and sculptor Ed Dwight, who, at 90 years and just over eight months old, made history as the oldest person to fly into space.

For Dwight, the flight marked a poignant completion of a circle: In the early 1960s, U.S. President John F. Kennedy directed NASA to integrate him into astronaut training in response to protests over the exclusion of non-white astronauts. However, Dwight fell victim to the harsh realities of racial struggles in the United States, being thrust into the space program without proper training and could not assimilate. He was officially dismissed after President Kennedy's assassination in November 1963.  It would be another two decades before the United States would send its first black astronaut into space. 

Dwight broke the record of actor William Shatner, who also reached the edge of space on a Blue Origin flight in 2021, at the age of 90 years and six months. The oldest person to have orbited the Earth so far remains veteran American astronaut John Glenn, who in 1998 convinced NASA to include him on a space shuttle flight at the age of 77.

Besides Dwight, the flight included five other passengers: Mason Angel, Sylvain Chiron, Kenneth Hess, Carol Schaller, and Gopi Thotakura. As far as is known, all of them paid the full fare for their tickets. While Blue Origin keeps pricing details undisclosed, estimates peg ticket prices between a quarter to half a million dollars per person. Dwight's flight was funded by a private foundation and a non-profit organization. To date, the company has flown 37 private astronauts, compared to 26 by its competitor in the space tourism market, Virgin Galactic, which is currently facing significant financial difficulties.

As mentioned, this was Blue Origin's first space tourism flight after a nearly two-year hiatus, following a setback in September 2022, when its New Shepard booster exploded during the launch of an unmanned spacecraft. The US Federal Aviation Administration (FAA) authorized the company to resume flights only after it has implemented over 20 fixes to the booster, spacecraft, and launch procedures.

Closing a circle after more than 60 years. Dwight disembarks from the Blue Origin spacecraft post-landing | Photo: Blue Origin

Taking Out the Trash

A report from NASA suggests that handling the large amounts of space debris in Earth's orbit may not be as expensive as previously estimated. The report, titled "Cost and Benefit Analysis of Mitigating, Tracking, and Remediating Orbital Debris," was authored by researchers at NASA's Office of Technology, Policy, and Strategy (OSTP) as a follow-up to an initial report published last year. The new document proposes ways for assessing the costs of space debris management including strategies like shielding satellites from impacts by small debris fragments.

Space debris encompasses all man-made  objects that are not active as satellites or spacecraft in Earth's orbit: from defunct satellites and rocket components to sizable fragments from space collisions, even down to tools discarded by astronauts and minuscule particles such as frozen fuel droplets or paint flakes. Traveling at tens of thousands of kilometers per hour, these objects pose risks of significant damage to operational spacecraft or create further debris upon collision with other fragments.

“This study allows us to start to answer the question: What are the most cost-effective actions we can take to address the growing problem of orbital debris?”  said Jericho Locke, the lead author of the report. “By measuring everything in dollars, we can directly compare shielding spacecraft to tracking smaller debris or removing 50 large pieces of debris to removing 50,000 smaller ones.” 

The researchers considered not only the direct costs of each approach but also the indirect costs, such as fuel consumption and reduced operational lifespan when activating a satellite's engine to change its orbit in order to avoid a collision with space debris. 

In recent years, several space debris removal missions have been planned, including one by Astroscale, a Japanese-owned international corporation. Its development center in Tel Aviv leads the development of detection and docking technologies, which are essential for both satellite lifespan extension in orbit and debris identification and retrieval. The company won a Japanese government contract to execute a mission by 2028, Astroscale aims to demonstrate its ability to closely inspect, photograph, and analyze a large defunct satellite in preparation for its removal from orbit. However, such missions are expected to  carry hefty price tags. Hence, NASA underscores the necessity of evaluating costs before embarking on large-scale solutions. "This study is part of NASA's work to rapidly improve our understanding of that environment as outlined in NASA's recently released Space Sustainability Strategy, by applying an economic lens to this critical issue," said Charity Weeden, head of the OSTP.

Looking at the problem by applying an economic lens. Illustration depicting space debris around Earth | Source: NASA

Exploring Cotton-Candy Exoplanets from Within

The planet Wasp-107b was discovered in 2017 orbiting a medium-sized star, roughly two hundred light-years away from us. Its volume is similar to that of Jupiter, but its mass is only a tenth that of the gas giant, leading researchers to estimate that it may have a cotton-candy-like texture. Its close proximity to its sun causes it to  complete an orbit in less than six Earth days. As a result, its atmosphere is extremely hot—standing at around 500 degrees Celsius.

In a study published last week, researchers managed to analyze the composition of Wasp-107b's atmosphere, and even its internal composition, using measurements from the James Webb Space Telescope. They were surprised to find that the methane (CH4) concentration in Wasp-107b's atmosphere was a thousand times lower than prior estimates, while its core was found to be much weightier than anticipated.

Using the space telescope's sensitive spectrometers, which analyze the composition of light wavelengths, which is altered by the chemical substances from which the are emitted or pass through, the researchers found that the Wasp-107b's atmosphere is abundant in sulfur dioxide (SO2), water vapor, carbon dioxide (CO2), carbon monoxide (CO), and heavy elements. However, methane levels were significantly lower than anticipated, compared to gas giants in our solar system.

The researchers hypothesize that Wasp-107b may have once had much more methane, but it decomposes due to its high atmospheric temperatures, creating the carbon oxides, the levels of which are  indeed higher than expected. According to the researchers this phenomenon can be attributed not only to the heat from the planet's sun, but also to an internal heat source, likely triggered by the strong gravitational forces of its parent star. "We had never been able to study this mixing process in an exoplanet atmosphere in detail, so this will go a long way in understanding how these dynamic chemical reactions operate,"  said David Sing, the head of the research team and  Professor of Earth and Planetary Sciences at Johns Hopkins University in the US. "This is now something we can do for lots of different gas planets in various systems. It's something we definitely need as we start looking at rocky planets and biomarker signatures," he added.

 Cotton-candy texture with a surprising gas composition and a heavier-than-expected core. The planet Wasp-107b as envisioned by an artist | Illustration: ROBERTO MOLAR CANDANOSA/JOHNS HOPKINS UNIVERSITY

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