The design for SpaceX’s Starship(aka. Big Falcon Rocket) is really starting to come together! Over the holidays, sections of the Starship Hopper (a miniature version of the Starship) were photographed being put together at the company’s South Texas Launch Site. By mid-January, the parts were fully-integrated, forming the body of the stainless-steel prototype that would test the spacecraft’s overall architecture.
What followed, earlier this month, were tests of the Starship’s hexagonal heat shields to determine if they would offer sufficient protection during re-entry. And now, in anticipation of the spacecraft’s eventual launch, SpaceX released an eye-popping new rendering of the Starship that shows what it would look like reentering Earth’s atmosphere.
When Elon Musk of SpaceX tweets something interesting, it generates a wave of excitement. So when he tweeted recently that SpaceX might be working on a way to retrieve upper stages of their rockets, it set off a chain of intrigued responses.
SpaceX will try to bring rocket upper stage back from orbital velocity using a giant party balloon
SpaceX has been retrieving and reusing their lower stages for some time now, and it’s lowered the cost of launching payloads into space. But this is the first hint that they may try to do the same with upper stages.
Twitter responders wanted to know exactly what SpaceX has in mind, and what a “giant party balloon” might be. Musk hasn’t elaborated yet, but one of his Twitter followers had something interesting to add.
If you're proposing what I think you are, an ultra low ballistic entry coefficient decelerator, then you and @SpaceX should come see what we have at the @UofMaryland . We've been working on this for awhile and just finished some testing pic.twitter.com/nJBvyUnzaK
Universe Today contacted Mr. Kupec to see if he could help us understand what Musk may have been getting at. But first, a little background.
An “ultra low ballistic entry coefficient decelerator” is a bit of a mouthful. The ballistic coefficient measures how well a vehicle can overcome air resistance in flight. A high ballistic coefficient means a re-entry vehicle would not lose velocity quickly, and would reach Earth at high speeds. An ultra low ballistic entry coefficient decelerator would lose speed quickly, meaning that a vehicle would be travelling at low, subsonic speeds before reaching the ground.
To recover an upper stage booster, low speeds are desirable, since they generate less heat. But according to Kupec, there’s another problem that must be overcome.
“What happens when these things slow down to landing velocities? If your center of gravity is offset significantly behind your center of drag, as would be the case with a returning upper stage, it can get unstable. If the center of gravity of the re-entry vehicle is too high, it can become inverted, which is obviously not desirable.”
So the trick is to lower the speed of the re-entry vehicle to the point where the heat generated by reentry isn’t damaging the booster, and to do it without causing the vehicle to invert or otherwise become unstable. This isn’t a problem for the main stage boosters that SpaceX now routinely recovers; they have their own retro-rockets to guide their descent and landing. But for the upper stage boosters, which reach orbital velocities, it’s an obstacle that has to be overcome.
“My research is specifically focused on how high you can push the center of gravity and still maintain the proper flight configuration,” said Kupec.
But what about the “giant party balloon” that Musk tweeted about?
Musk could be referring, in colorful terms, to what’s called a ballute. The word is a combination of the words balloon and parachute. They were invented in the 1950’s by Goodyear Aerospace. They can arrest the descent of entry vehicles and provide stability during the descent.
“…the balloon would have to be 120 ft. in diameter, and made of a high-temperature fabric…” – Professor Dave Akin, University of Maryland
Universe Today contacted Professor Dave Akin of the University of Maryland for some insight into Musk’s tweet. Professor Akin has been working on reentry systems for over 2 decades.
In an e-mail exchange, Professor Akin told us, “There have been concepts proposed for deploying a large balloon on a cable that is towed behind you on entry. The balloon lowers your ballistic coefficient, which means you decelerate higher in the atmosphere and the heat load is less.” So the key is to scrub your speed before you get closer to Earth, where the atmosphere is thicker and generates more heat.
But according to Professor Akin, this won’t necessarily be easy to do. “To get the two orders of magnitude reduction in ballistic coefficient that Elon has been talking about the balloon would have to be 120 ft. in diameter, and made of a high-temperature fabric, so it’s not going to be all that easy.”
But Musk’s track record shows he doesn’t shy away from things that aren’t easy.
Retrieving upper rocket stages isn’t all about lowering launch costs, it’s also about space junk. The European Space Agency estimates that there are over 29,000 pieces of space junk orbiting Earth, and some of that junk is spent upper stage boosters. There have been some collisions and accidents already, with some satellites being pushed into different orbits. In 2009, the Iridium 33 communications satellite and the defunct Russian Cosmos 2251 communications satellite collided with each other, destroying both. If SpaceX can develop a way to retrieve its upper stage boosters, that means less space junk, and fewer potential collisions.
There’s a clear precedent for using balloons to manage reentry. With people like Professor Akin and Quinn Kupec working on it, SpaceX won’t have to reinvent the wheel. But they’ll still have a lot of work to do.
Musk tweeted one other thing shortly after his “giant party balloon” tweet:
The Tiangong-1 space station has been the subject of a lot of interest lately. Though its mission was meant to end in 2013, the China National Space Agency extended its service until 2016. In September of 2017, after much speculation from the international community, the Agency acknowledged that the station’s orbit was degrading and that it would fall to Earth later in the year.
Based on updates from satellite trackers, it has been indicated that Tianglong-1 will likely reenter our atmosphere in March of 2018, with the possibility of debris making it to the surface. However, according to a statement made by a top engineer at the China Aerospace Science and Technology Corporation (CASTC), reports that the Chinese National Space Agency (CNSA) has lost control of the space station have been wildly exaggerated.
The statement came from Zhu Congpeng, a top engineer at the China Aerospace Science and Technology Corporation (CASTC). As he was quoted as saying to the Science and Technology Daily newspaper – a state-backed Chinese science journal – the CNSA is still in control of the space station, it’s reentry will be controlled, and it will not pose a threat to the environment or any population centers.
Previously, the CNSA claimed that the majority of the station would burn up in orbit, with only small pieces falling to the Earth. But according to Zhu Congpeng’s statement, when the station burns up in the atmosphere, the remaining debris will not jeopardize people, infrastructure or the environment anywhere on the surface. As Zhu Congpeng stated:
“We have been continuously monitoring Tiangong-1 and expect to allow it to fall within the first half of this year. It will burn up on entering the atmosphere and the remaining wreckage will fall into a designated area of the sea, without endangering the surface.”
As with previous missions – like the Mir space station, the Russian Progress spacecraft, and NASA’s Compton Gamma-Ray Observatory – the designated crash site is a deep-sea area in the South Pacific known as the “spacecraft cemetery”. As a further indication that the CNSA is still in control of Tiangong-1, Zhu claimed that the CNSA has been constantly monitoring the space station since the end of its mission.
“The latest bulletin shows that on December 17-24, 2017, Temple One runs on an orbit with an average height of about 286.5 kilometers (height of about 272.6 kilometers near perigee, height of about 300.4 kilometers at apogee and inclination of about 42.85 degrees), attitude stability,” he said. “There is no abnormal morphology.”
He also emphasized that the station’s reentry was delayed until September in order to ensure the the wreckage would fall into the South Pacific. In other words, the position of Tiangong-1 is something the Chinese have been monitoring closely, and they will continue to do so when it reenters the atmosphere this coming March. This latest statement comes on the heels of statements made by both China’s manned space engineering office and the Aerospace Corporation, which appeared to offer a different appraisal.
Back in mid-September, Wu Ping – the deputy director of China’s manned space engineering office – stated at a press conference that there was some chance that debris would land on Earth. While she was insistent that the odds of any debris surviving the passage through Earth’s atmosphere were minimal, it did suggest that the reentry would be uncontrolled.
This echoed the comprehensive report recently issued by the Aerospace Corporation, which stated that the Chinese space agency was unlikely to remain in control of Tiangong-1’s for the entirety of its reentry. Much like Wu, they also emphasized that the majority of the station would burn up on reentry and that it was unlikely that any debris would make it to the surface and cause damage.
As such, its not entirely clear if the reentry will be entirely controlled or not. But even if it should prove to be the latter, there is little reason to worry. As the Aerospace Corporation stated in their report:
“[T]he probability that a specific person (i.e., you) will be struck by Tiangong-1 debris is about one million times smaller than the odds of winning the Powerball jackpot. In the history of spaceflight, no known person has ever been harmed by reentering space debris. Only one person has ever been recorded as being hit by a piece of space debris and, fortunately, she was not injured.”
On top of that, the European Space Agency’s Inter Agency Space Debris Coordination Committee (IADC) will also be monitoring the reentry closely. They’ll also be using the occasion to conduct a test campaign designed to improve the accuracy of reentry predictions. And so far, all their predictions indicate that come March, people on Earth will be safe from falling debris.
So if you happen to live close to the equator, this coming March is sure to be an exciting time for sky-watchers! And if there’s any chance of debris landing where you live, you can sure you’ll hear about it well in advance.
File photo of a Russian Progress cargo freighter. Credit: Roscosmos Story updated with further details[/caption]
The spinning, out-of-control Russian Progress 59 cargo freighter met its undesired early demise when it fell from orbit early Friday, May 8, and was destroyed during the unplanned fiery plummet through the Earth’s atmosphere.
As a result of the loss of the unmanned Progress 59 spacecraft, which was bound for the International Space Station (ISS) on a routine resupply mission, the timelines of upcoming crew rotations and new launches are “under evaluation” – Universe Today learned according to Russian and American space sources.
The doomed Progress freighter “ceased to exist” after it reentered the Earth’s atmosphere 05.04 Moscow time on May 8, 2015 (10:04 p.m. EDT May 7) over the central Pacific Ocean,” according to an official statement from Roscosmos, the Russian Space Agency.
The consequences of the failure might cause “postponements of upcoming station crew changes to June” and blastoffs “to July” according to Russian space industry and media sources.
The vessel, also known as Progress M-27M, burned up minutes later and any surviving pieces fell over the Pacific Ocean.
“Debris fell about 900 kilometers west of the Marquesas Islands in the central Pacific Ocean,” a space industry source told the Russian news agency TASS.
“Roscosmos plans to adjust the program of flights to the International Space Station (ISS) due to the recent accident involving the Progress M-27M spacecraft,” according to the TASS rocket and space industry source.
Roscosmos quickly established an investigation board to determine the cause of the Progress failure and any commonalities it might have with manned launches of the Soyuz rocket and capsule, and report back by 13 May.
“The results of investigation of the incident related to “Progress M-27M” will be presented no later than 13 May following the completion of the state commission,” Roscosmos stated.
Russian mission controllers lost control of the Progress 59 spacecraft shortly after its otherwise successful launch to the ISS on April 28 from the Baikonur space center in Kazakhstan atop a Soyuz-2.1A carrier rocket.
Soon after detaching from the rockets third stage, it began to spin out of control at about 1.8 times per second, as seen in a video transmitted from the doomed ship.
After control could not be reestablished, all hope of docking with the ISS was abandoned by Roscosmos.
NASA officials said that the current ISS Expedition 43 six person crew is in no danger. The station has sufficient supplies to last until at least September, even if no other supplies arrive in the meantime.
“The spacecraft was not carrying any supplies critical for the United States Operating Segment (USOS) of the station, and the break up and reenty of the Progress posed no threat to the ISS crew,” NASA said in a statement.
“Both the Russian and USOS segments of the station continue to operate normally and are adequately supplied well beyond the next planned resupply flight.”
There is a stock of propellants onboard in the Russian segment that can be used for periodically required station reboosts.
According to TASS, “the cause of the accident with the Russian Progress M-27M spacecraft has not been established yet, Russian Deputy Prime Minister Dmitry Rogozin told journalists on Friday.”
“Not yet,” he said, answering a question on whether causes of the accident had been established.
Because the cause of Progress failure is not yet clear, the schedules for upcoming crew departures and launches to the ISS via Russian Soyuz rockets and capsules are “under evaluation,” according to sources.
There is a significant potential for a delay in the planned May 13 return to Earth of the three person crew international crew consisting of NASA astronaut and current station commander Terry Virts and flight engineers Samantha Cristoforetti of ESA (European Space Agency) and Anton Shkaplerov of Roscosmos, who have been aboard the complex since November 2014.
Virts and his crewmates were due to head back to Earth in their Soyuz capsule on May 13. According to Russian sources, their return trip may be postponed to about June 11 to 13.
“The return from orbit of the expedition which is currently there is suggested to be postponed from May 14 to June,” said a TASS source.
Their three person replacement crew on Expedition 44 were due to blastoff on the next planned manned Soyuz launch on May 26 from the Baikonur Cosmodrome in Kazakhstan. This launch may now be delayed as well, to mid or late July.
“More time will be needed to check already manufactured rockets,” said a source. “A manned Soyuz launch may be made in the last ten days of July.”
“The proposal was forwarded by a Roscosmos working group and has not been approved yet,” reports TASS.
An official announcement by Roscosmos of any ISS schedule changes may come next week since the scheduled return of Virts crew is only days away.
Another potential change is that the launch of the next unmanned Progress 60 (M-28M), could potentially be moved up from August to July, hinging on the outcome of the state commission investigation.
To date flights of the Progress vehicle have been highly reliable. The last failure occurred in 2011, shortly after the retirement of NASA’s Space Shuttle orbiters in July 2011. The loss of the Progress did cascade into a subsequent crew launch delay later in 2011.
The 7 ton Progress vehicle was loaded with 2.5 tons of supplies for the ISS and the six person Expedition 43 crew. Items included personal mail for the crew, scientific equipment, food, water, oxygen, gear and replaceable parts for the station’s life support systems.