Spinning Heat Shield Concept Could Provide a Lightweight Way to Survive Atmospheric Re-entry

One of the more challenging aspects of space exploration and spacecraft design is planning for re-entry. Even in the case of thinly-atmosphered planets like Mars, entering a planet’s atmosphere is known to cause a great deal of heat and friction. For this reason, spacecraft have always been equipped with heat shields to absorb this energy and ensure that the spacecraft do not crash or burn up during re-entry.

Unfortunately, current spacecraft must rely on huge inflatable or mechanically deployed shields, which are often heavy and complicated to use. To address this, a PhD student from the University of Manchester has developed a prototype for a heat shield that would rely on centrifugal forces to stiffen flexible, lightweight materials. This prototype, which is the first of its kind, could reduce the cost of space travel and facilitate future missions to Mars.

The concept was proposed by Rui Wu, a PhD student from Manchester’s School of Mechanical, Aerospace and Civil Engineering (MACE). He was joined by Peter C.E. Roberts and Carl Driver – a Senior Lecturer in Spacecraft Engineering and a Lecturer at MACE, respectively – and Constantinos Soutis of The University of Manchester Aerospace Research Institute.

The CubeSat-sized prototype heat shield designed by the University of Manchester team. Credit: University of Manchester

To put it simply, planets with atmospheres allow spacecraft to utilize aerodynamic drag to slow down in preparation for landing. This process creates a tremendous amount of heat. In the case of Earth’s atmosphere, temperatures of 10,000 °C (18,000 °F) are generated and the air around the spacecraft can turn into plasma. For this reason, spacecraft require a front-end mounted heat shield that can tolerate extreme heat and is aerodynamic in shape.

When deploying to Mars, the circumstances are somewhat different, but the challenge remains the same. While the Martian atmosphere is less than 1% that of Earth’s – with an average surface pressure of 0.636 kPa compared to Earth’s 101.325 kPa – spacecraft still require heat shields to avoid burnup and carry heavy loads. Wu’s design potentially solves both of these issues.

The prototype’s design, which consists of a skirt-shaped shield designed to spin, seeks to create a heat shield that can accommodate the needs of current and future space missions. As Wu explained:

“Spacecraft for future missions must be larger and heavier than ever before, meaning that heat shields will become increasingly too large to manage… Spacecraft for future missions must be larger and heavier than ever before, meaning that heat shields will become increasingly too large to manage.”

Wu and his colleagues described their concept in a recent study that appeared in the journal Arca Astronautica (titled “Flexible heat shields deployed by centrifugal force“). The design consists of an advanced, flexible material that has a high temperature tolerance and allows for easy-folding and storage aboard a spacecraft. The material becomes rigid as the shield applies centrifugal force, which is accomplished by rotating upon entry.

Wu and his team performing the drop test of their heat shield prototype. Credit: University of Manchester

So far, Wu and his team have conducted a drop test with the prototype from an altitude of 100 m (328 ft) using a balloon (the video of which is posted below). They also conducted a structural dynamic analysis that confirmed that the heat shield is capable of automatically engaging in a sufficient spin rate (6 revolutions per second) when deployed from altitudes of higher than 30 km (18.64 mi) – which coincides with the Earth’s stratosphere.

The team also conducted a thermal analysis that indicated that the heat shield could reduce front end temperatures by 100 K (100 °C; 212 °F) on a CubeSat-sized vehicle without the need for thermal insulation around the shield itself (unlike inflatable structures). The design is also self-regulating, meaning that it does not rely on additional machinery, reducing the weight of a spacecraft even further.

And unlike conventional designs, their prototype is scalable for use aboard smaller spacecraft like CubeSats. By being equipped with such a shield, CubeSats could be recovered after they re-enter the Earth’s atmosphere, effectively becoming reusable. This is all in keeping with current efforts to make space exploration and research cost-effective, in part through the development of reusable and retrievable parts. As Wu explained:

“More and more research is being conducted in space, but this is usually very expensive and the equipment has to share a ride with other vehicles. Since this prototype is lightweight and flexible enough for use on smaller satellites, research could be made easier and cheaper. The heat shield would also help save cost in recovery missions, as its high induced drag reduces the amount of fuel burned upon re-entry.”

When it comes time for heavier spacecraft to be deployed to Mars, which will likely involve crewed missions, it is entirely possible that the heat shields that ensure they make it safely to the surface are composed of lightweight, flexible materials that spin to become rigid. In the meantime, this design could enable lightweight and compact entry systems for smaller spacecraft, making CubeSat research that much more affordable.

Such is the nature of modern space exploration, which is all about cutting costs and making space more accessible. And be sure to check out this video from the team’s drop test as well, courtesy of Rui Wui and the MACE team:

Further Reading: University of Manchester, Acta Astronica

Spectacular Breakup of WT1190F Seen by Airborne Astronomers

Clouds hampered observations from the ground in Sri Lanka during the re-entry of WT1190F overnight, but a team of astronomers captured spectacular images of the object from a high-flying plane over the Indian Ocean very close to the predicted time of arrival. 

Peter Jenniskens of the SETI Institute and NASA Ames Research Center will operate eleven staring cameras with a wider field of view, including two spectographic cameras, to catch the reentry if pointing efforts fail. Credit: IAC/UAE Space Agency/NASA/ESA
Peter Jenniskens of the SETI Institute and NASA Ames Research Center is shown here before the flight setting up the eleven staring cameras with a wider field of view, including two spectographic cameras, to catch the reentry.  Credit: IAC/UAE Space Agency/NASA/ESA

The International Astronomical Center (IAC) and the United Arab Emirates Space Agency hosted a rapid response team to study the re-entry of what was almost certainly a rocket stage from an earlier Apollo moon shot or the more recent Chinese Chang’e 3 mission. In an airplane window high above the clouds, the crew, which included Peter Jenniskens, Mike Koop and Jim Albers of the SETI Institute along with German, UK and United Arab Emirates astronomers, took still images, video and gathered high-resolution spectra of the breakup.


Video and still imagery of WT1190F’s Reentry November 13, 2015

The group of seven astronomers hoped to study WT1190F’s re-entry as a  test case for future asteroid entries as well as improve our understanding of space debris behavior. Photos and video show the object breaking up into multiple pieces in a swift but brief fireball. From the spectra, the team should be able to determine the object’s nature — whether natural or manmade.

Wide view of the colorful fireball created when WT1190F burned up in Earth's atmosphere. Credit:
Wide view of the colorful fireball and breakup when WT1190F struck Earth’s atmosphere. More than 20 cameras were used to record the event. Credit: IAC/UAE Space Agency/NASA/ESA
Animation made on Nov. 12 when WT1190F was still in one piece in orbit about Earth. Credit: Marco Langbroek
Animation from photos made on Nov. 12 when WT1190F was still in one piece in orbit about the Earth. Credit: Marco Langbroek
Gulfstream 450 business jet, sponsored by United Arab Emirates and coordinated by Mohammad Shawkat Odeh from the International Astronomical Center, Abu Dhabi. There are only five windows available to observe the object. The observation teams comprise:
Flying observatory. This Gulfstream 450 business jet, sponsored by United Arab Emirates and coordinated by Mohammad Shawkat Odeh from the International Astronomical Center, Abu Dhabi, was used by the team to observe and record the re-entry. Only five windows were available to make observations. Credit: IAC/UAE Space Agency/NASA/ESA
SETI Institute staring cameras used for wide field observations of the re-entry. Credit:
SETI Institute “staring cameras” used for wide field observations of the re-entry. Credit: IAC/UAE Space Agency/NASA/ESA

GOCE Spacecraft Will Likely Make Uncontrolled Re-entry This Weekend

The Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite has been orbiting Earth in super-low orbits since 2009, mapping out variations in Earth’s gravity in extreme detail. But its fuel ran out in mid-October and the satellite began its slow descent towards Earth, being brought lower and lower by the effects of the atmosphere. Engineers predict it will re-enter completely and fall back to Earth sometime this weekend.

But no one can say for sure when or where the 1-ton satellite will fall.

With no remaining fuel to guide its re-entry there’s no way to nudge or steer its descent. And while most of GOCE is predicted to disintegrate in the atmosphere, several parts might reach Earth’s surface. Experts predict as much as 25% of the spacecraft will survive reentry, as many parts are made of advanced materials, such as carbon-carbon composites.

Today, engineers from the GOCE mission said that the spacecraft is predicted to enter into Earth’s atmosphere sometime during the night between Sunday and Monday, November 10-11, 2013. Break-up of the spacecraft will occur at an altitude of approximately 80 km. “At the moment, the exact time and location of where the fragments will land cannot be foreseen,” says ESA.

The GOCE spacecraft was designed to fly low and has spent most of its mission roughly 500 km below most other Earth-observing missions, at an altitude of 255 km (158 miles), but has recently been at the lowest altitude of any research satellite at 224 km (139 miles).

Its durable construction and sleek design allowed it to stay in space for longer than expected; it nearly tripled its planned lifetime.

With GOCE data, scientists created the first global high-resolution map of the boundary between Earth’s crust and mantle – called the Moho – and to detect sound waves from the massive earthquake that hit Japan on 11 March 2011, among other results.

Heiner Klinkrad, Head of ESA’s Space Debris Office at ESOC, Darmstadt, Germany said that when the spacecraft reaches altitudes below 100 km, then atmospheric density will drastically increase on the spacecraft. It will enter at about 25,000 km/hour, and aerodynamic pressure and heating will cause a break-up of the spacecraft at approximately 80km altitude, causing a large number of fragments.

“The risk to the population on ground will be minute,” said Klinkrad. “Statistically speaking, it is 250,000 times more probable to win the jackpot in the German Lotto than to get hit by a GOCE fragment. In 56 years of space flight, no man-made space objects that have re-entered into Earth’s atmosphere have ever caused injury to humans.”

An international campaign will be monitoring the descent, involving the Inter-Agency Space Debris Coordination Committee. The situation is being continuously watched by ESA’s Space Debris Office, which will issue re-entry predictions and risk assessments.

ESA says they will keep the relevant safety authorities permanently updated.

Sources: ESA, ESA Blog

Sleek GOCE Spacecraft Will Have Uncontrolled Re-entry into Earth’s Atmosphere

The sleek and sexy-looking GOCE spacecraft has been mapping Earth’s gravity for over four years, but soon its xenon fuel will run out and the satellite will end up re-entering our atmosphere. But no one can say for sure when or where the 1-ton satellite will fall.

The Gravity field and steady-state Ocean Circulation Explorer has been orbiting Earth at super-low orbits, mapping out variations in Earth’s gravity with extreme detail. Launched in March 2009, the GOCE spacecraft was designed to fly low and has spent most of its mission roughly 500 km below most other Earth-observing missions, at an altitude of 255 km (158 miles), but has recently been at the lowest altitude of any research satellite at 224 km (139 miles).

With its sleek, aerodynamic design, some have called it the ‘Ferrari of space,’ but we’ve just called it sexy, like a satellite straight out of a James Bond movie.

And the satellite has delivered with unique results of Earth’s ‘geoid’ — precise measurements of ocean circulation, sea-level change and ice dynamics, greatly improving our knowledge and understanding of the Earth’s internal structure. The mission has also been studying air density and wind in space. Its data also produced the first global high-resolution map of the boundary between Earth’s crust and mantle, called the Mohorovicic, or “Moho” discontinuity.

Mission managers predict that in mid-October 2013 the spacecraft will run out of fuel and the satellite will begin its descent towards Earth. There will be no remaining fuel to guide its re-entry, and while most of GOCE is predicted to disintegrate in the atmosphere, several parts might reach Earth’s surface. Experts predict as much as 25% of the spacecraft will survive reentry, as many parts are made of advanced materials, such as carbon-carbon composites.

But when and where these parts might land cannot yet be predicted, ESA says.

As the re-entry time nears, better predictions will be made. Re-entry is expected to happen about three weeks after the fuel is depleted.

ESA says that taking into account that two thirds of Earth are covered by oceans and vast areas are thinly populated, the danger to life or property is very low.

Recently, other larger satellites have made uncontrolled re-entries, such as NASA’s 6-ton UARS spacecraft and Germany’s 2.4-ton ROSAT in 2011 and the 13-ton failed Russian Mars probe, Phobos-Grunt in 2012.

About 40 tons of human-made space debris reach the ground per year, but the spread and size mean the risk of an individual being struck is lower than being hit by a meteorite.

An international campaign will be monitoring the descent, involving the Inter-Agency Space Debris Coordination Committee. The situation is being continuously watched by ESA’s Space Debris Office, which will issue re-entry predictions and risk assessments.

ESA says they will keep the relevant safety authorities permanently updated.

Additional info: ESA, BBC

New Plans for ESA’s Experimental Re-entry Vehicle

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ESA and Arianespace have signed a contract planning the launch of ESA’s new IXV (Intermediate eXperimental Vehicle) on Europe’s new Vega Rocket in 2014. Vega is Europe’s new small launch system and it is designed to complement the heavy Ariane 5 and medium Soyuz Rocket systems launched from French Guiana.

The small rocket is capable of a wide range of payloads up to 1.5 tonnes, compared to Ariane 5 which can lift 20 tonnes, making it especially suitable for the commercial space market. The Vega Rocket will launch the IXV into a suborbital trajectory from Europe’s Spaceport in French Guiana, IXV will then return to Earth as if from a low-orbit mission, to test and qualify new critical technologies for future re-entry vehicles.

Vega Rocket Credit: Arianespace

The IXV will reach a velocity of 7.5km/s at an altitude of around 450km and then re-enter the Earth’s atmosphere gathering data about its flight. The vehicle will encounter hypersonic and supersonic speeds and will be controlled with complex avionics, thrusters and flaps.

Once the vehicle’s speed has been reduced enough, it will deploy a parachute, descend and land safely in the Pacific Ocean.

This flight will record data for the next five VERTA missions (Vega Research and Technology Accompaniment – Programme), which will demonstrate the systems re-usable versatility.

Two launches a year are planned for the new programme and construction of infrastructure including mission control and communications networks is currently underway.

Development and completion of the design, manufacturing and assembly is now underway for a flight window between January and September 2014.

VERTA (Vega Research and Technology Accompaniment – Programme) Credit: Arianespace

Source: ESA

June 21 ATV Re-Entry: A Man-Made Fireball In The Sky

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The Johannes Kepler ATV (Automated Transfer Vehicle) has undocked from the International Space station and will re- enter Earth’s atmosphere on June 21st ending its mission in fiery destruction.

The ATV has been docked with the ISS since February, where it delivered supplies, acted as a giant waste disposal and boosted the orbit of the International Space Station with its engines.

The X-wing ATV delivered approximately 7 tonnes of supplies to the station and will be leaving with 1,200kg of waste bags, including unwanted hardware.

The Johannes Kepler ATV-2 approaches the International Space Station. Docking of the two spacecraft occurred on Feb. 24, 2011. Credit: NASA

On June 21st at 17:07 GMT the craft will fire its engines and begin its suicide mission, tumbling and burning up as a bright manmade fireball over the Pacific Ocean. Any leftover debris will strike the surface of the Pacific ocean at 20:50 GMT.

During the ATV’s re-entry and destruction there will be a prototype onboard flight recorder (Black Box) transmitting data to Iridium satellites, as some aspects of a controlled destructive entry are still not well known.

ESA says that this area is used for controlled reentries of spacecraft because it is uninhabited and outside shipping lanes and airplane routes. Extensive analysis by ESA specialists will ensure that the trajectory stays within safe limits.

There still are some chances to see the ISS and Johannes Kepler ATV passing over tonight, but if you in a location where you can see the south Pacific skies starting at about 20:00 GMT, keep an eye out for a glorious manmade fireball.

A shower of debris results as the ATV continues its plunge through the atmosphere. Credit: ESA

Read more about the re-entry at ESA.