Tag: Spaceflight

We tend to think of the Earth orbiting around the Sun along a path largely free from debris. However, this is not strictly true. Twenty-five years ago, scientists discovered that Earth orbits the Sun along with a giant ring of dust which appears to have originated within the asteroid belt that lies between Mars and Jupiter. This belt is made up of millions of rocks of all sizes, many of which over the millennia crash into one another and grind together, producing a lot of dust. This gradually falls towards the Sun as a result of gravity – but along the way, some of it is influenced by the Earth’s gravity, becoming trapped along and either side of the Earth’s orbit, forming a ring.

Observations of Mars by NASA’s Maven orbiter have also given indications that the Red Planet could have a ring – or at least, a proto-ring – occupying its orbit, while 10 years ago, astronomers discovered a ring straddling the orbit of Venus. Now a new study reveals little Mercury has a ring of dust lying along its orbit – although by rights, it shouldn’t.

Mercury’s ring was discovered entirely by accident – ironically, those responsible for its discovery, Guillermo Stenberg and Russell Howard of Naval Research Centre in Washington, DC, were attempting to find a dust-free region that is thought to surround the Sun, created by solar energy radiating outwards from our star. The idea being that determining the size of this dust-free region would both reveal more about the nature of the Sun and the evolution of the solar system. But instead of locating this area of “empty” space, the astronomers discovered the ring sharing Mercury’s orbit.

People thought that Mercury, unlike Earth or Venus, is too small and too close to the Sun to capture a dust ring. They expected that the solar wind and magnetic forces from the Sun would blow any excess dust at Mercury’s orbit away.

– Astronomer Guillermo Stenberg

The two scientists worked with images from NASA’s STEREO solar observatory. This pair of satellites  follow highly elliptical geocentric orbits. Over time, one of them pulls farther ahead of Earth while the other falls further behind. This means that together they provide stereo images of the Sun. In studying the images from the satellites, Stenberg and Howard noticed an area of enhanced brightness along Mercury’s orbit, indicative of a dust ring being present.

The question is – how did it form? There’s no answer to this yet; as Stenberg notes, the ring shouldn’t be there, and the lesson of Venus has revealed that it’s better not to assume common factors in the formation of these rings.

This is because initially, it was assumed the ring around Venus was the result of the same gravitational forces that have created the dust ring along Earth’s orbit. However, when astrophysicists Petr Pokorny and Mark Kuchner from NASA’s Goddard Space Flight Centre attempted to use extensive computer modelling to try to reproduce a dust ring matching the one in Venus’ orbit, they were unable to do so.

As a result, the two started researching and modelling possible explanations, and in a paper published on March 12th, 2019, the two suggest that the Venusian ring is the result of a previously undiscovered group of asteroids occupying the same orbit as Venus with a 1:1 resonance (that is, they complete one orbit of the Sun for every orbit Venus makes). Further, their research suggests that the group of asteroids are the remnants of a much larger asteroid ring that existed when the solar system was born.

The asteroid themselves have yet to be located – no easy task, assuming they do exist, as the Venusian dust ring is 25.5 million km (16 million mi) deep, and  9.6 million km (6 million mi) across, and bright enough to hide larger objects within it. However, if the asteroid are discovered, they would not only confirm the theory about how the dust ring around Venus’ orbit formed, but also hold clues to how the solar system formed.

Further SLS Changes

In my previous Space Sunday report, I covered the announcement by NASA that suggested  the Space Launch System rocket might have its initial launch delayed. Now it seems the system is to undergo further changes to both its initial flights and its future development.

As it was originally planned, the SLS was to have been initially launched in its Block 1 configuration. This would see the vehicle use what is called the Interim Cryogenic Propulsion Stage (ICPS) as its upper stage. After that, launches would switch over to using the Block 1B version, intended to use a more powerful upper stage called the Exploration Upper Stage (EUS), being built by Boeing Aerospace.

Given issues with the development of the EUS, in late 2018 NASA announced the first two SLS launches, referred to as EM-1 and EM-2, and designed to send a Orion vehicle on a month-long trip around the Moon, the first uncrewed, the second crewed, will utilise the Block 1 version of the rocket, with flights thereafter shifting to the Block 1B rocket to undertake tasks such as launching elements of the Lunar Gateway. Now, under the Trump Administration’s 2020 budget request, it appears the introduction of the EUS is to be deferred – possibly indefinitely, with NASA ordered to carry out all initial flights using the Block 1 variant of the rocket.

While the ICPS stage is more than sufficient to achieve the objectives established for EM-1 and EM-2, it is not powerful enough to meet all of the demandd of the proposed Lunar Gateway development. Instead, NASA is expected to supplement SLS flights to build the Gateway with the use of commercial launch vehicles, such as the United Launch Alliance Delta V, the SpaceX Falcon Heavy and  – potentially – Blue Origin’s New Glenn.

Continue reading “Space Sunday: dust, rockets, landers and a last image” →

SpaceX successfully completed the first demonstration flight of the Crew Dragon Capsule on Friday, March 8th, when the vehicle returned to Earth after a visit to the International Space Station (ISS).

As I reported in my previous space Sunday article, DM1 lifted-off from Launch Complex 39A at Kennedy Space Centre on March 2nd, rendezvousing with the ISS 27 hours later, when it successfully docked with the station. It remained at the station through until Friday, March 8th. At 07:30 GMT that morning the capsule and its service module detached from the space station and moved to its own orbit ready to make a re-entry into the denser atmosphere and a splashdown in the Atlantic.

This phase of the mission was regarded by SpaceX as the most critical part of the flight, and the one presenting the most risk to the vehicle. While based on Cargo Dragon, the Crew Dragon is a very different vehicle; the parachute system and backshell are new, the DM1 flight being the first time they would be used operationally. The Crew Dragon’s backshell, for example, is asymmetrical in order to accommodate the eight SuperDraco escape engines designed to get the capsule out of harm’s way in the event of a launch emergency, and which are not present in the Cargo Dragon. As SpaceX CEO commented ahead of the vehicle’s launch, this asymmetry could cause roll instability on re-entry, potentially resulting in vehicle loss.

As it turned out, after moving well clear of the ISS and positioned on a track for its eventual splashdown, C201, now separated from its service module, fired its thrusters at 12:53 GMT for a 15-minute re-entry burn. Once through the seating heat of re-entry, the craft  dropped into the denser atmosphere and passed the second of its final tests: deploying first its drogue parachute system and then the four main parachutes; in doing so, it recaptured the heyday of NASA’s Mercury, Gemini and Apollo capsules.

At 13:45 GMT, C201 splashed down in the Atlantic, close to the waiting SpaceX recovery ships. Making the return aboard the capsule was the instrument-laden flight dummy “Ripley” and a small payload from the ISS. The plushy toy used as a zero-gee indicator on the vehicle’s ascent to orbit remained aboard the ISS, where it has become a celebrity. Named “Earthie” (or “Earthy”, it’s not actually clear), the plushy has been treated to tours of the ISS, has been featured in photocalls and videos, and become something of a station mascot. It will be remaining on the ISS until the first crewed flight of the Dragon vehicle docks with the ISS later this year.

Fifty years after humans landed on the moon for the first time, America has driven a golden spike on the trail to new space exploration feat. It won’t be long before our astronaut colleagues are aboard Crew Dragon and Boeing’s Starliner vehicles, and we can’t wait.

 – NASA astronaut Anne McClain aboard the ISS, marking the depature
of Crew Dragon from the station

However, even before splashdown, NASA was indicating plans to start flying crew aboard the Crew Dragon might be subject to delay. Currently, a further flight of C201 is due in June. Again, uncrewed, it is intended to test the launch abort system. The first crewed flight is currently scheduled to follow that flight, some time in July. It will carry two astronauts up to the ISS where they will remain for several weeks. However, comments from NASA’s Aerospace Safety Advisory Panel seem to suggest the crewed demonstration flights of both Crew Dragon and Boeing’s CST-100.

There’s a lot of forward work to complete on both Crew Dragon and Boeing’s CST-100 Starliner vehicles. We’re not quite ready to put humans on either vehicle yet.

– Former astronaut Sandy Magnus, a member of NASA’s Aerospace Safety Advisory Panel

These doubts notwithstanding, Boeing and NASA have indicated that the first uncrewed flight of the CST-100 Starliner could take place in April. Referred to as Orbital Flight Test (OFT), this mission will lift off from Florida’s Cape Canaveral Air Force Station atop a United Launch Alliance (ULA) Atlas V rocket, and follow a similar profile to that of SpaceX DM1.

NASA SLS May Face Launch Delay

We are reassessing those dates to see if that date will work, based on making sure we have the vehicle ready, and ready to go fly safely. We are assessing that date. Our launch readiness date is still 2020, and we’re doing everything within our power to make sure that we support that.

– Jody Singer, director of NASA’s Marshall Space Flight Centre,
March 5th, 2019

With this words, the director of NASA’s Marshall Space Flight Centre, responsible for overseeing the development and construction of NASA new Space Launch System super booster, suggested the maiden flight of the rocket could be subject to further delay.

Singer did not give specifics on what might cause the delay following the statement, but in October 2018, NASA’s Office of Inspector General was sharply critical of both NASA and Boeing, the prime contractor for the rocket’s massive core  stage, for problems with that element. At that time, the office concluded that the first flight of the rocket – designated EM-1 – could not take place in the first half of 2020 as had been planned, so the launch date was then moved back to the latter half of the year. October 2018 also saw NASA order Boeing to slow down work on the system’s Exploration Upper Stage (EUS). Originally scheduled to be flown on the second test launch of the SLS, NASA has opted not to fly it until the third flight of the system.

Despite the concerns raised by Singer’s comments, the other major elements of the SLS are largely complete, including its two five-segment solid rocket boosters, upper stage and adapters, leading weight to the idea that it is the core stage that is causing problems. In the meantime, structural test articles of the vehicles, liquid hydrogen and liquid oxygen tanks will be tested in the coming months at Marshall, while the core stage is due to be transferred to NASA’s Stennis Space Centre in Mississippi for so-called “green run” testing which will see its four RS-25 engines are fired on a test stand, in late 2019 early 2020, a test that’s seen as a critical test on the road to launch readiness.

Continue reading “Space Sunday: capsules, rockets, hammers and stars” →

On Friday, February 22nd, Virgin Galactic’s VSS Unity completed a further test flight, its second time in just over two months, and in doing so set itself a new altitude record.

The space plane was released from its WhiteKnightTwo carrier, the VSM Eve at 16:53 UT, some 45 minutes after taking off from the Mojave Air and Space Port in California. The vehicle’s hybrid rocket moor was fired for roughly one minute, pushing the Unity and its crew of three to an altitude 89.9 km (56 mi), reaching a maximum velocity of Mach 3 in the process. After a successful “feathering” manoeuvre of the vehicle’s tail boom, Unity dropped back into the denser atmosphere and glided back to a runway landing in Mojave at 17:08 UT.

The flight, delayed by two days due to high winds over the planned flight test route, marked the first time the vehicle had carried a “passenger”: Beth Moses, Virgin Galactic’s chief astronaut instructor. She made the flight with David Mackay and Mike “Sooch” Masucci, respectively the company’s chief test pilot and lead trainer pilot. All three were making their first trips into space, Moses being aboard to provide practical validation and  data on aspects of the customer cabin and spaceflight environment from the perspective of “people in the back”. Her presence on the flight was not announced until after Unity had landed.

Beth, Sooch and I just enjoyed a pretty amazing flight which was beyond anything any of us has ever experienced. It was thrilling yet smooth and nicely controlled throughout with a view at the top, of the Earth from space, which exceeded all our expectations.

– Virgin Galactic chief test pilot David Mackay

Moses also kept an eye on the flight’s special payload – four science and technology demonstration packages provided by NASA under the agency’s Flight Opportunities Programme. Three of the packages had been flown on the Unity’s previous flight in December 2018.

Virgin Galactic have refused to indicate how many more test flights will be made before SpaceShipTwo starts carrying fare-paying passengers, although the company’s founder, Sir Richard Branson has indicated he hopes to fly on the vehicle in July 2019, possibly to mark the 50th anniversary of the Apollo 11 Moon landing. Speaking ahead of the February 22nd test flight, Mike Moses, president of Virgin Galactic and husband of Beth Moses, indicated that the company is in the “heart” of their flight test regime, and the focus is on expanding the envelope of flights, including their frequency, prior to committing to commercial flights.

The altitudes reached by Unity thus far (just over 80 km / 50 mi on the December 2018 flight and now 89.9 km) have caused some to call into question whether or not VSS Unity has really been in space – including Jeff Bezos, who is heading Blue Origin, Virgin Galactic’s clearest rival in the sub-orbital passenger market.

Speaking about his own company’s test programme with their New Shephard launch system, Bezos emphasised the operational difference between the reusable New Shephard rock and its crew / passenger carrying capsule and Virgin’s SpaceShipTwo. The New Shephard is specifically designed to reach altitudes of 100 km (50 mi), somewhat higher that Virgin Galactic have thus far achieved. 100 km is important, as it marks the position of the Kármán Line, broadly (but not exclusively) considered to be the point above which where aerodynamics cease having any real influence over an aircraft’s performance, making it reliant on astronautics. Thus, it is seen by some as the boundary of space.

One of the issues that Virgin Galactic will have to address, eventually, is that they are not flying above the Kármán Line, not yet … We’ve always had as our mission that we wanted to fly above the Kármán Line, because we didn’t want there to be any asterisks next to your name about whether you’re an astronaut or not. That’s something they’re going to have to address, in my opinion.

– Jeff Bezos, New Origins founder, commenting on Virgin Galactic, February 20th, 2019

However, things are actually not that clear-cut. There is no international law defining the edge of space; for example, the United States – from which both New Shepherd and Virgin Galactic will fly (at least initially in the latter’s case) considers the boundary to be 80 km (50 mi), which Virgin Galactic can clearly exceed.

Further, Theodore von Kármán, after whom the line is named, suggested the boundary could lie anywhere between 91 km and 100 km altitude. The ambiguity is exacerbated by a proposal to set the “edge” of space in international law as the lowest perigee attainable by an orbiting space vehicle – which would place it somewhere between 130 km (81 mi) and 150 km (93 mi), somewhat beyond the capabilities of either SpaceShipTwo and New Shephard, which tends to render arguments about altitude and boundaries a little moot, particularly given the fact that whether at 80-90 km above the earth or at 100 km, passengers on either vehicle will experience the same degree of weightlessness.

Continue reading “Space Sunday: tourist flights, landers, moons and rovers” →

I’ve written a lot about Planet Nine, the mysterious, yet-to-be-discovered world thought to be orbiting far out in the hinterlands of the solar system, and potentially responsible for the odd orbits of a number of bodies in the Kuiper Belt (referred to as Kuiper Belt Objects, or KBOs). Most recently – in June 2018 – I noted that one field of research suggested that while gravity could be responsible for the eccentric orbits seen with many KBOs, it might not have anything to do with the presence of another planet.

Now a new study – Shepherding In A Self-Gravitating Disk Of Trans-Neptunian Objects – further casts doubt on – but does not eliminate – the need for any planetary object being responsible for the odd orbits of Sedna and the other unusual KBOs. In it Professor Jihad Touma, from the American University of Beirut, and Antranik Sefilian, a PhD student in Cambridge’s Department of Applied Mathematics and Theoretical Physics, suggest a disc of icy material could be the cause.

The attraction for there being a planet responsible for teasing these objects into the odd orbits is that over the last 15 years, some 30 Trans-Neptunal Objects (TNOs) have been discovered in highly-elliptical orbits, all of which would appear to a large planetary object having some form of influence on them. However, despite extensive attempts to locate this mysterious body, possibly the size of Neptune, it has remained elusive – possibly because it doesn’t exist.

The Planet Nine hypothesis is a fascinating one, but if the hypothesised ninth planet exists, it has so far avoided detection. We wanted to see whether there could be another, less dramatic and perhaps more natural, cause for the unusual orbits we see in some TNOs. We thought, rather than allowing for a ninth planet, and then worry about its formation and unusual orbit, why not simply account for the gravity of small objects constituting a disc beyond the orbit of Neptune and see what it does for us?

– study co-author Antranik Sefilian

Instead, he and Touma modelled the full spatial dynamics of TNOs, taking into consideration the influence of the known giant outer planets in the solar system and a massive, extended disc of material beyond Neptune. Their results suggest that such a large – if yet-to-be-discovered – disc of material were to be orbiting the Sun at a great distance, it could give rise to TNOs occupying highly elliptical and exaggerated orbits around the Sun. In addition, they were able to model mass ranges and shapes for the icy disc and demonstrate how gradual shifts in its precession rate, could give rise to the wilder orbits seen with the 30+ eccentric TNOs.

If you remove planet nine from the model and instead allow for lots of small objects scattered across a wide area, collective attractions between those objects could just as easily account for the eccentric orbits we see in some TNOs.

– study co-author Antranik Sefilian

However, there is a problem with the theory – or two issues at this point in time. The first is that, like Planet Nine itself, it’s one things developing a computer model that demonstrates of a disc of distant material can influence TNOs and drive them into strange orbits, it is quite another to physically find it. The second is that attempts thus far made to estimate the mass of icy objects beyond Neptune have only added up to about one-tenth the mass of Earth – which is far too little to have any significant influence over TNOs. Part of the problem here is that as we’re inside the disc and looking out at it, it is incredible hard to sport the material that might be a part of it – something which Sefilian and Touma acknowledge.

But there is more than enough evidence found around other solar systems to suggest extended discs of icy material are actually quite commonplace, and so one could well by surrounding our own.  What’s required is a longer, more considered look and the space around us – something that may well take time. And even then, Touma and Sefilian acknowledge that while their study suggests there is no need for any mystery planet, the hunt for Planet Nine shouldn’t be entirely abandoned; it might be that both it and a distant icy disc of objects might be responsible for the “rogue” TNO orbits far outside the plane of the ecliptic.

New Horizons Returns Best View Yet of Ultima Thule

On January 25th, 2019 NASA and John Hopkins University revealed the most stunning picture of Ultima Thule thus far returned by the New Horizons mission as it flew by the Kuiper Belt object (KBO) on January 1st, 2019.
Obtained with the wide-angle Multicolor Visible Imaging Camera (MVIC) the image was captured when New Horizons was just 7 minutes from its point of closest approach to the KBO, and just 6,700 km (4,200 mi) from it.  With an original resolution of 440 feet (135 meters) per pixel, the image was stored in the spacecraft’s data memory and transmitted to Earth on January 18th/19th, where it went through a process designed to sharpen the image and enhance fine detail.

The oblique lighting of this image reveals new topographic details along the terminator, near the top. These details include numerous small pits up to about 0.7 km (0.4 mi) in diameter. The large circular feature, about 7 km (4 mi) across on the smaller of the two lobes, also appears to be a deep depression. It’s currently unclear whether these pits are impact craters or features resulting from other processes, such as “collapse pits” or the ancient venting of volatile materials.

This new image is starting to reveal differences in the geologic character of the two lobes of Ultima Thule, and is presenting us with new mysteries as well. Over the next month there will be better colour and better resolution images that we hope will help unravel the many mysteries of Ultima Thule.

– Alan Stern, New Horizons Principal Investigator

Continue reading “Space Sunday: planet 9, Ultima Thule and space vehicles” →