Tag: Astronomy

SpaceX is continuing to move towards a first flight-test ready stack of its massive Super Heavy vehicle and a proof-of-concept Starship payload carrier – although there is still some way still to go before an actual launch attempt can be made.

Following the test stacking of Booster 4 and Starship 20 on the launch table back in August (see Space Sunday: the Ups and Downs of Space Vehicle Development), Booster 4 was rolled back to the production facilities at the company’s Starbase centre at Boca Chica, Texas, to undergo a number of revisions.

Chief among these has been modification to the vent valve system, nominally used to allow excesses gaseous oxygen and methane to be vented from the rocket’s tanks as it naturally “boils off” due to temperature differentials the vehicle experiences when fuelled ahead of a launch. In particular, the vents for the booster’s lower tank now have covers that direct any gas downwards along the rocket’s body, and the vents for the upper tank force the gas outwards and away from the rocket.

This suggests that SpaceX plan to use the release of gas from the tanks as a means to help control the orientation of the rocket during its descent back through the atmosphere in a manner similar to a more traditional reaction control system (RCS). If this proves to be successful, it means SpaceX have further reduced Super Heavy’s mass by avoiding the need for separate RCS systems and tankage.

Another issue with rockets is that as the fuel tanks empty they lose internal pressure, and this can interrupt the steady flow of propellants to the engines. To prevent this, most launch systems utilise a reserve of helium that can be fed into the tanks as the propellants are burnt, maintaining the necessary tank pressure. To remove the mass created by a helium system, SpaceX have opted to use the rarer option of autogenous pressurisation. This draws a small flow of heated propellants before they reach the engines, and feeds this flow – in gaseous form – back up the outside of the rocket via dedicated pipes to be returned to the fuel tanks to re-pressure them.

The new vent systems and the piping of the autogenous pressurisation feeds where clearly visible as Booster 4 was rolled back to the orbital launch facilities on Tuesday, September 7th, and hoisted back onto the launch table, with the speculation iit may remain there until the actual launch attempt.

When this will be is unclear; the operation to hoist the booster into position showed the launch table itself is still being completed, being wrapped in scaffolding. It’s also not clear how much of the necessary propellant and electrical feeds have been installed in the launch support tower – although the Quick Disconnect (QD) arm that actually feeds propellants into the starship vehicle and provide it and the booster with electrical power has been installed (with further additions to come). Similarly, the actual tank farm that will supply consumables – water, propellants, etc., – to the pad to enable launches.

Even so, SpaceX CEO Elon Musk has suggested an initial static fire test with Booster 4 could come within the next week. Even if the majority of the required plumbing, etc., is in place, this seems possibly ambitious,  given that such a test will likely only come after at least one each of cryogenic propellant loading / pressurisation tests to ensure the system is ready for any static fire test.

How many static fire tests might be run is unclear; its unlikely that SpaceX will want to fire all 29 engines in the first test but will likely build up to it – perhaps starting with the three motors at the centre of vehicle, followed by a firing of all nine of the middle engines before progressing to firing all 29 engines. And it should be remembered any of these tests, from pressurisation through the engine firings, could result in the rocket sustaining damage or even being completely destroyed.

After the August stack test, Starship 20 was moved from the the orbital launch pad to sub-orbital launch pad B, where it has been undergoing an extensive examination of its thermal protection system (TPS) designed to protect it during entry into the atmosphere. The tiles on this system appear to have suffered more than the anticipated amount of stress / damage due to it being lifted up onto the booster by its snout in order to be stacked on the booster, requiring a lot of them to be replaced and others refitted / re-aligned. This work is now drawing to a close, but does point to a need for the tile system to be more robust during vehicle moving / operations.

Most recently, the vehicle has been receiving the six Raptor motors that will power it. This has sparked speculation that once this work is complete, Starship 20 could be ready to start its cryogenic and fuel pressurisations tests ahead of static firing test – again, possibly the inner three first, then all six.

A final element key to any launch attempt (and the full booster static fire test) is the granting of permission and a licence by the Federal Aviation Administration, which appears to be rightly determined not to be rushed into giving the OK whilst it is still conducting an extensive review of the Starbase facilities and their overall suitability for Super Heavy / starship launches  in the event of an accident (particularly after the airborne explosion of SN11in march 2021 resulted in debris falling to earth 8 km from the SpaceX facilities and close to a populated area).

Continue reading “Space Sunday: SpaceX, NASA and interstellar visitors” →

Some sections of the tabloid media became excited this week about “cracks” being discovered “on the International Space Station”, with one or two predicting the end of the ISS is now nigh.

The cause of the reports was the announcement by Energia NPO, the company responsible for fabricating the Russian-built elements of the ISS, that “superficial fissures” have been found in the outer skin of the Zarya module.

Zarya – also called the Functional Cargo Block (FCB) – was the first module of the ISS to be launched (November 1998), and was initially responsible for providing electrical power, storage, propulsion, and guidance to the ISS during the early years of assembly. However, as more specialised units, notably the Russian Zvezda module (attached to the aft end of Zarya), were launched, the role of the Zarya module has been gradually downgraded to the point where today it is primarily used for internal and external storage space.

Thus far, neither NASA nor Roscosmos have indicated whether or not the fissures have caused any internal pressurisation issues for the station. However, similar fissures – likely the result of exposure to extremes of temperature as the ISS passes between direct sunlight and the cold shadow of Earth and back every 45 minutes – were discovered on the Zvezda Module in 2019, and despite repairs in 2020 and 2021, they continue to be an annoyance.

Whether the Zarya fissures will become a similar issue can only be determined in time – but they are a reminder that while the ISS is not in imminent risk of a major failure, it is genuinely showing its age, particularly the three original modules – Zvezda, Zarya and Unity – all of which are at least 25 years old (including fabrication / construction time), and are potentially becoming increasingly vulnerable to fatigue. Such issues might also cause Russia to make further noises about withdrawing from the ISS after 2024, this time of the grounds of the station’s increasing age, so they can start work on their own space station.

The Accident – the Strangest Brown Dwarf

Brown Dwarfs are sometimes called “failed stars”, in that they have a mass that sits above the most massive gas giant planets we have so far discovered, but below that of the smallest stars. This leaves them incapable of achieving hydrogen fusion, hence the idea they have “failed” as stars. However, they are massive enough to give off considerable infra-red radiation, which tends to point to them being extremely old.

In reviewing data returned by the Near-Earth Object Wide-Field Infrared Survey Explorer (NEOWISE), citizen scientist Dan Caselden has discovered the strangest brown dwarf to so far be discovered – so strange it has been given the nickname “The Accident”.

Located around 50 light years from Earth, it is officially called WISEA J153429.75-104303.3 and classified a Class Y substellar object – the oldest and coolest classification of such brown dwarfs. All of which is really not that interesting; astronomers have discovered many brown dwarfs in local space around our solar system over the last 30 years.

What is strange about The Accident is firstly, it is spinning about its axis at a speed of 200 kilometres a second (that’s 720,000 km/h)- 25% faster than the next fastest stellar object of its kind.

The second – and more intriguing – thing is that The Accident has the oddest brightness pattern of any brown dwarf. Due to their nature, these objects only give off light in the infra-red wavelengths, and The Accident’s output is – at least in part – at the end of that part of the spectrum that points to it being really old: perhaps 13 billion years old – almost as old as the galaxy itself (13.6 billion years. This extreme age is also supported by The Accident’s rotational speed, something that could only be achieved via  thousands of encounters with massive stellar objects down the aeons.

But there’s a twist: The Accident is not consistent in its infra-red brightness, as it also “shines” in parts of the infra-red that indicate that it is a lot, lot, younger than the other data suggest, making the object an anomaly – and accident of nature, so to speak, hence its nickname. This difference in brightness has puzzled scientists, and has led to The Accident starting to get a lot of attention to determine what might be going on inside it.

Some of this attention is also devoted to studying it on the basis of its age – if it really is 13 billion years old, then it formed at a time when the galaxy was a very different place in terms of chemistry, a time when many elements we take for granted (carbon and methane being just two) simply could not exist. Thus, understanding its nature and composition could reveal more about the galaxy’s formation and birth. What’s more, that so strange an object should be found so relatively close to Earth suggests there could be many of these unusual brown dwarfs awaiting discovery.

Virgin Group Ups and Downs

Sir Richard Branson is having some ups and downs in his space endeavours.

The ups are with Virgin Orbit, the smallsat launching service that uses the LauncherOne rocket, lifted to altitude by a modified 747 before being launched, to place payloads of up to 300 KG to a Sun-synchronous orbit or 500 KG to low Earth orbit.

Following the first successful launch of a commercial payload to orbit at the end of June, the company has now passed a critical Federal Aviation Administration (FAA) environmental review that could allow it to use Andersen Air Force Base, on the island of Guam in the western Pacific Ocean, as a base for launch operations.

If final approval is granted – and the FAA do have reservations about Virgin Orbit being able to operate from such a remote location – the company plan to use Guam to make up to 25 air launches over a period of 5 years, possibly commencing before the end of 2021.

Following the success of the June launch, Branson noted that Virgin Orbit is to be capable of highly responsive launches from almost any point in the world. To this end, the company has already signed an agreement with Spaceport Cornwall (Newquay Airport) in the UK, and the Brazilian government has selected the company to provide launch services out of that country’s Alcântara Space Centre. These, together with Guam and their existing facilities at the Mojave Air and Space Port mean that Virgin Galactic may soon have four launch locations around the world from which it can reach a variety of orbital inclinations as required by customers.

The down is with Virgin Galactic, the sub-orbital, tourist-focused service. Following its first successful passenger-carrying flight in July (see: Space Sunday: Unity 22 Flies), the FAA announced on September 2nd that the the sub-orbital VSS Unity is grounded, following a review of that flight, forcing a halt to the company’s operations.

The review has been triggered following an article appearing in The New Yorker magazine stating the pilots on VSS Unity ignored a warning triggered during the vehicle’s powered ascent that should have caused them to abort the flight and return the the ground. The warning indicated the vehicle was not climbing at a sufficiently steep angle to remain within it’s “entry glide cone” – the volume of space in which it can make a safe unpowered glide back to a successful runway landing at the end of the flight – during its return to Earth, and so could miss the runway entirely.

While the company has defined The New Yorker’s report as “inaccurate”, telemetry from the Unity 22 mission shows that the vehicle did exceed the limits of FAA-defined “protected airspace” for one minute and 41 seconds during the descent to landing, further justifying the FAA’s decision to order the grounding, preventing any further operations by Virgin Galactic for the next few weeks.

Continue reading “Space Sunday: the ISS, SLS, brown dwarfs and other bits” →

On August 28th, 2021, Astra Aerospace attempted to make the fourth launch of its Rocket 3 vehicle designed to place payloads of up to 150 kg to Sun-synchronous orbits 500 km altitude.

After two unsuccessful and one partially-successful flights of the launch system, it was hoped that this flight, carrying an instrumentation payload for the United States Space Force under the Space Test Program (and which was not designed to separate from the launch vehicle), would be a complete success.

Lift-off from Pacific Spaceport Complex – Alaska on Kodiak Island (high northern latitudes being ideal for polar orbital launches) came at 22:35 UTC, and it was immediately clear the rocket was having something of an existential moment, experimenting with moving sideways away from the launch pad, rather than upwards.

After almost 20 seconds of moving thus, the vehicle decided that “up” was perhaps the better option, and proceeded to climb into the sky, performing more-or-less perfectly through an ascent to 50 km altitude, successfully passing “max-Q” (the period when a launch vehicle experiences the maximum dynamic pressures across its frame) in the process and throttling to full power in a press for orbit.

Sadly, due to the post-lift-off incident, the vehicle had exceeded its range safety limits, risking passage over populated areas on mainland Alaska. The order with therefore given to shut down the first stage motors let it crash back into the sea.

Subsequent analysis of data suggests that one of the 5 Astra-built Delphin motors powering the rocket’s first stage failed at launch, likely resulting in off-centre thrust that caused the vehicle to strike one of its launch mounts, resulting in the sideways tilt and motion. However, despite the loss of the vehicle, the fact that it autonomously recovered to make a successful ascent to a point where, but for range safety concerns, it would likely have achieved a successful orbit, is seen as a remarkable testament to the rocket’s guidance and flight control systems.

Further launches will be pending a complete view of this flight.

Mars Updates

The Mars 2020 rover Perseverance is getting ready to make a second attempt to obtain rock samples for analysis and storage.

As I recently reported, a first attempt at sample gathering didn’t end successfully when it was discovered after-the-fact that the rock selected for the sample was made up of material too fine to be retained within the rover’s drill / sample mechanism following drilling.

Abandoning that attempt, the rover was directed to travel 455 metres to a small ridge dubbed “Citadelle”, where it will now attempt to gather a fresh sample. The area was selected as it appears to be able to withstand erosion by the Martian wind better than the surrounding ground, and has a number of interesting rock formations in it.

In order to help ensure a sample has been collected post-drilling, a new step has been introduced into the process: once drilling has been completed, the arm and turret will be raised and positioned to allow the rover’s MastCam-Z cameras to image as a visual confirmation that there is material within it. Once confirmed, processing of the sample tube through to the rover’s on-board storage area will then be allowed.

Nor has the first “empty” tube been an entire waste – it now contains a sample of pristine Martian atmosphere, something the mission had intended to collect at some point, and so it will form a part of a sample cache of tubes the rover will at some point deposit on the surface of Mars in anticipation of collection by a future sample return mission.

While atop Citadelle, Perseverance will use its subsurface radar, called RIMFAX – the Radar Imager for Mars’ Subsurface Experiment – to peer at rock layers below it. The top of the ridge will also provide a great vantage point to look for other potential rock targets in the area.

NASA has also confirmed the next mission to Mars, due to be launched in 2024. In keeping with the agency’s approach to alternating surface missions with orbital missions, it has approved the ESCAPADE mission of twin satellites for launch in 2024.

Led by the University of Berkeley, California, the Escape and Plasma Acceleration and Dynamics Explorers mission is a relatively low-cost (under US $80 million including launch costs) attempt to put two small satellites, dubbed “Red” and “Blue” into orbit around Mars to further study the Martian atmosphere and its interactions with the solar wind.

The satellites will be launched using two Rocket Lab Electron rockets, with the company’s Photon satellite bus used to protect / power them during a low-energy, 11-month cruise to Mars. This marks a significant increase in Photon’s capabilities, the bus originally having been designed to support the launch of satellites into Earth or cislunar orbits. As such, the mission is seen as a “high risk” venture – but as the team behind ESCAPADE note, most missions to Mars come with a price tag of US $800 million or more, and roughly a 90-95% chance of success in reaching Mars / Mars orbit. ESCAPADE is estimated as having an 80% chance of success in doing the same – but at one-tenth the cost, thus making the increased risk in using Rocket Lab systems worth the effort.

Once in orbit, the mission will collect data that could help reconstruct the climate history of Mars and determine how and when it lost its atmosphere. ESCAPADE also will study the ionosphere of Mars, which can interfere with radio communications on the surface and between Earth and Mars colonists. Finally, with simultaneous two-point observations of the solar wind and Mars’s ionosphere and magnetosphere, ESCAPADE will provide a “stereo” picture of this highly dynamic plasma environment in the planet’s upper atmosphere.

And when it comes to human missions to Mars, a new study from the University of California Los Angeles proposes a novel way of reducing the impact of radiation during the journey to / from Mars: by launching during periods of high solar activity, notably the periods immediately following that of solar maximum, when the Sun is at its most active. While launching missions during periods of high solar radiation to reduce the risk of radiation exposure might sound counter-intuitive, there is some logical to the idea.

Simply put, interplanetary missions face two radiation risks – solar, which can be reasonably well mitigated against in a variety of ways (but not entirely avoided or made “safe”) and galactic cosmic rays (GCRs), which are considerably harder to deal with, and more devastating in their impact. However, during periods of high solar activity, the more energetic solar radiation actually deflects GCRs away from the solar system. So the UCLA study suggests that by launching crewed missions in the years immediately following a period of solar maximum could massively reduce exposure to GCRs without significantly increasing the risk from solar radiation.

Just how practical it would be to restrict missions to Mars to certain time frames within the Sun’s 11-year cycle is debatable. If we are to practically explore and possibly establish a permanent presence on Mars, missions will need to be a lot more frequent; so more practical research into things like garment materials, materials used in space vehicle design, etc., that could help mitigate both primary and secondary radiation would likely be far more practical. However, the bright spot in the UCLA study does suggest that if missions are kept to below 4 years duration, then radiation exposure could be seen as “acceptable” – and currently, the more favoured “opposition” class of mission of 2.5 to 3 years duration falls inside that limit.

Continue reading “Space Sunday: an “existential” rocket, Mars, and a bit on JWST” →