Space Sunday: SLS WDR-2; FRBs, JWST and UAPs!

Artemis 1 SLS on the Mobile Launcher 1 inside the Vehicle Assembly Building. Credit: NASA

Artemis 1, the planned first flight of NASA’s huge Space Launch System (SLS), is back on Pad 39B at Kennedy Space Centre and being prepared for another try at a full Wet Dress Rehearsal in what many are framing as a make-or-break for the new launch system. At the same time, the SLS programme has come under further critique by NASA’s own Office of Inspector General (OIG).

As I’ve noted in the past, the Wet Dress Rehearsal (WDR) is the final critical test for the SLS system, putting absolutely everything involved in a launch through its paces right up to just nine second before the rocket’s core RD-25 engines would light-off. The test is to ensure everything – the pad systems, the propellant loading systems, the rocket’s computers and avionics, the launch control systems, etc., are commissioned and ready for operational launch, with the data gathered from this first rocket going on to provide a baseline for checking future SLS vehicles as they go through pad preparations and launch in the future.

A graphic showing the tank filling which forms a core element of the WDR, currently scheduled for or around June 17yh, 2022. Credit: NASA

The first attempt at a WDR, back in April started with fanfare a high-profile roll-out of the pad by the first SLS, where it successfully completed a battery of tests prior to the WDR commencing, only to be followed by a series of issues that forced rocket and Mobile Launcher (ML-1) tower to be ignominiously rolled back to the Vehicle Assembly Building (VAB).

The June 6th roll-out was far more low-key, the rocket and ML own leaving the VAB atop the veritable crawler-transporter just after midnight and arriving at the pad in the morning sunlight. Since then, the vehicle and launcher have been going through check-out and connection to all the ground support systems, and a second WDR attempt is provisionally set for on or around June 17th, 2022.

In the meantime, NASA’s OIG has issued a report critical of another aspect of the programme: Mobile Launcher 2 (ML-2).

ML 1 was originally built for launching Saturn 1B and Saturn V rockets in the 1960s. It was then modified for space shuttle launches and again to handle SLS Block 1 launches. However, it is incapable of supporting launches of the bigger and more powerful SLS Block 1B and Block 2 vehicles (assuming the latter are built). So in 2018/19, NAS awarded a US $383 million contract to engineering firm Bechtel to supply a new Launcher – ML-2 – capable of supporting SLS Block 1B and beyond launches, with delivery slated for 2024, ahead of the then planned launch of Artemis 4, the first SLS Block 1B vehicle.

However, the OIG report reveals that ML-2 is spiralling out of control, with costs already exceeding US $440 million, and set to hit at least US $960 million, with doubt cast on Bechtel’s ability to deliver the Launcher in time for Artemis 4, even though that mission is unlikely to fly before later 2027 or early 2028.

Comparing ML-1 and ML-2. Credit: NASA

The report is primarily critical of Bechtel for multiple failures and lapses, but also points out NASA’s own folly in playing “yes man” to an accelerated Artemis programme. Originally, the US return to the Moon was to commence in 2028, but the Trump administration pulled that date forward to 2024; while that was clearly unachievable, NASA attempted to meet the goal. As a result, the ML-2 contract was awarded as “cost plus”, meaning that overruns would be met out of NASA’s pocket, rather than fixed price, which would leave Bechtel holding the purse for errors and delays on their part. NASA further compounded the issue by awarding the contract for the ML-2 design before the SLS Block 1B design had been finalised. As a result, the space agency immediately became liable for continued changes to the ML-2 design as the SLS Block 1B design evolved.

Currently, NASA is attempting to move the contract to a fixed price basis; unsurprisingly, Bechtel appear somewhat resistant to doing so.

FRBs: Far, Far Away – or a Lot Closer to Home?

First discovered in 2007, FRBs are intense, brief flashes of radio-frequency emissions, lasting on the order of milliseconds, thought to emit as much energy in a millisecond as our Sun does over three days – although such are the vast distances they must cover, by the time they reach us their signal strength is around 1,000 times less powerful than a mobile ‘phone signal being received from the Moon.

What causes FRBs is unknown. Most have been thought to originate outside our galaxy – although some have clearly originated within it. Many are heard only once; others appear to repeat on a highly random basis. By listening for and measuring some of the latter, it has been possible to localise their likely point of origin to an area of space. Then, using their dispersion measurement (DM) and overall red-shift, it has been possible to calculate their approximate distance.

ive hundred-metre Aperture Spherical radio Telescope (FAST. Credit:

The DM a measurement of the period between the high-frequency range of a radio burst reaching us and the lower frequencies, which tend to get more dispersed more the first they travel, and so take longer to reach us. It’s a small, but measurable amount. As the composition of interstellar space is known, this difference can be used to calculate signal attenuation over distance, and thus the approximate distance of the originating object from Earth.

This measurement can then be combined with the overall red shift exhibited by the signal to yield a similar distance result, thus allowing reasonable certainty as to how far away the originating object is. But that’s not the case with FRB 20190520B.

First detected in May 2019 by the Five hundred-metre Aperture Spherical radio Telescope (FAST) in Guizhou, China, in 2019, it was later picked up again by the Very Large Array (VLA) in New Mexico, USA in 2020 and subsequently by the Subaru telescope, Hawaii.

What is particularly interesting about this FRB is that taken on its own, its DM suggests it originates in a small galaxy beyond our own. However, when the DM / red-shift relationship is extrapolated, the result suggests the originating point is a lot closer to Earth – as in possibly within our own galaxy.

This might make 20190520B some weird outlier among FRBs – but as some have pointed out, it might also indicate to our entire assumptions about extra-galactic FRBs and the use of dispersion measurements as a kind of “cosmic yardstick” as being totally wrong; that we could actually be mistaking events occurring within our own galaxy that result in FRBs for something far more distant and exotic.

Right now, it’s too early to tell either way, but 20190520B has caused a considerable stir among astronomers, with many looking to step-up the search for more of these strange events.

Continue reading “Space Sunday: SLS WDR-2; FRBs, JWST and UAPs!”