Rocket rumbles give volcanic insights

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An “upside down volcano” (L) and an “upside down rocket” (R)

What do volcanoes and rockets have in common?

“Volcanoes have a nozzle aimed at the sky, and rockets have a nozzle aimed at the ground,” explains Steve McNutt, a geosciences professor at the University of South Florida in Tampa.

It explains why colleague Dr Glenn Thompson and he have set up the tools normally used to study eruptions at the famous Kennedy Space Center.

Comparing the different types of rumblings could yield new insights.

In the event of rockets, the staff thinks their seismometers and infrasound (low-frequency acoustic waves) detectors might potentially be used by the space companies as a different sort of diagnostic tool, to better understand the performance of their vehicles; or maybe as a way to identify missiles in flight.

In the case of volcanoes, the point is to take the lessons and.

It might be possible to develop systems that provide early warnings of a few of the dangerous debris flows associated with volcanoes.

Glenn Thompson and Steve McNutt: “Kennedy has powerful signs to test equipment ”

“It all began really as a way to test and calibrate our equipment,” says Glenn.

“We do not have any volcanoes in South Florida – clearly. But Kennedy provided some powerful resources, and it also gave our students the chance to learn how to set up stations and work with the information.”

The team has recorded the seismic and acoustic signals emanating from about a dozen rockets.

Many have been associated with launches; to what are called fire tests, in which the motors on a vehicle are ignited to check they’re 36, a few have been related.

But the event was that the SpaceX pad explosion in September 2016.

This saw as it had been fuelled a Falcon 9 rocket suffer a failure.

Lots of people will have seen the movie of the fireball. But Steve’s and Glenn’s gear caught information not apparent in that film.

Explosion: signals were detected by The gear over 26 minutes

By way of instance, they detected more than 150 distinct sub-events in the infrasound over the course of 26 minutes.

These were likely individual tanks, pipes or other elements bursting into flames.

The SpaceX explosion was an unusual occurrence, and it’s the activity that interests the group. And some clear patterns are starting to emerge in their analysis of “upside down volcanoes”.

“Since the rocket gets higher and higher and hastens, we see a decrease in the frequency in the infrasound – that’s basically a Doppler shift because the source is moving away from us,” says Steve.

“And then you get a coupling of the signal in the atmosphere into the ground and this creates seismic waves recorded on the seismometer.

“So, we get some common features between the infrasound and the seismometer, but then there is a little separation of the energy between the two.”

SPL A deadly pyroclastic flow heads down the flanks of the Soufrière Hills volcano in Montserrat

There is a lot but the pair think that they can distinguish the different types of rockets – to inform a Falcon.

There are subtle but significant divergences in their spectral signatures, which certainly reflect their distinct designs and styles of operation.

Is in describing moving resources, where in particular the rockets could have education for volcano monitoring.

A rocket is a very well understood procedure that is physical. Its properties and parameters – such as the size of the nozzle orifice, the thrust, the trajectory and the distance – are all known.

Acoustic signals and the related seismic should serve as templates to help decipher a few of the characteristics of eruptions that share similar behaviours.

Good examples of rapid movement in the volcano setting are the significant mass surges like pyroclastic flows (descending clouds of hot ash/rock) and lahars (mud/ash avalanches).

An objective of the team is to improve infrasound and seismometer systems’ characterisation of these phenomena.

This could result in useful alerts being sent to people who live around volcanoes.

“Assuming you can find a few safe places to put your tools which are reasonably close, you would get your advance warning,” explained Steve.

“What you’d do then is getting the time and the strength of the signal and then seeing it evolve to figure out which direction it’s going.

“If you can do this successfully then it’s possible to forecast with a couple of minutes in advance items like lahars and pyroclastic flows downstream.”

Glenn added: “I worked on [the Caribbean island of] Montserrat during the catastrophe from 1995 to 2011, and we did have a rudimentary system even then for monitoring the pyroclastic density currents coming down the slopes of the volcano.

“It was not quite a real-time program, but we hope with this sort of work that we can improve those calculations and make them more of an automated alarm system.”

The staff is currently looking for a permanent installation, although the equipment at Kennedy has been temporary.

In the New Year, Steve and Glenn are looking forward like everybody.

The Heavy should produce almost 23 meganewtons of thrust at lift-off, more than any rocket in operation now.

It’s sure to make for some seismic and infrasound signals.

Glenn Thompson and Steve McNutt detailed their work here at the Fall Meeting of the American Geophysical Union.

Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos