Spacecraft, heal thyself (Forwarded)

ESA News
http://www.esa.int

20 January 2006

Spacecraft, heal thyself

Building spacecraft is a tough job. They are precision pieces of
engineering that have to survive in the airless environment of space,
where temperatures can swing from hundreds of degrees Celsius to hundreds
of degree below zero in moments. Once a spacecraft is in orbit, engineers
have virtually no chance of repairing anything that breaks. But what if a
spacecraft could fix itself?

Thanks to a new study funded by ESA's General Studies Programme, and
carried out by the Department of Aerospace Engineering, University of
Bristol, UK, engineers have taken a step towards that amazing possibility.
They took their inspiration from nature.

"When we cut ourselves we don't have to glue ourselves back together,
instead we have a self-healing mechanism. Our blood hardens to form a
protective seal for new skin to form underneath," says Dr Christopher
Semprimoschnig, a materials scientist at ESA's European Space Technology
Research Centre (ESTEC) in the Netherlands, who oversaw the study.

He imagined such cuts as analogous to the 'wear-and-tear' suffered by
spacecraft. Extremes of temperature can cause small cracks to open in the
superstructure, as can impacts by micrometeroids -- small dust grains
travelling at remarkable speeds of several kilometres per second. Over the
lifetime of a mission the cracks build up, weakening the spacecraft until
a catastrophic failure becomes inevitable.

The challenge for Semprimoschnig was to replicate the human process of
healing small cracks before they can open up into anything more serious.
He and the team at Bristol did it by replacing a few percent of the fibres
running through a resinous composite material, similar to that used to
make spacecraft components, with hollow fibres containing adhesive
materials. Ironically, to make the material self-repairable, the hollow
fibres had to be made of an easily breakable substance: glass. "When
damage occurs, the fibres must break easily otherwise they cannot release
the liquids to fill the cracks and perform the repair," says
Semprimoschnig.

In humans, the air chemically reacts with the blood, hardening it. In the
airless environment of space, alternate mechanical veins have to be filled
with liquid resin and a special hardener that leak out and mix when the
fibres are broken. Both must be runny enough to fill the cracks quickly
and harden before it evaporates.

"We have taken the first step but there is at least a decade to go before
this technology finds its way onto a spacecraft," says Semprimoschnig, who
believes that larger scale tests are now needed.

The promise of self-healing spacecraft opens up the possibility of longer
duration missions. The benefits are two-fold. Firstly, doubling the
lifetime of a spacecraft in orbit around Earth would roughly halve the
cost of the mission. Secondly, doubling spacecraft lifetimes means that
mission planners could contemplate missions to far-away destinations in
the Solar System that are currently too risky.

In short, self-healing spacecraft promise a new era of more reliable
spacecraft, meaning more data for scientists and more reliable
telecommunication possibilities for us all.

For more detailed information, please contact:

Dr Ian Bond
Tel: +44 (0)117 928 8662
Email: i.p.bond @ bristol.ac.uk

Dr Richard Trask
Tel: +44 (0)116 33 17499
Email: r.s.trask @ bristol.ac.uk

Department of Aerospace Engineering
University of Bristol
Queens Building
University Walk
Bristol
BS8 1TR
UK

Dr Christopher Semprimoschnig
European Space Agency (ESA)
ESTEC
Materials Physics and Chemistry Section
(Mail-code: D/TEC/QMC) [Room BC 029]
PO BOX 299
Keplerlaan 1
2200 AG Noordwijk
The Netherlands
Tel: +31 (0)71 565 3990
Fax: +31 (0)71 565 4992
Email: christopher.semprimoschnig @ esa.int

Related links

* ESA's General Studies Programme
http://www.esa.int/SPECIALS/GSP/index.html
* Advanced Concept Team activities on Biomimetics
http://www.esa.int/gsp/ACT/biomimetics/index.htm
* Department of Aerospace Engineering, University of Bristol, UK
http://www.aero.bris.ac.uk/

In depth

* Self-healing spacecraft (video)
http://www.aer.bris.ac.uk/research/fibres/gfrp.html
* Study Report on "Enabling Self Healing Capabilities"
http://esamultimedia.esa.int/docs/gs...eport_4476.pdf

IMAGE CAPTION:
[http://www.esa.int/esaCP/SEMQKMMZCIE_index_1.html]
A time lapse sequence of self-repair taking place

Hollow fibres just 30 micrometres in diameter tread the new material. When
damage occurs, the fibres break releasing liquids that seep into the
cracks and harden, repairing the damage.

Credits: ESA