Jordi IsernInstitut de Ciències de l’Espai

(CSIC-IEEC)

MSc in Economics of Science & Innovation Innovation & Challenges:Nanotechnology & Space

(6d)Microgravity

Sometimes it is necessary to remove the gravityInfluence to understand how a phenomenon works!

The ambients with reduced gravity are called microgravity ambients μg = 10-6 g

One possible solution could be to move far away from the influence of the EarthBut this happens at a distance of 6.37 millions of km to obtain 1 μg

5 mIf a = g , t = 1 sIf a = 0.01g, t = 10 sIf a = 10-6 g, t = 1.000 s

There are easier issues!

Influence of gravity:•Thinks drop•Buoyancy•Sedimentation

1 2 3 4

Accelerated reference systems

F mg S ma

S is the force measured by theweighing machine

( )S ma mg m a g

1) a = 0; S = mg2) a > 0; S = m(a+g); larger weight3) a < 0; S = m(a+g); lower weight4) a = -g; S = 0

Systems to obtain microgravity ambients

Drop towers

NASA Lewis Research Center:# 2.2 s, 24 m tower# 5.2 s, 132 m tower

NASA Marshall Space Flight Center# 4.5 s, 100 m pipe

ZARM Bremen# 4.74 s, 120 m tower

Japan:# 10 s, tower + mine well 490 m

2htg

ZARM (Bremen)

17.000 m310-6g

240 cm

80 cm

Airplanes

Flight: 3 h, 40 micro-g events

Rockets

Residual accelerations of 10-5 g during minutes

The typical orbit of the Shuttle is about 320 kmheight. The microgravity ambient is excelent and experiments can last for a coupleof weaks

Skylab

MIR Space Station

International Space Station

Microgravity quality:

In orbit there are several residual forces that degrade the μg quality:

•Atmospheric drag •Centrifugal forces caused by the rotation of the satellite•Any object not placed at the center of masses moves in a different orbit

The residual gravity caused is ~10-6 g And is nearly stationary

The onboard operations introduce severeperturbations to the μg quality

•Fans, pumps, centrífuges, •Astronauts movements…

Residual accelerations ~10-4 g

One astronaut raised his arm 8 times!

Foton

Especialized platforms are more efficient!

Biotecnology

The main problems are sedimentation andconvection.

Sedimentation induces a bidimensionalcellular growth and perturbates the growthof crystals

Convectin introduces tensions and prevents the cellular or atomic aggregation

Insuline crystals

CombustionBurning is a selfsustained reaction that releases energy. It requieres fuel, an oxidizerand an ignition agent

Fuels can be solid (paper, wood, coal), liquid (gasoline, gasoil), gas (hydrogen, propane). Oxidizers can also be solid (perclore amonium), liquids (hydrogen peròxide), gas (oxygen).

Convection and sedimentation are critical for the flames

ESA microgravity research programme

ESA facilities already developed or under development :

• Material Sciences Double Rack• SLED - weightlessness on human vestibular system• BIORACK - study of cells and complex biological systems• ANTHRORACK - physiological measurements• Fluid Physics Double Rack - fundamental fluid properties• EURECA facilities - materials & life sciences research• Bubble Drop and Particle Unit• Critical Point Facility• Advanced Gradient Heating Facility• Autonomous Fluid Physics Module• Advanced Protein Crystallization Facility• Glovebox.