Microgravity

Gravity is a force that keeps our feet on the ground, the Moon orbiting around the Earth and all the planets in our Solar System orbiting the Sun.

It was first described by Sir Isaac Newton more than 300 years ago and, like any force, causes object to accelerate. The Earth's gravity causes objects to accelerate towards it at 9.8 m/sec2 (or 1g).

Anything in freefall appears to be weightless and so we describe this as zero-G or zero gravity. It is hard to achieve perfect weightlessness so scientists use the term microgravity (one millionth of 1g) to describe these conditions.

Vomit comet

Parabolic flights can achieve microgravity conditions for around 20-25 seconds at a time. This is when an aircraft climbs steeply before dropping back down again in a parabolic arc, rather like a roller coaster funfair ride. This may explain why the plane that provides parabolic flights at NASA is called the vomit comet! The vomit comet is how the weightlessness scenes were filmed for the Hollywood movie Apollo 13.

In Europe, parabolic flights are run from Bordeaux-Merignac airport in France. An airbus, operated by Novespace, flies a series of arcs allowing people 20 seconds of weightlessness at a time. The International Space Station (ISS) maintains its orbit due to gravity but the astronauts on-board experience weightlessness. This is because the ISS and its contents are also in freefall around the Earth while travelling at around 27,500 km per hour.

Why do scientists need microgravity?

If mankind is to travel further into our Solar System and beyond, then we need to understand what effects long haul spaceflight and microgravity will have on our bodies.

These missions can also simulate the conditions any new life forms would experience if they entered the Earth's atmosphere on meteorites. But microgravity experiments also have applications on Earth. Gravity affects many physical processes and this can make them harder to understand. By removing the effects of gravity, scientists can study different processes more easily.

In 2003, the independent Microgravity Review Panel recommended that the UK take part in the European microgravity research programme on the ISS and use other orbital and sub-orbital facilities.

UK scientists want to use microgravity to:

• Gain more accurate measurements of the properties of molten metals - this can improve the quality of nickel and titanium alloys, high-grade steel making and other industrial processes.
• Study muscle and bone wasting - these processes are accelerated by the absence of gravity. This is why astronauts need to exercise constantly during missions and, after long duration stays on-board the ISS, often need assistance walking on their return to Earth. Studying the effects of gravity on the body in space helps research into osteoporosis on Earth.
• Investigate the genetic effects of gravity on the growth of plants - these results will be vital for those working in agriculture. Plant experiments are part of ESA's Foton missions

Foton

FOTON-M3
Credit: ESA

UK scientists were involved in the most recent Foton mission, Foton-M3, which carried more than 40 ESA experiments ranging from fluid physics to crystal growth and exobiology. These included Biobox, which studied the effect of weightlessness on bones, and the Life Marker Chip (LMC) on its Biopan payload.

The LMC was proposed by scientists at Cranfield University, the University of Leicester, Carnegie Institute at Washington DC and DLR Germany. Its ultimate aim is to detect molecular evidence of life on the future ExoMars mission. For more details on microgravity, and some of the experiments that use it, please visit the microgravity website.

BNSC is seeking views on the current level of interest in microgravity research in the UK.