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Denis Thierion – Access to Micro-gravity. Parabolic Flights. A300 ZERO-G – 2003

Director of parabolic flights, CNES (Centre National d’Etudes Spatiales), Toulouse, France

First publication symposium Visibility – Legibility of Space Art. Art and Zero G. : the experience of parabolic flights, in collaboration with the @rt Outsiders festival, Paris, 2003.

Introduction

Subjected to the laws of terrestrial attraction, all objects are pulled toward the center of the earth. Obstacles (ground, building, table) break this fall, assigning each object or person the sensation of weight, that is to say gravity.

Nevertheless, under certain conditions, we can make certain effects of gravity disappear. This is the case for spationauts, who, once liberated from their weight, seem to float in their vessels. This is also what happens during parabolic flights, which allow one to experience weightlessness on earth for a few seconds.

Rocket-launchers and drop towers can also be used. However, since these devices are entirely automated, they cannot transport men.

Since 1988, the CNES has organized a parabolic flight program in order to carry out scientific experiments in weightlessness without using costly spatial apparatus. Since 1997, the organization has used a specially-equipped Airbus A 300 retrofitted by NOVESPACE: the A300 ZERO-G.

Each flight comprises a series of 30 parabolas during which the plane is in free fall for 20 to 25 seconds, thereby creating a situation of weightlessness. Previously untested experiments can then be conducted.

THE A300 ZERO-G

• Name : A300 ZERO-G
• Initiator : NOVESPACE (subsidiary of the CNES)
• Origin : Suggestion made by the CNES’s scientific programs management team
• Status : In progress.
• Owner and Manager of the Program: NOVESPACE
• Financing: CNES, ESA and NOVESPACE

• Clients : le CNES, l’ESA, le DLR, la NASDA, Spacehab, Guigné Technologies, Nec, Toshiba, etc…
• Objectives : to conduct scientific experiments through the recreation of the conditions of weightlessness, to run technological tests or pedagogical experiments
• 1st parabolic flight: 1997

An economical means to weightlessness

History of the Program

Parabolic flights were first introduced in France in 1946 and were conducted by the CEV (Centre d’Essais en Vol) to test plane equipment. This activity continued for roughly 15 years.

The CNES then decided to use parabolic flights for scientific purposes. The technical and financial feasibility of the project was proven in October 1988. One year later, the first campaign begins with a jet plane (Caravelle).

The star of postwar French aeronautics, the plane made close to 40 parabolic flight campaigns over a period of six years, all marked by NOVESPACE.

In 1997 the Caravelle Zero-G was replaced by the Airbus A300, the largest 0 g aircraft in the world. The acquisition of the Airbus A300 is paid for by the CNES while its subsidiary, NOVESPACE financed the retrofitting of the machine for parabolic flights. Work begins on the place in mid 1996 and the plane is certified for flight in May of the following year.

Vocabulary: The letter g designates the acceleration of terrestrial gravity. On the ground g is equal to 9.8 m/s². It also refers to the unit of acceleration (1 g = 9.8 m/s²).

Organization

Founded in 1986, NOVESPACE manages the program, organization and promotion of parabolic flights while the CNES and the ESA share the investment costs and those costs related to the maintenance of the planes.

NOVESPACE conducts between 6 and 7 parabolic flight campaigns per year on behalf of the CNES, ESA, DLR (German space agency) and European, American, Japanese industrial companies.

On the utility of parabolic flights

Introduced for the purpose of training astronauts, parabolic flights are primarily used to conduct scientific experiments and to test space technology. The 0 g plane has proven to be an excellent trial base prior to sending sophisticated tools into space.

While sounding rockets and space stations also are means of accessing microgravity, the parabolic flight is the most flexible and the least costly.

With parabolic flights, scientists have a flexible means of experimentation at their disposal. The waiting period between a proposal for an experiment and its realization is thus reduced to just a few months. Furthermore, scientists are present during the flight and can adjust their experiments as necessary.

A unique testing ground

An extensive field of investigation

The use of parabolic flights extends from the physical sciences to life sciences. Fluid mechanics, biology, human physiology, combustion and fundamental physics are among the most studied disciplines.

The nature of the experiments conducted aboard the A300 ZERO-G varies greatly: from testing the effect of a caisson used for draining blood from the bottom of the body during space flights to the study of the combustion of a drop of gasoline in a rocket-motor.

For several years, scholarly establishments have also been invited to design and conduct experiments aboard the A300 ZERO-G. The difference between weight and mass, the realization of an autonomous altitude control system…examples of projects developed by groups of fervent young people eager to experience the phenomenon of weightlessness.

The objective of this initiative is also to introduce these persons to science and the development and organization of a space project.

The Limits of Parabolic Flights

The conditions under which one attains weightlessness during parabolic flights are, in relation to space flights, limited in quality and in duration. The weightlessness recreated during these flights is thus 0.05 g, while it is 10-6 g

in an automatic space capsule. However, this quantity is sufficient for the study of numerous phenomena.

Successful Campaigns

A parabolic flight campaign consists of one flight per day over the course of 3 days. From 1997 to 2003, the Airbus A3000 ZERO-G successfully completed 133 flights, equivalent to 3,374 parabolas.

Roughly 739 experiments have been conducted. Among the most significant results we can highlight the following:

• On the scientific side : the study of the structure of granular areas in vibration, the study of combustion, the study of the role of microgravity on postural control and ocular-motor coordination, the study of cognitive aspects (the notion of internal referentials…). All of these studies have been the object of numerous publications.
• On the technological side: the test on the refolding of solar panels of the Japanese satellite COMETS that enabled the identification of a major faulty part and to validate its correction.

It is important to note that experiments in field of Life Sciences requiring healthy volunteers are conducted in accordance with the Huriet law.

The Airbus A300 ZERO-G is an authorized research center, all of the experimental protocols are submitted to an ethical committee and are the object of a declaration from the Ministry of Health.

Parabolic flight specifications

A Slightly Modified Aircraft

The A300 ZERO-G closely resembles a traditional plane with the exception of a few specific modifications.

The cockpit was retrofitted to satisfy the needs of a parabolic flight: the addition of accelorometric indicators, the displacement of certain command buttons to render the weightlessness phase more accessible, etc. The pilots are all experienced test pilots.

The cabin has also been entirely rethought. The number of seats has been reduced to 40, located at the front and the rear of the aircraft. The floors and walls are covered with a layer of foam in order to protect passengers and the experiment modules are fixed to the on a 100 m2 surface.

The addition of electrical panels, handrails, and the modification of the lights, etc.: the A300 ZERO-G was entirely retrofitted to optimize the work of researchers.

Finally, the electrical generation system and the inertial centers of the planes were modified to sustain successive periods of microgravity. A GPWS and a TACS were installed in order to facilitate missions abroad.

The Parabolic Principle

During the first phase of the flight, the plane maintains a steady horizontal flight. The pilot prepares for the parabolic maneuver by progressively increasing the speed of the aircraft to roughly 810 km/h, maximum speed authorized for this type of machine. He then noses up the aircraft to attain a 45° angle. During this maneuver, the passengers weight 1.8 times their terrestrial weight.

While the plane is ascending, the mechanic considerably reduces the engine thrust, to the point where it just overcomes the aerodynamic drag, and the pilot kills the lift. Like a projectile, the aircraft describes a parabola. Its passengers and the cargo are then in “free fall” in conditions similar to those of weightlessness.

Twenty seconds later, gravity rapidly returns. When the plane reaches an incline of 45° facing the ground, the mechanic increases the engine thrust while the pilot progressively resumes the lift. Once again, the passengers weigh 1.8 times their weight for another 20 seconds, before returning to a horizontal position. There is a two-minute interval between each parabola.

These maneuvers are repeated 30 times during each flight.

Technical principles

A few numbers for the A300 ZERO-G

Mass : 137 tons
Dimensions : 52 m (length) x 44 m (width), diameter 5,64 m
Surface of Testing Cavity : 100 m2
Measure of weightlessness : 5.10-2 g
Maximum Capacity : 40 passengers
Number of Experiments Aboard : 10 to 15
Home Base : Bordeaux-Mérignac International Airport

In 2003 the A300 ZERO-G has other usages: It is most commonly used by the ESA and the CNES within the scope of the ARTA program, in order to monitor pieces fallen from the Main Cryogenic Level of Ariane 5. A radar system, whose antenna is attached to the front cargo door, was installed aboard the spacecraft for this purpose. Other uses for the A300 ZERO-G are in progress, notably for European companies in the military field.