Aircraft parabolic flights provide repetitively up to 20 seconds of reduced gravity or weightlessness during ballistic parabolic flying manoeuvres, preceded and followed by periods of 20 seconds of 1.8 g's.

Parabolic flights are used to conduct short microgravity scientific and technological investigations in Physical and Life Sciences, to test instrumentation prior to space experiments to improve their quality and success rate, to confirm or infirm after a space mission results obtained from space experiments, and to train astronauts before a space flight. For microgravity scientists, aircraft parabolic flights are complementary and preparatory to space missions.


The main advantages of parabolic flights for microgravity investigations are:

- the short turn-around time: typically of a few months between the experiment proposal and its performance,
- the low cost involved: ESA provides the flight opportunity free of charge to selected investigators,
- the flexibility of experimental approach: laboratory-type instrumentation is most commonly used,
- the possibility of direct intervention by investigators on board the aircraft during and between parabolas,
- the possibility of modifying the experiment set-up between flights.

Aircraft parabolic flights are also the only sub-orbital microgravity carrier which gives the opportunity to perform medical experiments on human subjects in real weightlessness, complementing studies conducted in space and on ground in simulated weightlessness, such as immersion and bed rest.

Lastly, as Europe and the other international partners embarks in the building and utilisation of the International Space Station, aircraft parabolic flights can be considered as the first step toward the Station as the preparation of experiments, the microgravity testing of payloads and the training of astronauts will still be conducted during parabolic flights.

History of ESA parabolic flight campaigns

The European Space Agency (ESA) has organised since 1984 in the frame of its Microgravity Programme twenty six parabolic flight campaigns, using six different airplanes. More than 2650 parabolas were flown in total, yielding a cumulated total time of 14 h 45 min of microgravity in slices of 20 s, equivalent to nearly ten low Earth orbits. A total of 360 experiments were successfully performed.

During the very beginning of its parabolic flights programme (1984 to 1988), ESA conducted six campaigns from the Ellington airfield in Houston, Texas, on board NASA’s KC-135, a military version of the very successful Boeing 707 passenger jet.

In 1988, however, CNES invited the Agency to use their then newlyrefurbished Caravelle. This allowed ESA to establish a vigorous parabolic flightsprogramme in Europe. Thus, between 1989 and 1995, fifteen additional campaigns were flown on this aircraft. The sole exception during this time was ESA’s campaign No. 19 (1994) which, due to the temporary unavailability of the Caravelle, was performed on the Russian Ilyushin IL-76 MDK instead. In 1995 the Caravelle reached the end of its operational lifetime. Preparations were underway in CNES to modify prototype number 3 of the Airbus series of A-300 passenger jets for parabolic flights.

This aeroplane had never served in a regular airline, but had been used as a test frame for a number of novel Airbus technologies, such as the fly-bywire guidance system. Unlike the KC-135 and the Caravelle — well-known aeroplanes to the parabolic flights communities in the USA and in Europe — which have a military design background and can bear high acceleration loads, and whose engines are well-equipped to withstand the relatively long periods without lubrication during parabolic flights; everything about the Airbus was new.

It would be the first wide-body jet to fly parabolas, the first with turbo fan engines, etc. During the course of 1995, several trial flights were carried out by the Centre d’Essais en Vol (CEV), France’s organisation in charge of test-aircraft activities. The outcome of these flights confirmed the suitability of the A300 for its new role, and the refurbishment programme began in earnest at Sogerma Socea’s premises in Bordeaux (F). Renamed A300 Zero-G, the ‘new’ aeroplane was expected to become operational in 1996. Unfortunately, this was not the case since both the work and the flight certification process took longer than expected. Hence, in December 1996, ESA and CNES requested the assistance of NASA and performed their campaigns (ESA’s No. 23), in Bordeaux, on the KC-135. Meanwhile, the A300 Zero-G flew a number of parabolas which were used for qualification and for pilot training purposes.

The Airbus was ready at the beginning of 1997. A first mini-campaign was conducted in February for the Japanese space agency NASDA. It consisted of a single experiment for validating a solar panel deployment and retraction mechanism to be used in one of their satellites. Subsequently, during May 1997, CNES performed a full-size campaign which included twelve experiments. ESA’s twenty-fourth parabolic flights campaign, the subject of this article, was the third since the A300 Zero-G became operational.


Scientists are regularly invited to submit experiment proposals for the microgravity research programme of parabolic flights. Selected investigators are invited to participate in one of the future ESA campaigns. As far as possible, ESA will incorporate in each of its coming campaign an experiment proposed by students to promote microgravity research among students, tomorrow's scientists, in order to prepare for the utilisation of the International Space Station.

The Airbus A-300 Zero-G

Since October 1997, the Airbus A-300, based at the Bordeaux-Mérignac airport, France, is used by ESA and other space agencies for parabolic flight microgravity research.

The French company Novespace is contracted by ESA to provide for the campaign logistics and supervision of the experiment technical preparation. The 'Centre d'Essais en Vol' (CEV, French Test Flight Centre) provides all the in-flight support and flying personnel. The aircraft technical support is given by the Bordeaux based Sogerma company.

Organisation of a parabolic flight campaign

An ESA campaign is typically scheduled for two weeks, with the first week dedicated to experiment loading in the aircraft and the second week devoted to the flights. During the second week, a flight briefing, mandatory for all flying personnel, is held on the Monday afternoon.

Three flights of 30 parabolas are nominally scheduled for the Tuesday, Wednesday and Thursday mornings, with a flight lasting for about two and half hours. In case of bad weather or aircraft technical problem, a flight is delayed to the afternoon or to the morning of the next day. Investigators invited by ESA are therefore asked to foresee the Friday as a back-up flight day.

The flying area is usually a military air space zone either over the Gulf of Gascogne or over land, depending on meteorological conditions and availability of air zones.

Technical characteristics and flight procedures

The main technical characteristics of the Airbus A-300 cabin for investigators are
- a 20 x 5x 2.3 m (L x W x H) large experiment area,
- an environment of 18-25°C and 0.8 atm
- electrical power supplies of 220 V AC at 50 Hz, 28 V DC, 115-200 V AC at 400 Hz,
- an overboard ventline for combustion gases and pressure vessel purges,
- a continuous in-flight lighting,
- white foam padding covering walls,
- floor and ceiling to prevent injuries of free-floating personnel.

Detailed information on the aircraft and the applicable procedures for parabolic flights can be found in the User's Manual of the A-300 Zero-G.

Safety and health regulations

Safety of personnel and equipment are of paramount importance during ESA campaigns. Parabolic flights are considered as test flights, therefore particular precautions are taken to ensure that all in-flight operations are made safely and that flying participants are adequately prepared for repeated high and low gravity phases.

Prior to a campaign, support is provided to investigators in their equipment design and safety aspects. All experiments are reviewed by experts during visits to investigators' home laboratories. A safety review is held one month before the campaign where the integration of all equipment is discussed and the overall safety aspect of the campaign is assessed. Finally, a safety visit is made in the aircraft prior to the first flight to verify that all embarked equipment complies with safety rules.

All experimenters invited by ESA to participate to parabolic flights must pass a medical examination (FAA class III, valid for one year) and a hypobaric chamber physiological test (valid for three years).

For experiments proposed to be conducted on human subjects, medical protocols submitted by the investigators are reviewed by relevant Medical Boards to ensure that the proposed research is conducted according to established ethical and safety rules.

During the flights, specialized personnel supervise and support the in-flight experiment operations. A Flight Surgeon participates to all flights to supervise the medical aspect of in-flight operations and to assist flying participants in case of sickness. Due to the association of low and high gravity flight phases, motion sickness is quite common among participants to parabolic flights, sometimes hampering them to conduct their tasks. Prior to the flights, anti-motion sickness medication is made available on request of flying participants.
On-board investigators wear special ESA flight suits.

Flight opportunities for journalists

Since several years, ESA has adopted the policy of flying on each campaign qualified external observers, usually journalists, to report to the public on the on-going microgravity research sponsored by ESA.

Text excerpt from, dated 2003.