Drop Tower

Drop towers, like this one at NASA Glenn Research Center, offer a way to conduct microgravity analog experiments.  Contents experience between 5-60 seconds of free fall as the experiment plummets from the top of the tower.  The duration of free fall depends on the tower's height.

Advantages

This method is better suited for fluid characterization of the culture environment.  It is also affordable and allows repeat experiments.

Disadvantages

Free fall does not last long enough for some culturing experiments.  The sudden stop at the bottom of the tower will disrupt sensitive experimental contents.

+ Visit the 2.2 Second Drop Tower website

Parabolic Flight

Parabolic flight, where a specially modified jet alternates steep climbs with long drops (much like a roller coaster), generates 20 - 30 seconds of free fall.  A typical mission lasts 2 to 3 hours and consists of 30 to 40 parabolas.

Advantages

Multiple parabolas can be flown, allowing repeat experiments to be performed under the same conditions.  Flight maneuvers can be modified to provide any g-force level less than 1.

Disadvantages

Steep climbs that precede seconds of free fall create hypergravity.  This affects samples and confounds data.  Parabolic flight can also be expensive, making repeat experiments difficult.

+ Visit the Reduced Gravity Program at the Zero G website

Suborbital Flight

Suborbital rockets release a parachuted research payload, offer 4 to 12 minutes of free fall, sufficient time for some cell biology experiments.  Investigators can study cell movement, signal transduction, and characterization of fluid dynamics in the culture environment.

Advantages

A subset of cell biology experiments can be conducted with suborbital flight, but is not suitable for longer experiments to culture cell aggregates and tissues.

Disadvantages

Suborbital rockets can also be expensive, making repeat experiments difficult.

+ Visit the Suborbital Launch Program at Wallops Flight Facility

Stirred Bioreactor

The logical solution for ground-based cell culturing is to suspend cells in a growth medium with stirring technologies.  The growth medium is an isopycnic or constant density solution.  This produces a neutral buoyancy environment for cells.

Advantages

Suspended cells do not sediment and form monolayers.  They are also in a homogenous solution, where gradients do not form.

Disadvantages

The mechanical force of stirring produces both mechanical and hydrodynamic shear.  This disrupts normal cell aggregation and ultimately results in cell death.  Cells are also at rest and exhibit poor tissue morphogenesis.