When I was a wild and crazy youngster going to Devry we used to grow
(tomatoes, yeh that's the ticket) in a closet with what you can now
find called a bubbler. Very simple to setup and maintain. Have never
tried it with orchids but have used it for vegatables on the deck a
few years ago.
Basic 5 gall bucket nutr. mix in bottom, airstone or good air pump in
mix to splash it up. Plant root ball without soil or mix in mesh pot
stuck in lid hanging above liquid. bubbles pop up and fert. roots,
plant growes like a beast. Just add liquid once a week and Change
nutr. mix every couple of weeks.

dude
There are lots of ways to "do" hydroponics, with- and without inert
media.

Aeroponics is simply a term that indicates that the plant is suspended
in mid-air and its roots are misted with nutrients. Another, similar
methodology is the nutrient film technique (NFT) in which the plants
are suspended in mid-air, but there is a constant supply of nutrient
solution fed by a pump onto the suspension tray, and when it "leaks"
down, it forms a very thin film of solution on the roots. A further
variant is the "ebb and flow" method in which the nutrient solution is
pumped into the tray surrounding the root system on a periodic basis,
and then drains away.

If one adds an inert medium to provide the plant with mechanical
support, the three most common "mass planting" techniques involve
supplying the nutrient solution via either the "ebb and flow"
methodology or by periodic overhead sprays, or that in which a
constant, shallow depth of solution is recirculated through the
medium-holding tray and the capillary action of the medium does the
rest.

That last example is the closest thing to the technique I dubbed
"semi-hydroponics" - the single pot of inert medium with independent
reservoir that is manually watered - with the "semi-" added to
differentiate it from pumps, large trays or benches and a common
reservoir.