# What is this balloon for in this clean room and what is the proper name for the "stand" that is holding the satellite?

What is this balloon doing in this clean room and what is the proper name for the "stand" (white & blue) that is holding the satellite?

• Pretty sure the stand is a vibration tester. No idea what the balloon is for, huh. Feb 6, 2019 at 3:21
• No that is not for vibration test. This is >> isac.gov.in/facility/f-system-3.jsp Feb 6, 2019 at 6:52
• I'd call that a goniometer, but there may be a fancier name for it.
– uhoh
Feb 6, 2019 at 9:04

The balloon is used to support parts of the spacecraft that can't hold their own weight in 1 g - booms, appendages, etc.

As you can see from this cropped photo (from here), there is no hose to allow flowing extra gas into the balloon. It is simply connected to the object it supports by a tether.

The stand is called a "positioner" if it allows the spacecraft to be held at multiple angles. But often just referred to as "fixture" or "stand".

A 3-axis positioner can also be used. This is an elaborate fixture that holds the spacecraft at multiple angles to measure all mass properties (CG in 3 axes, MOI in 3 axes, and POI in 3 planes). It allows calculation of product of inertia based on moment of inertia measurement, so the entire inertia tensor can be derived with the use of a KSR instrument. The spacecraft positioner also minimizes handling of the spacecraft. The spacecraft is mounted in a vertical orientation; the positioner rotates the spacecraft to the various measurement positions and brings the spacecraft back to vertical for easy dismounting.

More, and examples here

• If there exist spacecraft components which can't hold their own weight in 1g, how are they going to survive launch? Oct 21, 2019 at 14:17
• @Intellex This is used for appendages that unfold after orbital insertion: antennas, solar panels, etc. It's a completely different loading situation; the folded case handles launch loads. Oct 21, 2019 at 14:19
• Is ISRO the only agency to use balloons, or others too use them? Oct 21, 2019 at 14:22
• It's not unknown; here's another example: directory.eoportal.org/web/eoportal/satellite-missions/i/… (scroll down) Oct 21, 2019 at 14:24
• – uhoh
Apr 14, 2021 at 23:45

Having looked at the various ISAC facilities, I suspect that is just an adjustable stand in one of the clean rooms.

Compare to this image search result for 'ISAC clean room':

The stand is adjustable to give easy access to all areas of the satellite without having to use ladders (which can fall over and damage the satellite).

A similar system (with only 1 degree of freedom) for car bodies is known as a rotisserie:

ISAC has removed all images of their test facilities from the HTML of their website, but the images are still there and can be found via an image search.

Example, this is a vibration test system at ISAC:

As for the balloon, I haven't found a reference. I suspect it's used to capture overflow helium during filling of the helium tanks in a spacecraft.

• Maybe the helium tanks are "washed" from remaining air by filling them partially and then releasing the mix of helium and air into the balloon until there is only pure helium in the tanks.
– Uwe
Feb 6, 2019 at 9:35
• Of course, as we've learned previously, it doesn't prevent damage to the satellite if you forget to bolt it down: space.stackexchange.com/q/1783/58 Feb 6, 2019 at 14:49
• With reference to this statement "Having looked at the various ISAC facilities..." Are you currently working at ISRO? Sorry to ask an irrelevant question, but it is related to one of my questions. Oct 23, 2019 at 13:25
• No. I only did an image search on the internet. Oct 23, 2019 at 13:36