SoylentNews is people
SoylentNews
from the I-feel-the-Earth^w^wMars-move-under-my-feet dept.
A NASA mission previously scheduled to launch a robotic lander towards Mars in March may face up to a two year delay due to a fault in a seismometer provided by the French space agency:
The InSight spacecraft was scheduled to take off between 4-30 March and land on the Red Planet six months later to examine Mars' geology in depth.
Nasa said it had decided to call off the launch because the agency was unable to fix a leak affecting the seismometer, which required a vacuum seal to cope with harsh conditions on Mars. The instrument is designed to measure ground movements.
"A decision on a path forward will be made in the coming months, but one thing is clear: Nasa remains fully committed to the scientific discovery and exploration of Mars," Nasa's John Grunsfeld was quoted as saying by the AFP news agency. The next time the earth and Mars are favourably aligned for a launch will be in 2018.
[More after the break.]
According to Wikipedia:
InSight is a robotic Mars lander planned for launch in March 2016. The name is a backronym for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport.
The mission's objective is to place a stationary lander equipped with a seismometer and heat transfer probe on the surface of Mars to study its early geological evolution.
Prior coverage: Mars Spacecraft Shipped to California for March Launch
(Score: 4, Informative) by LoRdTAW on Wednesday December 23 2015, @04:14PM
I was curious about the sensor design and dug up some details.
Mission details:
http://www.jpl.nasa.gov/images/insight/InSightLitho2015.pdf [nasa.gov]
The sensor is called : SEIS (SEISMIC EXPERIMENT FOR INTERIOR STRUCTURE)
http://insight.jpl.nasa.gov/seis.cfm [nasa.gov]
A detailed description of SEIS is here:
http://www.lpi.usra.edu/meetings/lpsc2012/pdf/2025.pdf [usra.edu]
and here:
http://www.mps.mpg.de/1976953/Insight_SEIS [mps.mpg.de]
The design of the sensors calls for a controlled internal atmosphere, most likely due to using differential capacitive sensors which will likely be affected by changes in gas makeup and pressure. So they hermetically sealed the device and something sprang a leak. The usual culprits in this case are feedthrough leaks which are glass or ceramic sealed. Another culprit, though much less likely as it would have been caught earlier, is a weld failure of the connector or housing. A feedthrough is basically a hole drilled in the wall of the device which has a conductor placed through it. They then plug that hole with some type of nonconductive media that seals the hole. In the case of aerospace components, especially space, the conductor is usually a bare solid pin. Some connectors are designed to be welded into the housing after manufacturing. The connector housing might even be machined right into the housing as in the case of single or multi pin connectors like D-sub. The pins are set in a fixture and the holes filled with glass or ceramic and vacuum baked until they melt and seal. Plastics are avoided as they can't stand up to the mechanical, heat, vacuum, and radiation stresses encountered in aerospace applications.
The connectors and enclosures are usually welded using electron beam or laser. Most of these types of systems are one shot sealed. Meaning, once sealed, they are unable to be opened without machining or being destroyed. The most reliable method of leak testing is vacuum mass spectrometer helium leak checking. Depending on the spec, the glove box gas mixture may have 10% helium mixed in to provide a trace gas in the sealed component. If the piece is sealed in a vacuum or no helium is allowed, we use pressure bombing to force helium into the unit via leaks (if they exist) and then sniff for that helium once it leaks out using the mass spec.
(Score: 0) by Anonymous Coward on Wednesday December 23 2015, @05:33PM
I have to wonder whether this got flight qualified at the component level. Did it go through vibe and thermal vacuum testing? If so, did they check it before and after each test? Why did this become an issue after delivering to the launch vehicle?
(Score: 2) by LoRdTAW on Wednesday December 23 2015, @06:14PM
I am sure it was thoroughly tested. But like murphy's law states: Anything that can go wrong, will go wrong. Most likely the components which were built and tested in a lab are not flight hardware. The actual flight hardware is likely a different instrument built from scratch to the spec developed in the lab. It should have worked if built using the same spec but there are plenty of variables to go awry during manufacture. Happens all the time and i've seen it happen to very critical, very expensive flight hardware going into satellites.
(Score: 2) by frojack on Wednesday December 23 2015, @09:54PM
I would have thought this was a long solved problem, since its not exactly rare to need instrumentation inside of a sealed tank in spacecraft.
You can't just bench test it, you need vibration, heating, cooling tests as well. You say it happens all the time, yet its rare to have a mission put on hold for what is supposedly a common necessity.
No, you are mistaken. I've always had this sig.
(Score: 1) by linkdude64 on Wednesday December 23 2015, @05:47PM
Thank you for sharing those findings and your wonderfully detailed explanation.