This is a collective page to document what we learn from preliminary research informally.
General guidelines:
What type of device (more specific than just “thermocouple”)?
What grade of device (on a range from hobby/DIY - industrial grade)
How do we use the device (power, signal connections, press a button, etc.)
How/where do we mount the device (epoxy, thermal tape, paste, frame, etc.)
What can go wrong with mounting and ways around it
EX: routing thermocouples in nose cone requires for wire to run into the airframe to reach the DAQ system, jeopardizing deployment of the nose cone
Potential solutions: use special wires that break during deployment, embed copper contacts into the airframe/nose cone shoulder
Based on the info collected above, what are the common price ranges?
Can you list some potential sensor candidates or suppliers? If so, please do.
Assignments:
Thermal - Eric & Juan
Vibration - Yasu
Chute/Airframe loads - Joanna & Jay
Flutter - Yasu
Thermal (Eric + Juan)
https://www.epj-conferences.org/articles/epjconf/pdf/2017/12/epjconf_efm2017_02075.pdf
Calibration is key
Temperature Calibration Uncertainty detailed in Guide to exp. Of Uncertainty in Measurement
“Intrinsic Thermocouples” might give us better spatial resolution (microtips)
https://www.epj-conferences.org/articles/epjconf/pdf/2017/12/epjconf_efm2017_02075.pdf
Seebeck effect
G,C,D are for high temp, K for VERY high temp
NiCr-NiAl used in experiment is oxidation proof, resistant to higher temps, reducing atmosphere, and sulphur compounds
“The thermocouple-based method has some limitations. One of the major problems is attaching a thermocouple to the surface to be measured. Incorrect bonding may cause the device to show a temperature lower than the actual one. When a thermocouple is used to measure the temperature of an element in a high frequency radio circuit, it may change the electrical characteristics of that circuit. A thermocouple fixed to a small electronic element may be responsible for the removal of heat from the element. As a result, the temperature displayed is lower than the actual temperature, i.e. one measured before the thermocouple was attached. Decalibration may lead to an error in measurement; it may change the electrical characteristics, which will make the reading inaccurate. Finally, an open thermocouple junction may also cause errors in temperature measurement [19]. “
Vibration (Yasu)
ceramic piezoelectric sensor/ accelerometer
single axis / triaxial accelerometer
Engineer’s guide to accurate sensor measurements: http://download.ni.com/evaluation/daq/25188_Sensor_WhitePaper_IA.pdf
what’s the effect of the constant acceleration/deceleration of the rocket on the sensors?
triaxial, +-500g, 2~7000Hz model(356B21): $1,125
figure: overview of triaxial accelerometers from NI (from white paper)
figure: dimensions of 356B21 accelerometer(from its product drawing, units in inches)
https://www.popsci.com/how-little-vibrations-break-big-rockets interesting article on the effect of vibration on rockets (but liquid-fueled rockets, so shouldn’t be a concern for us)
causes of vibration:
thrust oscillation
noise(pressure waves) from motor
explosive bolts
fluid flow phenomena
vibration mode of rocket
https://link.springer.com/chapter/10.1007/978-3-642-67208-8_34 Shock and Vibration Characteristic of Solid Rocket Vehicles
1979 paper from Japan
piezo vibration meters, flat response up to 2kHz
Falcon 9 User's Guide - SpaceXhttps://www.spacex.com/sites/spacex/files/falcon_9_users_guide_rev_2.0.pdf Falcon 9 User’s Guide
(for SpaceX customers)
shock loads during flight:(p.26)
release of launch vehicle hold-down at liftoff
stage separation
(fairing deployment, spacecraft separation)
2018/09/30
acceleration about 90m/s2(~9g) for 2012 rocket -> must consider range of accelerometer
±200g range
up to 1000Hz(z axis), 1300Hz(x,y axes)
“cross-axis compensation”: ±1.4%: how much perpendicular acceleration is coupled to signal (https://www.mouser.com/pdfdocs/an32_crossaxis_compensation.PDF)
sensitivity: 5.8~7.2mV/g -> 0.59~.73mV/(m/s2) (need calibration?)
Arduino’s analogRead() is 10 bits, so as a result 4.8mV/unit, 6.5~8.1(m/s2)/unit
$25
±16g, output resolution 13 bits
up to 3200Hz sampling
1/32 = 0.031g/bit = 0.3 (m/ss)/bit
$18
Chute (Jay + Joanna)
Load testing: http://www.futek.com/product.aspx?t=load
Need to know what kind of weight this thing needs to take: too much capacity implies too little precision
Upper bound 2000 lbs
Type of cell / how to install
https://sensor-con.en.alibaba.com/productgrouplist-803400380/Load_Cell.html?spm=a2700.icbuShop.0.0.120b4eb17iN3Gv cheap load cells from Shenzhen
These look like they’ll work, as long as we select a generous/correct mass range. Doesn’t look like we have a huge precision loss as the mass range increases.
From NASA Langley case file, they had problems with lead wire breakage- we should make sure we prepare for this problem
https://www.omega.com/prodinfo/strain-gauges.html
Pretty good website, introduces different types of strain gauges and gives recommendations
Karma strain gauges are good for use over wide temperature ranges
Around $50-60 from Omega
http://www.ni.com/white-paper/3642/en/
Another really good site talking about different strain gauges
https://www.digikey.com/products/en/sensors-transducers/strain-gauges/559
Lots of strain gauges here, strain range goes from .5% - 1.5%, resistance tolerances range from .15% to 30%
-limit output of load cell to input of teensy
-size and weight and price (total budget is $2000)
Fin (Yasu)
http://web.mit.edu/rocketteam/www/usli/2011-12/MIT%20RT%20CDR%202012.pdf
https://www.youtube.com/watch?v=OhwLojNerMU dope video demonstrating flutter
use GoPro?
GoPro Hero 7 black: $399
camera angle may be a problem, if you want to look at the fins
mirrorssss
A Historical Overview of Flight Flutter Testing - Wiredhttps://www.wired.com/images_blogs/autopia/2010/.../19960004074_1996104074.pd… A Historical Overview of Flight Flutter Testing
1995 NASA paper about Flutters
structurally ok?
2018/09/30
2012 rocket used a Casio digital camera
12.75MP photos
224x160 480fps
176g
GoPro Hero 7 Black
12MP photos
1080p 240fps
flutter frequency was about 35.3Hz for 2012 rocket (CDR 2012 p.59)
>70 fps camera required