CII Thermal Interface Guidelines
CII Thermal Interface Guidelines
Gaj Birur NASA CII Team
1
General Background CII Thermal guidelines effort started in March 2011 The major activities as of today include the following: Discussions with the CII team (from various NASA Centers) on the common approach to be used for developing the guidelines A review of the payload Thermal Interface Control documents used in the past spacecraft, ISS, and various science instruments (both Earth-orbiting and deep-space missions) Visits with other non-NASA centers (AFRL) to learn about their thermal interface requirements for hosted payloads Discussions with instrument providers and spacecraft vendors (before, during, and after CII Workshop I) Going through our (Gaj and Eric) own experiences on instruments & spacecraft as thermal leads during the past 25 years 2
Thermal Interface Goals The primary goal is to enable science instruments to maximize their chance for a ride on an Earth-orbiting spacecraft To allow the instrument to easily meet its thermal requirements when mated to a hosted spacecraft To cause minimal thermal perturbations on the spacecraft system or let the spacecraft perturb the instrument design To help a flight ready instrument to be accepted as a hosted payload without requiring significant modification to thermal design To help the instrument meet its science goals to full extent To help the instrument PI and designers to plan ahead their thermal architecture before a spacecraft (carrier) is selected
3
LEO Thermal Interface Assumptions Key assumptions in the CII thermal guidelines are: The instruments need to be nadir pointed in order to have a clear view of the Earth’s surface and/or limb The instrument radiators prefer to view deep space and do not want to be nadir pointed The instrument volume envelope and the mass are capped at 200 kg and one cubic meter Instrument is thermally isolated from the spacecraft and the neighboring instruments Instrument has its own thermal control (except for electrical power) Implementation details will be worked out between the spacecraft and instrument in an ICD once paired
4
Typical Low Earth Orbit Satellite Hosted Payload
Primary Payload Spacecraft (Carrier)
RAM Nadir
5
Thermal Interface Drivers A key thermal interface driver is the demand the instrument and spacecraft make on each other; Less demand leads to lower costs and better performance Typical instrument demand on spacecraft include: Survival heater power Instrument temperature monitoring by spacecraft Flight rules on spacecraft orientation restrictions, etc.
The required instrument radiator size can vary by a factor of four depending on the instrument location on spacecraft Certain payload operating temperature requirements (e.g., very low temperature or very stringent thermal stability) can impose severe constraints on spacecraft operation 6
Summary of Guidelines A table of guidelines documented in Thermal Guidelines document is given below 8.0 Thermal Interface Guidelines Document 8.4 8.5 8.6 8.7 8.8 8.9 8.10 8.11 8.12 8.13
Thermal Design at the Mechanical Interface Thermal Design Survival Power and Temperature Temperature Maintenance Temperature Monitoring Thermal Hardware Thermal Analytical Models Launch Thermal Environment Design Validation Thermal Verification
7
Feedback from Workshop 1 1.
Rewrite thermal spec 15W/m2 to include some minimum allowed, such as 15 W/m2 or 1 W, whichever is greater.
2.
Please add temperature sensors (~ 2) for monitoring payload when it is off
3.
Updated Thermal guidelines: “Interface conductance heat transfer at 15 W/m2 or 4 W, whichever is maximum”
Updated guidelines: “Instrument designer should assume that spacecraft may not be able to provide temperature monitoring of the payload when it is off”
Need a thermal radiator clear field of view to space and/or clear field of view without spacecraft interference to be defined as guidelines (or at least an option). Need more definition here than currently is
The updated Thermal Guidelines: “..the placement of the instrument radiator should be flexible such that in any of these spacecraft mounting configurations, the radiator can have the required view of space. Other recommendations include over sizing radiators to accommodate unexpected blockage from spacecraft or other payload surfaces. Unused area can be blanketed off,... etc”
8
Key LEO Thermal Guidelines -1/2 Examples of key thermal guidelines that maximize the opportunities to be paired with host spacecraft include: Thermally isolated instrument imposes minimal constraints on the host Flexible thermal design allows for favorable radiator position ID
Function
Guidelines
Rationale/Comment
8.5.1
Heat rejection to space
Use of heat pipes, high thermal conductivity straps etc if they can be accommodated
Allows radiator to be located in a desired orientation without putting constraints on spacecraft
8.5.2
Thermal Isolation
Thermally isolate the instrument from spacecraft
Makes the instrument independent of spacecraft & imposes least thermal demand on the spacecraft
8.5.3
Survival Use parts qualified to very low Reduces requirement for temperatures temperatures survival power 9
Key LEO Thermal Guidelines – 2/2
ID
Function
Guidelines
Rationale/Comment
8.5.4
Cryogenic temperatures
Use TEC or Cryo‐coolers to achieve required temperatures if needed
Allows instrument to be independent of spacecraft
8.5.5
High thermal stability
Use of high thermal capacity components (PCM storage etc), if needed
Short term transient can be handled easily
8.6.1
Survival Use mechanical thermostats for Instrument totally heater control survival heater control isolated from spacecraft
10
Louvers & Heat Pipes on EOS Aura Instruments
Signal Chain Evap/LHP
TES Instrument
MLS Instrument
11
Thermal Technologies for Instruments Aura/TES Thermal Hardware
High‐conductivity blades (M3)
Loop Heat Pipe
OCO‐ VC Heat Pipe
High thermal conductivity straps
Mechanical Cooler MER Battery Heat Switch
PCM Thermal Storage
12
GEO Considerations for Thermal From thermal perspective, the GEO spacecraft are similar to LEO on most of the thermal interface requirements The Earth’s IR flux and albedo on a GEO-mounted radiator is an order of magnitude lower (250 - 400 W/m2 vs. 6 - 8 W/m2) Earth’s lower IR flux at GEO allows for a placement of the instrument radiator located pointing to Earth
13
CII Thermal Guidelines – Conclusions The CII thermal guidelines are to help the science instrument developers maximize Earth-orbiting mission opportunities Understanding the constraints of the hosted LEO and GEO spacecraft will help the instrument developers design their instruments to be more acceptable This is an ongoing effort that involves both the Earth Science community and the spacecraft vendors
14
Back Up Charts
15
Thermal Interface Guideline Feedback-1 Thermal Guidelines 8.4.2 & 8.8.2 Concern Thermal interface guidelines
Recommendation 1) Rewrite thermal spec 15W/m^2 to include some minimum allowed, such as 15 W/m^2 or 1 W, whichever is greater. 2) Please add temperature sensors (perhaps 2) for monitoring payload when it is off
Attributable Comment 1) The guideline provides a recommended, not-to-exceed flux. It is intended to be used in conjunction with the Mechanical guidelines: specifically, the maximum recommended footprint. With this information, the payload team has an idea of both the recommended maximum heat transfer and flux transfer. This gives more flexibility to the design when compared to the often-used interface spec of a not-to-exceed thermal conductance. But the comment is well-taken. The guideline lacked completeness in that it did not specifically cite the relevant Mechanical guideline. As such, it appears to penalize payloads for using smaller footprints. The guideline will be re-written to account for the recommended Mechanical foot-print of 600mm x 420mm as shown below. At 15 W/m2, this yields a maximum recommended power of under 4W. The next version of the thermal guidelines will expand on the thermal interface conductance to include this include the following statement: “The conduction heat transfer at the Instrument-Spacecraft mechanical interface should be less than 15 W/m2 or 4 W, whichever is maximum”. 2) The feedback on monitoring the payload temperature when it is off, the following statement will be included either the Thermal Guidelines section or in the Data and Power Guideline section: “the instrument designer should assume that spacecraft may not be able to provide temperature monitoring of the payload when it is off.”
16
Thermal Interface Guideline Feedback-2
Thermal Guideline 8.5.6 Concern Major impediments that instrument provides have in using CII as currently defined. 2) Need a thermal radiator clear field of view to space and/or clear field of view without spacecraft interference to be defined as a guidelines (or at least an option). Need more definte here than currently is. Instrument designers will have no clue if they can be accommodated thermally without getting involved in detail with specific spacecraft providers.
Recomm.
Attributable Comment 3) Feedback was received on the clear field of view (FOV) of space for the instrument radiator(s). The request was to work toward an agreement with spacecraft providers to produce a minimum guaranteed FOV to cold space. While a certain level of cold space FOV may be guaranteed, the uncertainty in orbits, orientations, and nearby surfaces prevents futher specification. And without additional specification, a FOV value has limited value to the payload designer. At this time, the cii team can only give guidelines that will maximize the chances of utilizing the FOV specified once paired with a spacecraft. The following statement will be included in Thermal Guidelines: “the instrument designer should expect the instrument to be mounted to a side of the spacecraft which could be any of the six sides of the spacecraft (nadir, zenith, East, West, North, and South). The placement of the radiator on the instrument should be flexible such that in any of these S/C mounting configuration, the radiator can have the required view of space. Other recommendations include oversizing radiators to accommodate unexpected blockage from spacecraft or other payload surfaces. Unused area can be blanketed off,... etc
17
Gaj Birur NASA CII Team
1
General Background CII Thermal guidelines effort started in March 2011 The major activities as of today include the following: Discussions with the CII team (from various NASA Centers) on the common approach to be used for developing the guidelines A review of the payload Thermal Interface Control documents used in the past spacecraft, ISS, and various science instruments (both Earth-orbiting and deep-space missions) Visits with other non-NASA centers (AFRL) to learn about their thermal interface requirements for hosted payloads Discussions with instrument providers and spacecraft vendors (before, during, and after CII Workshop I) Going through our (Gaj and Eric) own experiences on instruments & spacecraft as thermal leads during the past 25 years 2
Thermal Interface Goals The primary goal is to enable science instruments to maximize their chance for a ride on an Earth-orbiting spacecraft To allow the instrument to easily meet its thermal requirements when mated to a hosted spacecraft To cause minimal thermal perturbations on the spacecraft system or let the spacecraft perturb the instrument design To help a flight ready instrument to be accepted as a hosted payload without requiring significant modification to thermal design To help the instrument meet its science goals to full extent To help the instrument PI and designers to plan ahead their thermal architecture before a spacecraft (carrier) is selected
3
LEO Thermal Interface Assumptions Key assumptions in the CII thermal guidelines are: The instruments need to be nadir pointed in order to have a clear view of the Earth’s surface and/or limb The instrument radiators prefer to view deep space and do not want to be nadir pointed The instrument volume envelope and the mass are capped at 200 kg and one cubic meter Instrument is thermally isolated from the spacecraft and the neighboring instruments Instrument has its own thermal control (except for electrical power) Implementation details will be worked out between the spacecraft and instrument in an ICD once paired
4
Typical Low Earth Orbit Satellite Hosted Payload
Primary Payload Spacecraft (Carrier)
RAM Nadir
5
Thermal Interface Drivers A key thermal interface driver is the demand the instrument and spacecraft make on each other; Less demand leads to lower costs and better performance Typical instrument demand on spacecraft include: Survival heater power Instrument temperature monitoring by spacecraft Flight rules on spacecraft orientation restrictions, etc.
The required instrument radiator size can vary by a factor of four depending on the instrument location on spacecraft Certain payload operating temperature requirements (e.g., very low temperature or very stringent thermal stability) can impose severe constraints on spacecraft operation 6
Summary of Guidelines A table of guidelines documented in Thermal Guidelines document is given below 8.0 Thermal Interface Guidelines Document 8.4 8.5 8.6 8.7 8.8 8.9 8.10 8.11 8.12 8.13
Thermal Design at the Mechanical Interface Thermal Design Survival Power and Temperature Temperature Maintenance Temperature Monitoring Thermal Hardware Thermal Analytical Models Launch Thermal Environment Design Validation Thermal Verification
7
Feedback from Workshop 1 1.
Rewrite thermal spec 15W/m2 to include some minimum allowed, such as 15 W/m2 or 1 W, whichever is greater.
2.
Please add temperature sensors (~ 2) for monitoring payload when it is off
3.
Updated Thermal guidelines: “Interface conductance heat transfer at 15 W/m2 or 4 W, whichever is maximum”
Updated guidelines: “Instrument designer should assume that spacecraft may not be able to provide temperature monitoring of the payload when it is off”
Need a thermal radiator clear field of view to space and/or clear field of view without spacecraft interference to be defined as guidelines (or at least an option). Need more definition here than currently is
The updated Thermal Guidelines: “..the placement of the instrument radiator should be flexible such that in any of these spacecraft mounting configurations, the radiator can have the required view of space. Other recommendations include over sizing radiators to accommodate unexpected blockage from spacecraft or other payload surfaces. Unused area can be blanketed off,... etc”
8
Key LEO Thermal Guidelines -1/2 Examples of key thermal guidelines that maximize the opportunities to be paired with host spacecraft include: Thermally isolated instrument imposes minimal constraints on the host Flexible thermal design allows for favorable radiator position ID
Function
Guidelines
Rationale/Comment
8.5.1
Heat rejection to space
Use of heat pipes, high thermal conductivity straps etc if they can be accommodated
Allows radiator to be located in a desired orientation without putting constraints on spacecraft
8.5.2
Thermal Isolation
Thermally isolate the instrument from spacecraft
Makes the instrument independent of spacecraft & imposes least thermal demand on the spacecraft
8.5.3
Survival Use parts qualified to very low Reduces requirement for temperatures temperatures survival power 9
Key LEO Thermal Guidelines – 2/2
ID
Function
Guidelines
Rationale/Comment
8.5.4
Cryogenic temperatures
Use TEC or Cryo‐coolers to achieve required temperatures if needed
Allows instrument to be independent of spacecraft
8.5.5
High thermal stability
Use of high thermal capacity components (PCM storage etc), if needed
Short term transient can be handled easily
8.6.1
Survival Use mechanical thermostats for Instrument totally heater control survival heater control isolated from spacecraft
10
Louvers & Heat Pipes on EOS Aura Instruments
Signal Chain Evap/LHP
TES Instrument
MLS Instrument
11
Thermal Technologies for Instruments Aura/TES Thermal Hardware
High‐conductivity blades (M3)
Loop Heat Pipe
OCO‐ VC Heat Pipe
High thermal conductivity straps
Mechanical Cooler MER Battery Heat Switch
PCM Thermal Storage
12
GEO Considerations for Thermal From thermal perspective, the GEO spacecraft are similar to LEO on most of the thermal interface requirements The Earth’s IR flux and albedo on a GEO-mounted radiator is an order of magnitude lower (250 - 400 W/m2 vs. 6 - 8 W/m2) Earth’s lower IR flux at GEO allows for a placement of the instrument radiator located pointing to Earth
13
CII Thermal Guidelines – Conclusions The CII thermal guidelines are to help the science instrument developers maximize Earth-orbiting mission opportunities Understanding the constraints of the hosted LEO and GEO spacecraft will help the instrument developers design their instruments to be more acceptable This is an ongoing effort that involves both the Earth Science community and the spacecraft vendors
14
Back Up Charts
15
Thermal Interface Guideline Feedback-1 Thermal Guidelines 8.4.2 & 8.8.2 Concern Thermal interface guidelines
Recommendation 1) Rewrite thermal spec 15W/m^2 to include some minimum allowed, such as 15 W/m^2 or 1 W, whichever is greater. 2) Please add temperature sensors (perhaps 2) for monitoring payload when it is off
Attributable Comment 1) The guideline provides a recommended, not-to-exceed flux. It is intended to be used in conjunction with the Mechanical guidelines: specifically, the maximum recommended footprint. With this information, the payload team has an idea of both the recommended maximum heat transfer and flux transfer. This gives more flexibility to the design when compared to the often-used interface spec of a not-to-exceed thermal conductance. But the comment is well-taken. The guideline lacked completeness in that it did not specifically cite the relevant Mechanical guideline. As such, it appears to penalize payloads for using smaller footprints. The guideline will be re-written to account for the recommended Mechanical foot-print of 600mm x 420mm as shown below. At 15 W/m2, this yields a maximum recommended power of under 4W. The next version of the thermal guidelines will expand on the thermal interface conductance to include this include the following statement: “The conduction heat transfer at the Instrument-Spacecraft mechanical interface should be less than 15 W/m2 or 4 W, whichever is maximum”. 2) The feedback on monitoring the payload temperature when it is off, the following statement will be included either the Thermal Guidelines section or in the Data and Power Guideline section: “the instrument designer should assume that spacecraft may not be able to provide temperature monitoring of the payload when it is off.”
16
Thermal Interface Guideline Feedback-2
Thermal Guideline 8.5.6 Concern Major impediments that instrument provides have in using CII as currently defined. 2) Need a thermal radiator clear field of view to space and/or clear field of view without spacecraft interference to be defined as a guidelines (or at least an option). Need more definte here than currently is. Instrument designers will have no clue if they can be accommodated thermally without getting involved in detail with specific spacecraft providers.
Recomm.
Attributable Comment 3) Feedback was received on the clear field of view (FOV) of space for the instrument radiator(s). The request was to work toward an agreement with spacecraft providers to produce a minimum guaranteed FOV to cold space. While a certain level of cold space FOV may be guaranteed, the uncertainty in orbits, orientations, and nearby surfaces prevents futher specification. And without additional specification, a FOV value has limited value to the payload designer. At this time, the cii team can only give guidelines that will maximize the chances of utilizing the FOV specified once paired with a spacecraft. The following statement will be included in Thermal Guidelines: “the instrument designer should expect the instrument to be mounted to a side of the spacecraft which could be any of the six sides of the spacecraft (nadir, zenith, East, West, North, and South). The placement of the radiator on the instrument should be flexible such that in any of these S/C mounting configuration, the radiator can have the required view of space. Other recommendations include oversizing radiators to accommodate unexpected blockage from spacecraft or other payload surfaces. Unused area can be blanketed off,... etc
17
