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To enable deep space missions, the capability to transfer and store cryogenic fuels (typically liquid hydrogen, methane, and oxygen) without significant leakage over long duration missions is critical. NASA has been actively developing zero boil-off cryocooler technology to reduce storage losses. Another source of fuel loss is from leakage at the fuel disconnect used for in-space refueling. Current designs use fluoroelastomer seals which are excellent for applications such as natural gas but are susceptible to embrittlement at the lower temperatures required for liquid hydrogen. In addition, the high contact forces needed to reduce leakage can cause cracking of the seals.
NASA is turning to the GrabCAD community for potential low or zero leakage cryogenic disconnect seal designs that could be fabricated and tested. We recommend that participants in this challenge are familiar with materials and methods commonly used for cryogenic sealing applications.
Due to the large temperature ranges, designs must ensure coefficients of thermal expansion in the materials used are considered. Designs should also allow more than one connect/disconnect operation so a one-time crushable material may not work. Finally, the design should be compatible with robotic connection and disconnection.
These designs could potentially use shape memory metals for the seals and support high contact forces to prevent leakage.
Background:
The NASA technology shortfalls list ID 792 (In-space and On-surface Transfer of Cryogenic Fluids) states: The ability to transfer a cryogenic liquid (usually propellant) from one tank to another is a strategic technology that is not mature. The issue is performing the transfer with minimal commodity loss and waste (unusable propellant in the supply tank). There are many aspects to transfer operations, such as Tank Pressurization, Liquid Acquisition, Line and Tank chilldown as well as cryo-couplers. Also having methods to extract the maximum possible commodity by using Liquid Acquisition devices or other methods/ techniques. This shortfall includes all of the elements required for efficient fluid transfer operations with acceptable risk tolerance. This includes modeling, testing to validate transfer models, cryo-couplers, etc.. Additional propellant resources (10-20%) are bookkept to guarantee mission success. Fueling large vehicles launched empty or partially filled will not be possible and refueling vehicles for reuse will not be possible if the shortfall is not closed. Lunar architecture is dependent on enabling technology. All Mars Transportation solutions currently under consideration are also dependent on these developments as enabling technology. The shortfall is also noted in ID 361 (Surface mating mechanisms).
The Challenge:
The cryogenic disconnect and seal should meet the following requirements.
The cryogenic disconnect…
… should support a cryogenic fluid flow rate of 10 - 2000 liters/minute.
… should be able to operate at temperatures ranging up to 20 to 400 K.
… should be able to operate at pressures ranging up to 1 to 7 Bar.
… should have a leak rate of ≤ 10-6 sccm GHe at the temperature range (20-400K).
… should be compatible with the space environment (vacuum, radiation, etc.)
… should be compatible with the launch environment (dynamic vibration, acoustics, humidity, etc.)
… should be within the following dimensional limits:
● ≤200 mm connected length
● ≤120 mm in outside diameter
● flow diameter 25-50mm
The cryogenics group at the Kennedy Space Center has extensive experience in loading cryogenic fuels in rockets but is always interested in innovative ways to improve existing components:
● C3Or2A-06_Manuscript_CEC 2023_VCR Fittings_062223 (002).pdf
● Low Separation Force Quick Disconnect Device | T2 Portal (nasa.gov)
Sponsor Owner:
Gabor Tamasy
Manager, Cryogenic Test Laboratory, NASA Kennedy Space Center
Judging criteria
Graphical Products
o CAD model of a cryogenic disconnect and sealing method that could be fabricated.
o Analysis showing thermal tolerances over the temperature range and predicted leak performance.
File Format Guidelines
o All text documents should be in Microsoft Word
o All animations should be compatible with embedding in Microsoft PowerPoint and separate viewing in Windows Media Player
o All final CAD models must be saved as STEP files
o Use a CAD file naming convention that makes it easy to determine how each file fits into the larger assembly.
Intellectual Property Considerations
o All material (including the CAD model itself and all written documents) must be free of any copyright restrictions
o Use only models, photos, or images created during the project unless you have obtained the right from the copyright owner for unrestricted use – do not blindly copy images from internet websites
o Images on .gov websites are often (but not always) public data; check before assuming
o Include documentation of any usage permissions
The Government is seeking a full government purpose usage license for further development of the concept. It is hoped that the winning concepts can be fabricated and tested in a follow-on activity, funded by NASA
Eligibility: Solutions from countries listed as Type 1, 2, or 3 on the NASA Designated Countries List are Not eligible for monetary prizes. The list is frequently updated, and the latest version can be found here. This challenge is not open to NASA Personnel.
ENTERING THE COMPETITION The Challenge is open to everyone except employees and families of GrabCAD and the Sponsor. Multiple entries are welcome. Team entries are welcome. By entering the Challenge you: 1. Accept the official GrabCAD Challenges Terms & Conditions. 2. Agree to be bound by the decisions of the judges (Jury). 3. Warrant that you are eligible to participate. 4. Warrant that the submission is your original work. 5. Warrant, to the best of your knowledge, your work is not, and has not been in production or otherwise previously published or exhibited. 6. Warrant neither the work nor its use infringes the intellectual property rights (whether a patent, utility model, functional design right, aesthetic design right, trademark, copyright or any other intellectual property right) of any other person. 7. Warrant participation shall not constitute employment, assignment or offer of employment or assignment. 8. Are not entitled to any compensation or reimbursement for any costs. 9. Agree the Sponsor and GrabCAD have the right to promote all entries. If you think an entry may infringe on existing copyrighted materials, please email challenges@grabcad.com.
SUBMITTING AN ENTRY Only entries uploaded to GrabCAD through the "Submit entry" button on this Challenge page will be considered an entry. Only public entries are eligible. We encourage teams to use GrabCAD Workbench for developing their entries. Entries are automatically given the tag "NASA_Cryogenic_Disconnects" when uploading to GrabCAD. Please do not edit or delete this tag. Only entries with valid tag will participate in the Challenge.
AWARDING THE WINNERS The sum of the Awards is the total gross amount of the reward. The awarded participant is solely liable for the payment of all taxes, duties, and other similar measures if imposed on the reward pursuant to the legislation of the country of his/her residence, domicile, citizenship, workplace, or any other criterion of similar nature. Only 1 award per person. Prizes may not be transferred or exchanged. All winners will be contacted by the GrabCAD staff to get their contact information and any other information needed to get the prize to them. Payment of cash awards is made through Checks mailed to the Winners. All team awards will be transferred to the member who entered the Challenge. Vouchers will be provided in the form of Stratasys Direct Manufacturing promo codes. We will release the finalists before the announcement of the winners to give the Community an opportunity to share their favorites in the comments, discuss concerns, and allow time for any testing or analysis by the Jury. The Jury will take the feedback into consideration when picking the winners. Winning designs will be chosen based on the Rules and Requirements schedule.
Schedule
This Challenge ends on Wednesday, September 25, 2024 at 11:59 Eastern Standard Time. Any Changes after the date will be considered as disqualifications.1st Place Amount: $3,000
# of Eligible Winners: 1
2nd Place Amount: $1,250
# of Eligible Winners:: 2
3rd Place Amount: $ 500
# of Eligible Winners: 3
1st Place Amount: $3,000
# of Eligible Winners: 1
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24 comments
DZEHU Itrch Shekn 10 days ago
super just not for us...
but the topic is interesting...
MysteriousH 9 days ago
Hello, very interesting challenge! Couple of questions:
1. How many demates/mates should it be able to handle? Other than the >1 stated.
2. Are solutions that include consumables allowed?
3. Can we assume that other systems ensure alignment of the connector?
4. Just to make sure google hasn't failed me "≤ 10-6 sccm GHe", would mean a leakage of 10e-6 (i.e. 10 micro) standard cubic centimeters per minute of gaseuos helium?
5. For the requirement to be compatible with robotics connection/disconnection does this mean that it shall not require human input? Or is it refering to something else?
6. The stated temperature range 20-400 K is that to cover overall space environment range or is it refering to the system being able to transfer gaseous or non-cryogenic fuel?
Gabor Tamasy 9 days ago
Dzehu - Yes, this challenge does require some specialize knowledge, but we are confident that among the many GradCAD users, there are some with experience in cryo-technology. Overall, we try to strike a balance between really broad challenges and those that are highly specific and address a smaller group of users.
Gabor Tamasy 9 days ago
MysteriousH here is the response to your questions:
1. Disconnect operational life on the order of 100 mate/demate cycles is would be sufficient.
2. Consumables are acceptable, but not desirable due to limited logistics availability and complication to replenishing consumables in space or on Moon/Mars systems.
3. Yes other umbilical mechanisms are assumed to provide alignment, connection and latching of the QD halves. Some compliance in the connector for minor misalignments would be a bonus but not required.
4. Yes we desire a leak rate of ≤ 0.000001 standard cubic centimeters per minute of gaseous helium at the cryogenic temperature range given.
5. Robotic connection/disconnection refers to the ability to use a robot to operate the disconnect, but the disconnect can be assumed to be installed in an umbilical carrier which can be grappled by the robot (refer to answer 3 above). The robot connect/disconnect operation can be autonomous without man in the loop, or teleoperated remotely by human operator.
6. The given temperature range is the desired operational range for this QD. Survival temperature range would cover the entire space environmental conditions. The low temperature limit would be the 20K for LH2 operation, but the high could be up to +127 °C (400K) for Lunar applications.
Nazarii Vareshchuk 8 days ago
Hello.
There are the following questions:
1. What are the requirements for corrosion resistance of materials? That is, from the list of possible substances, I assume that they can be aggressive. What is the approximate list of substances and their aggressiveness?
2. The task specifies a temperature range of 20-400K and a pressure of 1-7bar. does it mean a roughly proportional relationship (lower temperature lower pressure) or could it be 20K and 7Bar (if it's helium/hydrogen) ?
Thank you.
TARUN KUMAR DUTTA 6 days ago
Thanks for another Interesting challenging
Marcelo Valderrey 6 days ago
Hello @Gabor Tamasy:
.
I have prepared a schematic model of one of the coupling devices given as reference, in order to analyze what appears (to my understanding) to be an extensive transition zone during which the pressurized fuel communicates with the outside without being retained by the seals.
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I suppose I have not understood the concept of the device well, or perhaps it has some kind of frontal seal between the external parts in contact that prevents such leakage.
.
In any case, and regardless of my possible bad or good interpretation, I think it is useful to share with my colleagues this model for study that may help us to better focus on some design issues (beyond the seal materials that, obviously, are very important).
.
Thank you very much for any comments on this matter.
.
Kind regards,
Marcelo V.
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PS: I have published this model for study as if it were an entry of the challenge, simply so that it is easily visible to the participants. But then I can remove the "NASA_Cryogenic_Disconnects" tag and the model will still be available in my library for anyone who wants to use it.
Flaviano Crespi 5 days ago
Hello Marcelo, thanks for the post.
To solve the problem you have outlined, it would be enough to add a front O-Ring on the contact bushings. (how effective to demonstrate). I also think that the image is very simplified because it shows other obvious defects: the O-Rings in their movement pass over sharp edges, after a few actuations they would be pinched with consequent pressure losses
Marcelo Valderrey 5 days ago
Hi Flaviano!
The front o-ring is something I mentioned in my query:
"I suppose I have not understood the concept of the device well, or perhaps it has some kind of frontal seal between the external parts in contact that prevents such leakage."
However, the requests for "low coupling closing force" would have to be reviewed because it would be increased by the pressure needed for the seal to close effectively. To this end, I would prefer to try a frontal seal with multiple annular labyrinths (which would not increase the coupling closing force).
I also noticed the passage of the o-ring above the edges of the holes... but I suppose there are details not intentionally shown in the reference documentation.
Kind regards!
Flaviano Crespi 5 days ago
Hi Marcelo, I agree, the documentation is intentionally partial. As for the compression set of the front O-ring I think it is not very large, consider that there are also two other radial O-rings that must be compressed by the action of the male and in this case I think the resistance is greater. The sealing of a front O-Ring is effective even at low loads. I am curious about the concept of the labyrinth, with concentric steps?
Flaviano Crespi 5 days ago
@ Marcelo, It also depends on how fast the transition happens, if it's fast it would just be a little puff...
Nazarii Vareshchuk 5 days ago
Hello @Marcelo Valderrey
1. I think a short-term loss of gas is allowed, although it is not mentioned in the task. Perhaps this needs clarification from the customer.
1.1. This loss will always be there even with the frontal ring. since a certain amount of gas will remain in the cracks after the transfusion process. And after disconnection, this portion will be lost. although it is predictable, one-time, and not excessive.
2. The frontal ring can be radial when it seals along the radial surface of the left part. thus it will depend less on the compression force, although the gas pressure will still create the separation force because it will not be a symmetrical piston.
If the customer comments on the permissible gas loss at the time of connection, it will be useful.
Marcelo Valderrey 5 days ago
Hi Flaviano!
We will have to quantitatively evaluate the issues of closing force and what happens until it is established at its maximum level. You are probably quite right and it would be a simple solution (the front o-ring).
But there is something that remains a problem anyway: the fuel retained in this "dead zone" (even when the front o-ring works perfectly!) is fuel that will be lost when the system is decoupled. It may not be significant, but conceptually for the mechanism a "dead zone" of fuel accumulation should be reduced or, better yet, eliminated.
PS: I have not designed the labyrinth seal, but I would start by testing deep concentric rings. If I can, I will do some CFD simulation to see their behavior.
Marcelo Valderrey 5 days ago
Exactly Nazarii!
I was just commenting on this to Flaviano.
Everything is relative, and the "variable opening/closing time" may be a good way to minimize losses.
It is good that we begin these discussions on conceptual issues of design, before worrying about the issues of materials, wear, fragility and others that are vital but "postponable" compared to the kinematics and dynamics of the mechanism.
Marcelo Valderrey 5 days ago
I am very confident in the (long-proven) abilities of Flaviano and Nazarii to propose innovative mechanisms that consider these and many other design issues.
Flaviano Crespi 5 days ago
Considering that the loss limit is very low, perhaps it would be better to provide two operating states:
1 - Separate connectors, should be most of the time.
2 - Connectors in supply, which should last very little.
How long? And how many connections/year?
The two values would be used to design gaskets suitable for the two states. However, everything depends on the performance of the materials, you can fill pages and pages of calculations, but everything would depend on practical tests.
Marcelo Valderrey 5 days ago
Hi Flaviano!
I suppose (but I don't really know) that in the state you mention as "separated connectors" (for a long time) the tightness of both parts could be ensured through motorized valves with suitable internal bodies.
If so, the problem remains the "connectors in supply" state, although, in any case, if the maneuvering time were not too limited, those valves could still help the quick coupling (maintaining the tightness and limiting the pressure in the quick coupling, while it reaches its final safe position).
Flaviano Crespi 5 days ago
Hi Marcelo,
Right, then the given value is absolutely that of the connection device, whether the valves are closed or left open due to an anomaly.
Nazarii Vareshchuk 5 days ago
@Gabor Tamasy
"leaking ≤ 0.000001 standard cubic centimeters per minute of helium gas"
This is a rather small dose, which means 0.000001*60*24*365=0.5 cubic centimeters per year. So in 1000 years it will be half a liter. Even such a loss for such an ambitiously long journey is very small, if it is, for example, fuel.
So maybe these limits are too strict?
Marcelo Valderrey 4 days ago
@Gabor Tamasy
Just to make it clear:
"leaking ≤ 10e-6 = 0.000,010 sccm (no 0.000,001)"
Therefore, Nazarii's estimate would give 5 cc annually (no 0.5 cc).
Gabor Tamasy 3 days ago
Nazarii Vareshchuk here is the response to your questions, sorry for the delay:
1) We require corrosion resistant materials since these components need to be fabricated, tested and staged on the ground corrosion is not acceptable since it leads to contamination and can adversely affect the performance.
2) There is no correlation between the temperature and the pressure range. The disconnect must function at any temperature/pressure combination within the given range.
Gabor Tamasy 3 days ago
Marcelo Valderrey here is the response to your comment:
You can assume the disconnect will be connected and disconnected in a depressurized and purged state. This means there is no commodity present at the interface when the disconnect is mated or demated. We do want a sealing poppet check valve type of closure on the open ends of the disconnect to prevent contamination entering while disconnected.
Gabor Tamasy 3 days ago
Nazarii Vareshchuk response to your leak rate comment:
You are correct I was off by a decimal point using 1E-6, it should be 10E-6, but this leak rate is a target and is our normal leak check limit, but our goal is to select the disconnect which has to lowest leak rate. The discussion about O-rings is good but in our experience o-rings do not work well at the cryogenic temperatures. Pressure energized or metal to metal seals are the most effective, that is why we mention shape memory alloy as a potential candidate.
Marcelo Valderrey 3 days ago
@Gabor Tamasy
1.) Should the movements of the robot and umbilical carrier for connection, gripping and disconnection be exclusively linear (according to the axis of the pipe) or could they also be combined with a rotational movement?
2.) Are there specifications for the maximum force (and torque, if rotations are allowed) for connection, gripping and disconnection?
3.) During the fluid transfer operation, should the device be held in position without any external assistance, or can it be assumed that the robot and umbilical carrier maintain their position at all times?
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