SOW.pdf

Pre-Solicitation 80GRC018R0027

STATEMENT OF WORK

High Capacity 90 Kelvin Cryocooler for Thermal Control of Space-Based Cryogenic Systems, Conceptual/Preliminary Design Technical Specifications and Requirements

1.0 Scope

NASA is procuring the conceptual/preliminary design of a 120 - 150 W class 90 K cryocooler system that provides cooling to a NASA tube-on-tank broad area cooled shield. The designs developed with this procurement will be compared with the currently funded SBIR system concepts for further development options.

1.1 Introduction

NASA is currently investing in passive and active thermal control technologies that will enable long term in-space storage of cryogenic propellants in a zero-loss, or zero-boil-off (ZBO) state as well as enabling liquefaction of in-situ produced cryogenic fluids. This is in line with NASA's goal of increasing payload mass beyond low Earth orbit by improving the mass efficiency of high-performing cryogenic fluids in upper stages, landers, depots, or other surface assets that are required for long loiter and or transit periods.

This is also in line with NASA’s thrust for enabling the delivery of medium to large payloads to the lunar and Martian surfaces. With this goal in mind, the NASA has planned to advance the technology readiness of cryocooler technology for operation at temperatures associated with liquid oxygen and liquid methane (90 – 120 K) by increasing lift capacity, specifically, on the order of 120 - 150 Watts. This integrated cryocooler system would be integrated with NASA’s preferred tube-on-tank broad area cooled shield to remove heat from tanks to provide zero-boil-off, pressure control, or even liquefaction of cryogenic fluids in a space environment or on the Moon or Mars.

The scope of this procurement is for the conceptual/preliminary design of a flight-representative integrated cryocooler system, which NASA may later complete the design of along with the fabrication of an engineering development unit to integrate with a heat load at 90 K and a heat rejection subsystem in a to-be-determined test. To meet this objective, the cryocooler would be tested according to one or more of the options listed in Section 1.2. The cryocooler may also be non-operationally vibration tested in accordance with GEVS-SE requirements. The end goal is to develop a prototype cryocooler with a flight-representative thermal control system test that achieves 120 - 150 W of cooling capacity at 90-120 K.

1.2 NASA Utilization

NASA plans to use an eventual prototype integrated cryocooler system in one of several demonstrations that are being planned.

1.2.1. Nuclear Thermal Propulsion Operational Concept test

In order to demonstrate the capability of liquid hydrogen zero-boil-off and pressure control of a liquid hydrogen tank for a nuclear application, a large scale demonstration is being planned. The demonstration would take advantage of an existing large scale tank (3 – 4 meter diameter) and integrate both a 20 K and 90K cryocoolers to demonstrate the benefit of zero-boil-off and the capability to absorb heat during the

NTP engine operation. Due to environmental configurations of possible orbits that are being studied, the operational temperature of the 90 K cryocooler may be as low as 70 K.

The tank size and location of testing has not been determined (a few options are shown in Fig 1). The 20 K cryocooler would be procured separately. The 90-120 K cryocooler would be integrated into a thermal shield that cools portions of the tank structure and multilayer insulation to reduce the heat load to the 20 K liquid hydrogen tank. The cryocooler would be mounted inside the thermal vacuum chamber with the tank at a TBD location (depends on test facility and test tank). The generic integration scheme is shown in Fig 2. The method for heat rejection in this test is as of yet undetermined.

Figure 1: Possible NTP test tanks:

Multipurpose Hydrogen Testbed (left) and Structural Heat Intercept, Insulation, and Vibration Evaluation Rig (right)

Figure 2: Integration of 90 K cryocooler system in with liquid hydrogen tank

1.2.2. Propellant Liquefaction Testing

A prototype unit of a lander tank for liquefaction testing of ISRU produced propellants is currently in development. Initial testing will use a commercial cryocooler based system, however, it is desired to improve the fidelity of the cryocooler system used. The system will initially be integrated into the Small Multipurpose Research Facility (SMiRF) vacuum chamber at Glenn Research Center before being transported to a yet to be determined location to be a part of the ISRU integrated system demonstration.

The test tank is 1.25 m diameter x 2.0 m tall with 8 cooling loops that are manifolded at both the top and bottom as shown in Fig 3. The integration would be similar as to Fig 2, but with the cryocooler connecting to tubes directly on the tank. Mounting into the SMiRF vacuum chamber is as of yet undecided and will depend on the configuration and size of the cryocooler. The probable method for heat rejection in this scenario would be a water cooled plate. The commercial cryocooler is mounted at the top of the vacuum chamber on the side of an instrumentation port with the coldhead extended into the vacuum space.

Figure 3: Propellant Liquefaction Prototype test configuration

1.3 Convention and Notation

The convention used in this document, which indicates requirements, goals, and statements of facts, is as follows:

1.3.1. “Shall” – Used to indicate a requirement which must be implemented and its implementation verified.

1.3.2. “Should” – Used to indicate a goal which must be addressed by the design but is not formally verified.

1.3.3. “Will” – Used to indicate a statement of fact and is not verified.

1.3.4. In some cases, the values of quantities included in this document have not been determined and are designated as To Be Reviewed (TBR), To Be Determined (TBD) or To Be Supplied (TBS).

1.3.4.1. Where approximate values of such quantities are known and provide useful guides for development, the values are shown along with the TBR notation.

1.3.4.2. Where no value is yet known, a TBD is included.

1.3.4.3. Where a value is known, but has not been supplied to the Requirement Document book manager, a TBS is included.

1.3.4.4. Each requirement in this document should be uniquely numbered and identified by the presence of a tag at the beginning of the requirement statement in blue-gray text.

2.0 Documents and Definitions

2.1 Applicable Standards

AIAA-S-080 Space Systems - Metallic Structures AIAA-S-081A Space Systems – Composite Overwrapped Pressure Vessels (COPVs) GEVS-SE General Environmental Verification Specification for STS and ELV Payloads

2.2 Reference Documents

For background material, the following resources are recommended for review:

NPR 7123.1B Systems Engineering Processes and Requirements IEST-STD-CC1246E Product Cleanliness Levels – Applications, Requirements, and Determination NPR 7150.2A NASA Software Engineering Requirements NASA-STD-8739.8 NASA Software Assurance Standard NASA-STD-8719.13C NASA Software Safety Standard NASA-STD-8719.17 NASA Requirements for Ground-Based Pressure Vessels and Pressurized

Systems (PVS) NASA TP-2017-219389 Liquid Nitrogen Zero Boiloff Testing

2.3 Definitions and Clarifications

2.3.1. Unidirectional flow

Described, under steady flow conditions, by a constant mass flow rate m, average supply temperature Tsup, and supply pressure Psup or, equivalently by an enthalpy flow rate H = m·h, where h is the mass-specific enthalpy of the gas at Tsup and Psup. As the gas is circulated through the distribution network, H increases by a value equal to the heat transferred from the tank wall to the gas stream in the on-tank tubing plus any parasitic heat leaks into the connecting lines.

The gas temperature increases from Tsup to Tret, where Tret = Tsup + ΔT, and the pressure decreases from Psup to Pret, where Pret = Psup – ΔP. As defined in the equations for return pressure and temperature, ΔT is the temperature rise across the network and ΔP is the pressure drop (or the pressure head generated by the cryocooler).

2.3.2. Cooling capacity

The cooling capacity or lift Qlift of the cryocooler is defined by the steady flow properties of the working fluid at the supply and return. Explicitly, 𝑄𝑄𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙 = 𝑚𝑚 ∙ ∆ℎ = 𝑚𝑚�ℎ𝑟𝑟𝑟𝑟𝑙𝑙(𝑃𝑃𝑟𝑟𝑟𝑟𝑙𝑙,𝑇𝑇𝑟𝑟𝑟𝑟𝑙𝑙) − ℎ𝑠𝑠𝑠𝑠𝑠𝑠�𝑃𝑃𝑠𝑠𝑠𝑠𝑠𝑠,𝑇𝑇𝑠𝑠𝑠𝑠𝑠𝑠�� ≈ 𝑚𝑚𝐶𝐶𝑠𝑠∆𝑇𝑇

2.3.3. Working fluid supply/return limitations

The working fluid, the charge pressure, and the mass flow rate and supply temperature required at maximum-capacity operation cannot be explicitly specified, as they are dependent on the specific cryocooler design. They are, however, implicitly specified by the relation stated in

2.3.2. and by the following limitations, which are dictated by the test configuration:

Tsup < Tret < Tload K (the load wall temperature)

2.3.4. ΔP

This is the maximum expected pressure drop of the working fluid as it passes through the connecting lines and the load distributed cooling network. ΔP = Pret – Psup < 1.5 psi

2.3.5. Total supply/return mass flow rate full scale reading

Reading accomplished by the incorporation of an in-line flow meter, or by means of a calibrated relation between flow rate and some measureable operational parameter such as compressor displacement or rotor speed.

2.3.6. Integrated Cryocooler System

The cryocooler integrated with a method of delivering the refrigeration power to the NASA defined tube-on-tank broad area cooled shield.

2.3.7. Specific Power

The ratio of the integration cryocooler system input electrical power to cooling capacity (Watt/Watt)

2.3.8. Specific mass

The ratio of total integrated cryocooler system estimated mass for flight based on the ground design unit, including electronics, to cooling capacity (kilogram/Watt)

2.3.9. Broad Area Cooled Shield

A potential NASA load configuration that includes a small diameter tubing network that is attached to a propellant tank wall.

2.3.10. NASA defined load

A TBD cooling load supplied by NASA for integrated testing to occur at a NASA Test Site.

This may be a distributed cooling network or other simulated load.

Technical specifications and requirements for the high capacity 90K cryocooler are listed in Section 3.0.

Statements containing “will” were included in relevant sections in order to announce pertinent information exchanges between NASA and the Contractor.

3.0 Cryocooler/Circulator Technical Specifications and Requirements

3.1. Cryocooler Operational/Interface Requirements

The operational specifications of the integrated cryocooler system are fully defined by the requirements imposed on the three input/output interfaces: (1) The working fluid supply and return ports (interfacing with the distributed cooling network); (2) the heat rejection plate; and (3) the electrical connections (interfacing with the power, instrumentation, and control electronics). This is schematically illustrated in Fig. 4. Although the integrated cryocooler system is referred to and represented in Fig. 4 as a unit, it may be composed of multiple components.

Figure 4: Schematic diagram of the cryocooler and the working fluid distribution network

The cryocooler is represented as a "black box" where operational characteristics are defined by the three input/output interfaces

a. [301-01] The integrated cryocooler system shall provide a forced convection loop to transfer energy from the tank wall to the cryocooler using a tube-on-tank broad area cooling shield.

b. [301-02] The NASA tube-on-tank broad area cooling shield loop shall use neon as working fluid.

c. [301-03] The integrated cryocooler system shall be capable of supplying a unidirectional flow from the supply to the return.

d. [301-04] Module supply/return interfaces shall be stainless steel 2-1/8” rotatable, clearance hole conflat flanges with 1” nominal tubing as shown in Fig. 4 (“mated fittings”).

e. [301-05] All heat shall be rejected from the cryocooler at a single heat rejection interface, designed by the Contractor, as shown in Fig. 4 that is appropriate for ground testing.

f. [301-06] NASA will provide power as shown in Fig. 4 for any testing at a NASA facility per

Contractor requirements

3.2. Integrated Cryocooler System Functional Requirements

a. [302-01] The integrated cryocooler system capacity shall be controllable during operation to enable variation of the cooling capacity from the minimum to the maximum.

b. [302-02] During normal steady-state operation at 90 K, the minimum integrated cryocooler system cooling capacity shall be Qlift = 30 W.

c. [302-03] During normal steady-state operation at 90 K, the maximum integrated cryocooler system cooling capacity shall be Qlift = 135 W ± 12%, not including any parasitic loss due to integration.

d. [302-04] The integrated cryocooler system shall be capable of continuous operation at the maximum cooling capacity for a duration of 10 years at the environmental conditions listed in Section 3.3.

e. [302-05] The integrated cryocooler system shall be designed for 100 start-up transients.

f. [302-06] The integrated cryocooler design shall be capable of meeting flow and lift requirements with a load ΔP of at least 1.5 psi at the maximum cooling capacity.

3.3. Environmental Requirements

a. [303-01] The integrated cryocooler system shall be able to start and operate at environmental temperatures between 200 K and 300 K to simulate the startup of a cryocooler on-orbit. If needed, the addition of heaters in order to facilitate startup at low temperature conditions is acceptable.

b. [303-02] The integrated cryocooler system shall be able to start with the load at temperatures between 90 K and 300 K.

3.4. Instrumentation, and Control Requirements

a. [304-01] The Contractor shall include instrumentation required to monitor and control the integrated cryocooler system including the safe mode and or shutdown in the event of an unsafe or hardware damaging operating conditions.

b. [304-02] The Contractor shall provide instrumentation, control, and power connection diagrams.

3.5. Structural Requirements

a. [305-01] The integrated cryocooler system modules shall be designed to withstand static and dynamic structural loads while cryocooler is not operating according to the GEVS-SE (Section 2.4.1.3, Table 2.4-4, Section 2.4.4.1, and Section 2.4.5.1) for normal payload flight qualification.

b. [305-02] The contractor shall determine the vibration environment caused by the integrated cryocooler system.

c. [305-03] The integrated cryocooler system shall operate in a vacuum environment.

3.6. Relation to flight hardware: "Clear path to flight"

a. [306-01] The integrated cryocooler system specific power shall be 15 W/W or lower with a goal of 8 W/W, evaluated at the design cooling capacity from [302-03] with heat rejection at 300 K.

b. [306-02] The integrated cryocooler system specific mass shall be 0.8 kg/W or lower with a goal of

0.5 kg/W, evaluated at the design cooling capacity from [302-03].

c. [306-03] All heat transfer within the cryocooler shall be via the working fluid, via solid conduction, or via high-TRL heat transfer devices such as heat pipes.

3.7. Analytical Models of Cryocooler

a. [307-01] The Contractor shall provide an analytical model outlining the cryocooler predicted performance and a model quantifying parasitic heat losses at various points of lift.

b. [307-02] The Contractor shall describe the cryocooler system thermodynamic cycle on a T-S diagram.

c. [307-03] The Contractor shall provide a physical description of the parasitic loss or unusable lift of the cryocooler in addition to an analytical model of the parasitic loss.

d. [307-04] The Contractor shall provide a predicted cryocooler performance map with at a minimum between the temperatures of 70 K and 120 K.

3.8. Software Engineering

The integrated cryocooler package has been identified to include Class D software, per NPR 7150.2A.

a. [308-01] The Contractor shall provide software specifications including the architecture and overall system specifications.

4. Deliverables and Delivery Schedule

The period of performance is seven (7) months from date of award.

4.1. Kick-off meeting and site visit: Within three (3) weeks after date of award

The Contractor shall hold a kick-off meeting and site visit for NASA personnel. The expected duration is 2 hours for the kick-off meeting with site-visit duration as is appropriate. Presentation materials (e.g., PowerPoint charts) shall be considered deliverables.

4.2. Monthly progress reports and teleconference

Following the kick-off meeting, the Contractor shall report progress via teleconference to NASA at least once per month, the expected duration is less than an hour. They shall include progress made during the current period, plans for the next period, issues and concerns, and overall schedule status and be documented via PowerPoint or other appropriate formats. Presentation materials (e.g., PowerPoint charts) shall be considered deliverables.

4.3. Conceptual/Preliminary Design Review (at GRC): Within six (6) months after date of award

Entrance Criteria, tailored from NPR 7123.1B:

1. An agenda for the design review, success criteria, and instructions to the review board have been agreed to by the technical team, the project manager, and the NASA COR prior to the review.

2. The concept has been developed to a sufficient level of detail to demonstrate a technically feasible solution to the project needs and is ready to be baselined after review comments are incorporated, including:

a. CAD Models/Sizing/Mass

b. System Schematic/instrumentation plan

c. Power and control diagrams

d. Preliminary technical analysis

e. System performance models (mathematical description)

f. Integration of cryocooler system into tube-on-tank applications

3. A preliminary assessment performed by the team of top technical, cost, schedule, and safety risks and developmental challenges/long poles with identified management and mitigation strategies and options.

4. Preliminary engineering development assessment and technical plans to design and build a fully functional prototype to be integrated into a TBD NASA demonstration (reference section 1.2).

5. Other technical products for hardware and software elements, including:

a. Applicable standards that have been identified and incorporated

b. Heritage to previously developed and flight-qualified cryocoolers and “clear path to flight” supporting evidence

c. Preliminary Interfaces identified

d. Baseline operational concept.

e. Discussion of scaling considerations of the selected cryocooler technology and its limitations.

f. Software block diagram illustrating preliminary control/telemetry functionality

g. Preliminary requirements compliance matrix.

h. Preliminary cost estimates and margins for the prototype cryocooler development.

i. Preliminary integrated cryocooler system performance verification plan

j. Preliminary schedule for hardware and software development through prototype and flight units.

k. Rough order magnitude cost for flight unit development after successful prototype unit based on previous experience.

l. Any other information that the Contractor deems worthy of mention.

Success Criteria, tailored from NPR 7123.1B:

1. The top-level requirements are agreed upon, finalized, stated clearly, and consistent with the design.

2. The program cost and schedule estimates are credible to meet program requirements within available resources.

3. The flow down of verifiable requirements is complete and proper or, if not, an adequate plan exists for timely resolution of open items.

4. The design is expected to meet the requirements at an acceptable level of risk.

5. Definition of the technical interfaces (both external entities and between internal elements) is consistent with the overall technical maturity and provides an acceptable level of risk.

6. Any required new technology has been developed to an adequate state of readiness, or backup options exist and are supported to make them viable alternatives.

7. The program risks have been identified and mitigation strategies appear reasonable.

8. Adequate technical and programmatic margins (e.g., mass, power, memory) and resources exist to complete the development within budget, schedule, and known risks.

9. Technical trade studies are mostly complete to sufficient detail and remaining trade studies are identified, plans exist for their closure, and potential impacts are understood.

10. Preliminary analysis of the primary components have been completed and summarized, highlighting performance and design margin challenges.

11. Appropriate modeling and analytical results are available and have been considered in the design.

12. Heritage designs have been suitably assessed for applicability and appropriateness.

13. TBD and TBR items are clearly identified with acceptable plans and schedules for their disposition.

14. Manufacturability has been adequately included in design.

15. Presentation materials (e.g., PowerPoint charts) shall be considered deliverables. The expected duration is less than 8 hours.

4.4. Final Written Report: One (1) month after Design Review

Following the design review, the contractor shall prepare a non-proprietary report (in Microsoft Word or equivalent) addressing the topics presented at the design review. Report shall be delivered in PDF form to NASA as a deliverable. CAD models of the integrated cryocooler system conceptual/preliminary design shall be delivered to NASA as STEP files.

4.5. Deliverable Summary Table

SOW Section Description Location Due Date

4.1. Kick-off Meeting Vendor Award + 3 weeks

4.2. Monthly Progress

Reports Teleconference Monthly

4.3. Preliminary/ Conceptual

Design Review NASA GRC Award

+ 6 months

4.4. Final Report

(non-proprietary) N/A Design Review

+ 1 month

4.5. CAD model N/A Design Review

+ 1 month