Final_Responses_to_Industry.pdf

Questions and Responses to Request for Proposal (RFP), Solicitation No. 80GSFC19R0009;

Launch Lock and Vibration Isolation System (LLVIS)

1. In review of SOW, section 2.1.6 A, “The Contractor shall establish a method to provide access by Internet to authorized WFIRST Project personnel for working data products.” Question: Are we being asked to provide on-site or otherwise

Contractor’s intranet access to DCMA and/or GSFC personnel?

Response: The intent of this section 2.1.6 A was to provide an avenue to transfer data including designs, analysis, presentations and other communications directly to GSFC electronically. We intentionally worded it this way since there are many ways to make the transfer. Just needed a proposed method.

2. What moments and forces are allowed into the IC from the struts?

Response: IC is capable of reaction the loads shown in Table 3.

3. The spec is written based on natural frequency and Q without any information on the mass associated with this. Please either define the mass and have us derive stiffness and damping rate OR explicitly state axial stiffness and damping rate.

Response: There is a "Note" in Section 2.2.1 that directs the reviewers to consult with the schematic of transmissibility test configuration in Section 3.7.1, where a mass of 834 kg (1838 lbm) is specified for the transmissibility test and it is to be used to guide the design of the isolator in deriving the appropriate frequency and damping (or Q) that would meet the transmissibility requirement mandated in Figure 4 of Section 2.2.1.

4. What is the process to negotiate the LLVIS bus/IC flexures into the scope of this contract? Should this be proposed as an option or assumed in our baseline response, to then be addressed during contract negotiations?

Response: This should not be proposed as an option. The responsibility of the flexures at this point is GSFC so I would assume that would be the baseline.

5. Can WFIRST provide the referenced end flexure design?

Response: No still being worked.

6. What is the MagDamper Performance Test shown in Figure 2 and how does it differ from a Transmissibility Test?

Response: Do not understand this question. Figure 2 in WFIRST-SPEC-12739, Revision - Effective Date: March 5, 2019 refers to “General Arrangement of LLVIS on

WFIRST”.

7. Can we trade mass and volume allocations between the launch lock and isolator, provided we do not exceed the Integrated LL/Isolator values?

Response: Trading between allocations is acceptable.

8. SOW 2.2.2-A specifies a Kickoff Meeting shall be held 15 days after contract award.

The requirements listed in the SOW refer to many SRR-type activities including requirement flow down, preliminary ICDs, EDU and Qualification Verification Plan and Procedure, Mechanical Analyses, among several other labor-intensive items.

Response: We will hold this date.

9. CDRL PM-10 specifies the preliminary Kickoff meeting presentation package shall be delivered to GSFC 10 days before the Kickoff Meeting (i.e., 5 days ACA). Is there flexibility on either the due dates for these items or the scope of the review?

Response: We will hold this date.

10. How many on-orbit thermal cycles are expected and are they the full temperature excursions listed in table 9, pg.19 section 2.9.6.2?

Response: The on-orbit cycling will be to a much smaller temperature excursion than in table 9. That table outlines the maximum and minimum environment that was set to include margin and possible changes in design for the hardware around the LLVIS.

The number of smaller cycles is not easy to quantify because it would be due to electronics changing power states as well as orientation changes of the observatory.

11. SOW 2.2.4-E specifies “the Contractor shall incorporate the CDR and the MRR if possible in the same week.” Clarification needed that this is the LLVIS CDR, not the IC CDR?

Response: This statement refers to the LLVIS CDR.

12. SOW 6.3-G “The Contractor shall hold a post-test review with GSFC prior to test disassembly.” Clarification needed if this is for each test disassembly (i.e., every unit) or if this is just referencing the reviews already specified in SOW 2.2.4-G (just two total meetings).

Response: Review for every unit as baseline. This can be a telecom review after the first unit and should be conducted in a manner that requires minimum effort from the supplier after the test methods have been established.

13. REQ 2.2.2: States frequency requirement, however no associated mass is given making it difficult for the stiffness of the isolator to be derived.

a) Does this spec relate to a single isolator or hexapod?

b) Please provide system mass and geometry assumption or single isolator mass.

- OR -

c) Please provide the isolator stiffness directly.

Response: The reviewers should consult with the schematic of transmissibility test configuration in Section 3.7.1, where a mass of 834 kg (1838 lbm) is specified for the transmissibility test and is to be used to guide the design of the isolator to achieve a resonant frequency of 1.2 Hz +/- 0.06 Hz as stated in Section 2.2.2. The spec is for a single isolator.

14. REQ 2.2.4: States stiffness tolerance of 5% however REQ 2.2.2 states 5% for frequency. If one follows the frequency tolerance, then stiffness can vary by

10%. So which tolerance over-rides?

Response: The stiffness tolerance in 2.2.4 overrides.

15. REQ 2.2.5: What interface are they referring too? Is it the ends of the WFIRST provided flexures OR the just the isolator?

Response: At the ends of the isolator. The interface locations are defined in Figure 1.

16. REQ 2.2.6: This requirement states that lateral modes “should” not fall between

200-400 Hz, BUT REQ 2.2.5 says these modes “shall” be > 400 Hz.

a. What is the constraint assumption for REQ 2.2.6?

b. Should REQ 2.2.5 be “should” and 2.2.6 be “shall”?

Response: The configuration/system to be evaluated in REQ 2.2.6 is "Isolator + end flexures (GSFC provided)". The constraint, or "frequency stay-out zone", of 200-

400Hz is to avoid mode-coupling of the "Isolator + end flexures" local modes and Primary Mirror modes for achieving optimal jitter performance. The vendor "should" give it their best effort to achieve such design goal, i.e. no local modes of the "iso + flexure" system lie between 200-400 Hz. However if such goal is not obtainable GSFC will evaluate the system at the Observatory level and assess the impact of the local modes on jitter and provide recommendations. The > 400

Hz requirement specified in REQ 2.2.5 is for the isolator's local modes only, without the end flexures.

17. REQ 2.13.13: Will load vs cycles be provided for safe-life/fail-safe analysis?

Response: The number of cycles for analysis is defined in 2.9.3.

18. REQ 2.13.18: Will load vs cycles be provided for safe-life/fail-safe analysis?

Response: The number of cycles for analysis is defined in 2.9.3.

19. REQ 2.14.8: What are the electrical requirements for position sensors?

Response: General electrical requirements are provided. Any detailed requirements for the position sensors will be discussed and agreed to as part of the design effort. If there are particular requirements of concern or that drive the design, the supplier should identify them.

20. What are the lateral and local mode frequency requirements for the launch lock?

Response: No requirement for Launch Lock frequency. Stiffness is specified in 2.3.2 and 2.3.3.

21. REQ 2.3.4: In the spec the conversion to English is wrong, which values are the correct ones to use?

Response: Metric values are correct. Corrected English values appear in the table below:

Table 1 Launch Lock External Loads during Unlock

Component Load Design Level Loads

Axial 4388 N (986 lbf)

Lateral 3319 N (746 lbf)

Torsion (about longitudinal axis) 105 N-m (929 in-lbf)

Bending (perpendicular to longitudinal axis) 596 N-m (5275 in-lbf)

22. What are the allowable moments that can be dumped into the IC under the LLVIS stroke requirements defined in Table 5 on pg. 13?

Response: IC strength at the isolator interface will be evaluated based on the LLVIS design. It is not expected to be a driving condition.

23. Will Probable Cost Estimates be part of the evaluation of Cost?

Response: Yes if needed; per RFP Provisions M.3 and M.4.

24. Paragraph 2.2.4 A

The SOW states that a PDR shall be held prior to fabrication of the qualification units.

We prefer the following program flow.

PDR

Fabricate and test EDU (EDU testing completed prior to CDR)

CDR/MRR (We prefer to complete CDR prior to fabrication of qualification unit)

Fabricate and test qualification unit

Fabricate and test acceptance units upon successful completion of qualification testing

Is it acceptable to fabricate qualification units following CDR assuming the supplier can meet the desired deliverable schedule?

Response: Follow the SOW. Per Provision L.11, “provide any new or innovative methods, techniques, or technologies and fully explain how they impact the performance of the SOW under the proposed contract. Efficiencies should be quantified where possible.” However, please be advised that if the evaluation team finds the approach unacceptable, the proposed approach may receive a weakness or deficiency.

25. 2.2.1 Isolator Transmissibility

The Isolator transmissibility shall be less than the maximum requirement shown in Figure 4

Does this transmissibility requirement only apply in the isolator axial direction? Based on the coordinate system defined in Figure 5.

Response: Yes, the transmissibility requirement applies in isolator's axial direction only.

26. 2.2.2 Isolator Resonant Mode Frequency

The stiffness and damping properties of the Isolator shall be sized to produce an Isolator resonant frequency of 1.2 Hz +/-0.06 Hz as verified by analysis and the Isolator level axial transmissibility test.

Does the 1.2 Hz requirement and ±0.06 Hz tolerance only apply to the axial mode of the isolator?

Response: Yes, the 1.2 +/- 0.06 Hz requirement applies to isolator's axial fundamental mode.

27. 2.2.8 Isolator External Applied Load

The Isolator shall withstand an externally applied load of 890 N (200 lbf) axial tension and compression and 11 N-m (100 in-lb) bending moment simultaneously without damage or degradation of performance. (TBR1)

Is the isolator operational (unlocked) during the application of this load?

Can hard stops be implemented to alleviate load if unlocked?

Explanation of question: This requirement yields a maximum unlocked displacement that is an order of magnitude greater than the current technology can provide – within this industry – based on the desired suspension mode frequency as discussed below. This discussion assumes the answer to question 4a is ‘Yes.’

To support an 1838 lb mass with a spring at 1.2 Hz, the required stiffness is 271 lb/in. Just considering the 200 lb axial load, the resulting displacement of the module is 0.74” more than 5x the displacement from the feasibility study.

To develop a design that could meet this much larger displacement requirement, the isolator mass and volume allocation will most likely need to increase versus what is currently in the specification. It is unclear if any solution will be possible without relief from this requirement and others.

It is assumed that these external loads are developed during assembly of the vehicle due to interface flatness and hole position tolerances. Other programs have mitigated this issue with preloaded pinned joints. We realize that this end condition is not acceptable within the context of this solution.

Response: The loads in this requirement apply to the isolator or isolator section of an integrated assembly with the launch lock portion unlocked. The intent is that the loads in this requirement can be reacted by hardstops. It is not intended that the springs alone react these loads. These loads are specified to prevent damage in the event of inadvertent loading during handling and spacecraft testing. This is why the specification defined requirements for hard stops.

28. Can preloaded pin joints be included within the design architecture?

Historical programs that use flexures as end conditions had axial frequencies in the 10 Hz range and were not as sensitive to these external loads.

Response: Designs with joints that slip (break friction) during launch or on-orbit operation are undesirable/unacceptable.

29. 2.3.10 Minimum Number of Launch Lock Cycles

The Launch Lock shall be capable of a minimum of seven (7) unlock/lock cycles following delivery to GSFC. It shall meet all requirements after this number of cycles.

Please confirm that these are manual unlock/lock cycles.

Response: These are intended to be flight-like actuations. Refurbishment is acceptable after actuation per 2.3.5.

30. 2.9.1 Sine Vibration Levels and 2.9.2 Random Vibration Levels

Please confirm that sine and random vibration levels only apply when the isolation modules are locked.

Response: This question implies an integrated isolator/launch lock assembly. In the case of an integrated assembly, the sine and random levels apply with the launch lock portion locked.

31. Are the following 2.2.8, 2.3.4, 2.5.2, 2.9.5 and 2.9.6.1 applied at the same time or independently?

2.2.8 Isolator External Applied Load

The Isolator shall withstand an externally applied load of 890 N (200 lbf) axial tension and compression and 11 N-m (100 in-lb) bending moment simultaneously without damage or degradation of performance. (TBR1)

2.3.4 Launch Lock External Loads during Unlock

The Launch Lock shall unlock and comply with all applicable requirements while experiencing the applied external loads defined in Table 4, combined and applied in all directions, over the operational temperature range.

Table 4 Launch Lock External

Loads during Unlock Component

Load

Design Level Loads

Axial 4388 N (945 lbf)

Lateral 3319 N (675 lbf)

Torsion (about longitudinal axis) 105 N-m (606 in-lbf)

Bending (perpendicular to longitudinal axis)

596 N-m (4951 in-lbf)

Response: These requirements are intended to be independent.

32. Do the 2.3.4 loads turn into the loads in 2.2.8 after unlocking the isolators?

Response: The loads defined in 2.3.4 are unrelated to the loads in 2.2.8.

33. Otherwise, how do they go away? The proposed isolator will increase in length by

0.189”. The 0.189” axial stroke will introduce additional bending into the flexures.

Response: The loads defined in 2.3.4 are unrelated to the loads in 2.2.8.

34. Has the change in isolator length due to unlocking been considered in the gap requirements?

Response: Not specifically. The gap requirements were determined relative to the ideal deployed configuration including the effects of thermal distortion and assembly tolerance.

Additional work will be required to address the change in length due to unlocking.

35. 2.5.2 LLVIS Unit Stroke Requirements

The requirements for LLVIS Units are shown in Table 5. The components of stroke are defined in 2.5.1. For the Launch Lock and the Launch Lock portion of the Integrated Isolator/Launch

Lock, the stroke requirements apply in the unlocked mode. The components of stroke shall be applied simultaneously in all combinations.

Table 5 LLVIS Unit Stroke

Requirements Unit:

Isolator, Launch Lock, and Integrated

Isolator/Launch Lock

Stroke Component, mm (inches)

Axial, mm (in) Lateral, mm (in) Torsion, milliradians Bending, milliradians

+/-4.8 (0.189) +/-5.4 (0.212) +/-7 +/-10.1

Are the strokes in requirement 2.5.2 due to on-orbit thermal and integration misalignment?

Response: Yes.

36. If so do these strokes cover the loads in 2.2.8 and 2.3.4?

Response: As discussed above, the loads in 2.2.8 are for damage prevention for handling/I&T only. The defined stroke requirements are consistent with the loads in 2.3.4.

37. 2.9.5 On-Orbit Dynamic Environment

The Unit shall withstand the following on-orbit loading (Launch Locks in unlocked mode) over the survival temperature range. The loads are to be applied simultaneously.

Table 8 On-Orbit

Dynamic Loads

Component

Units Value

Force, axial N (lbf) 112 (25)

Force, lateral N (lbf) 74 (17)

Moment, bending N-m (in-lbf) 0.4 (3.9)

2.9.6.1 Operational Temperature Environment

The Unit shall meet all operational performance specifications while exposed to vacuum environment as defined in 2.9.7 and while exposed to the Operational temperatures in Table 9.

Do the strokes in 2.5.2 already include the effects of thermal?

Response: Yes.