***The following is provided for informational purposes to all
prospective respondents. The date and time for submission of responses
to RFI3-2147 remains unchanged.***

**Questions & Answers**

The RFI is not a requirements document. The intent of the RFI, as
stated, is to seek ideas and information from potential offerors for use
in government procurement planning. With this in mind, NASA is
requesting technology information and cannot provide specific direction
at this time. The following response to questions is provided to clarify
some of the desired characteristics for avionics products addressed in
the RFI.

Q1a: Are you restricting the supplier to an LRU-based solution or is a
rack with LRM(odules)'s acceptable?

No, we are not restricting the supplier to an LRU-based solution as
opposed to LRMs. This would be subject to trade.

Q1b: Is there an envisioned maximum size and power limitation on the
LRU(s)?

Maximum size & power for LRU has not been identified. Minimum size and
low power consistent with other design goals are important.

Q2a: What is the reliability requirement for the LRU/LRM?

High reliability is important as stated in the RFI; however, there is no
specific reliability number at this time.

Q2b: Does this require the same reliability levels for a single-string
system as for a multiple-string/redundant system?

No, not from a system standpoint. The RFI should not be interpreted as a
requirement that all of the levels of redundancy be implemented internal
to a single LRU, only that an LRU should be capable of supporting an
architecture that may have W, X, Y, or Z number of strings.

Q3: What are the goals for C-BIT and I-BIT?

Tell us what is achievable.

Q4a: Regarding definition of \"State-of-Art,\" does this include
commercial processors such as PowerPC or Pentium families or only
high-reliability processors?

Yes, all potential processors should be considered. We have not
eliminated any processor types.

Q4b: What are the \"lessons learned\" from the previous TA-3 avionics
subsystem effort?

-   We need to have buy-in from the TA-1 Architecture (i.e. vehicle)
    contractors for our avionics product(s)

-   Restricted Data Rights is a major concern and can be a major factor
    in gaining buy-in by the Architecture contractors.

-   We also need to be cognizant of the fact that advances will occur in
    the avionics and computing industry without NASA funding; we need to
    enable a 2^nd^ Gen RLV avionics architecture or framework that will
    allow us to take advantage of future capabilities that will become
    state-of-the-art by the time a 2^nd^ Gen vehicle actually flies.

-   NASA is also very interested in funding avionics work pertaining to
    improved operations and health management.

Q5a: Is a completely passive thermal control system envisioned in which
there are no moving parts for cooling in the entire vehicle? Is a
passive thermal control system envisioned in which there are no moving
parts for cooling in the modular LRU?

The goal is to eliminate active thermal control to the extent feasible.

Q5b: Does the active cooling mentioned in the RFI include the use of
heat transfer media such as air or water in the modular LRU or the use
of external heat sinks such as cold plates?

Yes

Q6: Are there any Pre-planned Product Improvement upgrades planned in
the Avionics system for the lifecycle of the SLI RLV?

No, there are no pre-planned upgrades. However, we look for ideas as to
how the RLV avionics system could be designed to incorporate (at minimal
cost and schedule impact) improved technologies as they become
available.

Q7a: Will the radiation levels (esp. SEU) differ by Design Reference
Mission Profiles?

Yes

Q7b: What are those radiation requirements?

The requirements must be determined by evaluation of the Design
Reference Missions that are currently being redefined

Q7c: Is it anticipated that launches will be required during active
Solar Flare activity?

Possibly.

Q8: Can you quantify and/or prioritize the LRU requirements in an
assumed level of importance?

No, not at this time. The listing of LRU attributes in the RFI are in a
random order.

Q9: Please clarify the definition of "widely available bus standard" and
your requirement for it (e.g., PCI, VME) as opposed to an Open System
architecture having a proprietary bus standard.

The high-speed data bus addressed in the RFI is a data bus for
interconnection between LRUs, not a backplane bus such as PCI and VME

Q10: Do BIT/ diagnostics needs address the physical wiring verification
and/or the health of the nodes/terminals on the bus?

Both

Q11: "A capability to modify all flight code and data by command, at all
memory locations is desired." What is the background on this
requirement? Has NASA considered the impact of FAA certification on this
requirement? For what would this capability be used?

No to FAA......Capability is to correct errors without a total
recompilation of flight code. Reduces maintenance costs and verification
and testing costs.

Q12: Please provide more definition of this requirement, e.g.,
timeline/command processor. What would this capability be used for, or
is this just a utility?

Timeline processor could provide mission profile and sequence and
specialized sequences such as payload operations and emergencies. This
has proved to reduce maintenance costs by an order of magnitude or
greater.

Q13: What is the definition of \"certifiable\" and to what standard?
Does this apply to the development tools?

Certifiable -- languages/libraries have gone through their own
verification program. Using certifiable languages reduces amount of
verification and cost vs. non-cert.

Q14: Please clarify "Low SW complexity factor."

Software Complexity as defined in IEEE Standard 729-1983:

The degree of complication of a system or system component, determined
by such factors as the number and intricacy of interfaces, the number
and intricacy of conditional branches, the degree of nesting, the types
of data structures, and other system characteristics.

There are commercially available tools such as McCabe that parse source
code and output a list of complexity measures.

Q15: Commercial SW such as VxWorks requires purchasing licenses. Would
NASA consider acquiring licenses of operating SW that has been flight
certified? If Yes, what are your requirements for this, e.g., Open
Architecture, 3^rd^ party supported?

Depends on architecture that is eventually used.

Third party software potentially drives costs up and reliability down.

Q16: What are the envisioned standard and agency for certification of
software languages and libraries?

DOD is the certifying agency, and ADA is the only language that is known
to be presently certified.