SATPC0043180 Tab 04 Specs Rev.pdf

Effective Date: September 30, 2026 Expiration Date: September 30, 2031

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National Aeronautics and Space Administration

Goddard Space Flight Center Greenbelt, Maryland

VASI-SNSR-SPEC-0002, Revision – Venus Atmospheric Structure Investigation (VASI)

NASA/GSFC Code 436

VASI Pressure Transducer Specification

GSFC VASI CMO (RP)

September 30, 2026

RELEASED

VASI Pressure Transducer Specification VASI-SNSR-SPEC-0002, Revision - Effective Date: 09/30/2026 iii Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

400-FORM-0002 (4/16/2014)

Preface This document is a Venus Atmospheric Structure Investigation (VASI) configuration control board (CCB) controlled document. Changes to this document require prior approval of the CCB Chairperson or designee. Proposed changes shall be submitted in the Technical Data Management System (TDMS) via a configuration change request (CCR) along with supportive material justifying the proposed change. Changes to this document will be made by complete revision.

All of the requirements in this document assume the use of the word "shall" unless otherwise stated.

Questions or comments concerning this document should be addressed to:

VASI Configuration Management Office Mail Stop: 436 Goddard Space Flight Center Greenbelt, Maryland 20771 iv Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

Change History Log

Revision Effective Date Description of Changes (Reference the CCR Approval Date)

Revision - 09/30/2026 Released per VASI-CCR-0004, approved 09/29/2026.

v Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

Table of TBDs/TBRs/TBSs [optional]

Action Item No.

Location Summary Individual/ Organization

Actionee vi Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

Table of Contents

1 INTRODUCTION

1.1 Purpose

1.2 Scope

1.3 Applicable Documentation

2 SPECIFICATION

2.1 Design Requirements

2.1.1 Configuration

2.1.2 Design Lifetime

2.2 Pressure Requirements

2.2.1 Pressure Range

2.2.2 Proof Pressure

2.2.3 Design Burst Pressure

2.2.4 Secondary Containment

2.3 Electrical Requirements

2.3.1 Pressure Output

2.3.2 Temperature Output

2.3.3 Excitation Voltage

2.3.4 Power

2.3.5 Grounding

2.3.6 EEE Parts

2.3.7 Connector

2.4 Accuracy and Precision Requirements

2.4.1 Accuracy

2.4.2 Temperature Compensation

2.4.3 Response Time

2.5 Leakage Requirements

2.6 Physical Requirements

2.6.1 Mass

2.6.2 Envelope

2.6.3 Process Port

2.6.4 Mounting

2.7 Materials and Compatibility

2.7.1 Cleanliness

2.8 Identification and Markings

2.9 Environmental Requirements

2.9.1 Temperature

2.9.2 Random Vibration

2.9.3 Shock

2.9.4 Acceleration

2.9.5 EMI/EMC

2.9.6 Radiation

Appendix A Abbreviations and Acronyms vii Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

List of Figures

Figure 1. Pressure transducers inside DAVINCI Figure 2. Pressure Transducer Configuration

List of Tables

Table 1. Random Vibration Levels Table 2. Shock Levels

Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

400-FORM-0002 (4/16/2014)

1 INTRODUCTION

1.1 Purpose

This document provides requirements for the design and development of pressure transducers for the DAVINCI Mission. These transducers will be part of the VASI pressure system (PRES) instrument.

1.2 Scope

VASI will have three pressure transducers mounted inside the DAVINCI Descent Sphere that will monitor the atmospheric pressure of Venus during its one-hour descent to the surface. The three pressure transducers cover the ranges 1 bar (14.5 psia), 10 bar (145 psia), and 100 bar (1450 psia). All are plumbed to a common manifold that is routed through the Descent Sphere shell to the pressure port as shown in Figure 1.

Figure 1. Pressure transducers inside DAVINCI.

1.3 Applicable Documentation

o VASI-SNR-SOW-0001, VASI Pressure Transducer Statement of Work o ANSI/AIAA S-080A, Space Systems – Metallic Pressure Vessels, Pressurized Structures, and Pressure Components o AWS D17.1, Fusion Welding for Aerospace Applications o IEST-STD-1246E, Product Cleanliness Levels – Applications, Requirements, and

Determination o NASA-STD-6016, Standard Materials and Processes Requirements for Spacecraft o GSFC-EEE-INST-002, Instructions for EEE Parts Selection, Screening, Qualification, and Derating o ASTM E595, Standard Test Method for Total Mass Loss and Collected Volatile

Condensable Materials from Outgassing in a Vacuum Environment

Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

400-FORM-0002 (4/16/2014)

2 SPECIFICATION

2.1 Design Requirements

2.1.1 Configuration

Pressure transducers shall be cylindrical with a process port and sensing diaphragm on one end, and an electrical connector on the other. See Figure 2.

Figure 2. Pressure Transducer Configuration

2.1.2 Design Lifetime

The Pressure Transducers shall meet the required timeline of 3.5 years pre-launch, a cruise time

2.8 years post-launch, and the required descent lifetime of 3 (three) hours for a total of 6.3 years.

2.2 Pressure Requirements

2.2.1 Pressure Range

The pressure transducers shall have the following designations and Maximum Expected Operating Pressures (MEOP):

a) Low Pressure Unit: 0-1 bar (0-14.5 psia)

b) Medium Pressure Unit: 0-10 bar (0-145 psia)

c) High Pressure Unit: 0-100 bar (0-1450 psia)

2.2.2 Proof Pressure

The pressure transducers shall be subject to a proof pressure at the process port as part of acceptance testing that is equal to 1.5 times the transducer’s MEOP:

a) Low Pressure Unit: 1.5 bar (22 psia)

b) Medium Pressure Unit: 15 bar (218 psia)

c) High Pressure Unit: 150 bar (2176 psia)

2.2.3 Design Burst Pressure

The pressure transducers shall be qualified to have the following design burst pressures at the process port that is equal to 2.5 times the transducer’s MEOP:

a) Low Pressure Unit: 2.5 bar (36 psia)

b) Medium Pressure Unit: 25 bar (363 psia)

c) High Pressure Unit: 250 bar (3626 psia)

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2.2.4 Secondary Containment

The pressure transducers’ secondary containment (volume exposed to the process fluid in the event of a sensing diaphragm leak or rupture) shall have a design burst pressure of at least 250 bar (3626 psia).

2.3 Electrical Requirements

2.3.1 Pressure Output

The pressure transducers’ signal output for pressure measurement shall be between 1.5 and 10 mV per Volt of excitation.

2.3.2 Temperature Output

The pressure transducers shall have a resistance temperature detector (RTD) installed inside the transducer that monitors the temperature of the sensing diaphragm. The pressure transducer RTD shall have a resistance of 1000 Ohms at room temperature. The RTD signal shall be accessible at the electrical connector. This purpose of this RTD is to improve the accuracy of the pressure measurement.

2.3.3 Excitation Voltage

The pressure transducer excitation voltage shall be 10 ±4 Vdc.

2.3.4 Power

The pressure transducer shall consume no more than 0.02 watts.

2.3.5 Grounding

The pressure transducer shall not tie its power return to its chassis.

2.3.6 EEE Parts

EEE Parts shall be selected, screened, qualified, and derated per GSFC-EEE-INST-002 level 3.

2.3.7 Connector

The pressure transducers shall have a circular six-pin connector on the end opposite the pressure port. Pins shall be (+)Power, (-)Power, (+)Pressure Signal, (-)Pressure Signal, (+)RTD, (-)RTD.

2.4 Accuracy and Precision Requirements

2.4.1 Accuracy

The Pressure Transducers’ Static Error Band accuracy shall be ±0.3% FSO or better using Best Fit Straight Line - Root Sum of Squares Method (BFSL-RSS).

The error value is given as percentages of full scale output, with each pressure transducer’s full scale output defined as the difference between the actual output at MEOP and the actual output at zero pressure at 20 ±3°C.

Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

2.4.2 Temperature Compensation

N/A

2.4.3 Response Time

The pressure transducers’ response time shall be 100 milliseconds or less.

2.5 Leakage Requirements

The pressure transducer shall have an external leak rate that is less than or equal to 1×10-6 standard cubic centimeters per second (sccs) helium when the pressure port is at MEOP and the transducers’ is in a vacuum.

2.6 Physical Requirements

2.6.1 Mass

The mass of each pressure transducer shall be 120 grams or less.

2.6.2 Envelope

The pressure transducer cylindrical body shall be less than 3.0 cm in diameter and less than 10.0 cm in length (including the electrical connector and process port).

2.6.3 Process Port

The pressure transducers shall have 304L or 316L CRES stainless steel process ports with the following dimensions:

Length: 3.81 to 5.08 cm (1.5 to 2.0 inches) Outer Diameter: 3.175 ± 0.05 mm (0.125 in. ± 0.002 in.)

Wall Thickness: 0.71 ± 0.05 mm (0.028 in. ± 0.002 in.)

2.6.4 Mounting

The pressure transducers shall have smooth cylindrical bodies that allow for mounting with “C” (ohm) clamps or “P” clamps.

2.7 Materials and Compatibility

The sensing diaphragm shall be made of 718 Inconel that is resistant to corrosion in a sulfuric acid environment. All other pressure transducer wetted materials shall be either CRES 17-4 PH, CRES 304L, CRES 316L, or similar. The process port shall be CRES 304L or 316L per Section

3.6.3. The transducer materials and welds shall show no degradation or loss of accuracy due to exposure for the mission life to any of the following fluids: Sulfuric Acid (at Venus), Carbon Dioxide, Air (0-100% relative humidity), Helium, Deionized Water, Argon, Isopropyl Alcohol, and Nitrogen. Polymeric materials shall meet ASTM E595 vacuum stability criteria of < 1% TML and < 0.1% CVCM.

2.7.1 Cleanliness

The internal wettable surfaces and external surfaces of the pressure transducers shall be cleaned to Level 100, R1 per IEST-STD-1246E.

Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

2.8 Identification and Markings

Each pressure transducer shall have the following information etched or inked on its external surface:

a) Manufacturer’s Name,

b) Model Number,

c) Serial Number,

d) Date of Manufacture,

e) Pressure Range,

f) Proof Pressure,

g) Excitation Voltage, and

h) Pressure and Temperature Output.

Additionally, each pressure transducer shall list the pin assignments on its external surface.

Inked markings shall be permanent and not be removable with isopropanol.

2.9 Environmental Requirements

2.9.1 Temperature

The pressure transducers shall have an operational temperature range of -40 to +121°C.

2.9.2 Random Vibration

The random vibration levels for the pressure transducers shall be as shown in Table 1.

Table 1. Random Vibration Levels

Freq (Hz) ASD Level (g2/Hz) Qualification Acceptance

20 0.020 0.010 32 0.164 0.082

150 0.164 0.082 175 0.080 0.040 500 0.080 0.040

2,000 0.020 0.010

OVERALL

(GRMS) 10.21 7.23

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2.9.3 Shock

The pressure transducers shall be qualified for the shock levels shown in Table 2.

Table 2. Shock Levels

Pressure Transducer Shock Levels Frequency

(Hz)

SRS (G), Q = 10

Acc/Flt PF/Qual 100 20 28

1,060 1080 1527 10,000 1080 1527

2.9.4 Acceleration

Quasi-static acceleration and deceleration represent the combination of steady-state accelerations and the low frequency mechanically transmitted dynamic accelerations that occur during launch and during entry into Venus’s atmosphere. The pressure transducers shall be designed to withstand 67.9 G without damage or degradation of performance. Loads are considered to act in any direction, one axis at a time.

2.9.5 EMI/EMC

This pressure transducer shall not be an emitter of or susceptible to electromagnetic signals.

2.9.6 Radiation

EEE parts and materials shall be selected for a total ionizing dose (TID) of 4.45 krad-Si (including 2× margin), behind 400 mils of equivalent aluminum shielding and 2 years non-operating lifetime, operating time is approximately one hour.

EEE parts shall not be susceptible to destructive single event latch-ups (SELs).

The design shall avoid or tolerate errors due to non-destructive single event upsets (SEUs).

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Appendix A Abbreviations and Acronyms

Acc acceptance BFSL best fit straight line CCB configuration control board CCR configuration change request CMO configuration management office CRES corrosion resistant CVCM collected volatile condensable material DAVINCI deep atmosphere Venus investigation of noble gases, chemistry, and imaging Flt flight FSO full scale output GSFC Goddard Space Flight Center MEOP maximum expected operating pressure NASA National Aeronautics and Space Administration PF proto-flight PRES pressure system RMS root mean squared RSS root sum squared RTD resistance temperature detector sccs standard cubic centimeters per second SEL single event latch-up SEU single event upset SPEC specification TBD to be determined TBR to be reviewed TDMS technical data management system VASI Venus atmospheric structure investigation