ASTM E2900 - 24

VIP免费

Carl 2024-09-04 53 263.42KB 10 页 16星币

Designation: E2900 −24
Standard Practice for
Spacecraft Hardware Thermal Vacuum Bakeout
1
This standard is issued under the ﬁxed designation E2900; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice establishes methods for thermal vacuum
bakeout of spacecraft and spacecraft components.
1.2 This practice deﬁnes the equipment, environment, and
certiﬁcation criteria for each type of bakeout.
1.3 The methods deﬁned in this practice are intended to
reduce component outgassing rates to levels necessary to meet
mission performance requirements of the contamination sensi-
tive hardware. Times, temperatures, and conﬁgurations con-
tained in this document have been found to provide satisfactory
results. Experienced operators may ﬁnd that other, similar
times, temperatures and conﬁgurations have provided satisfac-
tory results. If deviations from these criteria are deemed
appropriate, they should be detailed in the bakeout report.
1.4 This practice describes three bakeout methods: Method
A, using prescribed time and pressure criteria; Method B, using
prescribed QCM stabilization rate criteria; and Method C,
which measures the QCM deposition rate.
1.5 Determination of the acceptable molecular outgassing,
selection of the bakeout method, and determination of the
speciﬁc test completion criteria are the responsibility of the
user organization.
1.6 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accor-
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
2
E296 Practice for Ionization Gage Application to Space
Simulators
E834 Practice for Determining Vacuum Chamber Gaseous
Environment Using a Cold Finger
E1234 Practice for Handling, Transporting, and Installing
Nonvolatile Residue (NVR) Sample Plates Used in Envi-
ronmentally Controlled Areas for Spacecraft
E1235 Test Method for Gravimetric Determination of Non-
volatile Residue (NVR) in Environmentally Controlled
Areas for Spacecraft
E1546 Guide for Development of Fire-Hazard-Assessment
Standards
E1559 Test Method for Contamination Outgassing Charac-
teristics of Spacecraft Materials
E1560 Test Method for Gravimetric Determination of Non-
volatile Residue From Cleanroom Wipers
E1731 Test Method for Gravimetric Determination of Non-
volatile Residue from Cleanroom Gloves
2.2 Other Standards:
IEST-STD-CC1246 Product Cleanliness Levels and Con-
tamination Control Program
3
MIL-STD-1246 Product Cleanliness Levels and Contamina-
tion Control Program
4,5
MIL-P-27401 Propellant Pressurizing Agent, Nitrogen
5
ISO-14644 Cleanrooms and associated clean environments
3
FED-STD-209 Federal Standard, Airborne Particulate
Cleanliness Classes in Cleanrooms and Clean Zones
5,6
1
This practice is under the jurisdiction of ASTM Committee E21 on Space
Simulation and Applications of Space Technology and is the direct responsibility of
Subcommittee E21.05 on Contamination.
Current edition approved July 1, 2024. Published August 2024. Originally
approved in 2012. Last previous edition approved in 2019 as E2900 – 19. DOI:
10.1520/E2900-24.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at www.astm.org/contact. For Annual Book of
ASTM Standards volume information, refer to the standard’s Document Summary
page on the ASTM website.
3
Available from Institute of Environmental Sciences and Technology (IEST),
Arlington Place One, 2340 S. Arlington Heights Rd., Suite 100, Arlington Heights,
IL 60005-4516, http://www.iest.org.
4
MIL-STD-1246 may be used in lieu of IEST-STD-CC1246 by mutual agree-
ment of the parties in the contract.
5
Available from DLA Document Services, Building 4/D, 700 Robbins Ave.,
Philadelphia, PA 19111-5094, https://assist.daps.dla.mil/quicksearch/.
6
FED-STD-209 may be used in lieu of ISO-14644 by mutual agreement of the
parties in the contract.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
1

3. Terminology

3.1 Deﬁnitions:

3.1.1 ambient conditions, n—room temperature and pres-

sure.

3.1.2 bakeout, n—a process by which volatile molecular

contaminants are removed from a spacecraft component or

article by exposing it to vacuum and elevated temperature.

3.1.2.1 Discussion—When the intent is to describe an

action, this should be two words: to “bake out.”

3.1.3 cold ﬁnger, n—the device that is used in collecting the

sample of the residual gases in an evacuated vacuum chamber.

3.1.4 cold plate, n—a vacuum stable metal plate ﬁlled with

liquid nitrogen used to condense the volatile molecular (or

outgassing) contamination generated by the space component

undergoing the bakeout.

3.1.5 cold shroud, n—the metal lining of the vacuum

chamber (usually black painted or black anodized) used as a

heating device or when ﬁlled with liquid nitrogen, used to

simulate deep space.

3.1.6 cold wall test, n—a test conﬁguration used to simulate

deep space, requiring analytical view factors for the calculation

of outgassing rates.

3.1.7 hot wall test, n—a test conﬁguration, in which the

hardware is isothermal with the surrounding environment; it

assumes homogenous mixing for calculating hot outgassing

rates.

3.1.8 outgassing, n—the evolution of a gas from a material,

usually in a vacuum.

3.1.9 outgassing rate (g/s), n—the net rate of mass loss from

a material sample as a result of outgassing.

3.1.9.1 Discussion—Outgassing rate can be normalized per

unit sample surface area and expressed as g·cm

-2

·s

-1

or it can be

normalized per unit initial sample mass and expressed as

g·g

-1

·s

-1

3.1.10 pre-bakeout, n—to clean or condition, or both, a

vacuum chamber prior to its use for ﬂight hardware.

3.1.11 QCM deposition rate, n—the QCM output (or beat)

frequency change per unit time caused by the mass of a

molecular species condensing on the QCM crystal.

3.1.11.1 Discussion—The QCM deposition rate units may

be converted to g/cm

/s by multiplying by the mass loading

constant (m) provided by the vendor for the crystal used (that

is, for a 10 Mhz crystal, m = 4.42E-9g/cm

Hz).

3.1.12 QCM deposition rate stabilization (Hz/hr/hr), n—the

acceleration of the QCM deposition rate.

3.1.13 QCM thermogravimetric analysis (QTGA), n—a

technique in which a QCM is heated at a constant rate to

remove a collected deposit.

3.1.14 quartz crystal microbalance (QCM), n—a device for

measuring small quantities of mass using the properties of a

quartz crystal oscillator.

3.1.15 temperature stabilization, n—temperature stabiliza-

tion has been reached when the unit temperature is within 2 °C

of the speciﬁed temperature and the rate of change is less than

3 °C per hour as measured with the unit control thermocouple.

3.1.15.1 Discussion—This rate can be extrapolated over a

20 min sample time. For example, stabilization has been

achieved if two temperature measurements taken 20 min apart

are within 1 °C of each other.

3.1.16 total collection area, n—the sum of the surface area

in the vacuum chamber that is equal to or colder than the QCM

crystal temperature.

3.1.17 visibly clean highly sensitive (VCHS), n—visual in-

spection conducted at a distance of 15 cm to 50 cm (6 in. to

18 in.) with white light of at least 1076 lumens/m

(100 fc)

intensity; it may be accompanied by ultraviolet (UV) inspec-

tion as well.

3.2 Acronyms:

3.2.1 GN2—Gaseous Nitrogen

3.2.2 LN2—Liquid Nitrogen

3.2.3 MLI—Multi-Layer Insulation

3.2.4 NVR—Nonvolatile Residue

3.2.5 RGA—Residual Gas Analyzer

3.2.6 QCM—Quartz Crystal Microbalance

3.2.7 QTGA—QCM Thermogravimetric Analysis

3.2.8 TQCM—Temperature controlled Quartz Crystal Mi-

crobalance

3.2.9 VCHS—Visibly Clean Highly Sensitive

4. Summary of Practice

4.1 A vacuum chamber is conﬁgured in the same manner it

would be conﬁgured for the hardware bakeout, except that the

test article is omitted.

4.2 The empty chamber and its support equipment is

cleaned and inspected to VC-0.5-1000 per IEST-STD-CC1246.

Then, the chamber is evacuated and pre-baked at a temperature

10 °C above the hardware bakeout temperature, using the same

procedure used for the component hardware.

4.2.1 For Method A, the chamber is ready for installation of

ﬂight hardware after 24 h under vacuum and temperature and

a visual inspection.

4.2.2 For Methods B and C, the chamber is ready when the

measured QCM deposition rate, witness sample data, and

visual inspection results are acceptable.

4.3 The spacecraft component to be thermal vacuum baked

is exposed to an elevated temperature and a vacuum of 5.0E-5

torr or less for a speciﬁed amount of time or until the desired

outgassing rate is reached.

4.3.1 Method A—The bakeout is terminated at a speciﬁed

time limit and stabilized chamber pressure.

4.3.2 Method B—The bakeout is terminated when the QCM

deposition rate stabilizes to a speciﬁed level.

4.3.3 Method C—There is a bakeout phase and a certiﬁca-

tion phase. The hardware is exposed to the program speciﬁc

qualiﬁcation temperature (usually 10 °C above maximum pre-

dicted on-orbit operating temperatures) or the maximum toler-

able temperature of the component in accordance with Method

B. In the certiﬁcation phase, the temperature is lowered to the

E2900 − 24

predicted maximum on-orbit operating temperatures and the

rate is measured. This provides realistic information that can be

used to obtain outgassing rates in on-orbit conditions and also

provides information about the dependency of the component

outgassing rates on temperature. The bakeout is terminated

when the QCM deposition rate reaches a speciﬁed level.

4.3.4 At the end of the bakeout, witness plates are removed

and NVR wipe samples are taken of the cold plate.

5. Apparatus

5.1 Description—The bakeout apparatus consists of three

main subsystems: a vacuum chamber (including ground sup-

port equipment), a temperature control system, and a data

acquisition system. Methods B and C require a QCM.

5.1.1 Vacuum Chamber—The principle components of the

vacuum chamber are the pump, the chamber shrouds, and the

cryogenic cold plate if needed.

5.1.1.1 The pump should be capable of maintaining the

required pressure for a mean free path greater than the largest

dimension of the chamber. Diffusion pumps use oil to capture

gases and will increase deposition on the QCM. A cold trap

between the diffusion pump and vacuum chamber is recom-

mended to reduce backstreaming. Clean, oil-free pumps such

as cryogenic, sorption, and turbomolecular are preferred to

avoid backstreaming.

5.1.1.2 High Vacuum Gauge—An ion gauge or other gauge

capable of monitoring pressures below 1e-4 torr. See Practice

E296 for guidance in using ionization gauges.

5.1.1.3 Chamber Shrouds—The chamber shall be equipped

with an inner lining or shroud that provides temperature control

which is maintained cold for “cold wall” testing and hot for

“hot wall” testing. A bakeout box may be substituted for the

shroud for hot wall testing.

(1) Cold wall testing requires the hardware to be heated

while the chamber shroud is kept cold, typically at LN

temperatures.

(2) Hot wall testing requires an environment that is isother-

mal with the hardware, this is typically accomplished with a

bakeout box or the chamber shrouds. The bakeout box is an

enclosed structure which surrounds the hardware and provides

uniform heating of components. There are only holes in the box

to allow for a small planned vent and a view port for the QCM.

The chamber shroud is normally heated with hot GN

and the

heater plates operate using heater tapes or circulating hot ﬂuid.

Whichever heating system is chosen, it should be sufficient to

heat the item uniformly. Thermocouples should be placed

appropriately to insure uniform heating of the hardware.

5.1.1.4 Cold Traps—There are three different types of

equipment that can be used to trap contaminants: a LN

ﬁlled

cold wall of the shroud, a LN

ﬁlled cold plate/cold ﬁnger, or

the cryopump/diffusion LN

trap. The cold trap is kept cold

throughout the test and may be analyzed afterward for con-

taminant identiﬁcation.

5.1.2 Temperature Control System—All temperatures of the

bakeout hardware and the QCM are maintained by indepen-

dently controlled heaters to a precision of 62 °C.

5.1.2.1 Heating Equipment—In general, six different types

of equipment may be used to heat the component: a bakeout

box, heat lamps, resistance bars, heater plates, heater tapes, or

the chamber shroud. Methods A and B are independent of the

method of creating the environment temperature, while

Method C requires either a hot wall or cold wall conﬁguration.

(1) Arrays of heat lamps or resistance bars are commonly

used for solar panels.

(2) The chamber shroud or aluminum heater plates are

commonly used for electrical components. The chamber

shroud is normally heated with hot GN

and the heater plates

operate using heater tapes or circulating hot ﬂuid.

(3) Heater tapes can be used on the component directly, but

heater tape adhesives can bias the results and possibly con-

taminate the hardware.

5.1.3 Data Acquisition System—Data acquisition, storage,

and manipulation can be accomplished by any method that is

capable of monitoring QCM frequencies, QCM temperatures,

QCM heater/cooler voltages, hardware temperatures, chamber

pressure, and data collection times at speciﬁed intervals. The

system should be able to store collected data for later retrieval

and analysis. An automated, computer operated data collection

system is recommended.

5.1.3.1 The QCM heater/cooler voltage is used as a diag-

nostic tool. If there is signiﬁcant variation in the QCM

frequency, it may be related to poor QCM heater/cooler

control.

5.1.3.2 Data storage intervals should be short enough to

collect inherent variability of the QCM collection device. It has

been found that 1 min to 5 min between records is satisfactory.

5.1.4 QCM—The placement of the QCM has a signiﬁcant

effect on the measurement of outgassing rates. If the QCM

views hot chamber surfaces capable of re-emitting

contamination, such as it would in a hot box, the readings may

be artiﬁcially high. If it views a cold shroud, the readings will

be too low.

5.1.4.1 The QCM used for this test shall have a sensitivity

of at least 1.0E-08 g·cm

-2

·Hz

-1

. 10 MHz or 15 MHz crystals

meet this requirement and are typically used for this applica-

tion.

5.1.4.2 The QCM shall be thermally connected to a heat

sink enabling the QCM to operate in its full temperature range.

It may be necessary to cool the heat sink mounting bracket with

ﬂuid or gas to keep the temperature stable.

(1) The sink for a TQCM must be maintained at no more

than 40 °C above the crystal operating temperature (see TQCM

manual for details). This ensures that the indium seals will not

melt due to internal heat generated by the TQCM. It may be

necessary to heat a TQCM if the surrounding area is too cold

for its electronics. An alternative is to provide multi-layer

insulation to thermally decouple the TQCM electronics from

the cold environment.

(2) CQCMs are designed to withstand and perform at

cryogenic temperatures as well as any temperature up to the

maximum allowed by the manufacturer. This is often 80 °C.

5.1.4.3 For a cold wall test, the QCM deposition rate must

be monitored by the QCM positioned such that its ﬁeld of view

is completely ﬁlled by the item undergoing bakeout. Since the

QCM has a ﬁeld of view between 143° and 150°, this means

placing the QCM within several centimetres of the hardware. If

E2900 − 24

文档加载中……请稍候！
如果长时间未打开，您也可以点击刷新试试。

下载文档到电脑，查找使用更方便

亲，本站95%以上的标准规范都面向会员免费，办理VIP会员下载更省钱，平均每篇不到2元

立即下载 VIP免费下载

摘要：

ASTM E2900 - 24 是美国材料与试验协会发布的最新版本标准规范，主要针对先进制造技术中的材料性能测试与评估方法进行详细规定。该标准适用于航空航天、汽车、医疗设备等高端制造领域，旨在为工程师和研究人员提供统一的测试流程、数据记录要求及结果分析指南。通过遵循 ASTM E2900 - 24，企业能够提升产品质量的一致性、可靠性和可追溯性，同时降低制造过程中的不确定性和风险。该标准特别关注增材制造（3D打印）等新型工艺的验证与鉴定，帮助用户确保材料在极端工况下的力学性能和耐久性。无论是研发

展开>> 收起<<

ASTM E2900 - 24.pdf

共10页,预览4页

还剩页未读，继续阅读

声明：本文档系会员上传，若文档所含内容侵犯了您的版权或隐私，请立即通知，我们立即给予侵权申诉删除！

ASTM E2900 - 24

相关推荐

开通VIP享超值会员特权

相关内容

热门标签

举报选择: