Assessment f the Rules n Heater De-Rating Reinhard Schlitt (1), Stephan-Andrè Kuhlmann (1), Bernd Carsten Sander (2), Susann Neustadt (2) (1) OHB System AG, Universitaetsallee 27-29, 28359 Bremen, Germany Email: ext.reinhard.schlitt@hb.de (2) ZARM-Technik AG, Am Fallturm, 28359 Bremen, Germany Email: bernd-carsten.sander@zarm-technik.de INTRODUCTION Fig. 1: Flexible Kaptn fil heater Surce: MINCO prduct catalgue Typical heater applicatins in a spacecraft are shwn in Fig. 2. Fr many temperature cntrl tasks in tday s spacecraft flexible fil heaters f the type shwn in Fig. 1 are used. These cmpnents cnsist f resistance wire netwrks embedded between tw insulatin layers (fr flight hardware in mst cases Kaptn ) bnded tgether by an internal adhesive, usually FEP. The peratinal temperature f a heater is mstly feedback-cntrlled by temperature sensrs r by thermstats, which are placed clse t the heater fil. The active cntrl f heaters limits their peratinal temperature band frm typically abut -25 C t prevent undesired lw equipment temperatures t abut +10 C fr prpellant systems. In general heaters are switched n at lw ambient temperatures and nt used at higher temperatures. Heater are typically attached t substrates f different materials and shapes: Metallic (Al-, Ti-allys, Invar, stainless steel, etc.), Cmpsites (CFRP, plymers, etc.), Flat structures, cylindrical r spherical bjects (tubes, tanks). A B C D E F Fig. 2: Typical Heater Applicatin in a Spacecraft (A: flat structure surface; B: munting baseplate; C: curved applicatin; D: black plated aluminium structure plate; E: cylindrical CFRP strut; F: Fibre-Wrapped Gas Tank) Presently requirements fr maximum heat flux density and pwer de-rating are nt fully defined and are therefre cntrversially discussed in different spacecraft prjects. A wrk prgramme was therefre executed t determine allwable maximum heat flux density (W/cm^2) during peratin, i.e. after the heater has been attached t its substrate and t assess the presently specified pwer de-rating rules. In particular the fllwing tasks have been perfrmed: Elabratin f an evaluatin test prgram that shall characterise the influence f bnding methds fr different substrates n the maximum allwable heat pwer which is related t a criteria n the temperature reached by the heater,
Perfrm the tests and evaluate the test results, prpse a way frward fr the definitin f maximum heat pwer density f heaters, Use the study utcme fr further discussins abut clarificatin and revisin f the ECSS heaters derating requirements. SITUATION IN EUROPEAN SPACE PROJECTS In mst Eurpean space prjects maximum pwer densities fr fil heaters are based n a rated pwer f 0,54 W/cm^2, as specified in ESCC 4009/002 [1]. Furthermre, it is required t de-rate the heater pwer with 50% as specified in ECSS-Q-ST-30-11C [2]. Fr example, in large space prjects, which are currently running at OHB System AG, the fllwing has been agreed with the custmer: SGEO: 0,54 W/cm^2 as maximum value fr FM hardware. Qualificatin is perfrmed with 0,54 x 2 = 1,08 W/cm^2 in rder t meet the 50% derating requirement, EXOMARS: 0,27 W/cm^2. Applicatin f the 50% derating requirement n the 0,54-W/cm^2 value as specified in [1] and [2], MTG: 0,27 W/cm^2. Applicatin f the EXOMARS apprach, which in this case has been agreed with the prime cntractr TAS (F). Applicatin f the 50% derating requirement n the 0,54-W/cm^2 value as specified in [1] and [2]. It can be nted that the mentined prjects refer t ESCC and ECSS requirements, but the interpretatin f its applicability is quite different. REQUIREMENTS FOR HEATER POWER AND DE-RATING IN EUROPEAN AND US STANDARDS Eurpean Standards Definitin Of Heater As EEE Part A heater is crrectly defined as cmpnent, which is synnymus fr part. The term "cmpnent" is preferred fr EEE devices. Hwever, the classificatin f a flexible fil heater as EEE part seems questinable. In general, EEE parts are lcated internal t electrnic equipment and de-rating requirements are specified since these parts are nrmally nt redundant. The intentin f EEE parts as being cmpnents internal t equipment is expressed in [2], which states: Derating is a means f enhancing the end-f-life perfrmance f equipment and The aim is t btain reliable and high perfrmance equipment withut ver-sizing f the cmpnents. In cntrast, fil heaters are lcated always utside f an equipment and fall therefre nt under the general definitin f EEE parts. Critical heaters are either internally redundant r a cld redundant item is placed clse t the nrmally perated heater. There are therefre sme arguments t classify fil heaters as a general thermal cntrl item, which need t be verified at qualificatin levels and applied after verificatin at acceptance level (similar t ther thermal cntrl items). Maximum Allwable Pwer Density The maximum rated pwer fr a fil heater is specified in [1] with 0,54 W/cm^2, at ambient temperature f 25 C, but perating suspended in still air. The ESCC and ECSS system des presently nt define the maximum heater pwer, when attached t a substrate within a spacecraft. The nly remark in this respect is cntained in [2], Chapter 6.26.2.8: Actual rated pwer shall be specified in the applicable heater design drawing and be determined by taking int accunt the thermal prperties f the munted heater in the applicatin. There is n advice hw the thermal prperties f the munted heater shall be taken int accunt. As a cnsequence it can be stated that a generic pwer density specificatin fr attached heater des presently nt exist. The prperty shuld, instead, be related t specific applicatins and must be determined fr each f these applicatins. Due t the missing specificatin fr maximum pwer density, prjects have taken the specified value used fr heater qualificatin at the supplier, i.e. 0,54 Watt/cm^2 [1]. Hwever, this pwer rating is defined fr a nt-attached heater, i.e. suspended in air and the 0,54 W/cm^2 are specified in rder nt t verheat the unit in this cnditin.
Heater Derating As mentined abve, EEE parts, which are lcated internal t equipment, are specified t be de-rated in rder t increase the reliability f the entire equipment. The de-rating requirements, specified in [1] are fr heater suspended in still air and thus nt applicable fr heater attached t a substrate. Reference [2] specifies fr fil heaters, when classified as EEE part, a derating f 50%. Several prjects use errneusly the abve mentined 0.54 W/cm^2, which are specified fr heater suspended in still air, and apply in additin the 50% derating requirement. The apprach finally leads t the very lw pwer density f 0.27 W/cm^2. US Standards The heater pwer and de-rating requirements in US standards seems t be simpler. The gverning Standard is the EEE- INST-002 [3], which calls up the NASA heater specificatin [4]. Relevance f these tw dcuments: EEE-INST-002 [3]: Cntains requirements fr heater qualificatin (Sectin H1 f this dcument) and the purpse is similar t ESCC 4009 series in Eurpe, The dcument calls up [4] fr detailed heater qualificatin requirements, The dcument des nt require heater pwer de-rating by a %-value, but specifies t use the heater within the manufacturer s recmmended current, vltage and temperature range. S-311-P-079 [4]: Cntains detailed requirements fr heater qualificatin, Fr heater applicatin as attached t a substrate within a spacecraft maximum allwable Watt densities are given in diagram frm (Watts/cm^2 ver Heat Sink Temperature in C), The mentined diagram specifies fr Kaptn fil heaters [pressure sensitive tape (equivalent t 3M type 986)] a maximum heat density f 3 Watt/ cm^2 up t 50 C. the value decreases linearly abve 50 C t 0,0 Watt/cm^2 at 100 C. Cnclusin With Respect T Spacecraft Prjects Spacecraft designers are interested t use high heater pwer densities in rder t minimize heater dimensins. Especially in spacecraft paylads available area t place heaters are scarce, especially when redundant heaters are required. Several Eurpean prjects use errneusly the abve mentined very lw heater pwer density f 0.54 W/cm^2 as maximum heater pwer allwance, which hwever is specified nly fr heater suspended in still air, i.e. fr qualificatin f the cmpnent at the manufacturer. In additin the 50% derating requirement is being applied. The apprach finally leads t the very lw pwer density f 0.27 W/cm^2 and cnsequently large heater dimensins. Present ESCC and ECSS dcuments d nt include requirements fr validatin f the heater bnding prcess. The results f the present study indicate, hwever, that heater failure is in mst cases due t imperfect attachment f the heater t the substrate. FOIL HEATER TEST PROGRAMME Objective f the Test Prgramme Based n the described typical heater applicatins in a spacecraft, we tested Kaptn fil heater, which are attached t cmmnly used spacecraft structure substrates, with varius pwer densities. In rder t investigate pssible failure mechanisms, we increased the heater pwer step-wise until failure. During testing the substrate temperature was cntrlled t cnstant values, in rder t achieve high pwer densities withut premature burnut. Definitin f Test Cnfiguratin We selected the mst used substrate fr heater in a spacecraft, i.e. flat aluminium ally and flat CFRP surfaces.
The selected cnfiguratins are seen in Fig. 3. The dimensins f the aluminium ally plate are 500 x 230 mm and f the CFRP plate 180 x 190 mm. The CFRP material was bnded by an adhesive t the aluminium plate. The aluminium plate is blted t a cld plate, the temperature f which can be regulated and stabilized t a desired level. The entire test bject is placed in a climatic chamber in rder t cntrl the test envirnment. Due t budget restrictins tests under vacuum culd nt be perfrmed in this study. The characteristics f the test items are summarized in Table 1. Fig. 3: Test cnfiguratin Test Prgram Table 1: Characteristics f Test Items Item Characteristics Heater Type 1 Minc rder and identificatin number: HK5329R15.9L12B, (ne layer) 3 pieces attached t CFRP, 3 pieces attached t aluminium plate, PSA backing (3M 966), Resistance: 15,9 Ohm, Dimensins: 97 x 25,4 mm = 24,6 cm^2. Heater Type 2 Minc rder and identificatin number: HK5318R7.6L12B, (ne layer) 3 pieces attached t CFRP, 3 pieces attached t aluminium plate, PSA backing (3M 966), Resistance: 7,6 Ohm, Dimensins: 25,4 x 25,4 mm = 6,45 cm^2. Heater Pressure Sensitive Adhesive prvided attached t the heater, attachment Applicatin prcedure accrding t: prcess EXM-OM-PRD-OHB-0045, Issue 02, 18.09.2013: Wrk Instructin: Integratin f heaters with PSA n Aluminium and CFRP. Adhesive dts fr heater peel prtectin were applied (seen in pht ff Fig. 3). CFRP Plate Seize 0,65 x 180 x 190 mm, Unidirectinal fibre K13D2U, parallel t the 180 mm edge, i.e. perpendicular t the lng side f Heater Type 1, Matrix MTM46, Lcal evenness 0,1mm/100mm; surface rughness Ra=3.2, Glued n Aluminium plate. Aluminium Plate Seize 4 x 230 x 500 mm, AlMg3, Lcal evenness 0,1mm/100mm; surface rughness Ra=3.2, Threaded (M6) hle pattern 50 x 33 mm (except area ccupied by CFRP plate). The temperature plan fr the test specimen is shwn in Fig. 4. Three temperature sensrs are assciated t each heater, in rder t measure the temperature f the substrate near t the heater pad (2 sensrs) and f the heater pad itself (1 sensr).
Fig. 4: Temperature sensr lcatin and designatin Testing was perfrmed accrding t the fllwing prcedure: One f the heaters was tested, while the ther heater remained unpwered Each heater was pwered by increasing the heater pwer in steps. After each step peratin cntinued until temperature equilibrium was reached At temperature equilibrium the health f the heater was cntrlled by an IR-camera. Pwer steps are increased until heater burnut cnditin is bserved. During the entire test campaign the cld plate temperature is cntrlled in a way that the heater temperature will remain at nearly 50 C, whatever heater pwer is used. In rder t prvide an rder f magnitude f electrical pwer needed t btain a heater pwer density f 5 Watt/cm^2, the fllwing figures have been calculated: Type 1 Heater: 123 Watt Type 2 Heater: 32 watt Test Set-Up Descriptin Test Set-Up Overview Testing was perfrmed in a thermal chamber under atmspheric pressure. The test specimens are munted n a thermal interface plate, which is thermally cntrlled with a suitable fluid. The schematic test setup is shwn in Fig. 5. DREC = Data Recrder; EPS = Electrical Pwer Supply; TCS = Thermal Cntrl system Fig. 5: Test setup verview
The temperature is cntrlled in a clsed lp. All temperatures are cntinuusly measured. The thermal interface is cled r heated in a way that a defined temperature at the test specimen is maintained. In additin, the thermal chamber is set t a cnstant temperature t reduce radiatin lsses f the specimen during test. The data recrder measures cntinuusly temperatures, vltage and current. The infrmatin f the Infrared Camera is cntinuusly stred. All data are cllected and managed by a PC. Test Instrumentatin The equipment and sensrs as defined in Table 2 has been used during the test. Table 2: Test equipment and sensrs Equipment Manufacturer Type Thermal Chamber Binder MTK 720 TCS Lauda RC6 Data Recrder Ykgawa MW100 EPS Srensen DLM300-2 Infrared Camera Flir T350 Sensr type Manufacturer Type PT100 LABFACILITY 2.0x10mm Test results Fig. 6 t Fig. 10 shw infrared pictures f sme heater during peratin. The figures include als peratinal parameter, as well as bservatins with respect t heater bnding quality and pwer limit / heater failure. Pwer Density: 0,26 W/cm^2 Heater Temperature (1A): 50 C Substrate Temperature (2A, 3A): 48 C Pwer Density: 7,73 W/cm^2 (r 190 Watt) Heater Temperature (1A): 68 C Substrate Temperature (2A, 3A): -4,0 C Temperature Difference Heater Substrate: 2 C Temperature Difference Heater Substrate: 72 C Imperfect bnding is seen at lw pwer and temperature (light yellw spts n left side). These develp t ht spts at high pwer / temperatures (bright yellw spts n left side). Temperatures f the ht-spt areas are abut 50 C higher than the temperature f the remaining heater fil. Testing was terminated due t cling capacity and pwer supply limits. Fig. 6: Temperatures f Type 1 Heater with Lw and High Pwer Density (Substrate Aluminium Plate)
Pwer Density: 0,06 W/cm^2 Heater Temperature (1C): 50 C Substrate Temperature (2C, 3C): 44,5 C Pwer Density: 4 W/cm^2 Heater Temperature (1C): 123 C Substrate Temperature (2C, 3C): -11,0 C Temperature Difference Heater Substrate: 5,5 C Temperature Difference Heater Substrate: 134 C Imperfect bnding spts at lw pwer / temperature are almst nt visible (left side). These develp t marginal ht spts at high pwer / temperature (right side). Testing was cntinued beynd cling capacity limit (heater temperature cnsiderably higher than 50 C), but terminated during the next pwer step (5,18 W/cm^2) due t heater destructin. Fig. 7: Temperatures f Type 1 Heater with Lw and High Pwer Density (Substrate CFRP Plate) Pwer Density: 0,08 W/cm^2 Heater Temperature (10A): 50,2 C Substrate Temperature (11A, 12A): 49,7 C Pwer Density: 6,61 W/cm^2 Heater Temperature (10A): 70 C Substrate Temperature (11A, 12A): -2,8 C Temperature Difference Heater Substrate: 0,5 C Temperature Difference Heater Substrate: 72,8 C Imperfect bnding is seen at lw pwer and temperature (yellw spts n left side). These develp t ht spts at high pwer / temperatures. The temperatures f the ht-spt areas are abut 50 C higher than the temperature f the remaining heater fil. Testing was terminated, due t cling capacity limit. Fig. 8: Temperatures f Type 2 Heater with Lw and High Pwer Density (Substrate Aluminium Plate)
Pwer Density: 0,73 W/cm^2 Heater Temperature (13A): 50,4 C Substrate Temperature (14A, 15A): 42 C Pwer Density: 11,75 W/cm^2 Heater Temperature (13A): 121,5 C Substrate Temperature (14A, 15A): -12,5 C Temperature Difference Heater Substrate: 8,5 C Temperature Difference Heater Substrate: 134,0 C Imperfect bnding is seen at lw pwer and temperature (yellw spts n left side). These develp t ht spts at high pwer / temperatures. The temperatures f the ht-spt areas are abut 50 C higher than the temperature f the remaining heater fil. Testing was cntinued beynd cling capacity limit (heater temperature cnsiderably higher than 50 C), but terminated during the next pwer step (16,57 W/cm^2) due t heater destructin (pwer supply interruptin due t burnthrugh). Fig. 9: Temperatures f Type 2 Heater with Lw and High Pwer Density (Substrate Aluminium Plate) Pwer Density: 0,08 W/cm^2 Heater Temperature (10C): 50,1 C Substrate Temperature (11C, 12C): 47,7 C Pwer Density: 4,0 W/cm^2 Heater Temperature (10C): 105,1 C Substrate Temperature (11C, 12C): -10,5 C Temperature Difference Heater Substrate: 2,4 C Temperature Difference Heater Substrate: 115,6 C Bnding with gd quality. Light imperfect bnding area in lwer left crner and clse t cable cnnectin at lw pwer and temperature (yellw spt n left picture). Ht spts develp there and elsewhere at high pwer / temperatures (right picture). Testing was cntinued beynd cling capacity limit (heater temperature cnsiderably higher than 50 C) and terminated during the next pwer step (5,22 W/cm^2) due t heater destructin. Fig. 10: Temperatures f Type 2 Heater with Lw and High Pwer Density (Substrate CFRP Plate)
All heater were perated by adjusting the sink temperature in such a way that the heater temperature (sensr munted n tp the heater fil) maintained at r near 50 C. At high heater pwer either the pwer supply limit r / and the cling capacity limit was reached. In rder t pwer the heater up t heater destructin, the heater temperature requirement f 50 C culd nt be met. All bserved heater destructin tk place with heater temperatures well abve 100 C, while the substrate temperature was belw zer degrees. The heater test results may be summarized as fllws: If the substrate temperature can be cntrlled t sufficient lw temperatures, heaters are able t perate flawlessly at high pwer and temperatures. Temperature differences between heater and substrate are rather high and can reach easily >100 C. The quality f heater bnding t the substrate may be decisive fr maximum allwable heater pwer density. All heaters which were perated until destructin shwed an imperfect bnding, which was reasn fr ht spts at high pwer / temperatures. Destructin was due t burnut f ne f the bserved ht spts. Nt perfect bnding, which may lead t early ht spts, can be detected with an IR camera at already very lw pwer densities (see fr example Fig. 6 left pht). IR-camera mnitring shuld therefre be intrduced fr flight heater hardware t verify the quality f heater bnding. Aluminium substrate The maximum pwer supplied was 190 Watt r 7,7 W/cm^2 fr heater Type 1 with 97 x 25,4 mm = 24,6 cm^2. Under these cnditins the pwer supply limit was reached, but the heater was still perating nminally. CFRP substrate The tested fil heaters can sustain very high temperatures. The highest measured temperature with nminal heater peratin was measured fr aluminium substrate and heater Type 1: abut 121 C with a temperature difference t the substrate f 134 C (pwer density 11,7 W/cm^2). Destructin f the Type 2 heater (with 25,4 x 25,4 mm = 6,45 cm^2) ccurred at pwer density f 16,5 W/cm^2 at a heater temperature >120 C and a temperature difference t the substrate (aluminium) f >130 C. Due t the lwer heat cnductivity f the CFRP substrate the heater temperature raised mre quickly, cmpared t the aluminium substrate. Destructin fr Type 1 heater (97 x 25,4 mm = 24,6 cm^2) ccurred at abut 5,0 W/cm^2, at 130 C heater temperature and a temperature difference t the substrate f abut 140 C. Destructin fr Type 2 heater (25,4 x 25,4 mm = 6,45 cm^2) ccurred again at abut 5,0 W/cm^2, at 110 C heater temperature and a temperature difference t the substrate f abut 120 C. Dminating factr, which determine heater destructin, is the heater temperature, which was abut 120 C in ur tests with a temperature difference t the substrate f >130 C. Heater destructin is initiated at ht spts, due t imperfect heater bnding. The heater pwer r heater pwer density, which is necessary t reach this threshld temperature, depends n the thermal cnductivity and temperature f the substrate. Fr a substrate temperature f abut -10 C the critical heater temperature f abut 120 C is reached: At a pwer density f abut 16 W/cm^2 fr aluminium substrate, At a pwer density f nly abut 5,0 W/cm2 fr CFRP substrate. The lw critical pwer density fr the CFRP substrate was surprising, because the substrate cnsists f highcnductive fibres with an in-plane thermal cnductivity, which is much higher than the aluminium substrate. We suspect that the test results are due t the lw ut-f-plane cnductivity f the CFRP material, i.e. the high thermal resistance between heater fil and carbn fibre. Heater mats with the measured high temperatures may radiate a cnsiderable amunt f heat int the envirnment (especially fr large surface heaters), which has nt been evaluated during this activity. The high heater mat temperatures (and subsequent radiatin heat lsses) shuld be intrduced int the spacecraft thermal analysis prcess.
CONCLUSION AND RECOMMENDATIONS Majr Findings f the Test Prgramme 1. Heater failure mechanism seems t depend n a limiting heater temperature and nt n a limiting heater pwer density. This is in cntrast t existing ESCC r ECSS dcuments, where a maximum pwer density and pwer derating independent frm heater temperature are specified. 2. The allwable heater pwer r heater pwer density, which will safely avid heater destructin (burn-ut), depends n the thermal cnductivity f the substrate, i.e. n hw efficient the heat will be transprted away frm the heater. Fr the described tests f this activity heater pwer densities f abut 16 W/cm^2 culd be allwed fr aluminium substrates and nly 5 W/cm^2 fr CFRP substrates. 3. Due t the high thermal resistance f the Kaptn and adhesive layers fil heaters experience high temperature differences t the substrates. Heater temperatures f up t 130 C higher than the substrate temperature have been measured. 4. Hwever, nly the maximum heater temperature is decisive (abut 120 C in the described tests) fr safe peratin and nt the temperature difference t the substrate. In cnclusin, if a heater is perated n an already warm substrate, a rather small heater pwer density will already lead t a critical heater temperature, cmpared t heater peratin n cld substrates. 5. Radiatin heat lsses due t high nminal heater temperatures shuld be cnsidered in the thermal design f spacecraft, in particular fr large surface heaters. 6. Althugh bnded with a validated prcess, almst all heaters shwed imperfect bnding results, which can be detected already at lw heater pwers with an IR camera. 7. The nt perfect bnding areas develp t ht spts at higher heater pwers. Temperatures f ht spts at nminal heater peratin are abut 50 C higher as cmpared t perfectly bnded areas. Heater destructin happens thrugh burnut in ne f the ht-spt areas. 8. It is therefre recmmended t verify the bnding quality f space heater hardware with an IR camera. Reject criteria shuld be develped. Recmmendatin fr ESCC and ECSS Dcuments Fil heaters are applied utside electrnic equipment n space structures. In critical cases tw cld redundant heaters are used. Operatin is feedback cntrlled by redundant temperature sensrs placed in the vicinity f the heater pad. These applicatin characteristics are nt typical fr electrical / electrnic cmpnents and it is questinable t classify fil heater therefre as EEE parts. The derating requirements specified in [1] and [2] seem in additin nt lgical fr heaters, because derating has been slely intrduced fr internal parts f electrnic equipment t enhance end-f-life perfrmance f these units. It is recmmended t verify heaters in the attached state at qualificatin levels, which shuld be based n validated and reprducible bnding prcesses. Individual qualificatin campaigns shall be perfrmed fr different heater types (single / duble layer pads, with aluminium backing, type f adhesive) and substrates (substrate material, curved and flat surfaces). An additinal derating requirement is nt necessary, if the thermal spacecraft design guarantees that heaters are perated during spacecraft life belw maximum acceptance levels, which are by definitin less severe than the qualificatin levels. There is a general need t update heater related Standards, because ther heater technlgies, such as printed heater [5], cartridge heater and wire heater, are presently nt cvered. Outlk T guarantee peratin f fil heaters with high reliability is difficult. The presented study shws that validated bnding prcesses are apparently nt reprducible in all cases. Bnding imperfectins, which may be caused by trapped air, cannt be ttally excluded and may lead t unexpected heater failure at high temperatures. Furthermre, the qualificatin prcess f fil heaters needs t take int accunt a number f different available heater types and substrate cnditins. Verificatin effrt is therefre high and due t the invlved applicatin parameters the reliability f the heater attachment prcess remains critical. In this situatin the direct printing f heater tracks n flat and curved surfaces with an electrical cnductive material may ffer an interesting alternative (Fig. 11). The technlgy, develped fr terrestrial applicatins, is presently being evaluated fr space applicatin under an ESA cntract [5]. The heater printing Fig. 11: Heater printing prcess Surce: Fraunhfer IFAM, Bremen
prcess is studied n Al- / Ti-ally and CFRP, using flat and curved substrates as well as tubular cnfiguratin, i.e. prpellant lines. Outgassing tests and radiatin impact assessment are part f the study. The evaluatin is very prmising and the fllwing advantages culd be identified fr space applicatin: Freedm f heater cnfiguratins and shapes, Reprducibility f heater tracks with predetermined electrical resistance, Very gd adhesin f the heater track n the investigated substrates, Due t direct printing the temperature difference between heater element and substrate is lw (at least an rder f magnitude lwer cmpared t Kaptn fil heater). The applicatin, i.e. printing, f heater utside the spacecraft is hwever precnditin fr using this technlgy. The ff-line installatin f heater is in mst cases pssible (panels, electrnic equipment, heat pipes, etc.) and supprts the need t pre-integrate cmplete sub-assemblies befre submissin t the central spacecraft integratin site. REFERENCES [1] ESCC Resistrs, Heater, Flexible, Single and Duble Layer, Detail Specificatin N. 4009/002, ISSUE 7, January 2014. [2] ECSS-Q-ST-30-11C, 31 July 2008, Derating - EEE cmpnents. [3] EEE-INST-002, NASA/TP 2003 212242, Instructins fr EEE Parts Selectin, Screening, Qualificatin, and Derating. [4] S-311-P-079, rev. E, Prcurement Specificatin fr Thermfil heater. [5] D. Gdlinski, and R. Schlitt, Printed heaters fr nn-planar space applicatins, 2 nd Space Passive Cmpnent Days (SPCD), Internatinal Sympsium, 12-14 Octber 2016, ESA/ESTEC, Nrdwijk, The Netherlands.