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REPORT ON ALTERNATIVE DEVICES TO PYROTECHNICS ON SPACECRAFT

M. Lucy, R. Hardy, E. Kist, J. Watson, S. WiseNational Aeronautics and Space Administration

Langley Research CenterHampton, Virginia

Abstract

Pyrotechnics accomplish many functions on today’sspacecraft, possessing minimum volume/weight,providing instantaneous operation on demand, andrequiring little input energy. However, functionalshock, safety, and overall system cost issues, combinedwith emergence and availability of new technologiesquestion their continued use on space missions. Uponrequest from the National Aeronautics and SpaceAdministration’s (NASA) Program Management Council(PMC), Langley Research Center (LaRC) conducted asurvey to identify and evaluate state-of-the-art non-explosively actuated (NEA) alternatives to pyrotechnics,identify NEA devices planned for NASA use, andinvestigate potential interagency cooperative efforts. Inthis study, over 135 organizations were contacted,including NASA field centers, Department of Defense(DOD) and other government laboratories, universities,and American and European industrial sources resultingin further detailed discussions with over half, and 18face-to-face briefings. Unlike their single usepyrotechnic predecessors, NEA mechanisms aretypically reusable or refurbishable, allowing flight ofactual tested units. NEAs surveyed include spool-baseddevices, thermal knife, Fast Acting ShocklessSeparation Nut (FASSN), paraffin actuators, and shapememory alloy (SMA) devices (e.g., Frangibolt). Theelectro-mechanical spool, paraffin actuator and thermalknife are mature, flight proven technologies, while SMAdevices have a limited flight history.

There is a relationship between shock, input energyrequirements, and mechanism functioning rate. Somedevices (e.g., Frangibolt and spool based mechanisms)produce significant levels of functional shock. Paraffin,thermal knife, and SMA devices can provide gentle,shock-free release but cannot perform critically timed,simultaneous functions. The FASSN flywheel-nut releasedevice possesses significant potential for reducingfunctional shock while activating nearlyinstantaneously. Specific study recommendationsinclude: (1) development of NEA standards, specificallyin areas of material characterization, functioning rates,and test methods; (2) a systems level approach to assuresuccessful NEA technology application; and (3) furtherinvestigations into user needs, along withindustry/government system-level real spacecraft cost-benefit trade studies to determine NEA application fociand performance requirements. Additional surveyobservations reveal an industry and government desire toestablish partnerships to investigate remaining

unknowns and formulate NEA standards, specificallythose driven by SMAs. Finally, there is increasedinterest and need to investigate alternative devices forsuch functions as stage/shroud separation and highpressure valving. This paper summarizes results of theNASA-LaRC survey of pyrotechnic alternatives. State-of-the-art devices with their associated weight and costsavings are presented. Additionally, a comparison offunctional shock characteristics of several devices areshown, and potentially related technology developmentsare highlighted.

Background

Several recent incidents in which pyrotechnics couldbe responsible for spacecraft failures have raisedconcerns within the aerospace community regardingtheir continued use on spacecraft. Other reasons toexamine NEAs for spacecraft include: high functioningshock levels; overall operating and system costs;reusability; shrinking volume, weight, and powerbudgets; possible outgassing; emergence of newtechnologies; and the hazardous nature of pyrotechnicmaterials. In June 1994, at the request of the NASA’sPMC, LaRC formed an investigative team to examineNEAs and report findings. The team consisted of RobinC. Hardy, Edward H. Kist, Jr., Melvin H. Lucy, Judith J.Watson, and Dr. Stephanie A. Wise, who providedexpertise in mechanical systems and mechanisms, powerand electronic systems, pyrotechnics, and smart andactive materials technology. Anthony M. Agajanian -Jet Propulsion Laboratory (JPL), Charles S. Cornelius -Marshall Space Flight Center (MSFC), Frank M. Cumbo- Goddard Space Flight Center (GSFC), Dr. Rodney G.Galloway - United States Air Force-Phillips Laboratory(AFPL), and Darin N. McKinnis - Johnson SpacecraftCenter (JSC) provided technical assistance.

A review of mechanism symposia proceedings,pyrotechnic workshops, and a literature search intosmart actuators and structures were initiated. Contact wasestablished with NASA/DOD Pyrotechnic SteeringCommittee participants, NASA field centers, severalDOD groups, other government laboratories,pyrotechnic manufacturers, major aerospace contractors,universities, and European sources. A questionnaire wasissued to the supplier and user communities, andtelephone interviews with all identified points-of-contact were conducted. Over 135 organizations werecontacted, in-depth telephone discussions wereconducted with 75 selected contacts, and 18 of the lattermade technical presentations to the team. Thesepresentations were made on the West Coast on

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September 20-22, 1994 and on the East Coast September28-30, 1994; or by phone or visit to LaRC. On-sitevisits to several organizations took place in the Denver,CO and Washington, DC areas, and three ESArepresentatives were interviewed by phone. Discussionsprimarily involved spacecraft pyrotechnic alternatives;however, pyrotechnics used in launch systems, tacticalmissiles, aircraft, and even automotive applications wereincluded. Investigation findings were presented toNASA's PMC at JPL on March 28, 1995. A matrixidentifying NEAs as compared to pyrotechnics ispresented in Figure 1.

Significant Findings

The investigation’s significant findings are:(1) Alternative technologies exist and have been used orare planned for use on spacecraft. [(a) Five promisingtechnologies were identified; electro-mechanical spool,paraffin actuator, rotary separation nut, shape memoryalloy (SMA) devices, and thermal knife. (b) Themajority of alternatives are used for separation anddeployment. (c) No single technology is a panacea. (d)Not all technologies alleviate functional shock. (e) Theelimination of pyrotechnics is being pursued.](2) Alternative technologies require further development.[(a) Booster separation and staging is a critical area. (b)SMA based devices are the least mature. (c) Paraffin waxhigh transition temperature material needs development.(d) Standards are needed for NEAs.](3) There are currently no alternative devices for somepyrotechnic applications. [(a) No alternatives exist forapplications requiring high energy, rapid response, e.g.,ignition, detonation, valving, cutting and somereleases. (b) Mistakes of use and/or application causemany failures. (c) Pyrotechnic improvements are beinginvestigated.](4) Several industry and government small programs arepotential partners for a larger focused effort to developalternative technologies. [(a) SMA based devices havethe most commercial interest. (b) A high degree ofinterest was shown in forming partnerships to developNEA standards. (c) Most existing programs are oflimited scope and could be combined to more adequatelyaddress the needs of this area.]

Several interesting points considered worthy ofhighlighting include the following (order does not implyimportance): (1) The Naval Research Lab (NRL) hasdecided to replace pyrotechnics with NEAs on spacecraft.(2) Approximately 2/3 of the discussions involved SMA-based applications. (3) Several organizations arecurrently developing SMA-actuated separation nuts. (4)A very low shock, rotary release separation nut is beingdeveloped. (5) A thermal knife for performing releasefunctions was described. (6) Numerous paraffin actuatorapplications were identified, including one for apassively controlled solar array tracking mechanism.(7) A combination miniaturized, remotely

programmable, optically initiated, electrically fired,multiple functioning safe and arm (S&A) firing system isbeing developed. (8) A passive thermal detection andinitiation method to prevent munitions cook-off(chemical heat source with possible application toNEAs) was presented.

Pyrotechnics

Pyrotechnics consist of a broad family ofsophisticated devices utilizing self-contained energysources such as explosives, propellants and/orpyrotechnic compositions. Most pyrotechnics utilize ahot wire system consisting of a thin gage, highresistance bridgewire for terminating the electricalcircuit at the initiating material. These are low voltagesystems in which the bridgewire is heated to achieveauto-ignition of the material. When properly utilizedand packaged, pyrotechnics perform functions such asrelease, cutting, pressurization, valving, ignition,switching, and other mechanical work. Pyrotechnictechnology is mature and flight proven. Pyrotechnicstypically possess a minimum volume to weightrelationship as compared to other mechanisms, provideinstantaneous operation on demand allowingsimultaneity, have relatively long-term storagecapability, are rugged, highly reliable, possess a goodsafety record, are relatively inexpensive, require alimited amount of input energy to function, and produce ahigh energy output. Commercial applications forpyrotechnic systems are expanding and are enjoyinggood safety records. Pyrotechnics, however, are singleuse devices containing hazardous materials, and flighthardware reliability depends on batch testing. End-to-end built-in-test (BIT) is difficult. Pyrotechnics mayproduce contaminants, and they typically exhibit highlevels of functional shock (explosive and mechanical).

Functional Shock

Data from a 1985 paper by C.J. Moening1 indicatedthat through 1984 eighty-three shock related failures hadoccurred in approximately 600 launches. Over 50percent of these resulted in catastrophic loss of mission.Twenty-nine failures involved broken wires, leads andcracked glass; 28 involved dislodgment ofcontaminants; 22 had other shock-related effects, andfour involved relay chatter and transfer problems. In astudy performed for NRL by Hi-Shear Technology Corp.(HSTC), three sources of functional shock (referred to as"pyroshock") in a separation nut and each’s percentageoccurrence were identified: less than 10 percent resultsfrom the pyrotechnic event, approximately 50 percentfrom internal collisions within the device, andapproximately 40 percent from preload release in thebolt or joint. Compact systems aboard future small ormicro-spacecraft may be more strongly influenced by themajority of functional shock due to their small mass anddistance limitations which effect attenuation. Some

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examples of operational rates vs shock for pyrotechnicsand NEAs are presented in Figure 2

State-of-the-Industry

In 1988 LaRC performed a survey2 of NASA centers,JPL, and DOD to document pyrotechnic failures whichhad occurred in the previous 23 years, and identify theircauses. Responders indicated that of the 84 failureswhich had occurred over that period (throughout the lifecycle of the pyrotechnics being reported on), 12 failuresoccurred in flight. Of those 84 failures, approximately42 percent were attributed to a lack of understandingpyrotechnics, 25 percent to inadequate design, 15percent to inadequate manufacturing procedures, 11percent to quality assurance deficiencies, andapproximately 3 percent to misapplication of hardware.More recent incidents in which pyrotechnics are suspectseem to result from the misapplication of thistechnology. There are concerns that pyrotechnic valvesmay have contributed to several recent failures, and anindustry wide investigative process is now underway.Over the years basic designs, materials, andmanufacturing processes have been altered, andoperational procedures modified. These successivechanges have been made without integrated systemtesting to verify performance and reliability. It has beensuggested that designs, once successfully tested, shouldbe standardized. As a related issue, the pyrotechniccommunity is also highly dynamic and characterized bypersonnel mobility. Substitution of NEA technologieswill introduce a whole new set of concerns. Obviously,good design, review, and test practices are mandatoryrequirements of a safe and reliable system regardless ofthe actuation method involved.

Comparing Pyrotechnics to NEA Devices

One must perform a systems level evaluation toadequately compare pyrotechnics to NEA devices. Thisis being done to a limited extent by members of theaerospace community. All factors (e.g., preload,handling, storage, shelf-life, transportation,environmental exposure, functioning time,simultaneity, performance margin, reusability, end-to-end monitoring, number of devices, shock level, power,heritage, reliability, weight, cost, volume, testingrequirements, etc.) must be considered for a specificapplication. Several manufacturers, while trying tomaintain device heritage, are pursuing NEAs orpyrotechnic device shock reduction strategies withvarying degrees of success.

Cost Savings

Real cost savings are difficult to determine. At leasttwo studies have suggested achievable system levelsavings when pyrotechnics are replaced with NEAs; TRWestimated approximately $1M savings on the Tracking

and Data Relay Satellite System, and NRL estimatedapproximately $0.5 M in recurring and approximately$0.3 M non-recurring cost savings (total savings ofapproximately 24 percent) per spacecraft over aconventional hot-wire pyrotechnic system where 42pyrotechnics are involved to perform ten releasefunctions on their Spinning Upper Stage/SatelliteDisperser. Estimated savings result from reduced overallweight, safety approvals, hazardous material handlingand storage, testing and requirements, streamlined pre-launch operations, and reduced hardware needs. SomeNEA devices are fully resettable and reusable withoutdisassembly or refurbishment. During shock testing forLaRC3, Lockheed Martin Missile and Space Co.(LMMSC) and Starsys Research Corp. noted thatapproximately twelve tests per day could be performedusing NEAs vs one test per day when pyrotechnics wereinvolved. It should be noted that reducing devicefunctional shock may not necessarily negate the need forshock testing. Other events (e.g., shroud separation)may now predominate in which case shock testing,albeit at lower levels, may still be required.

Replacement Commitment

No combination of present or known emergingtechnologies has been identified which wouldcompletely eliminate pyrotechnics. NRL is the onlyorganization contacted to date with a firm commitmentto replace most, if not all, spacecraft pyro-mechanismswith NEAs. Any remaining pyrotechnic operationswould be performed with a laser initiated ordnancesystem (LIOS). In the telephone interview, some ESAparticipants also expressed an intention to replace somepyro-mechanisms with NEAs

Previous Improvements to Pyrotechnics

For approximately 20 years attempts to improvepyrotechnic device safety and reliability have been madeincluding decreasing sensitivity to inadvertentinitiation, insuring energy delivery and margin, andreducing contamination and functional shock.Exploding bridgewire initiators have been used incritical aerospace applications such as range safetyflight termination. Linear explosive products usinginsensitive secondary explosives are well proven inaircraft, launch vehicle, and missile applications andhave a significant safety record. Insensitive ordnancedevices improve safety as they incorporate secondaryexplosives, thereby preventing a missile or bomb frombeing accidentally or inadvertently detonated (e.g.,nuclear weapons). Exploding foil or semiconductorbridge (SCB) devices are used to initiate insensitivematerials, thereby improving safety and possiblyreducing costs. These latter devices are compatible withexisting ignition circuitry; typically need very short-duration, high-firing current and voltage (low totalenergy); exhibit fast functioning times; are highly

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repeatable; and permit tighter tolerance on all-fire/no-fire levels. These devices produce a high temperatureplasma or shock wave output, pass the one amp/one watt(1A/1W)/five minute no-fire requirement, areelectrostatic discharge tolerant, and are compatible withelectronic microcircuits.

For 30 years LIOS has been investigated in over 28projects. Some projects involved multiple eventfunctioning. LIOS uses laser energy and fiber opticcables to replace electrical wiring or explosive transferlines in moving energy from command systems topyrotechnic initiators or detonators. Typically thepyrotechnic charge is initiated directly with laserenergy. LIOS has potential for reducing cost, weight,sensitivity, and launch site operational restrictions ofexisting pyrotechnic systems. However, the onlyproduction line for the five-watt output laser diodes usedis shut down due to low demand, low yields and highcosts. Since August 1994, NASA, through a cooperativeagreement with the Ensign Bickford Co., has sponsoredLIOS work4 5 for solid motor ignition and launch vehicleflight termination, culminating in a 1995 Nike-Orionsounding rocket ignition/termination demonstration,and a Pegasus flight in which LIOS was used to ignitethree of the nine first stage fin rockets. In November of1995, to obtain safety data, LIOS flew as a "SolarExposure to Laser Ordnance Devices Experiment"payload on the STS-72 Spartan Vehicle. NRL isdeveloping a LIOS to demonstrate on their AdvancedRelease Technologies Spacecraft6 (ARTS). In a relatedNRL study, a weight savings of approximately 80percent is anticipated through the use of a LIOS. ThiokolCorp.-Elkton Division is developing a LIOS which usesa low energy laser to charge a capacitor adjacent to a SCBinitiator. The capacitor's energy is later discharged toeffect device initiation. Thiokol estimates a systemsweight savings of approximately 70 percent.

Alternative Technologies to Pyrotechnics

NEA Separation Nuts

G&H Technology Inc., Electro-Mechanical Spool and Separation Nut

The heart of various G&H NEAs is the electro-mechanical spool (Figure 3a). Linear motion of a springloaded plunger is restrained by a sectioned spool,overwrapped by a retaining wire, the latter held in-placeby a linkwire. Linkwire electrical characteristics werechosen to mimic a 1A/1W pyrotechnic initiator. Currentpassing through the linkwire causes it to fail, therebyreleasing the retainer wire and allowing separation of thespool halves. Movement of the spring loaded plungerinto the separated spool allows functioning of a toggle.The toggle allows use of two spools, thereby providingredundancy. Devices using the spool include separationnuts, pin-pullers, cable and ball release mechanisms,

tension release devices, electrical connectordisconnects, and other special configurations. Thesedevices represent mature, flight proven technologyhaving flown on a variety of spaceflight missions. Theyare highly reliable, provide fast actuation, possess highenergy output for limited power input, and are reusablefollowing refurbishment. The primary disadvantage ismechanical shock. Figure 3b illustrate this function in aminimum shock separation nut. The toggle releases thestored mechanical energy in the spring loaded portion ofthe mechanism to effect primary device functioning.Total functioning time is approximately 20 msec,allowing for simultaneous operation of similar devices.

Shape Memory Alloy (SMA) Devices

The shape memory effect (SME), studied for sixdecades, became the focus of serious investigation andapplication with development by NRL of the nickeltitanium (NiTi) family in the 1960s. The key to SME isthe occurrence of a transformation which is reversibleupon heating. Martensitic SMAs can undergodeformation which is retained until they are heated abovea critical transition temperature at which point a reversetransformation occurs. The martensite returns to theaustenitic parent phase thereby restoring the originalundeformed shape. This reversible transformation isrepeatable indefinitely provided the alloy does notexperience excessive strain or temperature. Because ofthe unique reversible martensitic transformation, SMAproperties show a very marked temperature dependence.The greatest force occurs when SMA is used in puretension or compression. Finished SMA products includesprings, strips, wires, and tubes for applicationsrequiring linear motion, torsion or bending. Inchoosing the applicability and SMA type, one mustconsider the operating thermal environment. SMA hashigh electrical resistance, and excellent corrosion andfatigue capabilities. SMA can be electrically heateddirectly. When SMA wire is used in a hard vacuum, itrequires approximately 1/4 the power to heat. Astemperature is directly related to current density passingthrough the wire, care must be taken to heat, but notoverheat the actuator wire. High current pulses can causeelectro-magnetic interference (EMI). If using secondaryheaters, some outgassing contaminants may be producedwhich must be captured by surrounding cold structure.SMAs generally exhibit notch sensitivity, and in someapplications tend to elongate with time. SMAadvantages include high work output, silent operation,design simplicity, and near step function operation.Disadvantages include environmental (thermal)capability, material notch sensitivity, improper SMAtraining leading to stress relaxation or pseudo-creepphenomenon, and, depending on size and configuration,the high power required to operate, and overallfunctioning time. There have been several SMA flightapplications; as a back-up boom release on the ISEE-Bspacecraft7, a solar array bearing pin off-load mechanism

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and unlatching mechanism on the Hubble SpaceTelescope solar panels, and as solar panel releases on theClementine spacecraft. As applications for SMAsexpand, there is a concomitant need for alloys which canperform at higher temperatures, and much of the presentresearch is devoted to high temperature performance. AsNiTi alloys are quite expensive, another SMA researchgoal is to discover lower cost alloys. A nearly universalneed was expressed for SMA standards, metrics, andtraining methods.

Hi-Shear Technology Corp. NEAs

HSTC is currently developing a NiTi actuated nut8,pin-puller, and cable release, all based on the samedesign concept. Their NEA No-Shock release nutconcept (Figure 3c) is resettable, and requires from 10 secto 1 minute to function. The bolt passes through a SMAslug containing an internal heater element. The threadedend of the bolt is engaged in a spring loaded segmentednut. When the SMA slug is heated to approximately 100C, it shrinks, thus, relieving the preload and allowingthe spring loaded segments to release the bolt. This nutcan be functioned approximately 50 times.

Lockheed Martin Astronautics (LMA)-Denver NEAs

LMA has been exploring several approaches to SMAactuated NEA separation devices; two9 under AFPLcontract, a Low Force Nut (LFN) (Figure 3d) and a TwoStage Nut (TSN) (Figure 3e), and FASSN under NRLcontract. The LFN and TSN have preload capabilities of1300 and 2500 kg, respectively, use redundant SMAinitiation, and a ball detent arrangement. Both areresettable and operate in less than 50 msec. The shortfunctioning time of the LFN and TSN is achieved byutilizing independent control electronics to preheat theSMA element to a temperature just below its transitiontemperature. The control electronics receive a pre-firesignal approximately 60 seconds prior to the signal fordevice actuation. The LFN utilizes mechanical advantageto reduce the required SMA initiation force, andincorporates SMA initiation, damper, and reset springs.The TSN utilizes SMA in an actuation cylinder (firststage) to remove bolt preload, and SMA springs (secondstage) to separate the nut segments. Both concepts arebaselined for flight as part of the AFPL MitiSat programand the Small Spacecraft Technology Initiative solararray release.

The FASSN (Figure 3f) is a joint LMA and StarsysResearch Corp. development. It fundamentally consistsof a housing containing a high lead, four start threadedbolt, rotary nut (which acts as a flywheel), and aredundant locking/unlocking mechanism. Thelocking/unlocking mechanism is a rotary SMA devicefurnished by TiNi Aerospace, Inc., but it can incorporatean electrical solenoid. The mechanism absorbs bolted

joint strain energy plus the energy in bolt retractionsprings, and converts 95 percent of it into kineticenergy which upon actuation becomes stored in theflywheel. The device is fully reusable, requires minimalactuation energy, and functions in less than 20 msec.NRL, under their ARTS II Program, is currentlyevaluating FASSN with a 4500 to 5900 Kg preloadcapability, and the concept has been tested at preloads upto 17,000 Kg.

NEA Release Mechanisms

Boeing Defense and Space Group (BDSG) NEAs

BDSG is investigating several NEA separationdevices, of which two use adaptations of the same NiTimechanical fuse concept10. They use fusible elements(wires or foil) as a SuperZip* replacement, and as afusible link to perform a release function--the latterdevice (Figure 4a) currently being flown on the NRLARTS I spacecraft. The first device, called the JSC-Structural Separation Feasibility Experiment, used 40,various length SMA wires (or foil elements) in an as-wrought, unannealed state as a mechanical "fuse" whichacts as the main structural interface. The separation jointmaintained and released a 900 Kg preload in less than asecond. The elements were arranged in eight 5-elementsubsets. The shortest (hence least resistance) element ineach subset draws the most current, heats the fastest, andreleases first. Due to NiTi’s inherently high electricalresistance, the material can be efficiently heated to itsannealing temperature, thus drastically reducing itsmechanical strength by an order of magnitude renderingit insufficient to maintain structural integrity. Power isswitched to each successive subset to minimize theamount of instantaneous power required; however, thiscontributes to longer release times. This zipperingeffect would be especially useful to separate payloadfairings. The concept is refurbishable--the testedhardware can be flown with only the NiTi elements beingreplaced. There are no shelf life limitations, safetyhazards, EMI, or radio frequency interference (RFI)susceptibilities. Preload can be gradually releasedresulting in little or no functional shock. There isminimal contamination potential, and no sealing isrequired. This approach offers enhanced ground testingcapability with minimal impact to surroundingsubsystems. If wires and foils are used as mechanicalfuses, and electrical power levels are sufficiently high soas to produce hot particles, this could produce anignition source in an explosive environment.

The second device (Figure 4a), called the NRL-FusibleLink Release device, utilizes a single unannealed fusibleelement and successfully released a 900 Kg preload inless than 200 msec. The fusible element was used alongwith a 25:1 mechanical advantage to retain a tension

* Trademark for Lockheed’s patented separation joint.

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link. Two spring loaded jaws capture the tension link,and the NiTi fusible link holds them in place. Thefusible link requires low voltage and high current(3V/45A AC) hence a closely coupled step-downtransformer and converter electronics are incorporated.Tests were also conducted at lower preloads whichshowed a corresponding increase in functioning time. Atzero preload the release time increased approximately 50percent. Separation times were consistently within 50msec under identical test conditions (preload and power).Functional shock was judged to be insignificant.

Lockheed Martin Astronautics-Denver

LMA developed a resettable 900 to 4500 Kg preloadhigh force thermal latch (HFTL)(Figure 4b). A lowmelting eutectic in a cylinder is hydrostatically loadedby a piston. Upon heating, the cylinder expandscreating an annular orifice around the piston throughwhich the liquid alloy flows. The piston translates to theunlatched position driven by the preload and drivesprings. The spherical ended latch bolt is freed from thesocket. Redundant heaters are used, and the devicefunctions within 360 seconds. The slide gate allowslatch bolt insertion or removal without heating thedevice.

Lockheed Martin Missile and Space Co.

The LMMSC NiTi Release Mechanism11 (Figure 4c) isto be used to deploy solar panels on the Gravity Probe"B" spacecraft, and as an antenna release for the CrossDipole Antenna Experiment. The device utilizes two-way actuation of bent NiTi rods with integral heaters fordeployment to release a captive toggle--release occurs inless than 125 seconds. Preload on the toggle isapproximately 66 Kg. A hole down the center of eachfully annealed rod accommodates the heater. This deviceproduces virtually no shock, is redundant, providesinterface flexibility, is reusable, is resettable, and iseasy to manufacture. The disadvantages are low preloadcapability, slow release, and lack of simultaneity. WithLMMSC assistance and using the same SMA rod withexternal heater as a torsion bar, Stanford Universitydemonstrated a solar array deployment mechanismconcept12. The torsion bar was mounted to a backbonestructure and transmitted torque through a right-angledrive system. The drive system then rotated an armwhich in-turn deployed solar panels.

NEA Pin - Pullers

G&H Technology Inc., Pin-Puller

Figure 5a depicts a commercially available, functionedG&H NEA pin-puller utilizing redundant spools. Thetoggle restrained a spring force of 245 Newtons actingon the retraction pin. The device functioned inapproximately 20 msec. with a 12.7 mm stroke.

Starsys Research Corp., Paraffin Wax Actuator

The heart of Starsys Research Corp. devices is theHigh Output Paraffin (HOP) actuator (Figure 5c).Numerous devices using the HOP have flown. Otherapplications include actuators, restraint mechanisms,powered hinges, and cover release systems. HOP usesconstrained volumetric expansion of a highly refinedpolymer at a well-defined transition temperature toproduce large hydrostatic pressure and perform work.The polymer can be varied to change actuationtemperature. The maximum non-actuation temperaturecurrently available is 110 C. Hydrostatic pressure istranslated to actuator extension through a hermetic"squeeze boot" seal. The device can be functionedrepeatedly. A redundant heating element is internal tothe HOP. The model IH-5055 actuator produces up to1550 Newtons/31.75 mm stroke in approximately 180seconds. Several items must be considered whenevaluating this concept. The HOP must be thermallyisolated to operate properly in cold temperatures, mustbe de-energized after extension has occurred, and itshould incorporate a hard stop. The mechanisms shouldincorporate a return spring, and the actuator rod shouldn'tbe retracted past the zero position. The gentle stroke ofthe actuator needs to be taken into account whendesigning release mechanisms. HOPs are mature andflight proven, produce no shock, are highly reliable, andfully reversible. They produce a high force output,provide precise, repeatable positioning, and areinsensitive to premature release from EMI, RFI, andelectromagnetic potential (EMP). Disadvantages includelong functioning time, non-simultaneous operation,high input power, and high temperature operatingconstraints.

TiNi Aerospace, Pin Puller and Rotary Actuator

The LeRC Small Business Innovation Researchcontract (NAS3-26834) for a TiNi Aerospace pin-pullerwas targeted towards a generic application that could bemodified to meet specific requirements. The conceptproven most practical resulted in a fast response devicewhich uses a SMA wire to releases a ball-detent, whichin-turn allows release of mechanical stored springenergy. The trigger mechanism (patent pending) isfundamental to TiNi’s current product line of pin-pullersand rotary actuator. Figure 5b illustrates a pin-pullerrated at 12.7 mm stroke and 110 Newtons. Alsoavailable are a 6.3 mm stroke and 22 Newton pin-puller,and a rotary actuator rated at 0.45 Joules with a 0.78radian rotational capability. The rotational actuator isused to actuate the FASSN separation nut. All devicescan be configured with a redundant SMA wire and a powercut-off switch. Each device can be manually reset.Planned uses of these devices are the JPL-Mars GlobalObserver and NRL ARTS spacecraft. Areas to considerwhen evaluating this design approach are SMA wire over

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stressing, over straining, over heating, and functionalshock resulting from the device’s stored energy spring.

Other NEA Devices

Fokker Space and Systems, Thermal Knife Release Mechanism

The flight proven, patented thermal knife hold-downand release mechanism13 (Figure 6a) is a simple,effective device based on thermal degradation of apretensioned Kevlar/Aramid cable. It is extensively usedby the Europeans and can release all deployablespacecraft appendages. The electrically heated ceramicknife gradually melt through the cable causing degradedfibers to fail thus reducing cable cross-section. Residualtensile failure of the cable results in a low energy release,leading to extremely low functional shock. Functioningtime is less than 60 seconds. The Kevlar/Aramidmaterial thermally degrades at about 700 C, and limitedoutgassing from the melting process is realized. Thespring loaded "blade" typically heats to 700 C with a1200 C maximum rating. The device requires a voltageregulator to remain within its operating range. Thedevice can be tested in-situ for approximately fiveseconds without causing cable damage. The deviceexhibits low weight and overall system costs, has a twoyear shelf life, and can be reused reliably up to eighttimes. Fokker has been negotiating with HSTC tobecome their U.S. representative.

TiNi Frangibolt

The commercially available, flight proven Frangibolt(Figure 6b) uses a SMA actuator to break a prenotchedtitanium bolt in tension. An external silicon heatercauses the actuator to elongate when heated, transitiontemperature being approximately 100 C. The notchedbolt stretches until it fails at the notch providingcontrolled breakage. This process reduces preload in thejoint and produces a reduced functional shock. It isreported that some functional shock measurements havebeen made indicating a reduction of two orders ofmagnitude over pyrotechnic devices. Currently availableFrangibolts can accommodate up to a 910 Kg preload andfunction in less than 25 seconds. The SMA actuator isreusable after cooling and recompression to itspreactuation length. Some heater outgassing may beexperienced. Several critical details must be understoodto produce a working Frangibolt type device. Materialcharacterization and proper bolt pre-notching areessential to the device's operation. The user must avoidbolt bending loads. Another concern, since resolved,was maintaining heater contact with the SMA slug duringheating as the slug diameter shrinks. Special attentionmust be paid to heater design14, or its attachment, toinsure sufficient contact. To control debris the user maywant to incorporate lockwire on the bolt head.

Some Comparative Functional Shock Test Results and Device Physical Characteristics

Massachusetts Institute of Technology-LincolnLaboratory in the mid 1970's, and later LaRC in March of1985 tested a G&H pin-puller (Figure 5a) and found highlevels of functional shock. At that time, LaRC’scomparison was made between the G&H device andseveral pyrotechnic devices. LaRC’s tests wereconducted on a biaxial Hopkinson bar and on a LaRCHalogen Occultation Experiment instrument mass model.From the Hopkinson bar, recorded peak g levels for theG&H device and a NASA Standard Initiator (NSI) firedSpace Ordnance Systems (SOS) Incorporated pin-pullerwere: in the transverse and axial directions, 680 and1278 g's for the G&H, and 923 and 1250 g's for the SOSdevices, respectively. The G&H pin-puller overallacceleration spectrum was below that of the variouspyrotechnic pin-pullers tested over most of the frequencyrange. The SOS pin-puller was previously obtained forthe NASA VIKING Mars mission.

In February, 1995, after presenting survey results toNASA's PMC, LaRC was invited to participate in acooperative, cost sharing effort with LMMSC to evaluatefunctional shock produced by several pyrotechnic andNEA release devices. A task was initiated under anexisting contract (Reference 3) to objectivelyinvestigate application of some NEAs to reduce smallspacecraft and booster separation event shock. Theprimary goal was to demonstrate NEA mechanisms forrelease functions and compare resulting shock levelswith those produced by standard pyrotechnic devices.Five different release mechanisms, immediatelyavailable from several sources, were tested on a singleinstrumented structural simulator, with and without masssimulators. This simulator represented a proposedLockheed Martin Launch Vehicle Commercial RemoteSensing Satellite radial panel. The pyrotechnicseparation nuts consisted of a 3/8-inch diameterOrdnance Engineering Associates (OEA) device, andHSTC 1/2-inch and 8 mm devices. The NEA devices werea G&H 3/8-inch diameter minimum shock separation nut,and FASSN release mechanism device (Figure 3f). TheFASSN device, an engineering feasibility demonstrationunit, was added to the task after it became apparent itmight substantially alleviate functional shock.

Figure 7 compares resultant shock response spectra(SRS)(Q=10) for the ninety-fifth percentile level forthese devices. Results are for multiple tests of the samerelease device design. The OEA 3/8-inch diameterseparation nut, preloaded to 3175 Kg, produced thehighest SRS, followed by HSTC’s 1/2-inch and 8 mmdiameter separation nuts. HSTC’s devices were notoptimized for "pyroshock" output. The HSTC 8 mmdiameter separation nut could only be preloaded to 1225Kg. The G&H separation nut generally showed loweroverall levels when compared to the pyrotechnic

8

devices. The FASSN concept, which could only bepreloaded up to 1905 Kg, produced the lowest SRS. Inseparate tests, in which FASSN preload was varied (1360to 1905 Kg), increasing preload had no observable effecton SRS level. Figure 8 compares LMA SRS data atvarious preloads for several NEA release nuts (i.e.,FASSN, LFN, TSN, and G&H low shock) against HSTClow-shock and OEA pyrotechnic devices. Device sizeand preload are indicated on the figure. These tests wereperformed on the LMA shock test plate. From theseresults it is obvious that several NEA release nutconcepts are available to relieve functional shockconcerns. Table I consolidates the SRS data herein into amore easily understood format, comparing the NEAs andpyrotechnics tested to the G&H low shock nut which wasused as the baseline. The table compares the order ofmagnitude difference in SRS over the frequency range ascompared to the baseline. Relative position in the table,with regard to the baseline, indicates a lessening orworsening of functional shock. Table II lists physicalcharacteristics of some NEA release mechanismsdescribed herein, some of these being used in thecomparative functional shock tests.

In June 1995, HSTC conducted tests for the LockheedMartin Astrospace-Princeton EOS-AM Program, usingoptimized internal cushioning in their 3/8-inch diameterlow-shock pyrotechnic separation nut initiated by twoNSIs. They demonstrated shock reduction factors ofapproximately 2.7 and 4.6 in peak g's when using a4536 and 2268 Kg preload, respectively. Tests wereconducted on HSTC’s shock plate.

Possible Related Technologies

Starsys Research Corp ., Smart, Passive Solar Panel Array Drive Mechanism

Although not an NEA, a unique application using theparaffin actuator was presented by Starsys; namely, aSmart, Passive Solar Panel Array Drive (SPSPAD)mechanism (Figure 9). SPSPAD is a passive, fullyautonomous solar tracking and drive mechanism whichcan be incorporated into a spacecraft where passive/autonomous 1 to 10 degree accuracy is desired. Itincorporates the paraffin actuator, a linear to rotationalmotion transmission, a sun sensor, an electrical circuit,and a hinge load bearing structure. It is approximately2.54 cm diameter, 15 cm long, weighs 0.68 Kg, andproduces about 14 Joules of work. The power required todrive the mechanism, which is derived from the solarpanel, will range from an average of one to 10 wattsdepending on rate and torque outputs required.

Spacecraft power production capability is a generalmission constraint. Small, simple, low-cost spacecrafthave used body-mounted solar cells or simple fixeddeployable solar panels to generate power. Increased orimproved power production involves more solar array

area, deployments, articulations, increased cellefficiencies, or a combination of these. These methodsto increase or improve power production effect cost,complexity, and reliability per watt of power produced,and all methods trend in the wrong direction. TheSPSPAD device has potential to provide a cost-effective,easily integrated, and reliable solution to powerproduction limitations; thereby optimizing solar powergeneration, saving payload weight, volume, power,command and control functions, and costs associatedwith same.

Starsys based their analysis on a 3-axis stabilized,nadir-pointing bus with body mounted solar panels onthe velocity and anti-velocity faces Panels could bedeployed from the spacecraft’s anti-nadir end to either a1.57 radian fixed position or articulated from the zerostowed position to 3.14 radians. Comparing results to asystem employing a standard stepper motor drive,Starsys drew the following conclusions regardingSPSPAD: drive mass decreased more than 60 percent,functional power decreased approximately 70 percent,drive costs were reduced more than 55 percent,considerably less volume was required, and lower partscount and complexity were coupled with higherreliability. The satellite would have increased powergeneration efficiency allowing improved missioncapabilities.

SPSPAD development should provide extremelyreliable actuation from a lightweight mechanism with acalculated transmission efficiency exceeding 90 percent.SPSPAD would operate independently of a flightcomputer and drive electronics, supply its own control(no software is required), eliminate encoders (it willsupport position feedback if required), and eliminatehigh-frequency drive vibrations. It would require simplepower input from the solar array and would be controlledby a simple electrical circuit with no other electronicparts required. It would require a simple wet lubricantsystem, but it would not incorporate any operatingparameters outside of typical lifetime issues which couldtrigger premature failure mechanisms. This conceptcould be used for antenna and wide band instrumentpointing platforms, louvers and radiator covers,instrument covers and shades, instrument autonomoussolar exposure protection, and solar collector arraypassive control for terrestrial power or thermalgeneration.

Thiokol Corp .- Elkton , Safe and Arm (S&A) and Initiation System

Thiokol Corp.-Elkton Div. has developed a newconcept for pyrotechnic device S&A and initiation15 thatincorporates several improvements made withpyrotechnics. Thiokol is developing for the miningindustry (Figure 10) a combination miniaturized,multiple function, remotely programmable, low-

9

powered, optically initiated, electrically fired,inexpensive, S&A and initiation system. Theirapproach can mitigate significant LIOS associateddisadvantages, namely; high power, optical damage,high-powered laser diode availability, higher weight,and larger volume. The heart of this system isincorporated in the initiator. Based on the miningrequirement, the system consists of a laser referred to asthe blast machine) which sends out optically codedsignals via a fiber optic cable to a terminal located up to305 m away. The terminal sends the signals to theinitiators on ten individual fiber optic channels. Eachchannel can accommodate up to 150 separatelyprogrammable initiators whose individual functioningtime can be set in 1-msec increments up to 500 msec.Each initiator has a built-in light emitting diode whichallows the blast machine to perform an end-to-end BIT toverify system integrity of each initiator.

Within the initiator (Figure 10), the received lasersignal charges a capacitor via a photodiode. Thecapacitor has a built-in bleed for discharge in the eventinitiation is halted. The capacitor cannot dischargeenergy to the SCB initiator unless a properly coded 16-bit fire-signal is received. Solid-state microelectronicsare used to decode signals, set timing, perform statusmonitoring, and control capacitor discharge. Thiokol isextending development of this system to launch vehiclesand upper stages. The system has application to aircraftegress, weapons delivery, or spacecraft functions wheremultiple, sequenced events are required. In one studyThiokol estimated such a system might weigh only 15percent of present hot wire systems, occupy only 20percent of the volume, and require only 10 percent of theinput energy if used on a typical two stage launch vehicleto perform two ignition and one separation functions.Optical cables can even be routed through compositestructures by using SMA to form the initial cavity in thestructure.

The Thiokol concept offers potential for aminiaturized S&A/initiating system that can performmultiple functions with no reduction in safety overcurrently used electro-mechanical designs. Thesecombined technologies marry new technology (i.e., low-power laser diodes, microelectronics, and digital coding)with well-established, highly reliable state-of-the-art(i.e., SCB initiators); thereby providing a smoothtransition between existing and emerging technologieswhich would assist acceptance of the latter. Figure 10shows a sectioned view of a typical blasting cap withmicroelectronics substituted, and compares a NSI to theSCB and a miniature initiator from ICI America.Partially due to standardization, the current NSI costsmore than $400 each. The NSI weighs 9.9 grams. Bothfactors do not lend themselves readily to cost reductionor miniaturization . The ICI miniature initiator headerassembly costs approximately $1.20 each and weighs0.15 grams. The SCB, which could be incorporated into

the ICI miniature initiator header assembly, costsapproximately $1.

The Thiokol concept provides a system possessingthese advantages: every function has a separate S&A;the system is inexpensive; reduced weight and enveloperequirements will be realized; the system provides asingle upgradable initiation control module to servicemultiple functions; functioning time is fast; improvedlaunch responsiveness will be realized through BITcapability; it meets MIL-STD-1901 for in-line ordnance;optical isolation provides protection against ESD, RFI,and EMP; it provides digital coding and multiple inhibitsfor increased safety; the fiber optic cable eliminatesexplosive transfer assemblies which provides saferhandling, eliminates explosive aging (service life)issues, and improves routing flexibility between stages.This concept appears to be a fruitful area worthy offurther exploration, especially in smaller spacecraftincorporating multiple functions.

Naval Air Warfare Center-China Lake , Intermetallic Thermal Sensor/Trigger

Naval Air Warfare Center, Weapons Division-ChinaLake, CA, is developing a device for active ventingsystems that mitigate the fast cook-off response ofvarious munitions. This device has been successfullyintegrated into the Advanced Medium Range Air-to-AirMissile thermally initiated venting system (TIVS)enabling the TIVS to mitigate intermediate-to-slowcook-off thermal threats16. This miniature, passiveintermetallic thermal sensor/actuator (Figure 11) mayprove useful in conjunction with an external heat sourceand NEA technologies (e.g., SMA, paraffin actuator,thermal knife) to function non-time critical spacecraftseparation/release/ deployment mechanisms. Thisdevice operates independently of all other systems,requiring no power except an external heat source (e.g.,solar or atmospheric entry heating) to raise itstemperature sufficiently to the initiating temperature.This passive device consists of a thin walled steel shellcontaining alternating wafers of lithium and tin alloywith copper coating the tin alloy to serve as a diffusionbarrier. As the device is heated and the lithium alloybegins to melt, a spontaneous and vigorous, gasless,exothermic intermetallic reaction occurs providingenergy to initiate a thermite charge in the end of thedevice. This end charge produces the principal thermaloutput of the device (the tip can approach 1093 C). Theprocess is fully contained and confined. Temperature atwhich the reaction initiates can be tailored fromapproximately 149 to 177 C, and the Army-PicatinnyArsenal, NJ is investigating initiation temperaturesdown to 93 C. There is no inadvertent actuation towithin 1.6 C of the trigger temperature. The device hasfunctioned successfully after cold soaking to -84.4 C.The current device concept is compact (approximately3.8 cm, 0.76 cm diameter, 0.71 cubic cm), lightweight

10

(approximately 25 grams), low-cost (approximately$400 each, produced in quantity), is insensitive to allother external stimuli, has a long shelf life, and is non-explosive. There is no other similar system which hasthe potential weight, volume and power reductions.

Existing Government Programs

NASA- HQ - Laser initiation program for pyrotechnic

improvement. JPL - Developed SMA wire pin-puller as a fail-safe

actuator for Hubble Aperture Window Mechanism inWide Field Planetary Camera II. (Contact: VirginiaFord).

JSC - Four year program studying pyrotechnicalternatives, particularly SMAs. Patented a SMAactuated segmented release nut. Have on-linedocument archiving system for pyrotechnics andalternatives. (Contact: Darin McKinnis).LaRC - Evaluated functional shock of various NEAswith pyrotechnic devices (Reference 3). Complete.(Contact: Melvin Lucy).LeRC - SBIR Contract No. NAS3-26834 with TiNiAerospace developing pin-puller for aerospaceapplications. Complete. (Contact: Doug Rohn).MSFC - Program for electromechanical actuationapplicable to release mechanisms as alternatives tospacecraft pyrotechnics (e.g., some HubbleTelescope appendages). (Contact: Charlie Corneliusor W. Neil Myers).

Other Government Laboratories-AF/Phillips Laboratory; Kirtland AFB - SMAactuation and release devices program, also a generalprogram for smart actuators and materials. AFPLconducts MiniSat flights demonstrating newtechnology. (Contact: Alok Das or RodneyGalloway).ARL-Adelphi - Semi-conductor bridge (SCB) programfor improvements to pyrotechnics. (Contact:Robert Reams).NRL - Use of pyrotechnic alternatives and laserinitiator technology in ARTS program. Previouswork on Clementine spacecraft. Procurement ofFASSN for evaluation. (Contact: Bill Purdy).

NAWC-China Lake - Heat source device, exothermicintermetallic thermal sensor/trigger. (Contact:James Gross).

Summary of Findings/Conclusions

Shock and safety issues have raised questionsconcerning continued use of pyrotechnics on spacemissions. Additionally, in today's environment ofsmaller spacecraft and the need to reduce overall systemcosts, the emergence of new technologies providesalternative methods to accomplish the functions oftraditional pyrotechnic devices. Alternative devicesexist which have been or are planned for use on

spacecraft. The majority of the alternative technologiesperform separation and deployment functions. Thesemechanisms include G&H spool based devices, Fokkerthermal knife, Starsys Research Corporation FASSN andparaffin wax actuators, and shape memory alloy (SMA)devices (e.g., TiNi Frangibolt). NEA mechanisms aretypically either reusable or refurbishable, allowing fortesting of the actual flight unit. No single technology,however, is a panacea. Some devices, such as theFrangibolt and the G&H spool based mechanisms, stillproduce high levels of functional shock. Paraffin andother SMA based devices can provide gentle, shock-freerelease but cannot perform critically timed simultaneousfunctions due to long actuation rates. A flywheel-nutrelease device possesses significant potential forreducing functional shock while activatinginstantaneously.

Although three alternative technologies (electro-mechanical spool, paraffin actuator, thermal knife) areconsidered mature, flight proven technologies,continued development is in progress. SMA devices aretypically the least mature of the technologies, althoughone SMA device, the Frangibolt, has been flown.Standards for all NEAs are needed, specifically in theareas of material characterization, functioning rates, andtest methods. A systems level approach will be neededto assure successful application of the new technologies.Recognizing that pyrotechnics will remain viable,industry and government are continuing to investigatetechnology improvements. Thiokol-Elkton isdeveloping a miniaturized, optically initiatedcombination safe and arm firing system. The Navy atChina Lake has developed a passive detection andinitiation device that may be incorporated as an energysource for both pyrotechnics and NEAs.

Several government and industry laboratories areinterested in potential partnerships to developalternative technologies with SMAs having the mostcommercial interest. Several NASA centers andgovernment installations have ongoing or completedprograms in the area of pyrotechnic alternatives.Industry expressed a desire to cooperate with NASA todevelop NEA standards to which their innovations couldbe shown to conform. An inter-agency ad-hoc teamshould be formed to define a need and strategy forpyrotechnic replacement technology efforts. This teamwould conduct a further investigation into needs of theuser community. The team would performindustry/government system-level cost-benefit studiesof real spacecraft to determine application foci andperformance requirements for NEAs. The investigationwould culminate in an industry/government workshop toprioritize identified technology needs and determineresource requirements and schedules.

To develop NEA standards and metrics,an NEA Steering Committee, similar to the

11

Pyrotechnics Steering Committee, should beestablished. The committee should initiallyinclude members of the ad-hoc team andrepresentatives from industry, academia,DOD, and others. NASA should pursueopportunities for flight of NEAs onspacecraft where reasonable. NASA shouldallocate resources to develop NEAs. SBIRand IPD team contracts, and partnershipsshould be considered. Pyrotechnicreplacements for functions such asstage/shroud separation and high pressurevalving should be considered.

Recommendations

The LaRC team recommends several actions as a resultof this investigation:

1. Form an inter-agency ad-hoc team to define need andstrategy for a pyrotechnic replacement technologyefforts.

a. Define user priorities, and payoffs. Conduct furtherexplorations of needs with the user community asLaRCs time and initial scope constraints preventedan in-depth investigation of this aspect of the pre-Phase-A study.

b. Compare NEAs to pyrotechnics using a system-level cost-benefit analysis. Using in-placecontracts, conduct up to two industry/governmentsystem level cost benefit trade studies of realspacecraft to define application foci and performancerequirements.

c. Define specific funding requirements for any neededdevelopment activity.

d. Conduct industry/government workshop toprioritize technology needs and schedules.

2. Solicit Small Business Innovation Research (SBIR)contracts; form partnerships with governmentlaboratories, DOD, industry. Conduct up to threecompeted IPD team contracts (expect cost sharing) toevaluate non-pyro stage/shroud separation devices,valves, latches, and releases, and demonstrate "soft"pyros and NEA devices capable of satisfying theidentified needs.

3. Develop NEA standards, metrics, and trainingmethods. Standard specifications needed include:basic material properties (comprehensiveengineering database), basic material procurement,processing (e.g., heat treatment, tempering, hot/coldworking), mechanical properties, training (e.g.,stretching and heating cycles, percentage of stretch,methods to increase recoverable shrinkage), testmethods, limitations of operability and amnesia, andterminology.

a. Establish an NEA Steering Committee (similar tothe Pyrotechnic Steering Committee).

b. Include NASA participation in the SMAAssociation.

4. Pursue opportunities for flight of NEAs onspacecraft, and educate the spacecraft community.Remain competitive with others flying NEAs.

_________________________________1 Moening, C.J., “Pyroshock Flight Failures,”Proceedings of 31st Annual Technical Meeting of theInstitute of Environmental Sciences, May 3, 1985.2 Bement, L.J., “Pyrotechnic System Failures: Causesand Prevention.” NASA TM 100633, June 1988.3 Contract NAS1-19241, “Mission Systems andOperations Analyses of NASA Space Station FreedomAdvanced Concepts,” Task 31, “Low-Shock BoosterRelease System Engineering FeasibilityDemonstration.”4 2nd NASA Aerospace Pyrotechnic Systems Workshop,Sandia National Laboratories, Albuquerque, NM, NASAConference Publication 3258, February 8-9, 1994.5 Applications of Laser Initiated Ordnance TechnologyTransfer Workshop, NASA-GSFC, NASA ConferencePublication 10182, April 25-26, 1995.6 Purdy, B., NRL; Fratta, M., Allied Signal Tech Serv.;Boucher, C., Ensign Bickford Aerospace, “LaserOrdnance System for NRL’s ARTS Program,” AIAA PaperNo. 93-2361, AIAA/SAE/ASME/ASEE 29th JointPropulsion Converence and Exhibit, Monterey, CA, June28-30, 1993.7 Brook, G.B., Fulmer Research Institute, Ltd., Powley,D.G., British Aircraft Corp., Ltd., “The Design andTesting of a Memory Metal Actuated Boom ReleaseMechanism,” 12th Aerospace Mechanisms Conference,NASA Ames Research Center, 1978.8 Webster, R.G., “No-Shock Separation Mechanism,”Patent No. 5,248,233, September 28, 1993, Hi-ShearTechnology Corp.9 Carpenter, B., Clark, C., Weems, W., Lockheed MartinAstronautics, Denver, CO, “Shape Memory ActuatedRelease Devices,” Proceedings of Society of Photo-Optical Instrumentation Engineers, 1996.10 Robinson, S.P., Boeing Defense & Space Group, “AVery Low Shock Alternative to Conventional,Pyrotechnically Operated Release Devices,” 2nd NASAAerospace Pyrotechnic Systems Workshop, Albuquerque,NM, February 8-9, 1994.11 McCloskey, T.E., Lockheed Martin Missile and SpaceCo., “Non-Pyrotechnic Release System,” Patent No.5,192,147, March 9, 1993.12 Choi, S.J., Lu, C.A., Feland, J., Stanford University,Stanford, CA, “A Nitinol-Based Solar Array DeploymentMechanism,” 30th Aerospace Mechanisms Symposium,NASA Conference Publication 3328, Hampton, VA, May15-17, 1996.13 VanHassel, R.H.A., Fokker Space BV, Leiden, TheNetherlands, “The ARA Mark 3 Solar Array Design andDevelopment,” 30th Aerospace MechanismsSymposium, NASA Conference Publication 3328,Hampton, VA, May 15-17, 1996.14 Busch, J.D., Bokaie, M.D., TiNi Aerospace, Inc.,Fremont, CA, “Implementation of Heaters on ThermallyActuated Spacecraft Mechanisms,” 28th Aerospace

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Mechanisms Symposium, LeRC, Cleveland, OH, NASAConference Publication 3260, May 18-20, 1994.

14

Pin pullers

SeparationNuts/Bolts Release Mech.

Actuators

Switches

Powered Hinges

Valves

Pyrotechnics G&H

Spools

H

H-M

M

M-L

ParaffinWax

ThermalKnife

SMA Devices

H

H

H

H

M

M

M

H-M

H-M

M-L

M-L

Device*

H

L

*Does not include Launch-vehicle or Booster-type applications

H -High M -Medium L -Low - none

M

H-M

M-L

Figure 1. Developed spacecraft applications of NEAs.

20000

15000

10000

5000

0.001 .01 .1 1. 10 100 1000

HSTC 1/4” sep. nut pyro

OEA 1/4” sep. nut pyro

G&H 1/4” low shock sep. nutTiNi 1/4” Frangibolt -SMA

LMA 1/4” LFN sep. nut -SMA*

LMA 1/4” TSN sep. nut -SMA*

HSTC sep. nut -SMA

HSTC pin puller -SMA

STARSYS Paraffin actuator (high rate)

Sho

ck, g

Rate, sec* From AFPL sep. nut device comparison study; Rate is for preload release only, not total functioning time.

LMA FASSN -SMA

Figure 2. Functional shock versus operational rates for some pyrotechnics and NEAs.

15

b. G&H low shock. c. HSTC no-shock.

Segments

Ring

SMA

Locking Sleeve

Segment

Spool

Plunger

Toggle

CompressionSpring

PlungerRestraining Wire

Spool Halves

Electrical Contacts

Linkwire

a. G&H spool.

SMA Damper &Reset Spring

SegmentSeparator

Sleeve

Segments

SMAInitiatorSpring

Plunger

SteelActuationSpring

d. LMA low force. e. LMA two-stage. f. LMA FASSN.

Bias Spring

SMA CylinderSegments

SMA Initiator Spring

Collet Anti-rotation Feature

Lock Arm

Thrust Bearings

Flywheel -Nut

Primary Latch

TiNi SMA Rotary Release

Figure 3. NEA Separation nuts - pre-release.

16

a. BDSG NiTi release device.

c. LMMSC NiTi release mechanism.

b. LMA high force thermal latch.

NiTi Fusible Link

Minimum Area

Housing

Torsion Spring

Cable Heater

Slide Gate

Drive Springs

Piston

Low MeltEutectic

Cylinder

Carrier

Latch Bolt

Released Toggle Latch

SMA Rod

Figure 4. NEA release mechanisms.

Pin

Cross-Pin

Drive-Spring

Reset-Spring PatentPending

Pin

CompressionSpring

ExpendedSpool

Plunger Toggle

a. G&H ; post-release.

Rod

Redundant Heating Element

Squeeze Boot High Purity Paraffin

c. Starsys HOP actuator; pre-release.

b. Ti-Ni; pre-release.

Figure 5. NEA pin-pullers.

18

High Temperature Out-put Tip

Figure 11. NAWC China Lake IntermetallicThermal Sensor/Trigger.

18

Thiokol Initiator- S/A System

NSI Thiokol SCB forInitiation System

Miniature Bridge-Wire Initiator

Figure 10. Thiokol miniaturized, programmable delay, SCB, electro-optical S/A and initiation system.

16

I/P Wire

Heater Pin

Spring (not drawn)Piston

Heater Element

Housing

FootplateHeater Stop

Clamp Block

a. Fokker thermal knife.

SMA Actuator

Heater and Insulation

Separation Plane

Actuator Elongated

Bolt Brokenin Tension

b. Ti-Ni Frangibolt.

Notched Bolt

Figure 6. Other NEA release devices.

1x105

1x104

1x102

1x103

1x101

1x100

1x102 1x103 1x104

Peak

Abs

olut

e A

ccel

erat

ion

- G

’s

1/6 - Octave Center Frequency - Hz

Supplier, Size, Preload OEA, 3/8, 3180 kg HSTC, 1/2, 3180 kg G&H, 3/8, 3180 kg HSTC, 8mm, 1230 kg LMMSC, 3/8, 1910 kg

*

Figure 7. Device comparison, LMMSC panel simulator with masses, SRS (Q =10), 95th percentile levels.

17

1x105

1x104

1x103

1x102

1x101

1x1001x101 1x102 1x103 1x104

Acc

eler

atio

n -

G’s

1/6 - Octave Center Frequency - Hz

500g Rule of ThumbLimit

Supplier, Size, Preload

OEA, 1”, 37K

HSTC Low Shock,

G&H Low Shock,

Original LMA FASSN, 7/8”, 37.5KLMA LFN, 1/4”, 3K

LMA FASSN, 1/2”, 10K

LMA TSN, 3/8”, 10K

0.8 f limit

Figure 8. LMA plate tests - functional shock comparison.

Return Spring

Spiral Cam

Spacecraft Body

HOP Actuator

Sensor with Switch Circuit

Solar Cell Sensorand Baffle

Solar Panel

HOP ActuatorDrive Direction

Return SpringDrive Direction

Figure 9. STARSYS Smart Passive Solar Panel Array Drive element layout.