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Lightband Slow-Down Mechanism

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Lightband Slow-Down Mechanism: Proposed Enhancementfor the Three Corner Satellite MissionAbstract1.0 IntroductionLightband Slow-Down Mechanism: Proposed Enhancement for the Three Corner Satellite MissionAuthors:Ervin Krauss, Anthony LowreyAdvisor: Chris KoehlerDeputy Director - Colorado Space Grant ConsortiumColorado Space Grant ConsortiumUniversity of Colorado at BoulderBoulder, CO [email protected], [email protected] Slow-Down Mechanism for the Lightband system was conceived to decelerate theseparation of the 3 Corner Satellite (3CS) stack. 3CS is a three-satellite stack built by ArizonaState University, New Mexico State University, and the University of Colorado at Boulder. Theprimary mission of this multiple satellite system is to perform stereoscopic imaging anddemonstrate communication capabilities of multiple satellites within a constellation. Lightband,a separation system developed by the Planetary Systems Corporation, connects the stack.Lightband requires the use of springs that separate 3CS at a rate of approximately 60 cm/s,compared to the desired rate of about 1 cm/s. A separation rate of 1 cm/s would increase theprimary mission lifetime to about 3 months. Currently, 3CS will have a primary mission life ofaround eight days. This led to the development of the slow-down mechanism, which initiallystops the Lightband system from fully deploying, and then separates the stack at the desired rate.The slow-down mechanism is a small addition to the Lightband system; having the primaryadvantage of low power consumption and easy integration with Lightband, requiring only a slightmodification to the system. The addition to Lightband can be incorporated on future missionsrequiring this capability. The mechanism is comprised of a solenoid and a latch pin, that whenenergized, activates a small spring that pushes the stack apart at 1 cm/s. With this addition toLightband, the 3 Corner Satellite would be able to sustain inter-satellite communications tentimes longer than it is currently planned to do so. 11.0 Introduction1.1 OverviewThe universities of Arizona State, NewMexico State, and Colorado started theThree Corner Satellite (3CS) mission to takestereoscopic imaging of the Earth anddemonstrate communications capabilitiesbetween satellites. While there is not aforeseeable problem with imaging, the inter-satellite communications of the mission isseverely limited by the current separation ofthe three-satellite stack. This led to theproposition that a mechanism be added tothe separation system to slow-down thedivision of the satellites, and extendcommunication capabilities.Lightband is the separation system thatconnects the 3CS stack and deploys it oncein space. Lightband, developed by thePlanetary Systems Corporation (PSC),requires springs that deploy the stack atabout 61 cm/s. For fear of losing reliabilityof Lightband, PSC suggested a mechanismbe added to Lightband to slow down 3CS tothe desired delta V of 1 cm/s. The Slow-Down Mechanism (SDM) was born.1.2 ObjectivesThe purpose of the Slow-DownMechanism is to reduce the severance of the3CS stack to 1 cm/s, providing up to threemonths of inter-satellite communicationafter deployment. With the current delta Vof 61 cm/s that the Lightband provides,communications between satellites is to lastabout 8 days, making the contribution ofSDM significant.The Slow-Down Mechanism itselfmust be small enough to fit between theLightband and satellite (a distance of about 1cm), as well be an easy add-on to Lightband.It is important to the 3CS mission that SDMchanges little from the current satellitesystem, save providing enough power tooperate the mechanism. 1.3 LightBand and Mechanism DescriptionThe LightBand system serves to not onlyseparate the 3CS satellite stack, but to alsohold it together. This system is composed ofa set of two nearly identical hexagonal rings,held together by leaf springs, which in-turnbolt to respective bulkheads of the satellite.Figure 1 shows the LightBand system to beused on the 3CS mission. 2Figure 1. The LightBand system shown herewill deploy two adjacent satellites.Each of the rings mounts to a bulkhead asdepicted in figure 2. Specially designatedattachment points along the perimeter of thebulkhead ensure a proper and secure fit ofthe LightBand.Figure 2. A rendering depicts a single ringof LightBand being mated with one of thebulkhead.The separation of the two rings is achievedby the stored energy of a set of 4 springsplaced symmetrically about the LightBandsystem. The placement of one of the springsis illustrated in figure 3 below.Figure 3. One of four springs that separatethe LightBand system.The leaf springs about the perimeter of LightBand serve to prevent the deployment of the system. Each of the leaf springs hook into specially machined grooves within one of the rings. The leaf springs are prevented from activating by a heat sensitive, liquid crystal based rope that wraps around the whole of LightBand. The rope is kept taught by a tensioning mechanism, and is activated by a nicrome wire based heater. The system activates through this heater, which weakens the rope, causing it to brake and deploy LightBand. The modification to the LightBand system serves to extend the primary mission life-time from 8 days to 3 months. The diagrams given in figures 9 and 10 illustrate the current design and the conceptual design modification, respectively.To realize the modification to the LightBandsystem, the SDM operates with thefunctionality and simplicity of a solenoid,where solenoid plunger is an integratedlatching mechanism for the current SDMprototype. The latch acts to hold onto themain spring assembly after primarydeployment of LightBand occurs. To initiatethe desired separation rate of 1 cm/s, asupplemental spring plunger imbeddedwithin the primary spring assembly pushesthe satellites apart after the latch holding themain spring assembly releases. Refer toFigure 10 for a diagram of the idealmechanism. 32.0 Design Process2.1 RequirementsMany constraints affect the design ofSDM. These include


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