**The most comprehensive collection of Shuttle, Ares, Orion and ISS related presentations and mission documentation, plus expansive daily processing documentation and updates are <\/em>available to download on L2<\/em><\/font> **<\/em><\/font><\/p>\n **ARES I LIVE UPDATE PAGES**<\/font><\/em><\/p>\n **ORION\/Exploration Vehicles LIVE UPDATE PAGES**<\/em><\/p>\n **ARES V \/ Mars LIVE UPDATE PAGES**<\/font><\/em><\/p>\n **EXPLORATION ALTERNATIVES (DIRECT, EELV) PAGES**<\/u><\/em><\/p>\n Aerospace industry analysis (adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n Thrust Oscillation Latest:<\/u><\/em><\/p>\n Thrust Oscillation (TO) \u2013 also known as \u2018Resonant Burning\u2019 \u2013 is a recognized characteristic of solid rocket motors. The concern relates resonant modes in the vehicle structure which are capable of harming the astronauts riding in Orion. <\/p>\n For months now, the Focus Team \u2013 or Tiger Team \u2013 have been working on potential mitigation options, and have been successful in finding multiple approaches that \u2013 in theory \u2013 could solve the issue, or at least reduce the vibration environment low enough for acceptable crew performance.<\/p>\n<\/p>\n <\/u><\/i><\/b><\/p>\n Active Pulse RCS:<\/p>\n<\/p>\n The anti-Thrust Oscillation RCS would be a totally new system, located on the aft skirt of the Ares I booster. Known as Active Pulse Thrusters (APT), documentation shows this system to hold the potential of reducing Thrust Oscillation by around 10 times that which is currently expected. <\/p>\n However, it would \u2013 as with most of the mitigation options \u2013 hold a mass impact on the vehicle, something Ares I has been struggling with since its early design cycles. <\/p>\n \u2018Performance and aft skirt design challenge: (around) 500 lbm (pounds mass) payload impact. Trade required for separation and booster deceleration. Add failure modes. Must survive aft skirt environments.\u2019 <\/p>\n The system consists of four pods, located around the aft skirt on the Ares I First Stage. Early graphics of a system \u2013 that are bound to mature if accepted as the way forward \u2013 show each pod will have a fuel tank, an oxidizer tank, a pressurant tank, and seven thrusters. <\/p>\n The downside of this concept \u2013 which is a completely separate system than the roll control system on the interstage \u2013 is the addition of failure modes, which would hit Ares I\u2019s LOC\/M (Loss of Crew\/Mission) numbers. <\/p>\n Also on the downside, the concept is a retro thrusting system (negative thrusting) \u2013 which would impact on Ares I\u2019s performance figures. <\/p>\n<\/p>\n <\/u><\/i><\/b><\/p>\n Isolation Mounts between the First Stage and the Upper Stage:<\/p>\n<\/p>\n This concept isn\u2019t likely to survive the trade study, should the issue of the Ares I Interstage structural strength come into question \u2013 given it adds flexibility to that area of the vehicle. <\/p>\n Other negative impacts are noted in associated documentation, and the concept itself is not deemed as capable of eliminating the issue of Thrust Oscillation to within required limits for the crew performance. <\/p>\n \u2018Most of the isolation carried on the Ares Upper Stage side of the interface. Would reduce loads to well within crew health limits, (but) still would not meet performance limit,\u2019 added the documentation on the first review of this concept. <\/p>\n \u2018May reduce payload by 1000 lbm. Reduces lateral stiffness unless mitigated in the design. Adds failure modes. Changes system modes for loads and control.\u2019 <\/p>\n Tuned Mass Damper (First Stage Parachutes):<\/u><\/i><\/b> <\/p>\n This concept is understood to be the favored option on its potential for solving the problem of Thrust Oscillation. <\/p>\n Working as either a passive or active system, this concept will still require maturity, given associated documentation shows it is projected to reduce Thrust Oscillation down to acceptable crew health limits, but not enough for crew performance requirements. <\/p>\n \u2018Tuned Mass Absorber: Use existing mass to counterbalance TO: 2X reduction for passive system, 3X reduction for active system. Payload impact less than other concepts,\u2019 noted documentation.<\/p>\n \u2018Immature design: May create problems for First Stage recovery system. Active control design is immature. Reduces loads to well below human health limit, but not performance limit. Adds failure modes.\u2019 <\/p>\n The system weight is classed as 1000 lbm, which consists of rails and springs under the top plate of the parachute platform on the First Stage. The active system would require a control system and associated battery power supply \u2013 all located under the aeroshell that houses the drogue parachute. <\/p>\n The passive system has a rail attachment on the forward skirt extension of the First Stage providing lateral support. Damping would be provided by springs attached through the ancillary ring. <\/p>\n All three concepts noted (on April 23) as heading through the trade study would require maturing to mitigate their negative issues, thus the eventual winner is likely to undergo a large element of refinement. <\/p>\n Current Ares I Mass Figures: Currently, end of April documented figures for Ares I places the Upper Stage dry weight as \u201cAllocated 30,800 pounds \u2013 Estimated 31,526 pounds.\u201d Interstage dry weight is documented as \u201cAllocated 7,270 pounds \u2013 Estimated 7,398 pounds.\u201d<\/p>\n Residual mass \u2013 only recently added \u2013 is classed as \u201cAllocated 0 pounds (due to it being a new factor) \u2013 Estimated 2,687 pounds,\u201d while the Upper Stage Engine\u2019s figures come in at: \u201cAllocated 5,450 pounds \u2013 Estimated 5,676 pounds.\u201d<\/p>\n The above figures \u201cdo not take into account any mass gain caused by thrust oscillation mitigation.\u201d<\/p>\n<\/p>\n <\/u><\/i><\/b><\/p>\n Ares I related testing:<\/p>\n<\/p>\n ATK and NASA will test fire another Space Shuttle Reusable Solid Rocket Motor (RSRM) on May 1, which \u2013 while checking into booster age-life certification, will also gain more valuable data on the motor for Ares I. <\/p>\n \u201cAnother test objective will help in the development of the Ares I crew launch vehicle and its launch pad acoustics, or sound measurements, will be taken using microphones placed outside the motor,\u201d noted ATK. \u201cThe data will be used to make predictions of Ares I acoustics during lift-off.\u201d<\/p>\n ATK remain on track to test fire a fully developed five-segment five segment motor in April, 2009. The Utah-based company are also on track for a full-scale launch abort motor test, using reverse flow motors \u2013 the four nozzles on the LAS (Launch Abort System) \u2013 in a vertical test stand.<\/p>\n The alternative abort system, known as MLAS (Max Launch Abort System) was believed to be winding down as a project recently due to mass and complexity issues. However, information points to this concept remaining alive, via special funding from what is described as \u201cManager\u2019s Discretionary Funding\u201d \u2013 which may allow for a test firing later this year.<\/p>\n One other related test has been postponed until the end of the year \u2013 namely the pad abort test. \u201cOrion pad abort test slated for September has been pushed to December,\u201d noted a NASA HQ memo recently.<\/p>\n","protected":false},"excerpt":{"rendered":" A trade study has begun on three leading candidates to mitigate Ares I\u2019s Thrust Oscillation problem, as the Tiger Team work through design immaturity and mass constraints. Active Pulse RCS (Reaction Control System) \u2013 mounted on the aft skirt, Isolation Mounts between the First Stage and the Upper Stage, and a Tuned Mass Damper are […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[],"class_list":["post-41427","post","type-post","status-publish","format-standard","hentry","category-news"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41427"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=41427"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41427\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=41427"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=41427"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=41427"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}<\/em><\/font>All of this article is based on documented L2 information. For an overview of how L2 works, <\/em>**click here for sample**<\/em><\/font><\/p>\n
\u2018Active Pulse Thrusters (RCS TO Damper): First Stage carries most of the design changes (Orion Service Module tanks change required),\u2019 noted associated documentation on this concept. \u2018Could provide 10X reduction in TO. Relatively mature thruster design. Self contained. Relatively mature control system.\u2019<\/p>\n
Based around the Ares I First Stage recovery parachutes, this concept\u2019s main negative points relate to the added weight that will make recovery of the first stage more difficult \u2013 added to the center of gravity moving farther forward. <\/p>\n
<\/u><\/i><\/b>
Also, the resulting mitigation concept for Thrust Oscillation will affect the current mass figures for Ares I, which remain tight. <\/p>\n