{"id":39014,"date":"2016-07-07T23:04:48","date_gmt":"2016-07-07T15:04:48","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/sls-mission-trajectory-mike-sarafin-outlines-the-ride-uphill-for-em-1\/"},"modified":"2016-07-07T23:04:48","modified_gmt":"2016-07-07T15:04:48","slug":"sls-mission-trajectory-mike-sarafin-outlines-the-ride-uphill-for-em-1","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/sls-mission-trajectory-mike-sarafin-outlines-the-ride-uphill-for-em-1\/","title":{"rendered":"SLS Mission Trajectory \u2013 Mike Sarafin outlines the ride uphill for EM-1"},"content":{"rendered":"

NASA managers are closing in on a mission trajectory plan for the new Space Launch System (SLS) rocket that is set to debut in 2018. Mike Sarafin, NASA\u2019s mission manager for the first Orion\/Space Launch System (SLS) mission, recently provided an early look at an outline of launch events and a high-level status of the process of designing the trajectory for the maiden flight.<\/p>\n

EM-1 Launch:<\/p>\n

Designated Exploration Mission-1 (EM-1), the first-ever SLS launch will send an uncrewed, second-generation Orion spacecraft on a three-week flight to orbit the Moon and return.<\/p>\n

Both the SLS and the Orion vehicles are still in development, while the trajectory design is in a preliminary phase \u2013 as the launch vehicle and spacecraft plans continue to mature.<\/p>\n

\"2016-07-07-220110\"\u201cWe\u2019re in the initial design phase,\u201d Mr. Sarafin noted in a recent interview with NASASpaceflight.com.<\/p>\n

\u201cWe have three design phases of the mission trajectory; we\u2019re doing the preliminary mission [trajectory design] phase, then we have a \u2018final\u2019 analysis [but] it\u2019s not the \u2018final\u2019, and then we have what\u2019s called a \u2018best-estimate\u2019 trajectory, so we\u2019re in that initial phase.\u201d<\/p>\n

Sarafin is a NASA Shuttle veteran, having previously worked in the Mission Operations Directorate (MOD) at the Johnson Space Center in Texas as Lead Flight Director of several Shuttle missions at the end of the Shuttle Program, the last being STS-132 in 2010.<\/p>\n

He most recently served as the Flight Director for the Orion spacecraft\u2019s first test flight, Exploration Flight Test-1 (EFT-1).<\/p>\n

As EM-1 Mission Manager, Sarafin is now working out of NASA Headquarters in Washington, D.C.  He will be the Chair of the Mission Management Team (MMT) for the mission, giving the final go to proceed for launch to Launch Director Charlie Blackwell-Thompson.<\/p>\n

\"2016-07-07-204204\"The SLS uses propulsion system elements similar to or derived from the Space Shuttle program and the sequence of events in the last few seconds before launch should be familiar to Shuttle watchers.<\/p>\n

About six seconds before T-0, the four RS-25 Core Stage engines will start and throttle up to 100% of their original, 1970s rated power level.<\/p>\n

Assuming the engines are healthy and the rest of the vehicle remains healthy, the two solid rocket boosters (SRBs) will ignite at T-0, lifting the vehicle off Launch Pad 39B at the Kennedy Space Center in Florida, as umbilical connections from the Mobile Launcher are cut and vehicle access arms swing away.<\/p>\n

With liftoff, the Core Stage engines will throttle up to 109% power level to help the SRBs, which are producing their peak thrust in the first approximately twenty seconds, accelerate the vehicle up and away.<\/p>\n

\"2016-07-07-144818\"\u201cTower clear is around\u2026seven, eight seconds into flight,\u201d Sarafin noted, \u201cthen we hit Mach 1 about a minute into the flight, and we may do a throttle-down around the area of maximum aerodynamic pressure, or Max-Q.  So about a minute into flight we may throttle the Core Stage engines.\u201d<\/p>\n

As with other ascent events and their timings, Sarafin explained why it remains to be determined whether the Core Stage engines will have a \u201cthrottle bucket\u201d in the Max-Q region.<\/p>\n

\u201cIt really gets into the atmospheric density [and] the actual mass of the vehicle,\u201d Mr. Sarafin explained, \u201cbecause mass and thrust need to be compared and we haven\u2019t finished building the elements yet.  So we\u2019ll need to get an actual weighing [of the vehicle], we\u2019ll need to understand the actual thrust-to-weight ratio of the vehicle.\u201d<\/p>\n

\"2016-07-07-144728\"A Max-Q Core Stage engine throttle bucket would cover the time from about 60 seconds to 80-90 seconds after liftoff, but the actual timing and how far down the engine throttles might need to step (if at all) is to be determined.<\/p>\n

Another area of flight where a short, shallow throttle bucket was discussed was in the pre-SRB separation time-frame to control loads on the SRB forward struts.  Mr. Sarafin said whether this will be necessary is still to be determined.<\/p>\n

The SLS Boosters burn for about 126 seconds and are jettisoned a little over two minutes into flight.<\/p>\n

\u201cSo we\u2019ve separated the boosters about two minutes and ten seconds into flight and then we jettison the spacecraft adapters, which are the panels that cover the [Orion] service module and the solar arrays,\u201d Mr. Sarafin continued.<\/p>\n

\"2016-07-07-210731\"\u201c[At] about three minutes, twenty seconds we\u2019ll jettison those panels.  And then twenty-five seconds later, the launch abort system gets jettisoned and that will expose the Orion capsule.  So now the crew module and the service module are in their space config.<\/p>\n

\u201cAbout eight minutes, ten seconds or so, we hit MECO \u2014 Main Engine Cutoff \u2014 and we separate from the Core Stage.<\/p>\n

\u201cNow it\u2019s the ICPS [that is in control] \u2013 the Interim Cryogenic Propulsion System \u2013 the upper stage that provides attitude control and [performs] maneuvers to circularize the orbit and perform the Trans-Lunar Injection.\u201d<\/p>\n

Mr. Sarafin also noted that the Core Stage engines will probably throttle back in the last several seconds of their burn to limit vehicle acceleration, but the timing will also depend on more precise determinations of the thrust-to-weight of the vehicle.<\/p>\n

See Also<\/h4>\n