http://forum.nasaspaceflight.com/index.php?topic=26853.msg1040482#msg1040482 Re: SLS Development Stage Update Thread« Reply #678 on: 2013-04-18, 14:56:11 » From a recent GAO report (http://www.gao.gov/assets/660/653866.pdf page 63):Quote[SLS project] officials will not know if the shuttle-era RS-25 engines as currently designed can meet SLS’s performance requirements without significant modifications until the engine preliminary design review.What are they doing to the SSME that makes its performance uncertain? Are they pushing its throttle level beyond shuttle levels and not sure if that'll work?
http://forum.nasaspaceflight.com/index.php?topic=22010.msg1042504#msg1042504Re: Live: Testing for the J-2X Upper Stage Engine« Reply #520 on: 2013-04-22, 18:41:54 »Hot-fire Tests Steering the Future of NASA's Space Launch System EnginesApril 22, 2013Engineers developing NASA's next-generation rocket closed one chapter of testing with the completion of a J-2X engine test series on the A-2 test stand at the agency's Stennis Space Center in Mississippi and will begin a new chapter of full motion testing on test stand A-1.<snip>"The A-1 is designed to allow us to gimbal, or pivot, the J-2X during a live firing and test the range of motion for the engine's flexible parts," said Gary Benton, manager of the J-2X test project at Stennis. "This type of testing hasn’t been performed since the space shuttle main engines were tested on the stand."Those space shuttle main engines, also called RS-25s, will make a return to the test stand in 2014. A collection of RS-25 engines, which were used to launch 135 space shuttle missions, will be rated to operate at a higher power level and used to launch the core stage of the SLS."While we will get valuable data on the engine from the firing and gimbaling of the J-2X, we're also re-testing the function of the A-1 stand," said Mike Kynard, manager of the SLS Liquid Engines Office at NASA's Marshall Space Flight Center in Huntsville, Ala., where the SLS Program is managed. "Using A-1 to work on the J-2X gives us a great opportunity to ensure the stand will be capable and ready to test the RS-25s."<snip>
In November 2012, NASA produced a preliminary estimate of $7.65 to $8.59 billion for the 70 metric ton version of SLS.
http://forum.nasaspaceflight.com/index.php?topic=26853.msg1040482#msg1040482 Re: SLS Development Stage Update Thread« Reply #678 on: 2013-04-18, 14:56:11 » From a recent GAO report (http://www.gao.gov/assets/660/653866.pdf page 63):Quote[SLS project] officials will not know if the shuttle-era RS-25 engines as currently designed can meet SLS’s performance requirements without significant modifications until the engine preliminary design review.
http://www.nasaspaceflight.com/2012/03/sls-specifications-take-shape-development-continues/For maximum power levels (percent RPL), the RS-25Ds will obtain 109 percent of rated thrust and have a standard throttle range of 65-109 percent – the same throttle range that could have been utilized by the engines with the Shuttle orbiters… though Shuttle typically defined a lower-limit 67 percent throttle and upper-limit 104.5 percent throttle range, with 109 percent reserved for abort contingencies.<snip>Comparatively, the RS-25E engines, which will enter service once the RS-25D manifest is depleted due to the lack of recoverability of the Core Stage of SLS to which the RS-25Ds will be mounted, will operate with a maximum power level (percent RPL) of 111 percent, a throttle range of 65-111 percent...
... "Status of Exploration Systems Development (Mr. Daniel Dumbacher)":http://www.nasa.gov/pdf/742964main_20130418_heoc_dumbacher.pdf...
The B-2 Test Stand at Stennis, originally built to test Saturn rocket stages that propelled humans to the moon, is being completely renovated to test the SLS core stage in late 2016 and early 2017. The SLS stage, with four RS-25 rocket engines, will be installed on the stand for propellant fill and drain testing and two hot fire tests.
Here's what the SLS core will look like in the B-2 test stand. Should be pretty awesome when they do they the test.
http://www.aviationweek.com/awmobile/Article.aspx?id=/article-xml/AW_05_06_2013_p22-574390.xml<snip>For example, the first four SLS flights will use surplus RD-25D space shuttle main engines, four at a time. The engines flew three at a time on much shorter vehicles than the towering SLS, which also will accelerate faster off the pad. That will create inlet pressures on the order of 300 psi, a higher level than the RD-25D can accommodate with only minor modifications, according to SLS chief engineer Garry Lyles. But the test stands at Stennis Space Center can only deliver 260 psi at the inlets, so the engines will be throttled back on the initial flights to hold the inlet pressures at 260 psi, Lyles says. The test facilities will be uprated when the follow-on RD-25Es come on line, he says. <snip>