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from the still-would-be-throwing-them-away dept.
NASA could use an engine developed by Blue Origin instead of the four RL-10 engines currently used by the Space Launch System (SLS):
[One] problem with legacy hardware, built by traditional contractors such as Orbital ATK and Aerojet Rocketdyne, is that it's expensive. And while NASA has not released per-flight estimates of the expendable SLS rocket's cost, conservative estimates peg it at $1.5 to $2.5 billion per launch. The cost is so high that it effectively precludes more than one to two SLS launches per year.
[...] [The RL-10] engines, manufactured by Aerojet Rocketdyne, are also costly. (Ars understands that NASA paid an average of $17 million for each RL-10 engine for the maiden Exploration Upper Stage vehicle). So in October, to power the EUS, the space agency issued a request for information to the aerospace community for "a low cost drop-in replacement engine to minimize program cost." According to the document, the initial set of four engines would be needed in mid-2023 to prepare for the third flight of the SLS rocket, known as Exploration Mission-3.
Then, after an extension of the deadline for responses beyond mid-November, NASA revised the RFI on December 1. The revised document no longer seeks a "drop-in replacement" for the RL-10 engine, rather it asks for a "low-cost replacement engine." Although this seems like a subtle change, sources within the aerospace industry indicated to Ars that it is significant. According to NASA, it was done to increase the number of responses.
[...] That would probably include Blue Origin's BE-3U engine, which the company plans to use for its upper stage on the New Glenn heavy lift rocket. This is a modified version of the BE-3 engine that powers the New Shepard rocket, which has now flown successfully seven times. Blue Origin has previously marketed the BE-3U to Orbital ATK for its Next Generation Launch System, which is looking for an upper stage engine. A single BE-3U provides about 120,000 pounds of thrust, which exceeds the 100,000 pounds of thrust provided by four RL-10 engines.
Just cancel SLS and give that money to SpaceX, Blue Origin, or anybody willing to launch competitively.
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(Score: 5, Interesting) by khallow on Monday December 18 2017, @04:48PM (6 children)
There are other safety issues. When you light up a solid rocket, it usually stays lit till it burns out. Also the problem that fireballs resulting from break up of a solid rocket motor are larger and hotter than their liquid-fueled equivalents. Meaning a beefier (and higher acceleration) escape system (launch abort system or LAS in the nomenclature) needs to be used in order for astronauts to survive such accidents during launch.
The final problem is that solid rocket motors are less efficient. They tend to have decent thrust-mass ratios (which are important), but terrible mass fractions (meaning you need a higher fraction of propellant to empty mass) to get the same level of delta-v.
Liquid-fueled boosters (particularly, with LOX/kerosene propellant) would neatly bypass a large number of big problems. But it means less profit for the Orbital-ATK cookie monster who will makes the current SRMs.
For example, Wikipedia says the mass of a fully fueled [wikipedia.org] first stage of a block one vehicle is almost 1000 metric tons (979 metric tons) to put 70 tons in space. Most of that mass is propellant with 85 metric tons of support structure and plumbing. Most of the rest is solid rocket propellant. The Shuttle SRBs are 590 metric tons. These are going to be about 25% larger (with some slight reduction in dead mass), so maybe 700-750 metric tons or so, just due to the SRMs (the rest is fluffier due to the use of liquid hydrogen in place of kerosene as fuel).
Sorry, it's a vehicle with very poor first stage specifications due to the insistence on solid propellant and LOX/liquid hydrogen. They could instead use LOX/kerosene for all of the rockets and get similar thrust-weight and better specific impulse (better mass fractions). They also wouldn't need to build a new crawler or hope the VAB never gets destroyed in an SRM-caused accident.
As an aside, if they're shopping around for a cheaper first stage rocket engine now, then they aren't going to launch in 2019. Expect further delays.
(Score: 3, Insightful) by takyon on Monday December 18 2017, @04:59PM (1 child)
Actually, it's pretty much guaranteed to slip to the middle of 2020. From a December 2019 launch date, so it was barely hanging in there. So we should begin thinking about how it could slip into 2021-2022 (and hopefully get cancelled entirely).
SLS rocket advancing, but its launch date may slip to 2020 [arstechnica.com]
SLS managers rally the troops to avoid EM-1 slip into 2020 [nasaspaceflight.com]
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2, Insightful) by khallow on Monday December 18 2017, @06:07PM
Else we'll get very expensive projects which will "suck the oxygen out of the room". It's the Space Shuttle all over again.
(Score: 2) by Grishnakh on Monday December 18 2017, @05:36PM (1 child)
I thought the whole point of using SRBs was to save money, because solid rockets are really cheap, and an inexpensive way of providing a lot of thrust, even if the mass fraction is poor, as long as you don't need to throttle it. So for this reason, I can see why they used them on the Space Shuttle, just for the initial launch to get the vehicle off the ground and up to speed, and then jettisoning them. However, using overly complex and expensive SSMEs burning LH2 seems to negate the cost advantages.
(Score: 2, Interesting) by khallow on Monday December 18 2017, @06:04PM
That's not the first time that has happened in an aerospace project. That Congress went gung-ho on this project despite the cost savings not matching the cost losses indicates, yet again, that the primary purpose wasn't to save any money.
Moving on, currently, they're looking at building, for the block 2, four liquid-fueled rocket engines anyway. So why not just build more of those rocket engines (say with their own copy of the first stage), and do away with that unnecessary logistics and operational complexity (Well, aside from the pork ecosystem, that is)? That's what Delta IV Heavy and Falcon Heavy did.
(Score: 1) by khallow on Monday December 18 2017, @06:05PM (1 child)
(Score: 1) by khallow on Monday December 18 2017, @06:09PM