What is "Man rated"?

[frodo1008]

True I had forgotten about the ability to throttle back the RS68, sorry about that, I retired in the year 2000.<br /><br />If they are going to use that many SSME's the only teo options that I can see are: (1) As the shuttle itself would have been retired by then, they are going to use SSME's that have already been used, thus the cost of replacing them would be far less than new engines. Or, there was a program to de man rate new SSME's and use other methods to bring the costs of such new SSME's way down. Perhaps NASA would start with used engines then switch to such new inexpensive SSME's when the supply of older used SSME's runs out. Wow six SSME's at once, that would be about 3 million pounds of thrust alone. or a little bit less than twice the thrust of the current Delta IV Heavy! If they use the SRB's also, they are getting up toward the thrust levels of the original Saturn V! 6 million lbs for the new config vs. 7.5 million for the Saturn V. Depending on what the upper stage thrust is like they could even come very close to the Saturn V abilities. That would be a VERY large and powerfull vehicle!!

 

[najab]

><i>In this scenario the SSMEs will not be cost effective because they will not be reused at all. </i><p>Well, the SSME's that they are proposing are the throwaway version that Rocketdyne says they can produce for under $15M per engine.</p>

 

[nacnud]

I thought it was $30M each for the throw aways?

 

[najab]

Oh. I remembered it was about a $20M savings, I thought the regular SSMEs were ~35-40M.

 

[frodo1008]

The last figure that I was given (and I retired in the year 2000) was for $25 million for a standard engine, and they were trying for $20 million. The original cost was $60 million way back in 1975 or so. However, per haps the overall program cost including all the R&D (and there was a whole lot of that) amortized over the entire program might very well come out to $60 million per engine. That is taking all the program costs and dividing by the total number of engines built may very well come to the $60 million figure. <br /><br />However, I once brought this kind of thingking up to some accounting types on some threads on SDC and they said that that only the direct production costs per engine should be counted. As my own areas of any expertise that I actually had were, Quality Assurance, manufacturing, and some engineering my expertise in the accounting field is very limited. Perhaps either you (shuttle_guy) or someone else here is better equiped to tell us both the actual price and how it is accounted for. Just off the top of my head $60 million seems a little high, and $15 million a little low depending on how the accounting would be done. To me at least $30 million seems more like it but it would be interesting to know the actual figure and how it was arrived at. <br /><br />Also, now that Rocketdyne is no longer a part of Boeing but now a part of United Technologies, along with Pratt & Whitey I wonder how that will affect things?

 

[dwightlooi]

I think there are a facts worthy of note:-<br /><br />(1) <b>SSMEs are not very powerful engines.</b> They make roughly 418K lbs at liftoff and 512K lbs in vacuum. Respectable figures, but less than the Delta IV's RS-68, the Atlas V's RD-180 or the good old F-1. It's outstanding quallities lie in it's reusability and very high specific impulse.<br /><br />(2) In terms of raw thrust, SRBs are the king of the hill even if their specific impulse tend to be at the bottom of the barrel. This is followed by hydrocarbon engines. In fact Hydrogen engines tend to be a little worse (for a given engine size) even compared to hydrazine derivative (MMH, UDMH, Aerozine, etc) + N2O4 room temperature storable propellant engines. Liquid hydrogen also takes up a lot of space necessitating very large tank(s) and consequently increased structural weight and inferior aerodynamics. The only reason LH2/LOX engines are being agressively pursued is because they have the highest specific impulse possible in a purely chemical rocket. Once in vacuum or near vacuum LH2/LOX engines rule the day because only mass and impulse matters and aerodynamics and bulk have no relevance. But, at lift off and during the earlier phases of the ascent, LH2/LOX propulsion is a liability. Hence, <b>the only reason LH2/LOX is being used as a first stage engine is because the rocket's designer feel that a single or two stage to orbit system is preferable to an additional hydrocarbon stage.</b><br /><br />(3) The following is a comparison of the available data on various engines:-<br /><br /><b>SSME (block II)</b><br /><br />Fuel type: LH2 + LOX<br />Thrust: 418,000 lbs (SL), 512,300 lbs (Vac)<br />IpSec: 363 secs (SL), 452 secs (Vac)<br />Chamber pressure: 3000 psi<br />Engine weight: 7,774 lbs<br />Engine type: Staged combustion turbopump cycle<br />Cooling: Regenerative cooling<br />Cost: Approximately $30-40 million per new engine<br /><br /><br /><b>RS-68</b><br /><br />Fuel type: LH2 + LOX<br />Thrust: 656,000 lbs (SL), 745,000 l

 

[georgeniebling]

I always thought "man-rated" had more to do with launch g-forces and what "they" (the shadow office of "They" controls everything) felt a human could take g-force-wise in a launch.

 

[georgeniebling]

I think I saw it back there somewhere but it might have just been a previous reference ... it's one of those Fridays.

 

[dwightlooi]

<i>I always thought "man-rated" had more to do with launch g-forces and what "they" (the shadow office of "They" controls everything) felt a human could take g-force-wise in a launch.</i><br /><br />If that is indeed that main issue, then there is no issue at all. The EELVs have much gentler acceleration profiles than an Atlas and we put men in those. Of course, unfortunately, that is not the main issue.

 

[halman]

pathfinder_01,<br /><br />It is my personal perception that the majority of NASA's spending over the last 20 years has been corporate 'welfare', programs which spend lots of money on design studies, prototypes, component testing, and then are suddenly canceled right before real contsruction would begin. This prevents hardware which would have no use from actually being built, while justifying the costs as 'valuable research.' Remember, until just recently, NASA had NO mandate to do anything in outer space beyond assembling the International Space Station. Government agencies have to be careful about creating their own goals and agendas, as Congress tends not to approve of that sort of thing.<br /><br />And also keep in mind that it is Congress, not NASA administration, which decides whether money will be available during the next budget cycle to complete what was started during this budget cycle. NASA gets blamed for a lot of Congress's screw ups. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[halman]

dwightlooi,<br /><br />After looking over your list of engines, I must say that the RD-180 seems like a superior engine. By using that in the first and second stages of a large booster, which was mass produced, I would think that launch costs could be brought down considerably. A configuration similiar to the Saturn series, with perhaps two RD-180's in the 'medium' stage and 4 or 5 in the 'heavy' stage would allow the versatility needed for either a CEV launch or a Heavy Lift launch. For 'Extra Heavy' launches, a half dozen solid strap-on motors could be added.<br /><br />Using conventional step-rocket, payload on top design, without any fancy reusable engines, piggyback cargo configuration, or huge Solid Rocket Boosters, a reliable, versatile, economical launch system could be developed in less than 7 or 8 years. A launch system like that could be in use for 20 or 30 years without major modification, with all components being mass produced, and then warehoused until needed.<br /><br />Then we could spend the big money on on-orbit stuff, or Lunar base stuff. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[dwightlooi]

<i>dwightlooi,<br /><br />After looking over your list of engines, I must say that the RD-180 seems like a superior engine. By using that in the first and second stages of a large booster, which was mass produced, I would think that launch costs could be brought down considerably. A configuration similiar to the Saturn series, with perhaps two RD-180's in the 'medium' stage and 4 or 5 in the 'heavy' stage would allow the versatility needed for either a CEV launch or a Heavy Lift launch. For 'Extra Heavy' launches, a half dozen solid strap-on motors could be added.<br /><br />Using conventional step-rocket, payload on top design, without any fancy reusable engines, piggyback cargo configuration, or huge Solid Rocket Boosters, a reliable, versatile, economical launch system could be developed in less than 7 or 8 years. A launch system like that could be in use for 20 or 30 years without major modification, with all components being mass produced, and then warehoused until needed.<br /><br />Then we could spend the big money on on-orbit stuff, or Lunar base stuff. </i><br /><br />I think that is what the Lockheed-Martin people are saying; that is what they are betting their Atlas V system on. Sales pitch or not, it does have some truth to it.<br /><br />The main concerns over the RD-180 is that it is NOT a US engine, not is it currently made in USA. The RD-180 is derived from the good old RD-170 (Used on the Energia) and the RD-171 (Used on the Zenith/Sea-Launch). It is a Energomash product, made in Russia. Lockheed-Martin has already secured the right to license built the engine in the USA. But, it is arguably a more complex and more highly stressed design than the SSME. The only reason it is about $12 million a pop is because the Russians are making it. Who knows how much a US built example will cost; it may be just as expensive as the SSME! The other thing is that a second round of moonshot and a mars shot is all about national prestige and bragging rights. Some people may ha

 

[halman]

dwightlooi,<br /><br />What I am trying to convey is that we need to design a new rocket for launches in the 20 to 30 ton range, and a booster that can bring that up to 60 to 70 tons. The EELV designs are just not up to lauching a CEV, unless that CEV has very little life support capability, and is built extremely light. People keep using the Apollo program for guestimating vehicle weights, which is ridiculous. Those vehicles were engineered for minimum weight at any economic cost, and were not to be reused. Disposable, if you please.<br /><br />We do not want to use the same design guidelines for vehicles which we will expect to fly numerous times, and which certainly should have considerable safety cushion built in to the life support system. For when the thruster gets stuck in the 'on' position, or the computer hiccups. This is not going to be 'exploration', 'pack as much science in as you can', 'those guys only have to put up with it for a couple of days' design, this needs to be work-a-day, week in, week out, take the punishment design. Which means mass, a lot more of it than a communication satellite. So lets build a rocket to fly that kind of hardware, specifically, because we will be using it for a few decades, if the past is any guidline. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[shoogerbrugge]

since we are talking about the modern rocket engines, I've got a question as well<br /><br />The RD-170 and RD-171 can in practice be re-used. The Energia strapons (which are the same as the first stage of the Zenit booster) were ejected and recovered for re-use. It is said that they could be used for up to 15 times, although this was never tried in practive off course. <br /><br />Does the RD-180 engine also have the lifespan and capability to reused and re-ignited like the RD-171? <br />What is keeping the current users of these engines from re-using them. I can see why the Zenit 3SL first stage can't be recovered, landing in the ocean. But what about the land launched Atlas 5 and Zenit 2?<br />Can the the RS-68 also be re-used if they figure out a way to recover it?<br /><br />If anybody could be of help, thanks!

 

[dwightlooi]

<i>since we are talking about the modern rocket engines, I've got a question as well<br /><br />The RD-170 and RD-171 can in practice be re-used. The Energia strapons (which are the same as the first stage of the Zenit booster) were ejected and recovered for re-use. It is said that they could be used for up to 15 times, although this was never tried in practive off course.<br /><br />Does the RD-180 engine also have the lifespan and capability to reused and re-ignited like the RD-171?<br />What is keeping the current users of these engines from re-using them. I can see why the Zenit 3SL first stage can't be recovered, landing in the ocean. But what about the land launched Atlas 5 and Zenit 2?<br />Can the the RS-68 also be re-used if they figure out a way to recover it?<br /><br />If anybody could be of help, thanks!</i><br /><br />Any liquid engine can be reused to some degree <b>IF</b> it can be recovered. The problem is that both the Delta IV and the Atlas V are essentially two stage to orbit vehicles. Unlike shuttle SRBs or russian strap-ons, their main engines burn out at very high altitudes and velocities. For example, with the Delta IV (medium), the main engine burn out at about 137 km altitude with the booster going Mach 16.2. For comparison, the Shuttle SRBs separate at 45km altitude at about Mach 4.5. Getting the booster core and/or the engine to survive re-entry and incorporating a system to allow the engine to land softly enough to be reused is a big challenge. Any such recovery system will also increase weight and bulk, reducing the rocket's precious payload capacity. EELVs cost $100+ million a pop to launch it's 8 to 12 ton payload. Sometimes it is not worth reducing that even by 10% just so you can save a a couple of millions on the engines for the next flight.<br /><br />There is the issue of whether an engine rebuild is worth the effort. The RS-68 and the RD-180 are both relatively cheap engines -- $6-7 million (RS-68) to $10-12 million (RD-180). The cost for r

 

[shoogerbrugge]

OK it makes sense now, thanks for the information.<br /><br />