Aren't SSME's too expensive to be disposable?

[mcs_seattle]

I haven't seen any concepts for recovering the SSME's used in the newly proposed NASA spacecraft. Do they intend for the SSME's to become disposable?

 

[shuttle_man]

Yes.

 

[nyarlathotep]

Post deleted by Nyarlathotep

 

[mattblack]

Or the RD-180. Converting the E.T. to a Lox/Kerosene container and mounting 3x RD-180s on the bottom would give about the same or slightly less performance than 5x SSMEs, in spite of the greater thrust of the 3x RD-180s. However, making disposable versions of the SSME, the most efficient cryogenic engine ever made, would be cheaper than you think. All the features that makes them re-usable could be downplayed a bit with little or no loss of reliabililty. And you could throttle them up to 109 or even 112 percent!!<br /><br />Also, the SSMEs are the Formula 1 of rocket engines. They are very light with their power:<br /><br />SSME: 7500 pounds each.<br />RS-68: 14000 pounds each.<br />RD-180: 11200 pounds each.<br /><br />So it seems that 5x SSMEs are the optimal compromise in thrust, isp and weight to get the desired performance. <div class="Discussion_UserSignature"> <p> </p><p>One Percent of Federal Funding For Space: America <strong><em><u>CAN</u></em></strong> Afford it!!  LEO is a <strong><em>Prison</em></strong> -- It's time for a <em><strong>JAILBREAK</strong></em>!!</p> </div>

 

[n_kitson]

I'm not sure I follow the benefit of light SSMEs if you require more.<br /><br />5xSSME = 37,500 pounds<br />3xRD-180 = 33,600 pounds<br /><br />That's a 9% saving if you're using RD-180s.

 

[CalliArcale]

The lighter the engine, the less of a cut it takes out of the payload capacity with its own dead mass. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[tomnackid]

Isn't NASA planning to use SSMEs modified for single use to save money? I THINK I read somewhere (ok, not exactly the best researched post) that there are many components of the SSME that can be removed or replaced with cheaper alternatives if the engine does not have to be used for multiple launches.

 

[barrykirk]

Well, the SSME does have a much higher ISP than the RD-180. So it is more efficient on fuel use. But how much do 5 SSME's cost versus 3 RD-180's? Also, and it is a minor point, the tanks and the fuel itself for a SSME are more expensive than for the RD-180. Kero is cheaper than Hydrogen and it is denser and easier to store. Kero has a higher viscosity so it won't leak out of tiny cracks in the tank or the plumbing, and it stores at room temp reducing the need for insulation.

 

[syndroma]

RD-180 costs $10mln.<br /><br />The Russian secret of cheap LVs - do not use hydrogen on the way to LEO.

 

[barrykirk]

kinda of like space x eh?

 

[tomnackid]

The REAL secret to cheap Russian launch vehicles: immense government spending going back to the Soviet/cold war era!

 

[syndroma]

But it doesn't explain why they're cheap NOW.<br />Everything inefficient died in 90's, when government spending reached almost zero.

 

[soccerguy789]

I don't thinkwe take a huge loss in not reusing SSME's. I think the reusabilty was origonally supposed to save tons of money in the shuttle program, before flight rate killed the dreams of the shuttle being a profitable design. <br /><br />I wonder how much they cost to build versus how much it Cost NASA to return 1 to flight. anyone with this info could help us all out a lot.

 

[barrykirk]

Remember, that the SSME may be the most efficient rocket engine ever designed. But it gets that efficiency at a price.<br /><br />It burns LH2 instead of Kero.<br /><br />That has the following disadvantages<br /><br />1) The turbo pumps are larger and more expensive.<br />2) The fuel tank is larger and requires more insulation.<br />3) The thrust is lower.<br /><br />It runs really hot... So, to handle that heat requires a lot of expense and complexity.<br /><br />It has an expensive nozzle.<br /><br />It uses a particularly efficient configuration of the turbo pumps, but that makes it more complex, expensive, and heavy.<br /><br />SpaceX is using Kero for a reason. It's cheap.<br /><br /><br />Who knows. By the time the Heavy lift launch vehicle is built, Space X will have the Falcon XV that will match it in payload capacity for less than half the cost.<br /><br />But then again, maybe not.

 

[propforce]

<i>"....Yes, the SSME in the non-resuable version is about $20 millon dollars cheaper. Only 40 million. ..."</i><br /><br />Knowing Rocketdyne, that $40M is guarantee to go up between signing the contract to CDR. <div class="Discussion_UserSignature"> </div>

 

[propforce]

<blockquote><font class="small">In reply to:</font><hr /><p>The Russian secret of cheap LVs - do not use hydrogen on the way to LEO. <p><hr /></p></p></blockquote><br /><br />Russian secret to cheap LVs is the same secret the Chinese use for everything --- cheap labor & exchange rate. <br /><br />You can buy the Russian SSME, the RD-0120, for a fraction of price. <div class="Discussion_UserSignature"> </div>

 

[trailrider]

While I have not done or seen the trade studies, there is another factor that may mitigate toward the use of kerosene (RP-1) instead of LH2. That is the bulk-density specific impulse. That combines the Isp x the density of the propellant. RP-1 (or similar hydrocarbons) are much denser than LH2. The result is that you can use a much smaller tank for RP-1 than for LH2. Whether the difference makes up for the lower Isp IN THIS APPLICATION, I don't know. But if you look at the Saturn I and IV designs, you will note that von Braun used LO2/RP-1 for the first stages and LO2/LH2 for the upper stages.<br /><br />By eliminating the reusable aspects of the SSME's you also eliminate the requirements for a recovery subsystem, reducing weight penalties. Can you recover components cheaply enough to make it worthwhile refurbishing and reusing them? YES! But the items recovered must weigh enough and be of high enough value to make recovery worthwhile. For example, the SRB's ARE recovered using parachutes (SRB-DSS...SRB Decelerator Subsystem). The intial cost of development of the SRB-DSS was about $24M in 1978 dollars. We paid for the development costs after the first three or four successful recoveries! (Been awhile, and I can't find the figures in my personal files.) (We lost one complete set of boosters due to inadvertant separation of the main deck fittings at the sep ring firing, due to the ringing frequency coinciding with the accelerometer settings...which Martin Marietta warned NASA-MSFC about when they decided to detach the chutes on water impact. Change to the sensing system eliminated this problem on subsequent flights.)<br /><br />The value of reusable SSME's and the complexity, versus the amount saved by recovering and reusing them, probably doesn't compute for the HLLV.<br /><br />Might not be what some want to hear, but it may, indeed be cheaper to throw stuff away than recover and refurb.<br /><br />Ad Luna! Ad Aries! Ad Astra!<br />Trailrider

 

[radarredux]

> <i><font color="yellow">Yes, the SSME in the non-resuable version is about $20 millon dollars cheaper. Only 40 million.</font>/i><br /><br />I read yesterday in AW&ST that NASA plans to use the already built SSME on the new systems. That is, when each shuttle is retired, its engines will see one more use on the new generation of rockets. That is one more avenue of cost saving.</i>

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>While I have not done or seen the trade studies, there is another factor that may mitigate toward the use of kerosene (RP-1) instead of LH2. That is the bulk-density specific impulse. That combines the Isp x the density of the propellant. RP-1 (or similar hydrocarbons) are much denser than LH2. The result is that you can use a much smaller tank for RP-1 than for LH2. Whether the difference makes up for the lower Isp IN THIS APPLICATION, I don't know. But if you look at the Saturn I and IV designs, you will note that von Braun used LO2/RP-1 for the first stages and LO2/LH2 for the upper stages. <p><hr /></p></p></blockquote><br /><br />Kerosene gets even better if you use cryogenic kerosene -- keep it really cold, and the density goes up even more. The Russians in particular made extensive use of cryogenic kerosene. They might still; I'm not sure. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[propforce]

<blockquote><font class="small">In reply to:</font><hr /><p>Kerosene gets even better if you use cryogenic kerosene -- keep it really cold, and the density goes up even more. The Russians in particular made extensive use of cryogenic kerosene. They might still; I'm not sure. <p><hr /></p></p></blockquote><br /><br />Hush Calli.... you're giving away all the trade secrets <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> </div>

 

[mikejz]

Actually, I remember reading somewhere that there were over 350 SSMEs produced. I'm not sure how many were used during the design/testing process. But that is still almost three SSMEs per shuttle flight.<br /><br />I would prefer greatly the RD-0120, i feel it would benefit all parties involved.

 

[barrykirk]

cryo propane is really good. It's almost as dense as regular kero, but higher ISP

 

[syndroma]

> <i>You can buy the Russian SSME, the RD-0120, for a fraction of price.</i><br /><br />You can't buy the Russian SSME, the RD-0120 because it's not in production anymore! And nobody knows how much will it cost to restore the production. And, honestly, nobody wants it, because even paper rockets of 100 tonnes class do not use hydrogen. Hydrogen is pain. Nobody wants the fate of Energia.

 

[darkenfast]

No, the Soviet Union's approach to space was never coherent. They never spent that much. The reason they can afford it today is that it relies on old, fairly simple, technology that has all it's development costs paid for, and has proven to be very dependable (and yes, we use that approach also, when it's appropriate). This runs everywhere from the factories that have been turning out the same booster to the minimalist approach at the launch sites. This is not a judgement, it allowed the prgram to survive the breakup of the Soviet Union and to market itself as the K-Mart of space. They are going to have to start moving on now, I believe. This approach will not work forever. <br />Edited to reflect that this post is a reply to a post above regarding massive spending by the Soviet Union.

 

[giofx]

?<br /><br />what's the fate of Energia? it performed flawlessly for its 10 flights