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NASA Makes Progress On Heavy-Lift  
User currently offlineDfwRevolution From United States of America, joined Jan 2010, 915 posts, RR: 51
Posted (7 years 11 months 1 week 14 hours ago) and read 2658 times:

NASA has annouced their decision to use the RS-68 engine to power the heavy-lift vehicle necessary for CEV missions beyond Earth orbit. This superceeds the earlier intention of using a SSME-derrived engine to power the vehicle:

The RS-68 has a unit cost of $20 million USD, dramatically lower than the re-usable SSME.



http://www.spaceref.com/news/viewsr.html?pid=20656

---------------

ASAIK, the CLV is still utilizing an SSME or J2 engine for the manned upper stage. Will increasing production for RS-68 lower the unit price of the Delta IV?

23 replies: All unread, jump to last
 
User currently offlineAreopagus From United States of America, joined Sep 2001, 1368 posts, RR: 1
Reply 1, posted (7 years 11 months 1 week 10 hours ago) and read 2611 times:

From 5 SSMEs to 5 RS-68s?! That is a serious step-up in power. I expected them to be able to make do with fewer engines by switching to the RS-68. I suppose it has to do with the reduction in Isp. And then the article says that to feed all those engines, the stage diameter would be increased from 27.5 feet to 33. That's a serious change from reusing Shuttle tooling. 33 feet was the diameter of Saturn V.

Yes, I would expect this to reduce the unit price of Delta IV, and obtain savings from shutting down the SSME line. So does this mean an increased chance of using D-IV to launch the crew module instead of developing the Stick?


User currently offlineDfwRevolution From United States of America, joined Jan 2010, 915 posts, RR: 51
Reply 2, posted (7 years 11 months 1 week 10 hours ago) and read 2606 times:

Quoting Areopagus (Reply 1):
From 5 SSMEs to 5 RS-68s?! That is a serious step-up in power. I expected them to be able to make do with fewer engines by switching to the RS-68.

I suspect they maintained 5 engines to preserve engine-out capability. There's nothing worse than blowing a half-billion dollar payload because an engine shuts-off prematurely.


User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 3, posted (7 years 11 months 1 week 8 hours ago) and read 2579 times:

Quoting DfwRevolution (Thread starter):
The RS-68 has a unit cost of $20 million USD, dramatically lower than the re-usable SSME.

Lower ISp though, too. Rocketdyne might be able to do something about that, such as add regenerative cooling instead of ablative. RS-68 also has a lower thrust:weight ratio than SSME.

Quoting DfwRevolution (Thread starter):
ASAIK, the CLV is still utilizing an SSME or J2 engine for the manned upper stage.

They've switched to J-2X to avoid the cost of air-start modifications for SSME. So the switch to RS-68 for the CaLV means the end of SSME.

Quoting Areopagus (Reply 1):
And then the article says that to feed all those engines, the stage diameter would be increased from 27.5 feet to 33. That's a serious change from reusing Shuttle tooling. 33 feet was the diameter of Saturn V.

They couldn't make it much taller (at the same diameter) without increasing the roof height at the Vehicle Assembly Building, so wider it is. No question, the CaLV is turning into a behemoth! Hardly anything left of Shuttle in it. I'm not sure if that's bad or good. Honestly, why don't they just switch to an F-1 based first stage and get rid of the SRBs now? Use four F-1As (2,000,000 pound thrust uprated F-1 developed in the '60s) in the core, with improved-RS-68 powered Stage 2. In the meantime, launch CEV on an improved Delta IV (using same improved RS-68s) and get rid of the solids and the J-2X and all the CLV development costs.

I'm glad NASA is changing things when they have to, instead of head-in-the-sand committment to a doomed design, but someone needs to finally say "enough! we're changing so many things, we need to start over with a clean sheet." Shuttle could have greatly benefited from such an order back in 1974 or so.

Quoting DfwRevolution (Thread starter):
Will increasing production for RS-68 lower the unit price of the Delta IV?

Yes, but not enough to matter. CaLV is only to fly twice a year, which is ten more engines a year. You won't get much economy of scale from that.

Quoting DfwRevolution (Reply 2):

I suspect they maintained 5 engines to preserve engine-out capability.

And guard against weight-growth in the CEV. NASA, knowingly or not, is taking a page from von Braun, who added the center engine of the S-1C simply because he didn't believe NASA's optimistic weight projections for Apollo. Turns out, Saturn V needed every bit of that extra performance from the center engine.


User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 4, posted (7 years 11 months 1 week 7 hours ago) and read 2555 times:

Quoting Thorny (Reply 3):
And guard against weight-growth in the CEV.

Um, make that weight-growth in the LSAM...  Smile

Although, technically, the CaLV is getting so big and powerful, it might not need the 1.5 launch concept anymore. Just put the CEV up top.


User currently offlineAerospaceFan From , joined Dec 1969, posts, RR:
Reply 5, posted (7 years 11 months 6 days 16 hours ago) and read 2488 times:

The RS-68 is one helluva engine. I often pass the Rocketdyne facility in Canoga Park, so the fact that it's going to be made there has sentimental meaning to me. And part of what's great about it is that Rocketdyne has an F-1 engine on static display right at the main entrance.

The RS-68 is also entirely American-designed and American-made and powers Boeing's new Delta series of rockets. It's the most powerful liquid-fueled engine designed in America since the SSME. Its main rival is made by Lockheed Martin and Energiya for Lockheed's Atlas series.

As I understand it, by an agreement newly approved by the U.S. government, Boeing and Lockheed will jointly operate Delta and Atlas under the United Space Alliance.

Way to go, NASA!

[Edited 2006-05-20 17:37:27]

User currently offlineAerospaceFan From , joined Dec 1969, posts, RR:
Reply 6, posted (7 years 11 months 6 days 16 hours ago) and read 2484 times:

While I can find the manufacturer's RS-68 page using Google, I can't see it on the menu at the P&W (Rocketdyne) Website. I wonder why they don't list it there.

http://www.pratt-whitney.com/prod_space.asp

You can see what is probably an older page here:

http://www.boeing.com/defense-space/space/propul/RS68.html

Edit: P&W only recently acquired Rocketdyne, so that might explain it. According to the Website, completion of the acquisition occurred in August, 2005. (Still, that's ten months ago. Time for them to update their site!)

[Edited 2006-05-20 17:47:36]

User currently offlineAerospaceFan From , joined Dec 1969, posts, RR:
Reply 7, posted (7 years 11 months 6 days 15 hours ago) and read 2471 times:

Wait a second -- in reading the NASA notice cited in the article, where does it say that the RS-68 has been chosen?

This is what it says:

Quote:
Description

NASA/MSFC has baselined the use of a lower cost version of the Space Shuttle Main Engine as the Core Stage Engine (CSE) for the proposed Cargo Launch Vehicle (CaLV). At this time, special studies are needed to evaluate and assess the processes and requirements necessary to develop and certify the CSE for the CaLV. The Core Stage Engine will be a highly affordable, expendable engine derived from the current Space Shuttle Main Engine (RS-25).

Pursuant to FAR 6.302-1, NASA/MSFC intends to purchase the special studies effort from Pratt & Whitney Rocketdyne (PWR), Inc., 6633 Canoga Avenue, Canoga Park, California, 91309-7922. The Rocketdyne organization, now a division of PWR, has designed and developed the RS-25 engine and has been responsible for its production, refurbishment, and improvements since 1972. Consequently, PWR is the only company that has the requisite expertise to perform these special studies, which are a follow-on to the development work they have been doing on the RS-25 engine.

It talks about purchasing the special studies effort, not the engine.

The following May 18, 2006 announcement from NASA -- not the one cited in the article -- does state what the article claims, however:

http://www.nasa.gov/home/hqnews/2006/may/HQ_06226_RS-68_ENGINE.html

The May 18, 2006 press release states:

Quote:

Dolores Beasley
Headquarters, Washington
(202) 358-1753

Kim Newton
Marshall Space Flight Center, Huntsville, Ala.
(256) 544-0034


May 18, 2006
RELEASE: 06-226


NASA's Exploration Systems Progress Report

NASA has chosen the RS-68 engine to power the core stage of the agency's heavy lift cargo launch vehicle intended to carry large payloads to the moon.

The announcement supersedes NASA's initial decision to use a derivative of the space shuttle main engine as the core stage engine for the heavy lift launch vehicle.

The cargo launch vehicle will serve as NASA's primary vessel for safe, reliable delivery of resources to space. It will carry large-scale hardware and materials for establishing a permanent moon base, as well as food, fresh water and other staples needed to extend a human presence beyond Earth orbit.

Recent studies examining life-cycle cost showed the RS-68 is best suited for NASA's heavy-lift cargo requirements. The decision to change the core stage engine required an increase in the size of the core propulsion stage tank, from a 27.5-foot diameter tank to 33-foot diameter tank, to provide additional propellant required by the five RS-68 engines.

The RS-68 is the most powerful liquid oxygen/liquid hydrogen booster in existence, capable of producing 650,000 pounds of thrust at sea level. In contrast, the space shuttle main engine is capable of producing 420,000 pounds of thrust at sea level. The RS-68, upgraded to meet NASA's requirements, will cost roughly $20 million per engine, a dramatic cost savings over the shuttle main engine.

The prime contractor for the RS-68 engine is Pratt & Whitney Rocketdyne of Canoga Park, Calif. Pratt & Whitney Rocketdyne is the same company that manufactures the shuttle main engine.

The RS-68 is used in the Delta IV launcher, the largest of the Delta rocket family developed in the 1990s by the U.S. Air Force for its evolved expendable launch vehicle program and commercial launch applications.

The cargo launch vehicle effort includes multiple project element teams at NASA centers and contract organizations around the nation and is led by the Exploration Launch Office at NASA's Marshall Space Flight Center in Huntsville, Ala.

The project office is part of the Constellation Program led by NASA's Johnson Space Center in Houston. Constellation is a key program of NASA's Exploration Systems Mission Directorate in Washington.



Still unclear to me is whether there will the same number (five) of engines used per vehicle.

[Edited 2006-05-20 18:16:18]

User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 8, posted (7 years 11 months 6 days 15 hours ago) and read 2462 times:

Quoting AerospaceFan (Reply 5):
Its main rival is made by Lockheed Martin and Energiya for Lockheed's Atlas series.

The RD-180 (Atlas 5) is actually built in Russia by Energomash. LockMart doesn't do anything but buy them. Had they won the EELV contract in the late 1990s, LockMart and Pratt & Whitney would have built an RD-180 production line in West Palm Beach. They didn't win, so they never built the line, and they have no plans to.

Quoting AerospaceFan (Reply 5):

As I understand it, by an agreement newly approved by the U.S. government, Boeing and Lockheed will jointly operate Delta and Atlas under the United Space Alliance.

By the looks of things United [Launch*] Aliance is dead. It's been a year since the deal was announced, and there appears to be no progress since then. Good riddance! Talk about the US handing over a complete monopoly on launch services to the mega-companies. Prices will skyrocket and innovation vanish if ULA comes to fruition. ULA could charge whatever it wants, and the DoD/NASA will have no alternative but to pay it. And ULA will have no incentive to improve Atlas or Delta, because the DoD/NASA would have to buy them no matter what ULA did.

In the meantime, DoD is stuck. EELV is too expensive to keep paying for two launch systems (Atlas and Delta), so DoD must either downselect to one or get the ULA merger through and hope there are cost reductions from that (keep dreaming, DoD.)

Atlas 5 is the better EELV, but it is dependent on Russian engines (and the concept of US RD-180 production appears dead) so there is no way DoD will ever select Atlas 5 as its only space launch system. Delta IV isn't as reliable and costs more, and Boeing stole LockMart data to win the original EELV contracts, so DoD can't just tell LockMart "sorry" and go buy a bunch of Boeings. Rock --> DoD <-- Hard Place.

*United Space Alliance is the company that operates the Space Shuttle for NASA. ULA was to be the combined Atlas/Delta production company.


User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 9, posted (7 years 11 months 6 days 15 hours ago) and read 2459 times:

Quoting AerospaceFan (Reply 7):

Still unclear to me is whether there will the same number (five) of engines used per vehicle.

Uh... it says so right there:

"The decision to change the core stage engine required an increase in the size of the core propulsion stage tank, from a 27.5-foot diameter tank to 33-foot diameter tank, to provide additional propellant required by the five RS-68 engines."


User currently offlineDfwRevolution From United States of America, joined Jan 2010, 915 posts, RR: 51
Reply 10, posted (7 years 11 months 6 days 14 hours ago) and read 2452 times:

Quoting Thorny (Reply 8):
Delta IV isn't as reliable

On what grounds? The only "failure" per say was the premature burn-out during the Delta IV Heavy test flight, and LM hasn't performed such a demonstration flight themselves. Are you basing it on the fact that the Atlas 5 has launched more payloads to date?

i.e. Atlas 5 = 100% (8/8) while Delta IV = 100% (3/3)


User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 11, posted (7 years 11 months 6 days 14 hours ago) and read 2448 times:

Quoting DfwRevolution (Reply 10):
On what grounds? The only "failure" per say was the premature burn-out during the Delta IV Heavy test flight, and LM hasn't performed such a demonstration flight themselves. Are you basing it on the fact that the Atlas 5 has launched more payloads to date?

i.e. Atlas 5 = 100% (8/8) while Delta IV = 100% (3/3)

The Delta IV-Heavy demo is a failure. There's no way around that. Had a real payload been aboard, the mission would have been a total loss. It doesn't matter that Atlas 5-Heavy hasn't flown yet. And the IV-Heavy demo turned out unrelated to the -Heavy configuration, Boeing was just lucky on earlier flights.

And launch-on-time stats put Atlas way ahead. The Delta IV on the pad today was on the pad almost a year ago, too. Still waiting. Only some of that can be blamed on the Boeing strike. It's a good thing MRO and New Horizons weren't scheduled to go up on Delta IVs.


User currently offlineBoeing Nut From , joined Dec 1969, posts, RR:
Reply 12, posted (7 years 11 months 6 days 13 hours ago) and read 2430 times:

Any word on whether NASA is planning to develop The Heavy Lift In Line Crew Design? (pg. 4, 5 & 12, all to the most right)

User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 13, posted (7 years 11 months 6 days 13 hours ago) and read 2428 times:

Quoting Thorny (Reply 11):
Boeing was just lucky on earlier flights.

I should add that it is totally understandable that Delta IV is not off to as good a start as Atlas 5.

Lockheed-Martin had 40 years of experience launching heavy-lift boosters from its Atlas and Titan experience to apply to Atlas 5.

Boeing only had medium-lift Delta II experience to draw on, so they were essentially starting from scratch (despite a few hardware and avionics items whose lineage goes back to Delta II and Delta III.)

Both LockMart and Boeing introduced intermediate vehicles to prove some of the technology before going up to EELV. Atlas III, using the same RD-180 engine as Atlas 5, was a complete success. Delta III, which mated a Delta IV upper stage to a stretched Delta II first stage, was an unmitigated failure.

Atlas 5 uses a proven engine (RD-180, a two-chamber version of the RD-170 used on Zenit) while Delta IV introduced a totally new engine.

Just from standard risk analyses, Delta IV had the tougher road to flight.


User currently offlineAerospaceFan From , joined Dec 1969, posts, RR:
Reply 14, posted (7 years 11 months 6 days 12 hours ago) and read 2419 times:

Thanks for the replies, Thorny, and for pointing out the number of engines.

User currently offlineAreopagus From United States of America, joined Sep 2001, 1368 posts, RR: 1
Reply 15, posted (7 years 11 months 6 days 9 hours ago) and read 2387 times:

Quoting Thorny (Reply 13):
Delta III, which mated a Delta IV upper stage to a stretched Delta II first stage, was an unmitigated failure.

The first Delta III failed due to poor modeling of vehicle dynamics, which caused the steerable solid boosters to run out of steering fluid, causing vehicle breakup. That was a Boeing screwup.

The second Delta III failed due to a breach in the upper stage's RL-10B2 engine. That was traced to poor brazing and process control at P&W.

The third Delta III succeeded in launching a demo satellite.

It looks to me like it was just the luck of the draw that the RL-10 failure occurred on a Delta rather than an Atlas. The score for that time period could just as easily been one Delta failure and one Atlas failure.

I agree with you that the performance shortfall observed in the Delta IV-H flight could well have happened to the earlier Delta IV flights. I hope they have fixed the problem, but the last I heard of it, it sounded like they had a programming workaround rather than a fix for the cavitation.

By the way, I once wrote that Delta III's upper stage was the same as Delta IVm's, but got shot down on the grounds that D-IVm has larger tanks.


User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 16, posted (7 years 11 months 6 days 8 hours ago) and read 2377 times:

Quoting Areopagus (Reply 15):
By the way, I once wrote that Delta III's upper stage was the same as Delta IVm's, but got shot down on the grounds that D-IVm has larger tanks.

There's more than one version of the DUS (Delta Upper Stage, a stupid name... this stage needs a name, Boeing!) the short tank flew on Delta III and Delta IV-Medium. The large tank is an option for heavier Delta IV-Ms and Delta IV-H.

Quoting Boeing Nut (Reply 12):
Any word on whether NASA is planning to develop The Heavy Lift In Line Crew Design? (pg. 4, 5 & 12, all to the most right)

Yes, it is called the Cargo Launch Vehicle, abbreviated CaLV.
But at present, the CEV won't be mounted on top as depicted in those illustrations. Instead, the CaLV will only launch the Earth Departure Stage with the Lunar Surface Access Module (LSAM) on top. The crew will launch on a new vehicle based on the Solid Rocket Booster and a new Stage 2, called the Crew Launch Vehicle, or CLV.

Now, I think we may well see a major rethinking of this project, and soon. NASA this week announced that the CaLV will no longer use the External Tank's diameter (27.5 feet) and will instead be 33 feet in diameter. And the CaLV will not use the Space Shuttle Main Engine, but instead use the RS-68 engine. There is hardly any Shuttle-derived material left in the CaLV.

So it's time for NASA to take a step back and say, "hey, now that the CaLV first stage is the same size as Saturn V, and we're using engines half again as powerful as the SSME, do we really need those Solid Rocket Boosters?"

The answer is no. Switch to an EELV for the early CEV flights (to the Space Station) and use two of the CaLVs (minus SRBs) for each moon mission.


User currently offlineBoeing Nut From , joined Dec 1969, posts, RR:
Reply 17, posted (7 years 11 months 5 days 18 hours ago) and read 2294 times:

Quoting Thorny (Reply 16):
Yes, it is called the Cargo Launch Vehicle, abbreviated CaLV.
But at present, the CEV won't be mounted on top as depicted in those illustrations.

That's what I was wondering. It seems to me that this concept would save having to launch the crew seperately, but obviously there are reasons why this is not possible.

I have to admit though, I hope the design retains the SRB's. That would be sweet to watch.


User currently offlineAerospaceFan From , joined Dec 1969, posts, RR:
Reply 18, posted (7 years 11 months 5 days 16 hours ago) and read 2281 times:

The SRB's haven't proved problematical since Challenger, so I'm okay with retaining them.

It sounds to me -- and maybe I'm wrong -- that a non-SRB version of the CaLV would be less powerful than one with the SRB's, even with the RS-68's.


User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 19, posted (7 years 11 months 5 days 15 hours ago) and read 2274 times:

Quoting AerospaceFan (Reply 18):
The SRB's haven't proved problematical since Challenger, so I'm okay with retaining them.

True, but they aren't using the Shuttle SRBs anymore. They're moving straight to the new Five Segment Booster, which will have a very different propellant load, different structural and aerodynamic loads, probably a beefed up thrust vector system and APUs, and some sort of roll control system (at least for the CLV version.) It is essentially all-new and will have to be completely recertified. And look what happened when the Air Force started stretching the SRBs for the Titan program... reliability went down, including one catastrophic explosion that wiped out a launch pad at Vandenberg.

Quoting AerospaceFan (Reply 18):
It sounds to me -- and maybe I'm wrong -- that a non-SRB version of the CaLV would be less powerful than one with the SRB's, even with the RS-68's.

You're right. But that's not the point. An SRB-less 33-ft / 5 RS-68 launch vehicle should be able to put about 110,000 lbs. into orbit. So instead of one 200,000 lbs. CaLV and one 50,000 lbs. CLV for each mission, why not use two SRB-less CaLVs? You end up with about 30,000 lbs. less payload, but for that sacrifice, you save several billion dollars developing the 5-segment SRB, the CLV Stage 2, and all the costs of putting the J-2 back into production. And if you can't live without that lost 30,000 lbs., you still have the option of sending up the CEV on an EELV. 2 or 2.5 launches instead of 1.5, but almost certainly much cheaper than 1.5 (even after paying for EELV upgrades such as re-engining the upper stage with an MB-60 or Cobra.)


User currently offlineAreopagus From United States of America, joined Sep 2001, 1368 posts, RR: 1
Reply 20, posted (7 years 11 months 4 days 11 hours ago) and read 2127 times:

Quoting Thorny (Reply 16):
There's more than one version of the DUS (Delta Upper Stage, a stupid name... this stage needs a name, Boeing!) the short tank flew on Delta III and Delta IV-Medium. The large tank is an option for heavier Delta IV-Ms and Delta IV-H.

Yes, I know about the two stage sizes for Delta IV. What I am referring to is that the smaller one is bigger than Delta III's second stage. From Astronautix's description of Delta IV Medium's 2nd stage at http://www.astronautix.com/lvs/deledium.htm :
Comments: Delta 3 second stage with hydrogen tank stretch.


Now that the CaLV is practically no longer Shuttle-derived, maybe they should just design a 33-ft diameter kero-burning first stage with five RD-170s (or F-1As).  duck 


User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 21, posted (7 years 11 months 4 days 9 hours ago) and read 2100 times:

Quoting Areopagus (Reply 20):
Yes, I know about the two stage sizes for Delta IV. What I am referring to is that the smaller one is bigger than Delta III's second stage. From Astronautix's description of Delta IV Medium's 2nd stage at http://www.astronautix.com/lvs/deledium.htm :

That's nitpicky  Smile

http://www.boeing.com/defense-space/space/delta/delta4/delta4.htm

"Second-Stage

Derived from the Delta III but with expanded capabilities, the Delta IV second stage possesses the following components:

* Pratt & Whitney RL10B-2 upper stage engine
* Two sizes of expanded fuel and oxidizer tanks"

So the only obvious difference between DIII and DIV Upper Stage is a stretched LH2 tank. Centaur's been stretched and widened a few times (and even comes in one- or two-engine versions), but its still Centaur.

Quoting Areopagus (Reply 20):

Now that the CaLV is practically no longer Shuttle-derived, maybe they should just design a 33-ft diameter kero-burning first stage with five RD-170s (or F-1As).

Well, not a chance for RD-170s. But now that the stage is 33 feet in diameter, how about *eight* RS-68s, in a Saturn IB style arrangement? Yee haw!


User currently offlineAreopagus From United States of America, joined Sep 2001, 1368 posts, RR: 1
Reply 22, posted (7 years 11 months 4 days 8 hours ago) and read 2084 times:

Quoting Thorny (Reply 21):
That's nitpicky

It may be, but like I said, I once got shot down in another forum for not knowing it, like I was really dumb.

Quoting Thorny (Reply 21):
But now that the stage is 33 feet in diameter, how about *eight* RS-68s, in a Saturn IB style arrangement? Yee haw!

How much mass would that be able to orbit without SOBs (strap-on boosters  Smile )?

Wait a minute -- the CaLV as proposed doesn't have an upper stage, does it? Just SOBs and core? So now we're talking SSTO?


User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 23, posted (7 years 11 months 4 days 5 hours ago) and read 2063 times:

Quoting Areopagus (Reply 22):

It may be, but like I said, I once got shot down in another forum for not knowing it, like I was really dumb.

Then they owe you an apology!

Quoting Areopagus (Reply 22):
Wait a minute -- the CaLV as proposed doesn't have an upper stage, does it? Just SOBs and core? So now we're talking SSTO?

Yes, it has the Earth Departure Stage, which (like S-IVB before it) will probably fire up for a short burn to achieve orbit. Saturn V technically could have gotten by without doing that, but it turned out to boost performance a little. CaLV will probably have to do it, though, because (in order for the rendezvous with the CLV) it's going to need to go somewhat higher than Apollo's parking orbit.

However, yes, should be able to do SSTO with a moderate payload. Keep in mind that Atlas did it in 1959 (Project Score) if you ignore the detail of dropping off its outboard booster engines halfway up. You can pull tricks like that with CaLV too, dropping the outboard engines half-way up (recoverable or not) and finish the ascent on the "sustainer" engine.

Another neat trick might be to replace the center RS-68 with an SSME for higher ISp later in the ascent where total thrust doesn't matter as much (at least on the SSTO missions.)


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