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CEV Plan Gets Overhaul  
User currently offlineCentrair From Japan, joined Jan 2005, 3598 posts, RR: 20
Posted (8 years 11 months 2 days 16 hours ago) and read 1919 times:

Space.com reports that NASA has made some changes to the CEV requirements.

- 18 feet (5.5 meters) to 16.4 feet (5 meters)
- requirement for a liquid oxygen/methane engine on the CEV service module and lunar lander dropped (Contractors must figure out the best one)
- plans to power the so-called Crew Launch Vehiclefs upper stage with a Space Shuttle Main Engine modified to start in flight dropped
- go with an updated version of the J-2 engine that was used on NASAfs Saturn 5 rocket.

Plans will save money on development, speed up the process, and save money in the long run.

So, I am not so surprised. Had a feeling that NASA would have to make changes to meet budget.


Yes...I am not a KIX fan. Let's Japanese Aviation!
26 replies: All unread, showing first 25:
 
User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 1, posted (8 years 11 months 2 days 5 hours ago) and read 1878 times:

Quoting Centrair (Thread starter):
Space.com reports that NASA has made some changes to the CEV requirements.

- 18 feet (5.5 meters) to 16.4 feet (5 meters)
- requirement for a liquid oxygen/methane engine on the CEV service module and lunar lander dropped (Contractors must figure out the best one)
- plans to power the so-called Crew Launch Vehicle�fs upper stage with a Space Shuttle Main Engine modified to start in flight dropped
- go with an updated version of the J-2 engine that was used on NASA�fs Saturn 5 rocket.

Plans will save money on development, speed up the process, and save money in the long run.

So, I am not so surprised. Had a feeling that NASA would have to make changes to meet budget.

Also, Crew Launch Vehicle will now be the new Five-Segment SRB instead of the standard SRB. They've traded upper stage performance (J-2 for SSME) for first stage (SRB) improvement. ATK has already test fired a FSB, albeit not a flight representative version, and they've long considered FSB to be a straightforward development. Let's hope they're closer to the mark than Rocketdyne was with its air-start SSME plans (which evidently were dropped when the projected development costs skyrocketed.)

Interestingly, the reduction in size of the CEV from 18 to 16 feet diameter and corresponding weight reduction will make it easier for NASA to dump CLV completely and switch to EELV (Delta IV, probably) if budgets start getting tight. I think we're about at 50/50 this will happen before 2007.

The methane engine cancellation is probably for the best. Mars is a long, long way off (probably NET 2030). Plenty of time to develop an ISRU engine for Mars later and not burden the ISS/Moon CEV derivatives with its development costs.


User currently offlineCentrair From Japan, joined Jan 2005, 3598 posts, RR: 20
Reply 2, posted (8 years 11 months 2 days ago) and read 1851 times:

Seems that NASA needs to really layout a series of missions (probably is) something like Apollo. A missions through Z missions or whatever.

That would allow for upgrades and development of a larger craft and applications. Apollo had them Block 1, 2 and 3 right? Is NASA going to do the same thing? It was a good system. Kraft was a smart guy (personal hero).



Yes...I am not a KIX fan. Let's Japanese Aviation!
User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 3, posted (8 years 11 months 1 day 23 hours ago) and read 1845 times:

Quoting Centrair (Reply 2):
Seems that NASA needs to really layout a series of missions (probably is) something like Apollo. A missions through Z missions or whatever.

I doubt they'll do that. I think the first CEV launch will go to the Space Station, there's really no need to waste a flight going nowhere, and the Station can be safe harbor if something goes wrong. Later flights will push the CEV harder, going all the way up to the 6 month staytime at ISS.

Once the lunar flight is ready, I think almost certainly the first flight will go to the lunar surface. We're not in a race with the Soviets this time, so there is no need for the huge risk of an lunar lander-less flight (Apollo 8 was an unplanned catch-up mission, not something NASA planned to do all along.) Note that they can't do an Apollo 8 without a lander anyway, as the LSAM lander (not the CEV) will be doing the lunar orbit insertion burn for Constellation.

I think the first Constellation lunar landing will be to a relatively easy equatorial landing site (very possibly a return to Apollo 15's geologically rich site at Hadley Rille) because the first landing will probably be the only one not in support of building a lunar base. The next few flights will be to the lunar poles, searching for the best location for a base, and then base-building will commence. Full scale exploration will commence after the base is built, with exploration missions being staged from there instead of from Earth.

Quoting Centrair (Reply 2):
That would allow for upgrades and development of a larger craft and applications. Apollo had them Block 1, 2 and 3 right? Is NASA going to do the same thing?

Apollo had Block I and Block II, although the early Block II's (rushed into production after the Apollo 1 fire in a Block I) were very much a combination of Block I and II hardware.

NASA is planning at least three versions of CEV, but I don't think they're calling them Blocks. No.1 is the 6-person ISS / Earth Orbit version. No.2 is the 4-person lunar version. No.3 is the 4-person Mars version.


User currently offlineCentrair From Japan, joined Jan 2005, 3598 posts, RR: 20
Reply 4, posted (8 years 11 months 22 hours ago) and read 1780 times:

Quoting Thorny (Reply 3):
but I don't think they're calling them Blocks.

Flight International: NASA Spells out CEV and Moon Landing Plans

And here is our answer. (NASA was watching weren't they)
Block 1A is a crewed, pressurised vehicle for low-Earth orbit missions; Block 1B is an uninhabited, pressurised vehicle for ISS resupply; and Block 2 is a crewed, pressurised vehicle for lunar missions. NASA expects minimal subsystem changes between Block 1A and 1B, while Block 2 should only see software changes.

Concerning contracts:
Lockheed Martin and Northrop Grumman/Boeing are competing for the CEV development contract, to be awarded by 7 August. The winner will provide a Block 1A and 1B CEV, an iron-bird test rig, and two gproduction CEVsh for risk-reduction flights (RRF).

What looks like phase 1:
CEV flights will begin in 2008 with tests of the launch abort system (LAS). Three risk-reduction flights will follow. RRF-1 will test the CEV launch vehicle first stage, with a dummy mass representing the second stage, CEV and LAS; RRF-2 will involve orbital insertion of the CEV followed by an emergency re-entry and landing. Although not confirmed by NASA, the third RRF, due no later than 1 May 2012, could be manned as it involves an ISS rendezvous and landing in the USA. RRF-3 will be followed by the first ISS crew flight that year.

Getting exciting...



Yes...I am not a KIX fan. Let's Japanese Aviation!
User currently offlineJwenting From Netherlands, joined Apr 2001, 10213 posts, RR: 19
Reply 5, posted (8 years 11 months 15 hours ago) and read 1753 times:

Ideally of course the transport from earth to orbit should be SSTO, and everything else assembled in orbit from local materials harvested from asteroids.
Lunar base construction should make use of local materials harvested from the lunar surface.

That way the mass that needs to be moved into and out of deep gravity wells is minimised, thus launch cost are minimised.

For a PR mission that's overkill but for a sustained effort it's essential.



I wish I were flying
User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 6, posted (8 years 11 months 7 hours ago) and read 1733 times:

Quoting Centrair (Reply 4):
Block 1A is a crewed, pressurised vehicle for low-Earth orbit missions; Block 1B is an uninhabited, pressurised vehicle for ISS resupply; and Block 2 is a crewed, pressurised vehicle for lunar missions.

Thanks! I haven't had a chance to read the full ESAS report yet (it's huge) but I didn't remember the term 'Blocks' from my quick-read.

Quoting Jwenting (Reply 5):
Ideally of course the transport from earth to orbit should be SSTO,

Not necessarily. SSTOs are likely to be quite expensive. It is entirely possible their price-per-pound (LEO) can be bettered by something like SpaceX's Falcon family or Kistler's K1, especially if the lower stage of each is made reusable (as current plans show.)

Quoting Jwenting (Reply 5):
and everything else assembled in orbit from local materials harvested from asteroids.

Well, that means you have to build a factory/refinery in space. The ISS has been hugely expensive enough, building a refinery and living quarters for its workers in deep space is going to be mind-bogglingly expensive. The refinery will have to be at the Moon or beyond. Trying to bring asteroid resources all the way down to low Earth orbit will be cost-prohibitive.

And it will be unnecessary. Antarctica is the much more realistic model for lunar bases. We didn't build McMurdo Base out of materials available in Antarctica. Everything was brought in. If there are hydrogen deposits on the moon, the differences between the Moon and Antarctica become very tenuous. Note that in Southern Hemisphere Winter, it might actually be faster to get back to the US from the Moon than it is to get home from McMurdo.


User currently offlineAerospaceFan From , joined Dec 1969, posts, RR:
Reply 7, posted (8 years 11 months 1 hour ago) and read 1690 times:

Quoting Thorny (Reply 1):
Interestingly, the reduction in size of the CEV from 18 to 16 feet diameter and corresponding weight reduction will make it easier for NASA to dump CLV completely and switch to EELV (Delta IV, probably) if budgets start getting tight. I think we're about at 50/50 this will happen before 2007

I agree that this would be a fallback position. I personally would like to see the CLV get funded, but not at the cost of the entire program. It's a close case whether I'd like to see the HLV get canned instead, but I don't think that that's feasible.

The Delta IV option sounds a little better than the Atlas V. The Atlas V requires Russian cooperation because, as I understand it, it uses just one type of engine, the RD-180, made in Russia, and what Lockheed Martin does is basically install the engine onto the rest of each Atlas V spaceframe. I don't think LockMart even manufactures the engine under license. (LockMart or its subs make the other parts of the booster, though, and is responsible for overall vehicle integration.) I don't know if we can afford to rely on Russia for any of our crucial heavy lift vehicles. Boeing's Delta IV is all-American designed and made. [See note, below.]

[Note: I'm editing this to reflect the fact that according to one source, Pratt & Whitney was to manufacture the Russian engine. Source: http://www.spaceandtech.com/spacedata/engines/rd180_sum.shtml . However, the source is dated and I'm not sure now if the RD-180's are imported or not.]

[Update/Edit: According to the following source, P&W has completed prototype parts based on Russia specifications that P&W intends to use along the way to establishing a U.S. production line. Production of the RD-180 in the U.S. is not expected before 2008, according to the source. http://www.space.com/spacenews/archive04/rd180arch_061604.html )

However, Atlas V has scored at least two huge successes (MRO and New Horizons), whereas Delta IV has scored only a partial one, and it seems they keep on delaying the next launch.

Of course, either one would have to be man-rated. [Update/Edit: The RD-180 is a man-rated engine in Russia, according to one source I found.]

Boeing and LockMart's joint venture would mean that their respective EELV rocket line, Delta IV and Atlas, respectively, would essentially share one corporate roof. The Pentagon having approved this arrangement, it looks like it will fly and thus take some competitive pressure off both of the boosters that might otherwise have killed one of them off. Either way, I'm rooting for the Delta IV and hope it does well.

[Edited 2006-01-24 01:38:05]

User currently offlineAerospaceFan From , joined Dec 1969, posts, RR:
Reply 8, posted (8 years 11 months 1 hour ago) and read 1685 times:

Not to post consecutively, but this message warrants separate consideration:
How the heck were they able to get ahold of the plans for the J-2? There were rumors that all the technical blueprints for the Saturn series of rockets were destroyed.

Doest this mean that they weren't?

And does this mean that they have the blueprints for the F-1 Saturn V first-stage engine?

What's cool is that I often see a display model of the F-1 at the old Rocketdyne (then Boeing, and now Pratt & Whitney) plant when I pass through that area of the West Valley.  Smile


User currently offlineJwenting From Netherlands, joined Apr 2001, 10213 posts, RR: 19
Reply 9, posted (8 years 10 months 4 weeks 1 day 13 hours ago) and read 1646 times:

Quoting Thorny (Reply 6):
Not necessarily. SSTOs are likely to be quite expensive. It is entirely possible their price-per-pound (LEO) can be bettered by something like SpaceX's Falcon family or Kistler's K1, especially if the lower stage of each is made reusable (as current plans show.)



Quoting Thorny (Reply 6):
Well, that means you have to build a factory/refinery in space. The ISS has been hugely expensive enough, building a refinery and living quarters for its workers in deep space is going to be mind-bogglingly expensive. The refinery will have to be at the Moon or beyond. Trying to bring asteroid resources all the way down to low Earth orbit will be cost-prohibitive.

Both are more expensive in the short term, but pay for themselves many times over in the long run.

That's why I stated that for a quick PR mission just building a very big rocket and blasting it to the moon like every other bit of 4th of July fireworks is the better option, but if we're serious (as IMO we should be) about permanent space habitation and colonisation we should get that infrastructure in place ASAP.



I wish I were flying
User currently offlineGDB From United Kingdom, joined May 2001, 13252 posts, RR: 77
Reply 10, posted (8 years 10 months 4 weeks 1 day 6 hours ago) and read 1624 times:

Both plans and production equipment for J-2 still exist.

There is another CEV planned, the unmanned, ISS supporting version (so a NASA version of the Progress craft).

I can see the merit of a first equatorial landing, the Apollo 15 site.
Why not take new batteries and new nav gear for Apollo 15's Rover?
Sounds kooky I know, but the Rover won't have rusted!
Get possibly a second (or third since the new lander will take two-4 man crew after all), rover for free.

I also understand setting up a probable South Polar base in time.
Before that however, I'd like to see some sites visited the Apollo scientists wanted to go to, but could not due to either the limitations of Apollo, or due to the cancelled missions;
Tycho - Southern highlands-check out the Suveyor there since 1968 too.
Mare Orientale - Large impact basin straddling near and far sides, also a useful test of small comms satellites needed for;
Tsiolkovsky - Fascinating Far side mare with huge central peak.

That's four missions, do-able in two years.
Then crack on with a base.


User currently offlineJwenting From Netherlands, joined Apr 2001, 10213 posts, RR: 19
Reply 11, posted (8 years 10 months 4 weeks 1 day 6 hours ago) and read 1618 times:

vacuum can do nasty things to materials...


I wish I were flying
User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 12, posted (8 years 10 months 4 weeks 1 day 5 hours ago) and read 1611 times:

Quoting AerospaceFan (Reply 7):
[Update/Edit: According to the following source, P&W has completed prototype parts based on Russia specifications that P&W intends to use along the way to establishing a U.S. production line. Production of the RD-180 in the U.S. is not expected before 2008, according to the source.

No, P&W has no plans to license build the RD-180. Atlas launch rates are vastly below what it would take for them to make money on the project. The license production scheme was Lockheed's answer to get the Air Force's "Assured Access to Space" guarantee in the event Atlas V won the EELV contract. But the Air Force insanely chose both Delta IV and Atlas V to win EELV contracts and more or less made it impossible for either vehicle to operate economically.

Quoting AerospaceFan (Reply 7):

Of course, either one would have to be man-rated.

Which shouldn't be a major challenge to either vehicle. Man-rating (which, in general, means whatever NASA wants it to mean at a given time... note that neither Russia's Soyuz or NASA's own Shuttle meets the strictest NASA man-rating requirements) just means a few more backup systems and more sensors to detect things going wrong in time to abort.

Quoting AerospaceFan (Reply 7):

However, Atlas V has scored at least two huge successes (MRO and New Horizons), whereas Delta IV has scored only a partial one, and it seems they keep on delaying the next launch.

Delta IV has flown completely successfully three times. A fourth, the test flight of the Delta IV-Heavy (three core version) was a partial success, achieving a lower-than-desired orbit.

At this point in its career, Delta IV has a better success record than Ariane 5 did at a similar point.

Quoting AerospaceFan (Reply 7):
Boeing and LockMart's joint venture would mean that their respective EELV rocket line, Delta IV and Atlas, respectively, would essentially share one corporate roof.

And eliminate competition, so Atlas and Delta will stagnate because United Launch Alliance has all the contracts sewn up and won't need to do much to improve them.

Unless, of course, SpaceX makes inroads with its Falcon series. But now SpaceX has to challenge one giant space conglomerate instead of being able to play one against the other and have a fighting chance to succeed.

Quoting AerospaceFan (Reply 8):
Not to post consecutively, but this message warrants separate consideration:
How the heck were they able to get ahold of the plans for the J-2? There were rumors that all the technical blueprints for the Saturn series of rockets were destroyed.

Doest this mean that they weren't?

Correct.

The Saturn V plans were never destroyed, that's just a myth raised whenever someone wants to say "our government is so stupid, they..." and need an example. There are plenty of real stupidities made by the government without having to make them up!

Both the Saturn V engines, F-1 and J-2 have been proposed as powerplants for new launchers periodically ever since Apollo. F-1 was to be the powerplant of the 1980s-era Advanced Launch System (or maybe it was the National Launch System, one immediately followed the other) and the 1990's era Reusable First Stage for the Shuttle, for example, and J-2 was to power the X-33.


User currently offlineAerospaceFan From , joined Dec 1969, posts, RR:
Reply 13, posted (8 years 10 months 4 weeks 1 day 5 hours ago) and read 1606 times:

Quoting Thorny (Reply 12):
The license production scheme was Lockheed's answer to get the Air Force's "Assured Access to Space" guarantee in the event Atlas V won the EELV contract. But the Air Force insanely chose both Delta IV and Atlas V to win EELV contracts and more or less made it impossible for either vehicle to operate economically

So, if I understand this correctly, Lockheed decided that P & W wouldn't need to manufacture RD-180's since the Delta IV, manufactured by Boeing, would be entirely domestically made. Interesting. I guess this also explains why P & W's website hasn't updated its RD-180 news section for a few years.

Thanks for the correction on the Delta IV. I was indeed thinking of the Delta IV Heavy when I mentioned the partial success. The question I have now is whether the Delta IV Heavy can be made as powerful as the "551" version of the Atlas V that lofted New Horizons last week.

Finally, it's great to know that we can still make the F-1 if we need to (as well as the J-2).


User currently offlineAreopagus From United States of America, joined Sep 2001, 1373 posts, RR: 1
Reply 14, posted (8 years 10 months 4 weeks 1 day 3 hours ago) and read 1592 times:

Quoting AerospaceFan (Reply 7):
[Update/Edit: The RD-180 is a man-rated engine in Russia, according to one source I found.]

That's a surprising claim, since the RD-180 is only used on the Atlas, and it is derived from the 4-chamber RD-170, which is only used on Zenit. Was RD-170 man-rated in preparation for launching people on Buran? (Energia's boosters were modified Zenit 1st stages.)

Quoting AerospaceFan (Reply 13):
The question I have now is whether the Delta IV Heavy can be made as powerful as the "551" version of the Atlas V that lofted New Horizons last week.

It is already more powerful. See p.18 of Nasa's Exploration Transportation Strategic Roadmap Meeting slides. Also see Boeing's Delta IV Heavy Growth Options for Space Exploration for a roadmap of upgrades all the way up to Saturn V class payload.


User currently offlineAerospaceFan From , joined Dec 1969, posts, RR:
Reply 15, posted (8 years 10 months 4 weeks 1 day 3 hours ago) and read 1586 times:

Quoting Areopagus (Reply 14):
It is already more powerful.

That's good to know. I will read that link with interest.

I really hope Delta IV makes it. I love the Atlas V, because it's been such a success with the MRO and New Horizons, but I can't wait until Delta IV Heavy shows its stuff. I want to be able to celebrate a completely U.S.-made rocket, even though I like the Atlas V.

Now, I remember the glory days of the Saturns. Entirely U.S.-made! See, back then, every booster advance seemed to give us more and more power. In fact, however, that was true only up to a point, since the Saturn V F-1 while more powerful than any other liquid-fueled engine, was less powerful than either one of the SRB's used on the Shuttle.

On the other hand, the Saturn V remains the heaviest and most powerful vehicle ever launched by the United States, if not the world. 7.5 million pounds of first-stage thrust, compared with somewhere around 6 million or so for the Shuttle.

And the F-1 was far more powerful than the SSME (Space Shuttle Main Engine).

The fact that they're probably going to be dumping the SSME for the J-2 seems like step backward, but the J-2 is a great engine in its own right. According to my reading of the specs, the J-2 has about half the power of the SSME (200K lbs. versus about 400K lbs., although I've also read a figure of 330K lbs. for the latter). The new version of the J-2 might be slightly brawnier.

As for the source of the information about the man-rating for the RD-180, I'll see if I can find it again, and if I do, I'll post a link in this thread.

Finally, as you may know, the RS-68, the engine developed for the Delta IV, is the first large rocket engine developed in the United States since the SSME, according to Boeing. Boeing has a nice webpage on the engine alone:

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

[Edited 2006-01-24 23:07:55]

User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 16, posted (8 years 10 months 4 weeks 1 day 3 hours ago) and read 1577 times:

Quoting AerospaceFan (Reply 13):
The question I have now is whether the Delta IV Heavy can be made as powerful as the "551" version of the Atlas V that lofted New Horizons last week.

It already is.

Delta IV Medium: 9,285 lbs. GTO*, 8,980 lbs. LEO#
Delta IV Medium (5,2)^: 12,890 lbs. GTO
Delta IV Medium (5,4): 14,475 lbs. GTO, 10,100 lbs. LEO
Atlas V 400: 16,843 lbs. GTO, 12,400 lbs. LEO
Atlas V 500: 19,110 lbs. GTO, 14,000 lbs. LEO
Atlas V Heavy: 27,800 lbs. GTO, 19,900 lbs. LEO
Delta IV Heavy: 28,950 lbs. GTO, 20,510 lbs. LEO

*GTO = Geosynchronous Transfer Orbit
#LEO = Low Earth Orbit
^ Fairing Size in meters, Number of Solid Boosters

For reference, Ariane 5 is 15,000 lbs. GTO and Space Shuttle is 56,000 lbs. LEO.

Quoting Areopagus (Reply 14):
Was RD-170 man-rated in preparation for launching people on Buran?

It was, but the modification from RD-170 to RD-180 will probably require some new man-rating work.


User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 17, posted (8 years 10 months 4 weeks 1 day 3 hours ago) and read 1576 times:

Quoting AerospaceFan (Reply 15):
The new version of the J-2 might be slightly brawnier.

The 200,000 lbs. thrust figure is that of the J-2 flown on Saturn IB and Saturn V. For Constellation, NASA is planning to use a derivative of the J-2S, developed late in Apollo for use on later production Saturn Vs, but never flown because further Saturn V production was cancelled. The S stood for "Simplified" but it was also more powerful, at around 265,000 lbs. thrust.


User currently offlineAreopagus From United States of America, joined Sep 2001, 1373 posts, RR: 1
Reply 18, posted (8 years 10 months 4 weeks 1 day 2 hours ago) and read 1570 times:

Thorny, I think your table has some columns reversed, as the LEO payloads should be greater than the GTO payloads.

User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 19, posted (8 years 10 months 4 weeks 23 hours ago) and read 1548 times:

Quoting Areopagus (Reply 18):
Thorny, I think your table has some columns reversed, as the LEO payloads should be greater than the GTO payloads.

No, they're correct. Most of today's launch vehicles are optimized for geosynchronous missions and take a payload hit if that's not your destination.

Basically, they're hauling along a big upper stage for a mission that only needs a small one, but they can't do away with the upper stage completely, and they can't put too much more mass on top of the upper stage than a GEO mission would, because the rocket can't lift it all and isn't designed structurally for that much weight. (Boeing has toyed with a "Delta IV-Lite" version that uses a Delta II upper stage instead of the bigger Delta IV Upper Stage.)

This all partially explains why NASA chose the SRB over the EELVs for the Crew Launch Vehicle. For CEV missions, the EELV will probably require a new upper stage, and NASA decided they might as well start with a more powerful Stage 1 if they have to build a new Stage 2.)


User currently offlineAerospaceFan From , joined Dec 1969, posts, RR:
Reply 20, posted (8 years 10 months 4 weeks 23 hours ago) and read 1545 times:

Quoting Thorny (Reply 19):
This all partially explains why NASA chose the SRB over the EELVs for the Crew Launch Vehicle

So do you disagree that NASA would seriously consider stepping down from an SRB-based CLV and use a Delta IV or Atlas V?


User currently offlineAreopagus From United States of America, joined Sep 2001, 1373 posts, RR: 1
Reply 21, posted (8 years 10 months 4 weeks 8 hours ago) and read 1517 times:

Quoting Thorny (Reply 19):
No, they're correct. Most of today's launch vehicles are optimized for geosynchronous missions and take a payload hit if that's not your destination.

Let me direct your attention to http://www.boeing.com/defense-space/...a/delta4/docs/DeltaIV_overview.pdf . The table given there is

Variant -- GTO LEO
DIVM 4210 8120 (all kilograms)
DIVM+(4,2) 5845 10430
DIVM+(5,2) 4640 7980
DIVM+(5,4) 6565 11475
DIVHeavy 13130 23040

And it makes sense. When going to GTO, you put the upper stage with its payload into a low parking orbit, and then do another burn while crossing the equator to convert LEO to GTO. If you were going to stop at LEO, you could substitute payload for the propellant required to do that burn. Or, you could use that same propellant earlier to get additional payload to LEO.


User currently offlineThorny From , joined Dec 1969, posts, RR:
Reply 22, posted (8 years 10 months 4 weeks 1 hour ago) and read 1488 times:

Quoting Areopagus (Reply 21):
Let me direct your attention to http://www.boeing.com/defense-space/...a/delta4/docs/DeltaIV_overview.pdf . The table given there is

Interesting. My figures are from the Aviation Week 2006 Source Book.

However, there is a point of no return on putting big LEO payloads on a GTO-designed booster. You can't stick 50,000 lbs. of payload on top of a Stage 2 that's only designed to handle 20,000 lbs. even if you plan to burn the Stage 2 to make up the extra delta-v. If the rocket can handle that much weight, then it is seriously overbuilt for its bread-and-butter GTO missions. Hence my comment that rockets (EELVs, H-II, and Ariane 5 anyway) are optimized for GTO. I seriously doubt that Delta IV or Atlas V can achieve payloads anywhere near the LEO figures given by them, and NASA's studies saying that the EELVs can't handle a CEV without modification tend to support this.

Quoting AerospaceFan (Reply 20):
So do you disagree that NASA would seriously consider stepping down from an SRB-based CLV and use a Delta IV or Atlas V?

I'd like to see some serious numbers on the CLV Stage 2 first. It hasn't been an official going concern a year yet, and NASA has already downsized and re-engined it. Not a good sign. Its selling point was its largely off-the-shelf heritage with heavy payload. If CLV now will rival EELV upgrades, then its time to reconsider.


User currently offlineAreopagus From United States of America, joined Sep 2001, 1373 posts, RR: 1
Reply 23, posted (8 years 10 months 3 weeks 6 days 5 hours ago) and read 1448 times:

Quoting Thorny (Reply 22):
My figures are from the Aviation Week 2006 Source Book.

Publications have been known to make typos. I have pointed you to the Boeing publication that shows LEO capability to exceed GTO capability for all Delta IV models, and to the NASA document that shows the same for both Delta IV and Atlas V. You can find the same for Atlas V at ILS's web site, http://www.ilslaunch.com/atlas/atlasv/ .

Quoting Thorny (Reply 22):
However, there is a point of no return on putting big LEO payloads on a GTO-designed booster.

I certainly agree with that. Indeed, for LEO missions, the Titan IV would omit the 3rd stage altogether.

Quoting Thorny (Reply 22):
I seriously doubt that Delta IV or Atlas V can achieve payloads anywhere near the LEO figures given by them,

I think that's rather cynical. Boeing's and ILS's customers might not like it if they overpromised payload weight and ended up dumping their satellites back into the atmosphere.

Quoting Thorny (Reply 22):
Hence my comment that rockets (EELVs, H-II, and Ariane 5 anyway) are optimized for GTO.

That's certainly true for Ariane 5, but I think much less so for the EELV's, which have much greater thrust in their core 1st stages. The low thrust of their 2nd stages is not so good for LEO, though. Lockmart offers a 2-engine Centaur to help out with LEO missions. If they ever put the RL-60 into the upper stages, that would help. I don't think Lockmart reduces the strength of the Centaur when configured with a single engine, so there might be a bit of a weight penalty paid by GTO missions for the benefit of LEO missions.

Certainly a heavier satellite will require beefier support structure. I think the difference in stresses over most of the vehicle would be minor, because the engine thrust is the same and the heavier payload results in lower acceleration. If the additional payload is achieved by simply not loading the propellant for the GTO injection burn, the different stresses occur only in the top stage. But I don't know that any flights have been actually conducted that way.


User currently offlineCloudy From , joined Dec 1969, posts, RR:
Reply 24, posted (8 years 10 months 3 weeks 5 days 9 hours ago) and read 1411 times:

Quoting Thorny (Reply 22):
I'd like to see some serious numbers on the CLV Stage 2 first. It hasn't been an official going concern a year yet, and NASA has already downsized and re-engined it. Not a good sign. Its selling point was its largely off-the-shelf heritage with heavy payload. If CLV now will rival EELV upgrades, then its time to reconsider.

Perhaps this is what NASA really wanted all along. They wanted the smaller CLV, but they needed to rule out the EELV's for political and beauraucratic reasons. They first proposed the large CLV to make the shuttle hardware decision look better, but switched to what they really wanted once the shuttle derived hardware system was made.

It just wouldn't do to use non-NASA hardware for human space exploration, even just to go into low earth orbit. It weakens their control, and it would preserve a lot of NASA and contractor jobs to keep using as much of the shuttle system as possible. It also preserves jobs in key congressional districts. The more you spend, the more power you have. Also,shuttle hardware may really be better for the heavy lifter they are planning..........

Note that this theory is probably not the whole story. Government programs are nearly driven governed by a complicated mess of political and technical motivations. But I would doubt it is entirely false either. I doubt NASA would go for the EELV unless there was no other reasonable option. Its just not in their culture to do so.


25 Areopagus : So what are they going to call the new upper stage? S-IVc? If they plan a new hydrogen stage using a J-2S (or SSME), would it make sense to adapt shor
26 AerospaceFan : Gee, this down-sizing business has me worried about whether NASA is starting to dither. I don't like dithering. It's costly.
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