Upd: Ares V super-rocket

[Dr Mordrid]

NASA has revamped the specs for the Ares V lunar cargo rocket and in the process have turned it into a fire-breathing beast more powerful than the venerated Saturn V.

Height: 381.1 feet vs. 363 for the Saturn V

Engines: 2 extended length SRB's + 6 RS68 liquid engines vs. 5 liquid engines for the Saturn V

Ground thrust: 11,760,330 lbs vs. 7,648,000 lbs for Saturn V

Lunar throw weight: 71.1 metric ton vs. 47 metric tons for Saturn V.

And this is still not enough as almost 75 metric tons will be necessary because of the weight of the Altair lunar lander and its cargo, which would include components for a lunar base and lunar rovers for the astronauts.

As it is they'll be running those RS68's at 108% throttle at launch, so there's still a lot of work to do.

[Jammrock]

75 metric tonnes! Wow, that's one huge payload. Can any of the SpaceX rockets handle that kind of load?

[KRSESQ]

From the Ares V fact sheet:

The first test flight of the Ares V is planned for around 2018. The first crewed lunar excursion is scheduled for launch in the 2020 timeframe.

Good thing we're not in any freaking hurry.

Kevin

[Dr Mordrid]

LEO numbers are better for general comparisons;

SpaceX Falcon 9 Heavy: 30 mt - which is also Titan IV territory
Saturn V: 108 mt
Ares V ver.1: 140 mt
Ares V ver.2: 180+ mt, might have to be 200 to get the throw they need for Altair plus lunar base cargo.

BUT, this doesn't take into account that SpaceX has expressed the intent to create a scaled up Merlin 2 engine, the Merlin 3, which will deliver at least 1.5 million pounds of thrust each. Merlin 2 is a half sized version of the Merlin 3, so scaling up won't be too hard. Cluster a bunch of Merlin 3's together and you have a major league lunar cargo rocket.

They have stated that it will wait until the current crop is finished being brought to active status, meaning the Falcon 3 Heavy.

There is also a big argument over if they should even build Ares I or Ares V. The problem is that originally they were intended to use shuttle derived hardware to save development costs. Well...that went to hell when they figured out that the shuttle 4 segment SRB's weren't powerful enough to lift the Orion spacecraft to orbit in its original form or to lift the required load in Ares V.

After reducing the size and weight of Orion several times it was determined that a larger SRB would be needed, so they spec'ed 5.5 segment SRB's. Barely powerful enough, plus there are vibrational stresses inherent to SRB's they're still trying to solve. Unsolved they would shake the whole assembly apart.

The SRB power problem continues with Ares V plus it was originally to use a shuttle tank...which of course was too small to carry the fuel load required and too weak to hold the now larger SRB's. Solution: a new tank design.

Ares V was also supposed to use 3-4 space shuttle main engines (SSME) for reusability, but they are too expensive to maintain so expendable RS68's were selected. Also gone was the use of an SSME on the 2nd stage, so a revampped Saturn 2nd stage engine was specced - something that needed to be built from scratch at a high cost.

So...what is the alternative? Direct 2.0

Direct has been designed by NASA engineers as an alternative that really does use shuttle hardware in pretty much un-modified form. Direct family;




If used for Mars misisons the largest Direct 2 rocket would be the Jupiter III which would use two shuttle tanks, 4 shuttle SRB's plus more engines in the core 'tube'. 260 mt to LEO. BIG f'ing rocket

[Nowhere]

Is there any particular reason why NASA insists on using only two SRBs per "shuttle tank" in every design that surfaced/that I've seen?

Sure, perhaps they couldn't have used easily more than two with the Shuttle, but with the orbiter/its wings out of consideration...why not try four? (like Energia, which could, in Vulcan configuration, scale to eight for some massice LEO mass; too bad it's dead, one of downsides of Soviet Union collapse...worse, politics prevents ressurection of Energia even now - it's boosters are made in Ukraine, and I don't see Russia cooperating on such project with a country that's "uncertain" when it comes to its affiliations)

[Dr Mordrid]

Energia wouldn't do any good as its maximum theoretical throw was 98 mt to LEO, about 54.5% the throw of the Ares V ver.2 (some are already calling it the "Ares VI"). Nowhere near enough.

More interesting would be if as you suggested the Russians had built the Vulkan-Hercules: 8 Zenit's and an Energia-M. It was to lift 175 mt to LEO, but was never built and still below the Ares V/VI's 180 mt in current configuration.

I say "current configuration" because just tonight a 6 segment SRB (shuttle = 4) has been mentioned to get Ares V/VI over 200 mt LEO/75+ mt lunar. Love to see that pup launch at night.

The shuttle tank can't take the physical loads four 4 segment SRB's would produce, even with reinforcement. That straight from Shuttle engineers.

Remember that those SRB's are huge: 149.16 feet (45.5 m) long, 12.17 feet (3.7 m) in diameter, 1,300,000 pounds (590,000 kg) at launch and 2,800,000 lbf of thrust each.

This is a heavy load even for the original shuttle tank, but they now use the SLWT - super light weight tank, which while strong due to its aluminum lithium 2195 tanks in no way could handle the 11 million lbf of thrust and 5,200,000 lbs of mounted mass such a setup would require.

Another problem is the harmonic vibration inherent in SRB's of any type. You can see the difference in cabin footage of the shuttle vs. footage in Soyuz. Soyuz gets a pretty smooth ride but the shuttle passengers almost get their teeth rattled out.

Soyuz video (cabin footage starts at 2:45)....

Shuttle video (launch @ 2:50)....

4 of those could wreck gear on the way up and/or destroy their own mounts. This is already a problem with Ares I...so bad that without new vibration dampers it could destroy the whole stack, and that's with just one SRB modded with 5.5 segments instead of the 4 segments used with the shuttle. Of course this comes at the cost of weight, which could again cause Orion to be shrunk.

Lots of people think a better option would be to go Direct or to man-rate the Atlas V for Orion, which is in the process of man-rating already because or the United Space Alliance (Lockheed + Boeing)/Bigelow deal signed April '07 and their continuing work with SpaceDev for launching the Dream Chaser spaceplane.

A big plus for Direct is that it could launch Orion plus another 48 mt of cargo to the ISS. Ares I would be lucky to just get Orion + 2 mt of cargo there.

[Nowhere]

I see...but if they'll have to reengineer the tank anyway, perhaps leaving the possibility of using 3 or 4 SRBs would be a good idea? Assuming of course that vibrations don't render this impossible...

The launch videos were quite eye-opening in that regard...more reason to like Soyuz more

And yes, Energia could launch "only" 100 tonnes to LEO while beeing launched from Baikonur. Look how that orbit (ISS) influences LEO payload of DSD CLV in one of images you posted. So I'd say that Ares V and Energia aren't that far, and considering that Energia will have over 30 years when Ares launches...

BTW, "maximum theoretical throw" of first version of Energia was 175 tonnes in Vulcan configuration, it's just that it was killed before it had a chance to flew like that. And having in mind that this number is also "from Baikonur"...

[Dr Mordrid]

Far more reason to like multiple small liquids like Falcon 9 or Soyuz vs. solids or mostly solids. Multiple liquids give you redundancy (if one fails shut it down and throttle up the rest) and the smoother thrust.

Falcon 9 goes that one better by putting Kevlar blast blankets between the engines & turbopumps and a combination of explosion blankets and an armored plate between the engine mount and the lowermost fuel tank. Yes, they have purposely blown up engines and turbopumps to test the blankets and they work.

Redundancy squared.

Another problem with >2 SRB's on Ares V/VI is that with them being;

a. by far the largest part of the thrust profile using just 2 and
b. un-throttleable (as are all SRB's)

you can't throttle back far enough with just the liquid rockets for going through "Max Q" -- the period of maximum dynamic pressure.

Max Q with the shuttle occurs at about 35,000 ft (11 km) or about 1 minute after launch, before which the shuttle has to throttle back to just 65% power. An Ares V/VI with 3-4 SRB's couldn't power down that far if it shut down all 6 liquids, not to mention that the RS68 isn't re-startable and can only throttle back to 57%.

This is also a concern with Ares I as it has no liquids at all plus the longer 5.5 segment SRB has even worse vibrational issues than the 4 segment used on the shuttle.

A long term solution might be the creation of large hybrid solid rockets to replace the SRB's; huge versions of those used on SpaceShipOne etc. They have the ability to be throttled, shut down and restarted and they are now becoming advanced enough to generate the thrust required. In addition their fuel is largely non-toxic (LOX or nitrous oxide + hard paraffin or HTPB) vs. the SRB's toxic mix of ammonium perchlorate, powdered aluminum and other nasties.

[Nowhere]

@Max Q: So...ignite, for example, only half of SRBs at launch? Hm, that might also help with vibration problems...

Seriously...too bad they have inherent problems, especially since they're bad-ass when it comes to thrust/etc. (and I have sentiment to this concept video http://youtube.com/watch?v=V1vKMTYa40A - in this scenario SRBs are pretty much required)

PS. And I'm not sure if Soyuz is among rockets that benefit from multiple small engines...its looks are deceiving (4 nozzles per rocket engine). More praise for its reliability, I guess...

[Dr Mordrid]

MaxQ in solids is handled differently; they change the grain of the fuel and/or the configuration of the central core to accomplish a "throttle down" & "throttle up" at the appropriate times.

The fuel grain itself can be adjusted by changing the size of the granules of the various components of the solid fuel; aluminum powder, HTPB (synthetic rubber), ammonium perchlorate etc. plus the binders.

The central core is a "tunnel" up the center of the fuel grain whose shape can be used to adjust the burn rate. Contrary to popular belief solid rocket fuels don't burn from the bottom up but from the inside out.

The problem with too many SRB's in Ares V/VI is that their percentage of thrust is so high that the "throttle down" part of their burn additively is still too high.

Examples of propellant grains/cores vs. thrust curves (AKA thrust schedules). The star and dual composition designs are often used to throttle down/throttle up for MaxQ when it's necessary. The shuttle SRB's use the star pattern. Below that is the thrust curve for a shuttle SRB.