Ares vs. Jupiter Rocket Designs

[Viper Daimao]

I read an article at Space.com about a little tiff at NASA about a competing rocket design some employees have been working on off hours. They claim it is more efficient and half as expensive as the Ares rockets. They call it Jupiter.

Does anyone else know any more about this? It sounds like these guys want to stop the Ares project right when it's about to test fly and only have some calculations and blueprints if that. But are they right in their claims of superior design?

 

[BenBurch]

Ares is, in my opinion, an accident waiting to happen. Solid fueled rockets are not a good idea on a man-rated vehicle. Too much can go wrong too explosively.

 

[Viper Daimao]

Ares is, in my opinion, an accident waiting to happen. Solid fueled rockets are not a good idea on a man-rated vehicle. Too much can go wrong too explosively.

Do you know if the other design, Jupiter, also uses solid fuel?

 

[BenBurch]

Do you know if the other design, Jupiter, also uses solid fuel?

No I do not.

Were this my call, I would launch unmanned spacecraft on big inexpensive boosters, and have a man-rated small liquid fueled booster to loft small capsules into space to meet them. Think Gemini-Titan. That was a sufficiently large system to do the job. Those capsules do not need to support people for three months, they just need to dock with the previously launched things that can.

 

[Jimbo07]

Ares is, in my opinion, an accident waiting to happen. Solid fueled rockets are not a good idea on a man-rated vehicle. Too much can go wrong too explosively.

Actually, despite the infamous event of 1986, SRBs have a good safety record, numbers-wise. They are also apparently easier (less risky) to handle on the ground. That said, Soyuz has also been very successful. This is a debate that won't go away soon. That is, by my limited understanding, SRBs may not be astoundingly superior, but they are not so inferior as to render the debate moot.

Were this my call, I would launch unmanned spacecraft on big inexpensive boosters, and have a man-rated small liquid fueled booster to loft small capsules into space to meet them.

Well, that is, in theory, what's happening. Ares I will launch a crew capsule and Ares V will launch heavier unmanned payloads. The capsules themselves do not have to support the crew for six months, but they do need to remain capable of doing so in an emergency, much like the current task for Soyuz.

 

[BenBurch]

Jupiter does have an SRB component; http://en.wikipedia.org/wiki/DIRECT

 

[Travis]

I was under the impression that the Ares I would be liquid fueled. Is that incorrect?

 

[BenBurch]

I was under the impression that the Ares I would be liquid fueled. Is that incorrect?

Yes. Its first stage is a huge solid fueled rocket.

http://en.wikipedia.org/wiki/Ares_I

 

[Travis]

Yes. Its first stage is a huge solid fueled rocket.

http://en.wikipedia.org/wiki/Ares_I

Ahhh, maybe I'm thinking of an earlier proposal then.

 

[lumos]

Ares is, in my opinion, an accident waiting to happen. Solid fueled rockets are not a good idea on a man-rated vehicle. Too much can go wrong too explosively.

I'll have to disagree with your statement. Solid boosters (SRB) are far safer "explosively" than a liquid fueled booster. I can't think of any solid boosters that have exploded during launch (but if you know of one, please tell me.). Solids are very safe. The Challenger accident was not caused by the explosion of the SRB but by the SRB leaking hot gases into the external tank, igniting the explosion of the external tank. The explosion was the liquid fuel (O2 and H2) used for the Shuttle main engines. Leaking hot gases such as those on the original shuttle SRBs on a spacecraft like Ares I would not endager the spacecraft nor would it explode the spacecraft.

The problem with the SRB for the first stage of Ares I is primarily structural and acoustic. The SRB could potentially "shake" the spacecraft apart due to its long, flexible structure and large vibrations. Making the spacecraft more rigid to prevent breakup due to vibration would add mass. Adding mass is bad, shaking is bad, flexibility on the launch vehicle is bad. We have a lot of tradeoffs.

Personally, I like the Jupiter concept (I scanned the proposal) and I believe that it would have been an easier, initially cheaper, but not safer, option. (due to it's commonalilty with the existing Shuttle components) Once the design (vibration/acoustic) issues for Ares I are worked out, it will be an extremely safe and efficient spacecraft.

If I were to recommend a re-design, I would try to replace the Ares I first stage SRB with a liquid fueled first stage. The 2nd stage of Ares I is already liquid (cryo O2 and H2). This would make the launch vehicle similar to the Ares V without the 2 SRBs, similar to the Saturn V, and similar to the Titan.

There were a lot of political maneuvers on the part of ATK, the manufacturers of the SRBs, to sell the SRB stage as "common" from the shuttle to Ares. Unfortunately, they are now talking about a 5.5 segment SRB compared to a shuttle 4 segment SRB. The SRB's were also not designed to launch a large mass on top of it. If you'll notice, most solids you'll see, are strap on boosters and/or mounted on the sides of a liquid fueld first stage.

 

[jadebox]

I can't think of any solid boosters that have exploded during launch (but if you know of one, please tell me.). Solids are very safe.

You're right. The propellant in the SRBs is not an explosive and no solid boosters have exploded.

Several times a month, I fly rockets that use solid propellant motors made with basically the same propellant (APCP) as in the SRBs. APCP actually burns slower than typing paper. It's how quickly it produces a large volume of gas while burning - not how fast it burns - that makes it an effective rocket propellant.

A problem with solid propellants is that, once lit, there's little direct control over the thrust during the flight. But, Ares, like the Shuttle, is using solid propellant for just the first stage. The second stage can be throttled to compensate for any variations in the perfomance of the solid booster.

There's also the problem that a solid propellant booster can't be easily shut down in case of a problem. During the Challenger accident, the Range Safety Officer fired explosives placed on the SRBs which broke open the cases. The drop in pressure caused the solid propellant to stop burning. But, you can't do something like that while the booster is still near the crew vehicle.

In the case of the shuttle, abort procedures are rather limited. The shuttle has to be high enough to glide to an emergency landing. Even if the Challenger astronauts had recognized the problem, they probably would not have been high enough to make a safe abort.

With the Ares, however, its much more likely the crew would survive a problem with the booster or second stage because the escape system could pull them quickly away from the rest of the rocket.

As far as Ares vs. Jupiter, NASA's response is at:

http: // www. nasa. gov /pdf/256922main_Direct_vs_%20Ares%20_FINAL_62508.pdf

I think it's cool that people are think about this in such detail. I'd love to help design a system that will transport people to the moon then Mars. But, I think the people at NASA have some idea of what they are doing and that the problems with Areas will be worked out.

The real question is whether NASA will receive the support it needs to keep us at the forefront of manned space exploration and technology in general.

-- Roger

 

[BenBurch]

lumos, look at the GPS 2R launch.

All it takes is a crack in the fuel element.

 

[mhaze]

Rockets are extremely dangerous, this simple fact should be recognized. NASA becoming safety-neurotic will only repress the industry further. How to get people into space? Simple.

Open bidding.

 

[neutrino_cannon]

Solid fuel rockets are fine and dandy for getting up into low orbit, but after that they're not so hot. A solid fuel rocket is a binary sort of proposition; it's either on or off, and there aren't any speeds in between. You can't turn it off once it's on either. This strikes me as suboptimal for orbital slingshots and other fancy maneuvering.

Add to that that I don't think anyone's come up with a solid fuel composition that matches even LOX/kerosene for specific impulse.

But for the first stage, I'm not entirely sure what's gained by a liquid fuel rocket. Trickier to move around on the ground, lower thrust-to-weight ratio, during the part of the mission where T/W ratios matter, and you're saving weight through superior specific impulse at the one point where that doesn't really matter.

 

[BenBurch]

Solid fuel rockets are fine and dandy for getting up into low orbit, but after that they're not so hot. A solid fuel rocket is a binary sort of proposition; it's either on or off, and there aren't any speeds in between. You can't turn it off once it's on either. This strikes me as suboptimal for orbital slingshots and other fancy maneuvering.

Add to that that I don't think anyone's come up with a solid fuel composition that matches even LOX/kerosene for specific impulse.

But for the first stage, I'm not entirely sure what's gained by a liquid fuel rocket. Trickier to move around on the ground, lower thrust-to-weight ratio, during the part of the mission where T/W ratios matter, and you're saving weight through superior specific impulse at the one point where that doesn't really matter.

I just think back to the Gemini launch pad abort where the command pilot was able to shut off the Titan when it was not generating enough thrust. ( Somehow, I managed to be home sick from school for every launch. )

 

[mhaze]

Actually, yes, you can turn a solid rocket off. This is old stuff: Precision targeting of (range of) ICBM solid rockets was done by integrating acceleration, and blowing a hole in the casing at the exact moment when the correct amount of thrust had been provided.

Down close to the ground, in the initial launch, huge amounts of mass ejection are required. Further up, longer burn times are needed, some throttling, then pulsed burns for the final "circularization" of the orbit.

Solid rockets have exhibited reliability within an acceptable range for manned spaceflight.

I'm not sure that's saying a lot....

 

[neutrino_cannon]

Wait... you turn off a solid fuel rocket by destroying the integrity of the fuel column enough that it can no longer generate thrust?



Hybrid rockets are looking better and better.

 

[mhaze]

Wait... you turn off a solid fuel rocket by destroying the integrity of the fuel column enough that it can no longer generate thrust?

Hybrid rockets are looking better and better.

Exactly right. Just as the main Shuttle engines disengage the ET when there is still fuel in it - it is the very accurate "DeltaV" number which is required from a stage. Future use of the past stage is nominal if not disadvantageous. This can be seen from the calculus of the basic multistage rocket equation.

Some new hybrid designs may provide sufficient impulse, fuel burn rate limits total thrust.

 

[neutrino_cannon]

Exactly right. Just as the main Shuttle engines disengage the ET when there is still fuel in it - it is the very accurate "DeltaV" number which is required from a stage.

So throttleability of solid fuel boosters is basically a non-issue; the delta-v required for each leg of the mission is nailed down hard enough that the rockets can be made to exactly the right size (with a little wiggle room on top).

Future use of the past stage is nominal if not disadvantageous. This can be seen from the calculus of the basic multistage rocket equation.

Agreed, no need to drag along dead structural weight.

Some new hybrid designs may provide sufficient impulse, fuel burn rate limits total thrust.

IIRC some of the newer hybrid propellant combos have better Isp than solids.

 

[mhaze]

So throttleability of solid fuel boosters is basically a non-issue; the delta-v required for each leg of the mission is nailed down hard enough that the rockets can be made to exactly the right size (with a little wiggle room on top).
Agreed, no need to drag along dead structural weight.
IIRC some of the newer hybrid propellant combos have better Isp than solids.

Yeah, you got it. Isp isn't that big a deal though for 1st stage, it's massive mass ejection that counts - speed is low to some machs on 1st stage - nozzle is thus inefficient ...

Look for more simple hybrids on private ventures, that's where the action will be.