Moonshot, CEV Modifications

DarkNemesis618 writes "In the latest round of budget cuts, NASA introduced plans to modify the CEV for the planned Moon landing in 2018. The original plan called for an engine used on the space shuttle to be modified for the CEV. The new plan is to use an updated J-2 engine. The J-2 engine was first used on the Saturn V rocket which took the Apollo astronauts to the moon in the late 60's early 70's. It is not expected to save any money in the near-term, but in the far term, it should be a cost saver since the technology already exists and is proven. In the 10 Apollo launches aboard the Saturn V rocket, there were no problems with the launch vehicle."

Comments

Let's see...

[Jafafa Hots]

Modify a less-efficient, 40 year old design that hasn't been produced in several decades, or modify a more-efficient currently-used design. Choose the former because it "already exists?"

What am I not getting here?

Re:Let's see...

[SnowZero]

The shuttle engine is not currently capable of in-air ignition, while the J-2 engine did exactly that for Apollo. The shuttle engine would thus have to be modified, while the J-2 engine would not. So it's more like 10 times vs 0.

P.S. This is pretty clearly written in the article.

Re:Let's see...

[Burdell]

The SSME is higher efficiency in terms of thrust vs. mass. However, that isn't the only measure to be considered. Each SSME costs a lot more to build, because they were designed to be reused (IIRC the current plan is to not reuse the new vehicle's engines). The SSME is throttleable, but if that is not needed, it is an added complexity and expense. The J-2 was designed to be throw-away.

Also, there are some questions about the SSME for the new vehicle. The SSME would be used in upper stages that are lit in-flight. The SSME has only ever been lit sitting still, on the ground, at sea-level atmospheric pressure and temperature. The J-2 was used on upper stages of the Saturn V, so it is proven in that capacity.

Not really a surprise

[AKAImBatman]

Note that this isn't really a surprise to those who have been following the CEV development. The original plan called for a modification to the SSMEs for multiple restarts as the J-2 (the upper stage engine for the Saturn V) is no longer in production. However, there was a lot of discussion inside NASA that restarting production on the less powerful J-2 would be cheaper, faster, and easier than trying to modify the more powerful (but far more complex) SSME to do the job.

To give quick rundown on which engines are which:

SSME (Space Shuttle Main Engines) - LHOx Fuel - 1.8 MN
SRB (Solid Rocket Booster) - Solid Fuel - 14.7 MN
J-2 (2nd and 3rd stage Saturn V) - LHOx - 890 kN
F-1 (1st stage Saturn V) - Kerosine - 6.7 MN

The SSME and J-2 are directly comparable, and the SRB and F-1 are directly comparable.

Re:Not really a surprise

[LWATCDR]

"In addition, NASA has no infrastructure for Kerosene fuels,"
Atlas V?
Also what is the specific impulse for an F1 first stage VS an SRB?
Yes the SRB has more static thrust but I think the F1 is equal to it in specific impulse. Plus the F1 allows for an on pad shut down and is probably easier the vector than an SRB.
BTW the Specific impulse for the SRB is 268.8 For the F1 it is 304.8.

Using modern AlLi alloys for the tanks an F1 powered first stage might still be a good option. The real reason is cost. The SRBs are cheaper short term.

Re:Not really a surprise

[AJWM]

The startup sequence for the F1 is hairy as all get out (taking about 7 seconds from "ignition sequence start" to full power). Furthermore, while it may be apocryphal, Harry Stine once told me that the ignition sequence was controlled by a patch-panel programmed computer and that the documentation for the patches was long since lost and those people that knew how to do it have mostly died off.

The F1 ignition sequence includes steps like pre-filling the inlet tubes with a hypergolic mix to actually light the thing, diverting some of the fuel (kerosene) to the hydraulic system for the gimbal actuators, a controlled chill of the lox plumbing without getting the kerosene plumbing too cold (don't want any frozen lumps in there), starting the gas generators to power the turbopumps, etc. -- not necessarily in that order. The SRB ignition sequence is basically just detonating a small bomb at the top of the hollow solid fuel core.

Personally I like the idea of resurrecting the F1, but the difference in experience and reliability levels between F1 and SRB vs J2 and SSME are considerable -- and in the latter case the J2 start is simpler than the SSME start.

2018?

[Etnie]

I'm a bit confused as to how it takes us longer to get to the moon now than it did in the 60s.

Project Apollo was announced July 28th, 1960. July 20th, 1969, we set foot on the moon. Just under 9 years. (My dates may be a bit off.)

Even if you say the new project starts now, that's still 12 years. How frustrating.

Re:2018?

[Kesch]

There's probably a Murphy's Law of Government somewhere that the time it takes a government body to complete and action is directly proportional to the amount of regulations and oversight that exists. Regualtions and oversight are in turn directly proportional to the age and size of the government.

Re:2018?

[AKAImBatman]

I'm a bit confused as to how it takes us longer to get to the moon now than it did in the 60s.

1. Money. If we spent as much today as we did on the Apollo program, we'd be able to get a craft ready in a very short period of time. (Note that while NASA receives more than enough money, most of it goes toward the Space Shuttle's maintenece and other projects.)

2. Technology. The industry that produced the Saturn V doesn't exist anymore, so it is not really possible to produce it again. We can produce a new rocket like the Saturn V (or buy off the Energia, take your pick), but that would just give us another moonshot rocket. What we want to build this time is an infrastructure that will keep us on the moon instead of merely sending up a few tons there and back.

If there was an emergency, I imagine we could get to the moon inside two years. Most of the lander equipment can be remanufactured and lifted by the Space Shuttle, and strap-on boosters could be lifted to propell the module. But that's not the point. That's why we're doing this the right way this time. Or to put it in perspective, the Apollo missions started out with 2,900 tons of hardware. They came back with about 6 tons. That means that they expended 2,300 tons of hardware to get 3 people to the moon and back. That's a hell of a lot of waste! :-)

Headlines in 2020

[j_cavera]

I can see this one coming:

In the latest round of budget cuts, NASA introduced plans to modify the CEV for the planned Moon landing in 2038. The original plan called for an updated J-2 engine first used on the Saturn V rocket. The new plan is to have a guy sitting on the outside with a fire extinguisher. The fire extinguisher engine was first used in a high-school physics lab in the 1930s. It is not expected to save any money in the near-term, but in the far term, it should be a cost saver since the technology already exists and is proven.

- Jim

And yes, I AM a rocket scientist...

some numbers

[Quadraginta]

Apollo cost about $135 billion in 2005 dollars, and the CEV is expected to cost $15 billion.

There's an opinion piece as to how NASA

[multiplexo]

is turning the CEV into the same sort of flying clusterfuck as the Space Shuttle at:

http://www.space.com/adastra/adastra_tumlinson_060 130.html

At this point I would rather save money by ending NASA's manned space program instead of continuing to piss money down ratholes such as the Shuttle, ISS and now the Crude Exploration Vehicle all of which are just ways for NASA to hand money to large aerospace companies so that they can pad their bottom lines and continue to bribe congressmen.

Re:No problems?

[rcw-work]

I seem to rember in Apollo 13 the center 2nd stage engine, a J-2, went out early.

Dangerously strong pogo oscillations, which could have ripped the engine off the rocket, happened to trip a pressure sensor which caused the computer to shut down the engine.

Pogo was reduced to tolerable levels by the end of the Apollo series, and later engines such as the SSME were designed to eliminate it entirely.

Misleading.

[DerekLyons]

In the 10 Apollo launches aboard the Saturn V rocket, there were no problems with the launch vehicle.

This is a bit misleading, the summary starts out talking about the engines, the swaps to the launch vehicle. In fact, the J-2 engines had considerable problems on the flight of Apollo 6. The pogo problem was not cured until Apollo 14. (In fact, though it was overshadowed by later events, it came quite close to causing an abort on Apollo 13.)

In fact, when the Apollo series is looked at critically - one becomes astonished by the number of near misses and diving catches. NASA was lucky, very lucky.