Sunday, May 22, 2011

What now for NASA?

Attending the STS-134 launch and the lift/mate for STS-135 has left me elated, but with a sadness. My pass allows me to attend the rollout of "the stack" from the VAB to the pad next week and the night landing of STS-134, not sure if I'll be attending.


There is a lot of hard feeling about the end of the Shuttle program, for the first time the U.S. will be without a spacecraft being actively developed. How did we get here??? Many want to blame the Obama administration for killing the Constellation Program, but the truth is more complicated than that.


After the loss of Challenger back in 1986 it was obvious that while the Shuttle was a magnificent engineering achievement, it would never be as easy and cheap to operate as claimed, and it had a deep flaw: the inability of the crew to escape a malfunctioning booster. As far back as 1978 an alternative system had been proposed where the cargo would be put on the top of the stack instead of on the side of the booster.



This "in-line" variant of the STS system would allow a greater variety of payloads to be carried since the payload diameter would not be limited by the constraints of being next to the ET. However, until the loss of Challenger this variant remained a paper rocket.

Subsequently this proposal was revived, and evolved into a program called the National Launch System. Using many of the same construction and operating parts from the Shuttle system, it was an evolutionary step.




The NLS made it as far as the Preliminary Design Review before it was cancelled in the early 1990s. Various reasons have been cited, but no matter what, if it had been funded it would have been flying long ago.



After the loss of Columbia a call was once again made for an alternative to the shuttle. The Ares I and the Ares V boosters were proposed, along with the return of a capsule (Orion) for transportation of astronauts to and from orbit.

The Ares V was supposed to be the "heavy lift"booster, but unlike the NLS system that built on existing STS hardware such as the 4 segment SRBs and the 8.4m ET, the Ares V required the development of a new 5 segment SRB, and the construction of a new 10m external tank.

The Ares I was a combination of a 5.5 segment SRB developed from the Shuttle combined with an upper stage powered by an Apollo era J2 engine, updated for digital controls and advances in rocket engine technology such as an expandable nozzle.



From the start the Ares Program generated controversy. Critics called the Ares V the "Franken-rocket", and at one point in it's growth it was proposed that the rocket would have to be tilted to fit out of the VAB. The Ares I suffered from a myriad of issues, but the most serious was called "thrust oscillation".

When a solid rocket motor burns it's not a smooth combustion, but it gives off a considerable amount of vibration. Comments made by Shuttle astronauts always refer to how rough the ride is under the solids and how smooth the ride is after they burn out and the liquid hydrogen/oxygen engines take over. This vibration is called "thrust oscillation" and in a Shuttle launch the vibration is absorbed by a large I-beam going through the ET structure connecting the two boosters. 

However, in a single SRB booster such as Ares I there would be no such system to absorb the vibration, and studies showed that the vibration could be severe enough to present hazards to the crew. A system was under development but the addition of it ate into the already marginal boost capability of the Ares I system, which had been further reduced as performance goals were not met. 

With the many problems cropping up in the Constellation Program engineers at Marshall quietly began resurrecting the NLS. Insinuations about reprisals directed toward engineers speaking out about the problems with the NASA directed Ares Program have been reported but never confirmed, but the end result is that a group of engineers worked on their own time to bring the NLS back under the name "Direct Launch" with the boosters being called the Jupiter class.



Using proven 4 segment SRMs and the existing 8.4m ET, it was believed that had this system been given the go-ahead it would have been operational within 3 years, with the "long pole" being the software to control the rocket.In addition, the basic Jupiter J-130 would have had an excess of capacity, allowing much of the systems eliminated from the Orion capsule as a result of the short comings of Ares I to be brought back.





With the problems in the U.S. economy in 2007/8, and involved in 2 wars, it was determined that NASAs Constellation Proposal was simply unaffordable and the program was cancelled. NASA was directed to return to a more Shuttle-derived launch system, but it is once again undergoing mission creep and is back up once again to a 5 engine Saturn-class booster, and it's doubtful it will ever fly.

In the meantime, NASA is continuing funding of the Commercial Launch systems. Elon Musk's Falcon 9 rocket has flown the first privately developed capsule in orbit, and has a plan for it to be human rated. There are other contenders in the field, and history will show what the outcome is.


Irregardless of what happens in the future, I don't believe history will be kind to those who passed up the work on the NLS in favor of the Ares Program. Instead of continuing to throw money at the Russians to fly U.S. astronauts on Soyuz spacecraft to the ISS, they should have been flying on U.S. made Jupiter rockets.

No comments:

Post a Comment