Falcon 9 Question ...

[jfb]

IMO, one of the key reasons the Space Shuttle couldn't reach its full potential was because it was weighed down with pork. Everything had to be compromised because of pork.

I wouldn't call the Shuttle "pork" the way I call SLS "pork".  STS wasn't merely a jobs program designed to keep the legacy space manufacturing sector employed; it was actively used for real exploration.  It would have been better to start with a proof-of-concept vehicle that could have been iterated as needs evolved, but the .gov doesn't work that way.  Unfortunately, NASA had to get buy-in from many different stakeholders to build STS, and as a result the system was way over-scoped IMO.  But, you know, you have to start somewhere. 

SpaceX has the advantage in that they can see what NASA did right as well as wrong and improve on the vision.  They also have the advantage of 40 years' worth of advances in materials and manufacturing technology.  Looking back on it now, STS was damned ambitious for the mid-1970s. 

It is true that SpaceX are not currently burdened with having to satisfy a bunch of different stakeholders with their own agendas, but don't believe for a minute that private aerospace is free of political wtf-ery. 

[smartcooky]

IMO, one of the key reasons the Space Shuttle couldn't reach its full potential was because it was weighed down with pork. Everything had to be compromised because of pork.

I wouldn't call the Shuttle "pork" the way I call SLS "pork". 

I watched a documentary on the Challenger disaster last night. Now even thougn I am very familar with the details surrounding this, I tried to put that aside and go in as if I had fresh eyes as someone finding out this stuff for the first time.

What I saw was infuriating. The five engineers at Morton-Thiokol, including Roger Boisjoly, Robert Ebling and Arnie Thomson knew that Challenger was in grave danger of blowing up, and tried to stop the launch. They failed because they were overruled by bean counters who wilted under pressure from NASA executives who used thinly veiled threats about upcoming contract negotiations.

Of course its history that the actual cause of the explosion was the failure of the field joint, in particular, in the cold temperatures on launch morning compromised the rubber O-Ring's ability to expand into the joint to seal it off. The joint was a flawed design, but the more important issue is that there was no need for field joints in the first place, and there would not have been any had it not been for pork. There was a company (Aerojet) who could have built the SRBs in a single piece, and delivered them by barge to The Cape. They initially won the recommendation but thanks to some lobbying by some Utah politicians, NASA administrator Dr. James Fletcher overruled this and awarded the contract to Morton Thiokol in Utah. The SRB's could not be transported over land in one piece, so they had to be made in sections. From there, its simple logic. Sectioned SRBs require field joints, one piece SRBs do not.

One piece SRBs = no field joints = no Challenger disaster.

This article is about the SRBs and the political machinations behind the STS. It is well worth the read even 30 years after the disaster.

http://www.tsgc.utexas.edu/archive/general/ethics/boosters.html

[Halcyon Dayz, FCD]

IMO, one of the key reasons the Space Shuttle couldn't reach its full potential was because it was weighed down with pork. Everything had to be compromised because of pork.

Not just pork, it had to comply with DoD requirements too.

[raven]

IMO, one of the key reasons the Space Shuttle couldn't reach its full potential was because it was weighed down with pork. Everything had to be compromised because of pork.

Not just pork, it had to comply with DoD requirements too.

Some, like the immense crossrange capability of those delta wings was never used. How sad is that? Almost as sad as the Soviet equivalent languishing, nay, rotting in a hanger until said hanger collapsed and destroyed it. Alas, poor Buran, we hardly knew ye.

[ka9q]

The most fuel-efficient hoverslam F9 landing would have no entry burn, and it would light all nine engines for the landing burn. The latter part is not practical because it would make the guidance and timing even more spectacularly critical than it already is, and the stage would break up on entry without an entry burn to slow it down.

Remember the "Oberth effect": the efficiency of a rocket is directly proportional to its speed, if we define "efficiency" as the amount of payload kinetic energy added (or removed, for a landing burn) per unit of propellant burned. That's where the hoverslam comes from in the first place; you wait as long as you can to build up as much velocity as possible, then remove it at the last possible moment as quickly as you can. You also want aerodynamic drag to do as much of the work for you as possible.

But that drag would be so great at re-entry that the stage would break (or burn) up, so you have to make it survivable by spending a little fuel before entry. Again, you want to wait until the last possible moment to do the entry burn, to build up velocity to maximize the efficiency of the entry burn.

In effect you are making two hoverslam landings, first "on" the atmosphere and then on the actual ground. It's just that only the second hoverslam (the real one on actual land) has to be done at zero velocity to be survivable; the first "landing" only has to be slow enough to survive the collision with the atmosphere.