Print 59 comment(s) - last by sigilscience.. on Mar 3 at 4:49 PM

NASA still unsure how to end Constellation and move forward

NASA has been plagued with financial issues and a continued lack of innovation, but now faces the equally daunting task of leaving behind the Constellation program.

President Obama and numerous space observers have been appalled at how poorly operated NASA has been in the past, with internal struggle and political opposition expected to make change even more difficult.  NASA Administrator Charles Bolden has garnered support from some politicians who said the White House is doing whatever it likes instead of working with experts.

As part of the agreement to end Constellation, NASA is expected to pay $2.5 billion to contractors already working on the Ares Rockets, Altair lunar lander, and Orion space capsule.  However, it's unknown how accurate the $2.5 billion estimate is, even though NASA relied on its own analysts and industry analysts to calculate the price.

NASA originally hoped to return to the moon by 2025, as other space nations plan to send lunar spacecraft and manned missions in the same time frame.  China, Japan, Russia, India, and several other developing space programs have expressed interest in landing on the moon by 2030 -- space industry observers think China will be the next country to reach the moon.

The 2011 budget has likely ended any chance of NASA returning to the moon, with private companies expected to help transport astronauts into space.

President Obama must now try to limit ongoing bickering as he works with NASA, private contractors, and legislators during his presidency.  The U.S. space agency will now rely more on the private contractors until current funding problems are sorted out in the future.

Comments     Threshold

This article is over a month old, voting and posting comments is disabled

RE: The moon
By porkpie on 3/1/2010 8:37:47 PM , Rating: 4
Wow, so many misconceptions. Where to start? Let's pick this:

"NTR is not suitable as a first stage engine"

Any engine that has a thrust:weight ratio better than one can work as a first stage engine. Your larger mistake, though, is in assuming you even need multiple stages with a nuclear rocket. Chemical rockets need staging because their performance is so can't afford to carry around a few hundred thousand pounds of empty tankage. With a nuclear rocket, your fuel to payload ratio is radically shifted. If you use a NTR as a first stage, it will almost certainly be your only stage.

" Yes Nerva achieved an isp of 850 sec, you might get 900 sec..."

You just don't understand how huge of a difference that would make. The Shuttle carries 3.9 million pounds of fuel, just to lift a meagre 8400 lbs to geosynch orbit.

An Isp of 900 wouldn't just triple the payload, it would increase it to over one million pounds, an astronomical increase. If you don't believe me, do the math yourself. The rocket equation is enormously sensitive to changes in Isp when you're near an asymptote.

"... but you cannot get substantially more than this because of the basic physics limitations of materials"

Sorry, this is wrong on a few counts. First of all, our materials science has progressed dramatically in 35 years. We can build stronger materials, able to withstand much higher heats.

A large number of noted physicists have seen no "basic physics" limitations on building nuclear thermal rockets with performance in the 1500+ Isp range. An even larger number of scientists and aerospace engineers have concluded that chemical rockets are "a dead end", and that the only way we'll ever drastically reduce launch costs is to use nuclear propulsion (or some even more radical method, such as beanstalks, railguns, or ground-based lasers).

RE: The moon
By porkpie on 3/1/2010 9:37:30 PM , Rating: 3
To add to the above, here's a lengthy evaluation of a single-stage-to-orbit nuclear thermal rocket (the Nuclear DC-X) done a few years ago for the Air Force, by a Ph.D. astrophysicist:

Nuclear not suitable for a first stage engine? Honestly, I don't where people dream up this stuff...

RE: The moon
By randomly on 3/2/2010 6:18:55 AM , Rating: 1
The LANTR concept referred to in the study is essentially a LH/LOX chemical high thrust first stage with a NTR upperstage. My point stands NTR T/W ratio is unsuitable as single stage to orbit without a chemical booster.

RE: The moon
By porkpie on 3/2/2010 7:28:54 AM , Rating: 2
Huh? You either didn't read the link, or have decided to purposefully misrepresent it. The design is a single-stage nuclear-powered SSTO.

You might have been fooled by seeing a small LOX tank in the design. That's not for chemical power, however...the addition of denser LOX into the reaction mass early in the flight cycle increases thrust, though it temporarily lowers Isp.

RE: The moon
By randomly on 3/2/2010 1:46:39 PM , Rating: 2
You should read the papers you cite more carefully.

Half the total engine power is derived from the chemical combustion.

RE: The moon
By porkpie on 3/2/2010 2:19:51 PM , Rating: 2
There is a 90% power boost when the LOX afterburner is operating. So? It's still a single stage nuclear rocket, and the majority of total impulse is obtained from nuclear power.

Trying to say this somehow "proves" nuclear rockets are unsuitable for liftoff is without merit. We've been building high thrust chemical rockets for three quarters of a century. It's not surprising that our first attempts to build a nuclear one would draw upon that heritage. The very first cars we built looked liked horse carriages also. That didn't mean they *had* to be designed in that manner.

RE: The moon
By randomly on 3/2/2010 6:10:22 AM , Rating: 1
You are confusing thrust to weight ratio of the rocket with thrust to weight ratio of the engine. You need a much higher engine thrust to weight ratio than 1 for a usable first stage engine. NTR only has a T/W of around 8:1. It's suitable as an upperstage engine but you need a chemical booster stage to get it off the ground.

Yes high isp makes a big difference, but unfortunately NTR incurs a very high penalty because of the high tankage weight and high mass fraction of the engine and shielding. Your 8400 lb to million pound payload increase is not even remotely achievable.

From the study you link below I see you found that materials science has NOT progressed as rapidly as you hoped and I was correct that the isp limit is around 900 sec.

The 1500 isp number you are quoting comes from a hypothetical vapor core reactor concept which is unsuitable for high thrust atmospheric use at best, and at worst unworkable concept due to fissionable material loss rates. The fact that the author of those studies Samim Anghaie has been charged with defrauding NASA out of $3.7 Million for those studies doesn't help their credibility either.

RE: The moon
By porkpie on 3/2/2010 7:25:38 AM , Rating: 3
"From the study you link below I see you found that materials science has NOT progressed as rapidly as you hoped and I was correct that the isp limit is around 900 sec."

For shame, now you're just outright lying. The study specifically states the Nuclear DC-X concept would have a theoretical Isp in the range 2,00-4000 seconds (page 52) for a FFH-based NTR. It even mentions a nuclear engine (page 49) that hit 972 secs...and that was just a small LANL project without much funding.

Please read the links before you attempt to discuss them.

"The 1500 isp number you are quoting comes from a hypothetical vapor core reactor "

Err, no. Now you're ignoring basic physics. A gas core reactor operates at far higher temperatures, and has a theoretical Isp in the range of 3000 all the way up to 15,000 Isp. The only way you can get a gas core reactor down to such low Isp, in fact, is with some hybrid solid-gas type designs, such as the nuclear lightbulb concept:

" The fact that the author of those studies Samim Anghaie was charged with defrauding NASA..."

You've descended into fantasy now. The study I linked was authored by Dr. Eric Davis, and it was done for the USAF, not NASA. NASA itself has done similar studies, done by many different people:

RE: The moon
By randomly on 3/2/2010 3:06:59 PM , Rating: 2
If you check the very first paper YOU cited you'll find they quote the exact same 900 sec isp limit I mentioned.
The 972 isp LANL engine was a design proposal not an actual engine and the figure didn't include the isp hit from the 15% residual fuel needed to cool the engine core after shutdown to keep it from melting from the residual decay heat.

The magical Fission Fragment Heated NTR with the 2,000-4,000 isp (that large range should make you suspicious from the get go) is a theoretical concept with no assurances that it can actually be made to work. You do realize that FFHNTR spews the radioactive fuel and waste out in the exhaust. The original concept is also a low thrust designs for in space use.

I quote from your report:
In order to design such a reactor, highly fissionable nuclear fuels such as Americium (Am) or Curium (Cm) must be used.These fairly rare fuels are produced from reprocessed spent nuclear fuel (via the extraction of
Pu-241 and Am-241), which is a very expensive multistep process.

If you look into that I think you'll find the costs and problems involved are considerable.

The FFH NTR, Gas core, and Light bulb designs besides all being hypothetical engines suffer from the same problem of radioactive fuel loss into the exhaust stream. This doesn't help the NIMBY problem.

This is the same techno-masturbation that results in people thinking Shuttle launch costs would only be $10 million, or that Tokamak fusion will become a cost effective energy source any day now. These wildly optimistic paper concepts almost never survive the process of actual implementation and never without becoming a shadow of it's former promise.

Remember how nuclear power was supposed to promise energy too cheap to meter?

Unfortunately Samim Anghaie is not fantasy, he was front and center in NASA's gas and vapor core reactor research. The studies I was referring to were Anghaie's on the characteristics and performance of Gas and Vapor core reactors. His work was often cited by others in the field. It doesn't completely discredit the field but it should be a reminder not to take everything you read as gospel.

Is Russia doing NTR development for LEO access? No. They abandoned their efforts long ago. Is China working on NTR? No. Is any space agency in the world doing NTR research for LEO access? No.

Maybe they know something you don't.

RE: The moon
By porkpie on 3/2/2010 6:39:51 PM , Rating: 2
"Is Russia doing NTR development for LEO access? No."

Is Russia doing ANY development for LEO access at present? No. They shut down Energia after a couple launches because they couldn't afford it. Attempting to portray this as some sort of failure of the technology itself is just nonsense.

NASA and the US military has repeatedly put forth proposals for nuclear propulsion. They are just as repeatedly shut down for budgetary and political reasons.

But you know better than all those aerospace engineers and physicists, don't you?

You keep spewing the same mantra, without ever giving one single source to back up your claims. Now its time to put up or shut up. Show just ONE reputable source that claims a nuclear SSTO is technically infeasible. I've given you plenty of sources that demonstrate otherwise.

"His work was often cited by others in the field. It doesn't completely discredit the field but it should be a reminder not to take everything you read as gospel."

This is your most laughable bit yet. Because one person who once did some NTR studies diverted some funds for personal use, that's supposed to not only invalidate all his own research-- but reflect on everyone else in the world's research as well?

Did you spin the little propeller on your hat before you typed that little gem? I'm done here. With illogic like this, I can see debate is futile.

RE: The moon
By sigilscience on 3/3/2010 4:49:46 PM , Rating: 2
" Yes Nerva achieved an isp of 850 sec, you might get 900 sec..."
Comparing NERVA to whats possible with nuclear is like trying to say Goddard's first toy rockets in the 1920s are the best we can do with chemical rockets.

“So far we have not seen a single Android device that does not infringe on our patents." -- Microsoft General Counsel Brad Smith
Related Articles

Most Popular ArticlesFree Windows 10 offer ends July 29th, 2016: 10 Reasons to Upgrade Immediately
July 22, 2016, 9:19 PM
Top 5 Smart Watches
July 21, 2016, 11:48 PM

Copyright 2016 DailyTech LLC. - RSS Feed | Advertise | About Us | Ethics | FAQ | Terms, Conditions & Privacy Information | Kristopher Kubicki