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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.

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RE: The moon
By randomly on 3/1/2010 4:06:43 PM , Rating: 3
This is just fantasy.

There is no indication that NTR would lower launch costs to LEO in any way from current chemical launch vehicles. Even if you dismiss the political/environmental arguments the economics of the technology are unpersuasive when applied to realistic vehicles and launch rates.

NERVA was only an upperstage engine and Prometheus is a low thrust NEP engine suitable only for in space operation.

I'm very in favor of developing nuclear based Earth Departure stages like Prometheus, but that doesn't address the problem of the high cost to LEO.

There are no easy solutions in rocket science. There are no brute force solutions as much as one may wish for them. Everything is operating on the hairy edge and solutions require a very careful balance of science, technology, and economics. They don't call it Rocket Science for nothing.


RE: The moon
By porkpie on 3/1/2010 4:33:57 PM , Rating: 4
"There is no indication that NTR would lower launch costs to LEO "

Huh? A NTR engine could easily have 3-4X the Isp of the Shuttle's main engines (450s) or 5-6X an SRB. Even more importantly, that performance derives from an easily controllable reaction...rather than sitting on several million pounds of highly explosive chemicals, attached to boosters that can't be shut off once lit.

Even NERVA (1970s technology) managed an Isp of 850s..and burn times of up to 90 minutes.

With performance like that, you can design a launch vehicle for much longer burns and much lower g-forces. That dramatically reduces the stress on the vehicle and payload, thus increasingly reliability and reducing costs. Furthermore (if you assume Isps in the 1500s range) you wouldn't even need aerobraking for reentry, eliminating the massive heat and single largest failure point for any existing reentry vehicle.

Honestly, your post couldn't be more misinformed. Chemical engines operate on the 'hairy edge' because there is just barely enough energy in chemical reactions for us to reach orbit....and no energy left over for us to slow down to reenter once we get there. But with, say, a gas-core nuclear nuclear engine, you could vacuum-seal a '64 Chevy and fly it safely to orbit and back.


RE: The moon
By randomly on 3/1/2010 7:54:58 PM , Rating: 1
Wrong.

NTR is not suitable as a first stage engine. Yes Nerva achieved an isp of 850 sec, you might get 900 sec but you cannot get substantially more than this because of the basic physics limitations of materials. This is at best only 2x what the SSME achieves on the shuttle. Although the isp advantage is substantial NTR brings with it a whole host of drawbacks too such as a high mass fraction, shielding problems, abort problems, residual heat problems and so on. It's not clear at all that the isp advantage outweighs all the other drawbacks and that you'll end up with a cheaper cost to orbit.

Just because it's 1960's technology doesn't mean we can do much better today. This isn't electronics. The RL-10 rocket engine was first tested in 1959. With an isp of 464 sec it has not really been improved on substantially in half a century.

ISP isn't everything. You have to look at the cost of the whole system. Why do you think Spacex went with a Kerosene/Lox engine with an isp of 304 compared to a Hydrolox engine like the SSME with an isp of ~450. Cost.
The highest measured isp is 542 sec with a tripropellant of Lithium, Fluorine, and Hydrogen. Why doesn't anybody use this combination? Overall system cost.

You are just assuming that since the isp performance of NTR is higher that a rocket using that technology will automatically perform better and cheaper. This is not the case. A great deal of the advantage of an NTR upper stage is negated by the weight of the engine and shielding. This is similar to the significant performance hit a LH/LOX stage takes due to the extra weight of the fuel tanks because the density of LH is so low.

As an engineer familiar with this area I can tell you are just speculating with insufficient information and knowledge about the subject. You are obviously an intelligent person but you don't know what you are talking about in this field. Please do some research and get your facts straight instead of trying to win an argument by force of personal intensity. You cannot alter the laws of nature by sheer force of will.

In science and engineering you cannot pick and choose the facts that support your preferred world view. There are no perfect or right answers to anything. As soon as you become emotionally attached to a viewpoint you have lost your objectivity and your ability to clearly analyze a problem and you end up like the AGW extremists (on both sides).


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 low...you 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:

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA426465&...

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:

http://nuclearspace.com/Liberty_ship_pg10.aspx

" 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:

http://trajectory.grc.nasa.gov/projects/ntp/index....
http://www.grc.nasa.gov/WWW/RT/2004/PB/PBM-mcguire...


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:
quote:
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
quote:
" 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.


RE: The moon
By porkpie on 3/1/2010 11:49:02 PM , Rating: 3
"Why do you think Spacex went with a Kerosene/Lox engine with an isp of 304 compared to a Hydrolox engine like the SSME with an isp of ~450. Cost."

And finally to correct this error. RP-1 (kerosene) rockets aren't used just because kerosene is cheaper. They're used because a) they have a significantly higher thrust than H2, b) a higher Isp per unit volume than H2, c) they're safer (about 1/4 the explosive hazard), and d) more reliable (no need for refrigeration, except for your oxidizer if you use LOX).

The real kicker is the higher thrust and higher Isp-density, though. Under many scenarios, that can actually give an RP-1 based rocket better performance than H2, once you factor in drag and parastic tankage losses into your mass fraction.


RE: The moon
By randomly on 3/2/2010 6:59:48 AM , Rating: 2
There was no error. You are missing the point.

It might have been a little more obvious if I had asked why Spacex uses a Kerolox engine for their upperstage engine. A HydroLox upperstage would about double their payload capacity, yet they don't use one. Why is that? Because it doesn't currently make business sense due to the overall costs vs the needs.

I'm well aware of all the technical pros and cons of LH/LOX vs Kerolox engines but these are all subordinate details to the overall goal of minimizing cost to orbit for the mission requirements. Higher performance is not an advantage if the total system cost increase outweighs the performance advantage. Reusable rockets are not an advantage if their operating costs are higher than expendables.

You are making the same mistake as was made on the Shuttle. A high performance but very expensive reusable system is not a cost effective approach compared to expendables if you cannot achieve high enough flight rates to give it a cost advantage. We don't have the money to achieve anywhere close to the kinds of flight rates needed.

Real rocket designs are driven by overall COST concerns, not just by technical performance.


RE: The moon
By porkpie on 3/2/2010 7:50:08 AM , Rating: 2
So far you've done nothing but talk wildly, gotten several basic facts incorrect, and misrepresent the supporting data I've given -- all without giving any of your own.

A huge number of noted physicists and aerospace engineers have concluded that nuclear propulsion offers far more promise than chemical. It doesn't take much intelligence to understand why...even the worst nuclear engine we can build offers twice the performance of the best chemical one. With a little additional engineering, nuclear rockets can best chemical ones by an 8:1 or better Isp ratio, which calculates into payload:fuel ratios a thousand times higher.

It's easy to understand why The Space Shuttle never achieved a high flight rate. Look at the design -- strap on boosters, an external tank, tens of thousands of incredibly fragile thermal tiles...in 7 different flavors, no less. All sitting on top a pile of the most highly explosive fuel you can imagine, and tied to thrusters that can't be shut off once started. It's a nightmare.

None of that is necessary with a nuclear SSTO. The design is far simpler...and the massive performance advantage allows you to build a much stronger frame that doesn't ride so very near its design limits.

The Shuttle, for instance, experiences g forces of slightly over 3, and is only designed for a limit of 5g. That right there violates the basic "2:1 or more" safety factor engineers prefer to design around. The Shuttle also experiences heats of up to 3000F, which causes a multitude of maintenance, degradation, and safety issues. Again, this would not be necessary on a high-performance NTR.

Now, do you have anything from a reputable source to counter anything I'm saying?


RE: The moon
By porkpie on 3/2/2010 7:56:49 AM , Rating: 2
"I'm well aware of all the technical pros and cons of LH/LOX vs Kerolox engines but these are all subordinate details to the overall goal of minimizing cost..."

The Saturn V was fueled with kerosene. Do you actually believe that NASA -- in the heady days of the Apollo program -- was trying to pinch pennies?

I've already demonstrated to you the large number of reasons why RP-1 is a preferable fuel to H2 in many situations In designs like SpaceX's Falcon (or the Sat V), RP-1 gives you a higher performance envelope, due to the

In fact, The Shuttle's own SRBs don't even use H2 -OR- kerosene, but simple aluminum powder as fuel...a mixture that gives a lowly Isp of less than 250s. Why? Thrust, man, thrust.


RE: The moon
By randomly on 3/2/2010 2:19:14 PM , Rating: 2
You are rambling about commonly known aspects of propellant technologies but still completely missing the point.

Which particular technology is chosen for a particular application is driven by how it IMPACTS THE OVERALL COST OF THE PROJECT.

Higher performance options are not always the best choice if the performance advantage is outweighed by the increased overall costs they incur.

Spacex uses a Kerolox upperstage engine because of COST reasons not performance.

I repeat my original point that it is not clear at all that using NTR for LEO access makes any economic sense given foreseeable budgets and lift requirements.

NTR for earth departure stages is another matter, but for LEO access no country is seriously working on NTR designs anymore.


RE: The moon
By porkpie on 3/2/2010 6:29:05 PM , Rating: 2
"Spacex uses a Kerolox upperstage engine because of COST reasons not performance"

Did NASA use kerosene for Saturn V because of cost? Did they use aluminum powder to fuel the Shuttle SRBs because of cost?

Compared to the cost of a launch itself, the price differential between kerosene and liquid H2 is minimal. The real issues here are performance, safety, and reliability.


RE: The moon
By delphinus100 on 3/3/2010 4:08:43 AM , Rating: 2
Nuclear thermal rockets capable of Earth to LEO are possible, but NERVA wasn't it, in spite of its respectable Isp.

Still, in a country that went nuts over the RTGs in Cassini, it won't be easy to re-start work on high power reactors for rocketry anytime soon...


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