Potentially Habitable Planet Found

[RickSp]

Quote by: fushigi Cool. What about if you could eliminate the whole "generating escape velocity" part of the equation--if the ship was built in / launched from space? Would it make much difference? I remember reading a while back that superconductor technology could then be used to produce your energy, since space is pretty close to zero kelvin... this is all just speculation since I'm not an engineer/physicist. fushigi

My calculation was really, really simple. Anyone can see that our current technology just won't work.

I ignored getting all that mass into orbit (which is a mindboggling process by itself). I ignored the mass of the ship, crew and most of the fuel. All I did was to take the mass of a shuttle rocket booster and see how much force it would take to accelerate it to one G for one year. The calculation is just Force = Mass times acceleration.

I took half the mass of the rocket booster (a crude adjustment for the fuel that burned off during the flight) times the acceleration of 9.8 m/s^2. That is the average constant force required for acceleration. Multiply that force by the time (one year) in seconds which yields the rocket rating in N-secs. Comparing the minimum required rating to that of existing rockets, including the never tested nuclear rockets, and you will find that the current technology is inadequate by over an order of magnitude. Add in the additional fuel, crew and spaceship weight and the difference is several orders of magnitude.

Our existing technology just won't work. Very simple.

[iclaudius]

Z, I'd be fully willing to admit I'm wrong (especially in this area, which I clearly know nothing about), however Rick has a point. If the "technology" is only theory, then it isn't technology at all... it's theory. I know this post is kind of redundant, but I'd like to somehow see a conclusion to this discussion. Do you still believe it's possible to do what you say?

[RickSp]

Quote by: iclaudius Z, I'd be fully willing to admit I'm wrong (especially in this area, which I clearly know nothing about), however Rick has a point. If the "technology" is only theory, then it isn't technology at all... it's theory. I know this post is kind of redundant, but I'd like to somehow see a conclusion to this discussion. Do you still believe it's possible to do what you say?

Even if the untested "technology" had been flying for years, it still lacks the thrust for its mass to come anywhere close to do what it needs to do to reach the planet in an acceptable period.

You can't drive a Model T Ford to the moon and conventional or even nuclear powered rockets can't reach near light speed in a year or ten years. It is just the basic physics.

[iclaudius]

Quote by: RickSp Even if the untested "technology" had been flying for years, it still lacks the thrust for its mass to come anywhere close to do what it needs to do to reach the planet in an acceptable period. You can't drive a Model T Ford to the moon and conventional or even nuclear powered rockets can't reach near light speed in a year or ten years. It is just the basic physics.

I'd still like to hear it from Z.

[RickSp]

Quote by: iclaudius I'd still like to hear it from Z.

Regardless. After being repeatly insulted by him I don't expect anything enlightening.

It's like Earth, but it will take 285,000 years to get there

The fastest probe launched is New Horizons, now en route to Pluto at 21 kilometres a second. It would take 285,000 years to reach Gliese, and the technology required to significantly speed up spacecraft is still way beyond the realm of feasibility. Even a probe that could travel at the speed of light, the fastest possible speed, would take 20 years, the same time as a message sent from a radio telescope.

Even if one improved the New Horizon's technology by a factor of 1000 (!), the trip would still take 285 years each way. The technology just isn't there.

[ZNFYRH]

Quote by: iclaudius Z, I'd be fully willing to admit I'm wrong (especially in this area, which I clearly know nothing about), however Rick has a point. If the "technology" is only theory, then it isn't technology at all... it's theory. I know this post is kind of redundant, but I'd like to somehow see a conclusion to this discussion. Do you still believe it's possible to do what you say?

I don't mean for this to sound the wrong way, but did you read the document I linked in post #73?

It covers the results of tests run on nuclear thermal rockets from 1955 to 1973.

That should raise some flags... they were building these rockets 30 years ago!!!

It was tested, so this isn't just theory.

There are multiple variations of this rocket design, and if you skim the documentation, you'll see that they calculated specifications and results and have actual results.

In many of the design variations, the rocket was cooler and gave better output than initially suggested. Just start on page 291 and you can see tables of figures comparing predicted results with actual results for just one of the designs.

One of the reasons this rocket didn't see much development is referenced in this article here:

Technical and Political Life of a Nuclear Rocket

The great thing about that page, in addition to a finger on the pulse of the political perception of nuclear propulsion, is that you can see a picture of a NERVA rocket being tested.

Again... not just theory. They made it work.

While the rocket could fire at maximum output for almost 2 hours, this was done rarely as there was a lack of storage for the water vapor. This wouldn't be a concern in space.

Some more info here:

[2.0] Advanced Space Rocket Propulsion Systems (1)

... discusses how the initial tests were proof-of-concept and not intended for flight (hence the name KIWI, a flightless bird). Future work with the U.S.S.R. led to the Timberwind project, which still ran into problems with erosion.

Some great info summarizing the projects is here:

Nuclear Rocket Propulsion@Everything2.com

You'll notice, at the end of the article, they mention the P&W TRITON propulsion system.

PRATT & WHITNEY THERMAL NUCLEAR ROCKET ENTRY: TRITON

Good info on TRITON and how it is in the last phase of design. It has not been built yet, but they already have a strong grasp on what materials they would need and how to put it together.

This actually leads in to the point I was making...

The technology exists. It has been tested. It was found to be costly and inefficient. But it worked. That's the important part.

The TRITON is based on existing technology and just needs the funding, and that was back in 2004.

I want to make this perfectly clear yet again...

"Inefficient" is not the same as "doesn't work." And I will continue to question the intelligence of someone who says such a thing. As I mentioned, the internal combustion engine used in automobiles is terribly inefficient. Over 60% of the energy going into it is lost as heat.

Semantics or not, technicality or not, as long as a rocket can accelerate at 9.8 m/s^2 while still carrying the load of its own fuel, my point is still valid. Sure, you'd need a whole lot of rockets, but it would still work.

That's the only point I was making.

[RickSp]

Z, your nuclear rocket lacks the thrust to accelerate its mass to anywhere close to the speeds that you have claimed. Period. End of story.

F=Ma. The physics is the physics. It doesn't matter how many rockets you use. Each rocket has too much mass for the thrust they develop. Adding more rockets just adds more mass. You can never get the accelaration you need. a = F/M. More rockets increases the force and the mass at the same rate so the acceleration never increases. The physics is simple and obvious.

Your rockets, aside from being far too risky to ever fly, don't work for interplanetary flight. Get over it. (Run your own numbers. The results are obvious.)

[ZNFYRH]

RickSp

Prove it.

I already gave extensive numbers.

You do it yourself.

And link to where you get the numbers from.

As long as you get to be cocky, I get to be rude.

Go ahead and show me I'm wrong instead of tell me.

And use one of my sources to get the numbers... you have many to choose from.

[RickSp]

Quote by: ZNFYRH RickSp Prove it.

Give me a break. I've done that already. I guess you aren't paying attention. Or do you need me to show you the multiplication?

The numbers were based on a shuttle rocket booster, the most powerful chemical rocket ever built. Your too-risky-to-ever-fly nuclear rocket promised, though never delivered, results three times greater than chemical rockets, which still means that it needs to be twenty thousand times more powerful to do what you claim.

Your idiotic suggestion that you just need more rockets only demonstrates that you misunderstand basic physics. F= Ma. Increasing the mass and force equally does nothing to increase the acceleration.

To repeat myself:

OK, I got bored waiting so I ran my own back of the envelop numbers. I am an engineer but not in aeronautics, so the figure are rough, but it doesn't take a rocket scientist to see what is going on.

The largest rocket booster available today is from the space shuttle. Fully loaded it has a mass of about 590,000 kg and a rated thrust of about 1.2 MN-s give or take.

Ignore the mass of the crew, the ship, the supplies and everything else and just look at the mass of the rocket itself. Also ignore the fuel required to decelerate or to accelerate and decelerate going home. Look only at the amount of thrust required to accelerate the rocket all by it's lonesome to near light speed.

The numbers aren't pretty.

It would take a constant thrust of something like something like 2.9 MN for a year or 91,000BN-s to accelerate a 590,000 kg rocket to near light speed. (I approximated the burn rate to be linear so I used an equivalent average mass as half of the starting mass to account for fuel burn-off.)

But the shuttle rocket only has a capacity of 1.2MN-s, so you need a rocket 70 thousand times more powerful than our current technology can produce.

Adding more rockets doesn't help because you add more mass. The current rockets do not have sufficient rated thrust/kg to come anywhere close to what is needed.

Bottom line to accelerate for a year at 1 G requires a rocket with an absolute minimum rating of 154MN-s/kg. The shuttle rocket is rated at 2,100 N-s/kg.

Of course to actually make the trip and come back requires a capacity of four, five or six times this, so we would need rockets several hundred thousand times more powerful than those available today.

Today's technology doesn't work. Period. End of story. Not even close.

[ZNFYRH]

Quote by: RickSp Give me a break. I've done that already. I guess you aren't paying attention. Or do you need me to show you the multiplication?

You haven't done it already.

Since you're pushing the issue, you're telling me that nuclear thermal rockets do not provide enough thrust. So prove it.

Don't cite your other post. Prove it using any of the links I've given that have the figures in them. I'm telling you, I already did it and the numbers work out.

Again... for clarity... you did not use the numbers for the type of rocket I'm talking about.

How far are you going to insist on pushing this? You say something cocky like "do you need me to show you multiplication" and get away with it, so now back it up. Just use the numbers from my examples and prove me wrong.

Quote by: RickSp The numbers were based on a shuttle rocket booster, the most powerful chemical rocket ever built. Your too-risky-to-ever-fly nuclear rocket promised, though never delivered, results three times greater than chemical rockets, which still means that it needs to be twenty thousand times more powerful to do what you claim.

It did deliver. Go read the NASA PDF document I linked. Go right to the end where it lists the actual results. Why do you insist on being like this when I've found multiple references?

Quote by: RickSp Your idiotic suggestion that you just need more rockets only demonstrates that you misunderstand basic physics. F= Ma. Increasing the mass and force equally does nothing to increase the acceleration.

We were warned to watch the language. Not only were you condescending in the beginning, but that bolded part should be enough.

Let me make it simple... if the mass of a thing is 14K and the thrust is 34K, then adding another one makes the mass 28K and the thrust 68K.

With just one, you can add an additional 20K before you exceed an acceleration of 1G. With two, you can have 40K of additional mass.

With every additional booster, you get another 20K of allowable mass.

[RickSp]

OK this is just getting boring. If you don't get it, that is your problem not mine.

Your NASA pdf says that the too-risky-to-ever-fly nuclear rockets promised to deliver up to three times the thrust of chemical rockets. That isn't anywhere close enough to developing the necessary acceleration. Period.

Let me make it simple... if the mass of a thing is 14K and the thrust is 34K, then adding another one makes the mass 28K and the thrust 68K.

The point is that current rockets cannot accelerate their own mass to near light speed, not to mention their mass plus a payload, to close to light speed. Adding more rockets doesn't help. Do you understand F=Ma ? Doubling both mass and force doesn't change the acceleration. Can't get more basic than this.

I doubt your numbers and it would be nice if you used consistent terms. You use kilogram as both a unit of mass and force. No wonder you are confused.

If you can provide consistent figures for mass, thrust and burn time I can prove that your untested rockets won't work. Stick to kilograms for mass, and Newtons for force. Provide the source so I can check your figures. The calculation is obvious and really simple.

[ZNFYRH]

Nope, you don't get to start accusing my figures.

You're now being evasive.

Just use the figures provided in the links and prove me wrong.

By the way...

If M = 14,000 kg and F = 34,000 N, then a = 2.43 G with 20,000 kg to spare for fuel.

If we add another booster, M = 28,000 kg and F = 68,000 N, then a is still = 2.43 G, but we now have 40,000 kg to spare for fuel.

The difference is that now you have more mass to spare.

[RickSp]

OK you won't give me your numbers. You want me to dig them out of your links? Not likely. Put up or shut up.

The figures you have shown are amusing. They are obviously based on toy test-bed rocket engines. A rocket with a mass of 14,000kg with 20,000 kg fuel. So the total mass is 34,000kg? The space shuttle booster has a loaded mass of 590,000 kg. Yours is a play-toy.

But OK, even with the numbers you have provided, it is still obvious that your toy rockets won't cut it.

You specified that to get the planet in a reasonable time that it would be necessary to accelerate at one G for a year. (That was your criteria, not mine.) Looking only at the mass of your little rocket, ignoring any payload or ship weight, it doesn't come near to meeting your criteria.

Take your toy rocket of 14,000 Kg and 20,000 Kg of fuel for a mass of 34,000 Kg. Allowing for burn-off of fuel, subtract half the fuel for an average mass of 24,000 Kg. To accelerate it at 9.8 m/s^2 (one G) results in a force of 235,200 N for a full year.

Oops. Your rocket has a thrust of 34,000 N or 14% of what is required.

It gets worse.

You have not provided the burn rate of your rocket. The shuttle booster burns for about 100 seconds. Assuming yours does as well your rocket generates 3,400,000 N-secs or 0.00005% of the minimum 7,417,267,200,000 N-secs required just to accelerate the mass of your rocket alone for a year. The rocket alone without paylood comes no where close to cutting it. Increasing the number of rockets does nothing at all.

[Jason]

Z and Rick,
You have both been banned from this thread.

[fushigi]

Too bad they had to keep flaming each other. Reading the factual parts of this debate has actually been quite stimulating.