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Moving beyond LEO

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Skyskimmer

Guest
We can all I think agree for the most part that getting to leo is being talken care of by private industry, as well as space habitats. The big question I think now is how will we move beyond, low earth orbit.


To me it's seems the only pratical way to do it, is to go nuclear. the nerva reactors or whatever they be called. Does anyone have any insight on how much such a program would cost, and how it could get done. It would seem obvious that it's exactly what is needed yet there seems to be no mention of it.
 
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vulture4

Guest
I cannot accept the premise. Human spaceflight beyond LEO is pointless without technology that makes it worth the cost. Constellation is too expensive by at least a factor of ten. It would be worthwhile to invest in new technology that can lower the cost of spaceflight. But BEO human flight using ELVs is too expensive to be sustainable. Neither NASA nor America have the money for pointless stunts.
 
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Skyskimmer

Guest
vulture4":bumqbvh4 said:
I cannot accept the premise. Human spaceflight beyond LEO is pointless without technology that makes it worth the cost. Constellation is two expensive by at least a factor of ten.
Constellation is multi billion dollar proof that there's something extremely wrong with nasa. It's not rocket science anymore, it's rocket economics. Ironic when you think about it. If we want to get to mars we need to go nuclear, unless it's a one time deal. Just construction radiation shielding, and simulated gravity alone, create the necessity to grab elements from the moon.
 
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vulture4

Guest
Most of the cost of Constellation is in getting into LEO, not getting beyond it. That's why the Shuttle was built. While nuclear-electric propulsion would save some mass, possibly 50% in the propulsion stage, it cannot achieve the factor-of-ten cost reduction that is needed. The first step towards human spaceflight remains a fully reusable launch system.
 
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Skyskimmer

Guest
vulture4":35q9ytuo said:
Most of the cost of Constellation is in getting into LEO, not getting beyond it. That's why the Shuttle was built. While nuclear-electric propulsion would save some mass, possibly 50% in the propulsion stage, it cannot achieve the factor-of-ten cost reduction that is needed. The first step towards human spaceflight remains a fully reusable launch system.
Spacex style rockets can easily get the cost of space down to 1000 per kilo with a increase in volume. Reusable may happen but it doesn't matter it's no longer the limiting factor. Nuclear can't be used from earth but it can be used in orbit and beyond.

People gotta get out of this idea that getting to orbit is still the main problem we face. The main issue he getting beyond just circling the globe.
 
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rcsplinters

Guest
I am often amused by the attempts to compare costs of craft and boosters that have entirely different design criteria and mission profiles. Almost equally amusing is the willingness to place great faith in equipment that a single launch which displayed some unpredicted behavior during its flight. Fixable? Probably, but that remains to be demonstrated.

First, there is exactly one human rated craft (post shuttle) on the planet. Soyuz. There is exactly one commercial HSF operation on the planet. Soyuz. and it is heavily subsidized by Russia. Somehow, from the total absence of track record, complete lack of human rated craft and booster, a market place with insufficient demand to support an industry and a federally funding competitor that could, if desired, fly for free, apparent absence of a viable business model and obvious dependance on risk assumption by the american tax payer, we are expected to reach the conclusion that commercial HSF LEO is already an overwhelming success? Sorry. NO!

Now I said that to say this. Commercial HSF has little or no relevence to operations beyond LEO. The businesses, ok, business (SpaceX) engaged are focused on meeting their current contracts and trying to shake out a booster/capsule to do that for cargo. HSF is years down the road for them and may suffer from current contract commitments. Anything beyond LEO just isn't in the cards. Musk himself has suggested this. I get the feeling that SpaceX is feeling the curse of success. They have cargo contracts and have a lot of work to do to satisfy those. Legally, they come first.

Moving beyond LEO is going to cost billions and I won't be surprised to see 100 - 200 billion for anything significant. With much, more for a landing. NASA will be the leader in making that happen or it won't happen. Commercial involvement will be for cargo, if at all due to lack of heavy lift capabilty. We're missing crew modules, storage modules, avionics modules and on and on for operations beyond LEO. These will be few in number meaning that the business model will be cost plus. The mission will be science and technology development as there is nothing out there to drive a business model. Unless you spend the R&D money which is huge in this case, there will never be anything out there to drive a business model.

I'm not seeing any viable proposal to have HSF operation beyond LEO which seems to acknowledge reality that is an order of magnitude cheaper. The cost for few models I've read about that seem credible is weighted in the operations beyond LEO, not the ride uphill. Bottom line is that mission beyond LEO and the development required to conduct such a mission is going to be very expensive and very dangerous. We need to accept those costs and risks or step away from the challenge. Once simply can't walk out the front door and proclaim "New Space" is here.

Getting off the soap box, I will say that I think the market for commercial cargo services to LEO and somewhat beyond is pretty optimistic. I think that commercial HSF is possible but its a product with no market. I think that any human operations beyond LEO is cost plus. You can't put 4 guys in a sardine can and send them off for 6 - 18 months. The solution must deal with these factors.
 
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DarkenedOne

Guest
rcsplinters":2cjzb386 said:
I am often amused by the attempts to compare costs of craft and boosters that have entirely different design criteria and mission profiles. Almost equally amusing is the willingness to place great faith in equipment that a single launch which displayed some unpredicted behavior during its flight. Fixable? Probably, but that remains to be demonstrated.
RC why are NASAs paper rockets any better. At least the Falcon 9 has been developed and tested successfully, which is much more than can be said about any NASA rocket. In fact NASA despite several attempts NASA has not successfully developed a new rocket since the Shuttle.

First, there is exactly one human rated craft (post shuttle) on the planet. Soyuz. There is exactly one commercial HSF operation on the planet. Soyuz. and it is heavily subsidized by Russia. Somehow, from the total absence of track record, complete lack of human rated craft and booster, a market place with insufficient demand to support an industry and a federally funding competitor that could, if desired, fly for free, apparent absence of a viable business model and obvious dependance on risk assumption by the american tax payer, we are expected to reach the conclusion that commercial HSF LEO is already an overwhelming success? Sorry. NO!
I acknowledge the fact that fact that the Soyuz was subsidized in the fact that the Soviet Union developed it and worked out the kinks in the system, but there is no evidence whatsoever that its current operational costs are subsidized. If so then you would have to wonder why the relatively poor Russian space agency would be subsidizing launches for the relatively rich US government space agency.

Second of no one is considering commercial crew to be a success.

Now I said that to say this. Commercial HSF has little or no relevence to operations beyond LEO. The businesses, ok, business (SpaceX) engaged are focused on meeting their current contracts and trying to shake out a booster/capsule to do that for cargo. HSF is years down the road for them and may suffer from current contract commitments. Anything beyond LEO just isn't in the cards. Musk himself has suggested this. I get the feeling that SpaceX is feeling the curse of success. They have cargo contracts and have a lot of work to do to satisfy those. Legally, they come first.
This is where you are incorrect. Any vehicle traveling from Earth beyond LEO

rcsplinters":2cjzb386 said:
Moving beyond LEO is going to cost billions and I won't be surprised to see 100 - 200 billion for anything significant. With much, more for a landing. NASA will be the leader in making that happen or it won't happen. Commercial involvement will be for cargo, if at all due to lack of heavy lift capabilty. We're missing crew modules, storage modules, avionics modules and on and on for operations beyond LEO. These will be few in number meaning that the business model will be cost plus. The mission will be science and technology development as there is nothing out there to drive a business model. Unless you spend the R&D money which is huge in this case, there will never be anything out there to drive a business model.

I'm not seeing any viable proposal to have HSF operation beyond LEO which seems to acknowledge reality that is an order of magnitude cheaper. The cost for few models I've read about that seem credible is weighted in the operations beyond LEO, not the ride uphill. Bottom line is that mission beyond LEO and the development required to conduct such a mission is going to be very expensive and very dangerous. We need to accept those costs and risks or step away from the challenge. Once simply can't walk out the front door and proclaim "New Space" is here.

Getting off the soap box, I will say that I think the market for commercial cargo services to LEO and somewhat beyond is pretty optimistic. I think that commercial HSF is possible but its a product with no market. I think that any human operations beyond LEO is cost plus. You can't put 4 guys in a sardine can and send them off for 6 - 18 months. The solution must deal with these factors.
To be honest with you RC human spaceflight like everything else is governed by a simple economic concept. The worth of the benefits or at least the perceived benefits have to be greater than or equal to the cost. At the moment HSF beyond LEO just is not worth the expense.

Now there are two things that can change this situation. The first and most obvious is that the expense can decrease. This objective can be accomplished through both technological innovation and decrease in standard operations. The second less obvious, but equally important game-changer is the introduction of additional incentives.

Commercialization of HSF really serves very well to accomplish both of these objectives. First by establishing a space tourism and space research market they will increase the benefits of HSF beyond mere exploration. Secondly economics also states that HSF is an economy of scale, thus more participants brings down the cost per participant substantially. This fact is one of the things that makes unmanned spaceflight so much more cost effective. NASA simply does not need to design, produce, or operate its own unmanned launch capacity. NASA simply purchases the capability for a faction of the cost it would take to develop its own.
 
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Gravity_Ray

Guest
I know whenever rcsplinters talks about this issue, he ends up pissing everybody off. I know he pisses me off whenever he says “cost plus is the only way to go”.

But we have to agree that most of his points are major points that are real. There is NO economic reason to go BLEO. There are no human rated US rockets. There are not human rated capsules at the moment either. There are no Landers either.

So he is correct on all counts.

But we cannot accept that because these things don’t exists, they cant exist. I don’t agree that cost plus and NASA is the only way to go forward. This model was around for over 40 years and didn’t produce anything except a joy ride for a few people circling the Earth.

So obviously we have to look at other options, and those options are Bigelow, SpaceX, and Boeing. Public human space flight is a no-go. The administrations that come and go are purely political so they don’t really care about HSF. The congress is populated by idiots and pork. NASA has to dance to a different tune every 4 years (you can not have an HSF that is based on 4 year cycles).

Bigelow has proved that the inflatable module is real, there are 2 of them up there right now (true they are not the full size ones, but the concept is proven). SpaceX has proven they can launch rockets (true the Falcon 9 is not human rated, but once cargo is delivered to the ISS it is human rated because the astronauts will have to float in it to get cargo and the technology will be proven). The CST-100 is just a capsule and Boeing has shown it can make capsules.

So in reality, NASA will not and should not be in the business of cost plus contracts to get rockets and capsules to LEO anymore. The only thing NASA should do is support them by paying them to do the work for NASA.

The real issue is why should humans go to BLEO? That question will be answered soon, but Bigelow and Boeing and SpaceX. Things are not done, well, until they are done. There are other countries that have now signed an understanding with Bigelow that they want to go to space. There will also be private companies (pharmaceuticals, etc..) that will want to go up there as well. So private will go to LEO, but when will we go to BLEO? Anybodies guess
 
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rcsplinters

Guest
Ray,actually, you caught my point pretty much dead center. Let me make a few little corrections to your interpretation of my discussion.

First, the mission is to go beyond LEO. That's a national directive set by the president, past president, congress and NASA. and we can argue the merits of that directive. For purposes of my discussions, I accept them and contemplate our options. My reason for this is that we are going to spend billions in that direction. We can't continue to start and stop workable solutions because we decided we don't like the price.

Second, we simply must have capabilities to achieve that mission that we don't have. We have exactly one business model that might succeed and that's cost plus. Granted, LEO is a different story, but that's not the mission we're discussing so commercial is very nearly irrelevent with respect to HSF BEO. NOW, cargo is another matter and I think commercial has a big role to play there. This says that the solution for the mission will not be completely cost plus.

Third, work beyond BEO is research. Once does not assume a return on research, instead you gamble on valuable spinsoffs and useful alternative applications. In this manner, the apollo program was very likely cost effective, even though it was cost plus. I frankly think we know so little about interplanetary travel involving humans, that we stand to gain hugely in technology just from the attempt.

Lastly, where commercial is concerned, we are talking a mission where 1 - 2 excursions per year or two would be the expected demand. The requirements for the mission are harsh, significantly exceeding those of LEO where home is a few hours or few days away. So do we design all our LEO equipment to go to Mars or do we design LEO efficiently and tailor make those items used for research purpose specific? We know the answer to that question. Purpose built stuff (and I'm not talking boosters here) is almost always cost plus. For example, tell your contractor you want to build your house using 3.9" by 4.85 inch studs. He'll say SURE! Cost plus.

Its pretty simple, om 2011 we are going to start building (again) a series of boosters to throw enough weight in orbit to achieve a specific mission. It is going to be cost plus. After that, assuming we don't start over again, we are going to begin building a series of purpose build craft to take us to specific destination. There'll be less than 10 -15 of those craft most likely in the next 20 - 35 years. That's going to happen cost plus because no business is going to want to play anyother way. The only other choice is to abandon the mission. And this is my point, in the end. If you don't support the cost and methodology, then you can't support the mission and then we are stuck in LEO. There is simply no other option on the table for that particular mission. Further I don't see private industry making any sort of aggressive gesture (as opposed to some executive engaging if flights of the imagination) to provide or even propose such an option for anything beyond LEO.

I think the big question that we have to answer as proponents of human space flight is whether we support that mission. If we do, then there is no means to do it on the cheap in my opinion. That I believe is the central point of disagreement. Some believe our choice is between the high cost and low cost answers to the problem. In my case, I believe the choice is to pay the high price or abandon the mission. There is no credible low cost answer.
 
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bdewoody

Guest
The moon is BLEO and if we redirect our efforts back to where they should be a regularly scheduled, say at least quarterly flight to the moon will be required. To do this I believe three ship types will be needed. The first is a means to achieve earth orbit to get crews and supplies off the earth. The "space elevator" is still a long way off and I don't think we can wait that long. The space shuttle comes to mind and could be refined further as needed. The second is a earth-moon transfer craft which would stay in space indefinetely being refueled eventually while in moon orbit. The third would be a moon lander which would rendesvoux with the transfer vehicle to move crew and supplies to and from the moon base. This system would eventually build a robust space industry which could then concentrate on building space craft in moon orbit to go to Mars, Jupiter or an asteroid.
 
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Skyskimmer

Guest
First off the idea that spacex got it's hand full with contracts is laughable. Sure it will be busy for the next 2-3 years but after that it's gonna be surely able to increase it's volume once some confidence in their product is maintained.

Secondly I don't have any idea why private can't be a major aid in going bleo. Sure they have to get heavy lift going, but I think that's easily acheiveable by 2020-2025, at a cost much lower than constellation or any other company. With these lower launch costs alot of the economics of bleo will change aswell, Heavy designs will be much more approachable if they cause a net cost reduction, no more of this over designed/tested stuff that nasa gets on with.

third howcome hasn't mentioned anything about nuclear.

also this nasa assumption thing really grinds my gears. There hands are tied with alot of programs that they're not willing to dump, a national economy that's heavily in debt, lack of public support, and alot of questions of direction. Europe/russua/china/brazil/india have a lot of unrealized potential, and they certaintly have a lot more room to grow than nasa.
 
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bdewoody

Guest
Remember that currently there are treaties in place limiting the use of nuclear power in space. And rockets that have nuclear engines will be by necessity heavy. Maybe they could be built on the moon, if the moon have enough raw nuclear elements. A nuclear powered planetary space vehicle would not have an atmosphere on the moon to pollute
 
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Skyskimmer

Guest
bdewoody":2v8ht0v9 said:
Remember that currently there are treaties in place limiting the use of nuclear power in space. And rockets that have nuclear engines will be by necessity heavy. Maybe they could be built on the moon, if the moon have enough raw nuclear elements. A nuclear powered planetary space vehicle would not have an atmosphere on the moon to pollute
The treaties stuff is a bit of a joke a tricky joke, but a joke non the less. Most countries of the world either have nuclear sub's nuclear reactors or nuclear bombs. I'm sure something could be figured out quite easily. Don't get me wrong I don't think it'll be a free game type of thing, but there will be some allowance to be made. They send uranium fuel up with the lastest space rover if I remember right.
 
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pathfinder_01

Guest
bdewoody":29bonfl7 said:
Remember that currently there are treaties in place limiting the use of nuclear power in space. And rockets that have nuclear engines will be by necessity heavy. Maybe they could be built on the moon, if the moon have enough raw nuclear elements. A nuclear powered planetary space vehicle would not have an atmosphere on the moon to pollute
To my knowledge there are no laws against NTR or nuclear reactors in space both have been put into space. However there are treaties against nuclear weapon storage or testing in space (making things like the Orion concept troublesome). There are ways to use an NTR without poluting the atomsphere. I personally am not in favor of NTR too expensive heavy and not enough gain for the hassle.
 
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rcsplinters

Guest
While I thought there was some treaty requirement in that reactors in space took some sort of sign off by Russia and maybe even the Chinese, there are huge political barriers.

Remember Cassini. You'd have thought that death due to Plutonium poisoning was virtual certainty for all life on earth.

Frankly, I think the transport of nukes to LEO might be a niche for commercial cargo, given the expectation of 110% success rate (I jest, I jest). BDE has a point. Legal or political, there are issues with throwing nukes up hill.
 
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stevekk

Guest
We really need an alternative to chemical rockets for getting off this planet, or at least better chemicals. We wouldn't need to design a new "Heavy" lift rocket if 80-90 percent of the weight being lifted was cargo instead of liquid or solid rocket fuel. Nuclear doesn't help, unless it works as a first stage rocket motor so I can eliminate most of the weight of the RP-1 / LOX / etc.
 
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DarkenedOne

Guest
pathfinder_01":11t4szsy said:
bdewoody":11t4szsy said:
Remember that currently there are treaties in place limiting the use of nuclear power in space. And rockets that have nuclear engines will be by necessity heavy. Maybe they could be built on the moon, if the moon have enough raw nuclear elements. A nuclear powered planetary space vehicle would not have an atmosphere on the moon to pollute
To my knowledge there are no laws against NTR or nuclear reactors in space both have been put into space. However there are treaties against nuclear weapon storage or testing in space (making things like the Orion concept troublesome). There are ways to use an NTR without poluting the atomsphere. I personally am not in favor of NTR too expensive heavy and not enough gain for the hassle.
Why is nuclear not worth the hassle. I'm sorry I do not understand how anyone who has bothered to take two seconds to research what nuclear rockets could do even in the 1960s could say they are not superior to chemical rockets.

They are leaps and bounds above chemical. They are far more efficient and would require far less propellant in order to get to a given destination.
 
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Yuri_Armstrong

Guest
rcsplinters":3h2yyz99 said:
Ray,actually, you caught my point pretty much dead center. Let me make a few little corrections to your interpretation of my discussion.

First, the mission is to go beyond LEO. That's a national directive set by the president, past president, congress and NASA. and we can argue the merits of that directive. For purposes of my discussions, I accept them and contemplate our options. My reason for this is that we are going to spend billions in that direction. We can't continue to start and stop workable solutions because we decided we don't like the price.

Second, we simply must have capabilities to achieve that mission that we don't have. We have exactly one business model that might succeed and that's cost plus. Granted, LEO is a different story, but that's not the mission we're discussing so commercial is very nearly irrelevent with respect to HSF BEO. NOW, cargo is another matter and I think commercial has a big role to play there. This says that the solution for the mission will not be completely cost plus.

Third, work beyond BEO is research. Once does not assume a return on research, instead you gamble on valuable spinsoffs and useful alternative applications. In this manner, the apollo program was very likely cost effective, even though it was cost plus. I frankly think we know so little about interplanetary travel involving humans, that we stand to gain hugely in technology just from the attempt.

Lastly, where commercial is concerned, we are talking a mission where 1 - 2 excursions per year or two would be the expected demand. The requirements for the mission are harsh, significantly exceeding those of LEO where home is a few hours or few days away. So do we design all our LEO equipment to go to Mars or do we design LEO efficiently and tailor make those items used for research purpose specific? We know the answer to that question. Purpose built stuff (and I'm not talking boosters here) is almost always cost plus. For example, tell your contractor you want to build your house using 3.9" by 4.85 inch studs. He'll say SURE! Cost plus.

Its pretty simple, om 2011 we are going to start building (again) a series of boosters to throw enough weight in orbit to achieve a specific mission. It is going to be cost plus. After that, assuming we don't start over again, we are going to begin building a series of purpose build craft to take us to specific destination. There'll be less than 10 -15 of those craft most likely in the next 20 - 35 years. That's going to happen cost plus because no business is going to want to play anyother way. The only other choice is to abandon the mission. And this is my point, in the end. If you don't support the cost and methodology, then you can't support the mission and then we are stuck in LEO. There is simply no other option on the table for that particular mission. Further I don't see private industry making any sort of aggressive gesture (as opposed to some executive engaging if flights of the imagination) to provide or even propose such an option for anything beyond LEO.

I think the big question that we have to answer as proponents of human space flight is whether we support that mission. If we do, then there is no means to do it on the cheap in my opinion. That I believe is the central point of disagreement. Some believe our choice is between the high cost and low cost answers to the problem. In my case, I believe the choice is to pay the high price or abandon the mission. There is no credible low cost answer.
And this is why I have a problem with the OP's hostility towards NASA. Why or how could a private company go beyond LEO? I do believe they have a role to play by assisting NASA with things such as cargo like you mentioned, but even going to the moon would require such a monumental effort that no company could do it by themselves.

I also do not understand the cost issue. We should be more than a nation of consumers, we should be willing to pay the $40 billion or so it takes for Mars Direct. Like Robert Zubrin said, the goal should be Mars by 2020- we know how to do it, it's just that nobody has the political will enough to make it happen which is sad. America would become heroes to the world again just like we were back in the 60's, and it would be great for the populace and give every American a recent accomplishment that we can all be proud of. These kinds of things you just can't put a price on, and any sort of expectation to go back to the moon, Mars, or wherever cheaply is simply ridiculous. And not giving NASA the money that they need to accomplish these great missions and constantly giving them mixed messages is not only unfair but also unamerican. NASA is almost certainly the greatest American agency and they are only getting .5% of the budget when they should be getting at least 15% of the budget. Imagine what they could accomplish with that kind of money and the goal of Mars by 2020. I think we would see a lot get done.
 
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DarkenedOne

Guest
Yuri_Armstrong":2h5gggey said:
And this is why I have a problem with the OP's hostility towards NASA. Why or how could a private company go beyond LEO? I do believe they have a role to play by assisting NASA with things such as cargo like you mentioned, but even going to the moon would require such a monumental effort that no company could do it by themselves.

I also do not understand the cost issue. We should be more than a nation of consumers, we should be willing to pay the $40 billion or so it takes for Mars Direct. Like Robert Zubrin said, the goal should be Mars by 2020- we know how to do it, it's just that nobody has the political will enough to make it happen which is sad. America would become heroes to the world again just like we were back in the 60's, and it would be great for the populace and give every American a recent accomplishment that we can all be proud of. These kinds of things you just can't put a price on, and any sort of expectation to go back to the moon, Mars, or wherever cheaply is simply ridiculous. And not giving NASA the money that they need to accomplish these great missions and constantly giving them mixed messages is not only unfair but also unamerican. NASA is almost certainly the greatest American agency and they are only getting .5% of the budget when they should be getting at least 15% of the budget. Imagine what they could accomplish with that kind of money and the goal of Mars by 2020. I think we would see a lot get done.
The biggest problem NASA has is that they adopt these ambitious missions without the money to pay for it. The result is that they end up spending a huge amount of money and get absolutely nothing done. NASA has done this the the national Space Plane and most recently with Constellation. This process is so incredibly inefficient. Every time you spend billions of dollar and years of time only to cancel the project it is pretty much the worst thing you could do. Simply flushing the money down tolit would be more productive because at least then you lose less time. Personally I do not care at all for deadlines and goals that NASA sets for human spaceflight. They have been broken so many times that they are utterly meaningless.

As far as Mars Direct goes there is just no way that it will be accomplished for $40 billion. As It was projected for to cost NASA $40 billion just to build the Ares I/Orion system, and that was only capable of reaching LEO and had an endurance of about half a year. Constellation was projected to cost over $100 billion and that was going to the moon. Honestly how anyone can believe that NASA can reach Mars for $40 billion dollars?

Honestly all I want to see some progress, some indication that we are moving into the future. That is why I supported Obama's policy. The objectives he set were going to benefit manned spaceflight, but more importantly of all they were quite doable with a high degree of confidence. Extending the ISS, supporting commercial HSF, and developing new technologies were all things that do not require hundreds of billions and I had no doubt NASA could accomplish them with a significant amount of money to spare.

One thing that I have learned in my life is that it is infinitely better to set small goals and accomplish them than it is to set ambitious goals and fail. Whatever we choose to do we must accomplish it.
 
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Yuri_Armstrong

Guest
A reasonable point of view, and one that is difficult to argue with. But you do not need Orion to go to Mars, I don't even think it was designed with Mars in mind. Robert Zubrin actually stated that it could be done with $5 billion, but he tacked on the extra amount due to the almost inevitable bureacracy and irresponsible spending that usually comes with any large agency.

What my worst fear is that the commercial alternatives do not work and since NASA decided to cancel the shuttle before a replacement was ready we will be stuck riding the Soyuz for the next 10 years, ISS is de-orbited, and then no more American manned space flight. That would truly be a sad day, so I guess for now what is most important is that we do get a replacement for the shuttle so we can preserve our leadership in space.

Now what I am interested in here with Obama's plan is the variety of private companies developing vehicles. Is it possible that NASA may end up using all of them to some degree? Or will they simply stick with only one ship to use?
 
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pathfinder_01

Guest
DarkenedOne":18jo3jkp said:
pathfinder_01":18jo3jkp said:
bdewoody":18jo3jkp said:
Remember that currently there are treaties in place limiting the use of nuclear power in space. And rockets that have nuclear engines will be by necessity heavy. Maybe they could be built on the moon, if the moon have enough raw nuclear elements. A nuclear powered planetary space vehicle would not have an atmosphere on the moon to pollute
To my knowledge there are no laws against NTR or nuclear reactors in space both have been put into space. However there are treaties against nuclear weapon storage or testing in space (making things like the Orion concept troublesome). There are ways to use an NTR without poluting the atomsphere. I personally am not in favor of NTR too expensive heavy and not enough gain for the hassle.
Why is nuclear not worth the hassle. I'm sorry I do not understand how anyone who has bothered to take two seconds to research what nuclear rockets could do even in the 1960s could say they are not superior to chemical rockets.

They are leaps and bounds above chemical. They are far more efficient and would require far less propellant in order to get to a given destination.

In theory a NTR would have about twice the ISP of a chemical rocket. In reality the mass of shielding required and the mass of the reactor itself eats into the performance of the rocket till you get something that isn’t quite as good as expected. In addition a NTR can only be used 2-3 times. Not counting the radioactive exhaust. I am in favor of nuclear electric propulsion but of course it too has issues.
 
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pathfinder_01

Guest
Yuri_Armstrong":3ovi833h said:
A reasonable point of view, and one that is difficult to argue with. But you do not need Orion to go to Mars, I don't even think it was designed with Mars in mind. Robert Zubrin actually stated that it could be done with $5 billion, but he tacked on the extra amount due to the almost inevitable bureacracy and irresponsible spending that usually comes with any large agency.

What my worst fear is that the commercial alternatives do not work and since NASA decided to cancel the shuttle before a replacement was ready we will be stuck riding the Soyuz for the next 10 years, ISS is de-orbited, and then no more American manned space flight. That would truly be a sad day, so I guess for now what is most important is that we do get a replacement for the shuttle so we can preserve our leadership in space.

Now what I am interested in here with Obama's plan is the variety of private companies developing vehicles. Is it possible that NASA may end up using all of them to some degree? Or will they simply stick with only one ship to use?

Bolden has stated that he wants at least two providers. Bigelow states he wants two providers.
Blue Origin has not released much information so I when I say commercal I mean Dragon, CST100, and Dream Chaser.

The ISS lifeboat issue hasn’t been resolved .The Obama plan would have increase the crew by one creating the need for a lifeboat other than Soyuz and the commercial crew companies don't want to tie their craft up at the ISS. Orion is likely to be the lifeboat(even if it also does BEO) but I can see a future where a company provides it(Dragon Lab has a two year shelf life and Dream Chaser would be easier on injured crew than any capsule).

What isn’t resolved is the model. Taxi or rental? I expect both models could be used. Taxi to the ISS and perhaps rental or Orion to Hubble for a deorbit mission.

The Boeing CST100 although storeable for 7 months can only support a crew for 48 hours. Space X, Blue Origin and Dream Chaser have not posted their endurance yet. Orion can support a crew of 4 for 21 days and storeable 6 months. Commercail can hold a crew of 7, Orion 6.

Orion is estimated to cost 800 million a unit(in the form that can both launch and land with crew. Crew return only would be cheaper). Orion would require the most expensive launcher to launch (Delta IV heavy or SLS). Not to mention that it is disposable(well you can reuse about 45% of it). All of the commercial ones are reusable and the most expensive one is Dreamchaser and it is expected to cost this much a unit but be much more reusable.Commercail most likely will launch on launch on Atlas. CST100 and dragon can launch on Atlas, Falcon 9, and Delta.

Even if commercial went bust and NASA had to buy them out they could still be ahead. Nasa has yet to commit to purchasing more than the test flight Orion and SLS won’t be ready till 2016 at best(more likely never but that is another thread).
 
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DarkenedOne

Guest
pathfinder_01":3i7gqd65 said:
DarkenedOne":3i7gqd65 said:
Why is nuclear not worth the hassle. I'm sorry I do not understand how anyone who has bothered to take two seconds to research what nuclear rockets could do even in the 1960s could say they are not superior to chemical rockets.

They are leaps and bounds above chemical. They are far more efficient and would require far less propellant in order to get to a given destination.

In theory a NTR would have about twice the ISP of a chemical rocket. In reality the mass of shielding required and the mass of the reactor itself eats into the performance of the rocket till you get something that isn’t quite as good as expected. In addition a NTR can only be used 2-3 times. Not counting the radioactive exhaust. I am in favor of nuclear electric propulsion but of course it too has issues.
So there are a number of things you are missing here.

First of all, ISP has absolutely nothing to do with mass of the engine itself. It depends on the exhaust velocity of the propellant. The higher the exhaust velocity the more ISP you get regardless of the engine size.

Secondly even if the nuclear powered rocket engine was 10 times are large as its chemical counterpart it would still be significantly better for the high delta-v transfers. Trips to the moon or Mars and back will require significant velocity changes. Higher ISP rockets are going to be useful for these missions.

Thirdly in space who cares about radiation. It already has tonnes of radiation. Thus who cares about radioactive exhaust, or radiation from the reactor. The reactor could just run open core. The only concern is for the crew, which can be solved by doing things like placing the fuel tank between the reactor and the crew compartment just like in regular rockets. Then again the crew has to be protect from the substantial amount of space radiation as well.

Lastly nuclear-electric is less powerful and less efficient than nuclear thermal. Nuclear electric is essentially where we generate heat from the nuclear fission process, that heat is then converted into electricity with substantial loss, then converted back into heat the propellant in a plasma reactor. This process of course requires a great deal more mass in the generators, heat radiators, and plasma rockets. Nuclear thermal on the other hand heats the propellant directly from the fission process, thus energy is not lost in the conversions.

Personally I believe that some hibred of the two concepts is best.
 
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pathfinder_01

Guest
DarkenedOne":2kwawj3z said:
pathfinder_01":2kwawj3z said:
DarkenedOne":2kwawj3z said:
Why is nuclear not worth the hassle. I'm sorry I do not understand how anyone who has bothered to take two seconds to research what nuclear rockets could do even in the 1960s could say they are not superior to chemical rockets.

They are leaps and bounds above chemical. They are far more efficient and would require far less propellant in order to get to a given destination.

In theory a NTR would have about twice the ISP of a chemical rocket. In reality the mass of shielding required and the mass of the reactor itself eats into the performance of the rocket till you get something that isn’t quite as good as expected. In addition a NTR can only be used 2-3 times. Not counting the radioactive exhaust. I am in favor of nuclear electric propulsion but of course it too has issues.
So there are a number of things you are missing here.

First of all, ISP has absolutely nothing to do with mass of the engine itself. It depends on the exhaust velocity of the propellant. The higher the exhaust velocity the more ISP you get regardless of the engine size.

Secondly even if the nuclear powered rocket engine was 10 times are large as its chemical counterpart it would still be significantly better for the high delta-v transfers. Trips to the moon or Mars and back will require significant velocity changes. Higher ISP rockets are going to be useful for these missions.

Thirdly in space who cares about radiation. It already has tonnes of radiation. Thus who cares about radioactive exhaust, or radiation from the reactor. The reactor could just run open core. The only concern is for the crew, which can be solved by doing things like placing the fuel tank between the reactor and the crew compartment just like in regular rockets. Then again the crew has to be protect from the substantial amount of space radiation as well.
NTR are not 10 times better than chemical. More like twice as efficient in terms of ISP but slightly less thrust than chemical.
I know that ISP has nothing to do with the mass of the rocket but two other things do. Thrust to weight ratio and dry mass.

A NTR could in theory take an equal mass to the moon as a chemical one but with about half the propellant. However when you use the rocket equation you have to count the dry mass of the rocket . This is where the performance hit occurs. The mass of shielding and the mass of the reactor are much higher than the mass of the fuel tanks and engines of the chemical rocket.

In the real world this means that the nuclear rocket needs more propellant to account for this mass than a chemical one. This is what I mean by performance hit and this is why lightweight nuclear reactors and shielding is important for both NTR and NEP.
A similar thing happens in the case of chemical rockets. LOX/Hydrogen is in theory gives better performance than LOX/Kerosene and Hypergolics. In reality LoX/Hydrogen is better but not by as much as you would expect by ISP alone. The density of Kerosene and of hypergolic means that a tank that hold an equal amount(in terms of energy) is smaller and masses less than the one needed for hydrogen. Additionally the mass of the insulation needed to keep the Hydrogen cold counts against it.

Thrust to weight ratio is another thing to consider. In the case of NTR it is similar but less than a chemical rocket which causes greater gravity losses than a chemical one. Again requiring a bit more propellant.

In terms of lunar travel, a NTR would take 4 days to make the trip as opposed to a chemical one that would take 3 days due to lower thrust. While not horrific the edge would go to chemical. NTR could be better for large cargo. When it comes to in space travel with people the faster trip time is usually better.

In terms of mars travel an NTR makes more sense. It could get there a month or two faster than a chemical rocket because it could accelerate for a longer period of time.

The other hassle is the radioactive exhaust. While there are trajectories that can be used to prevent radioactive exhaust coming back to earth the fact that you need to worry about stuff like this is an hassle. Not counting the expense of a nuclear reactor and so on.

Honestly when it comes to mars chemical, NTR, and electric propulsion are all valid ways to get there. I prefer NEP because it offers hope that you can learn to reuse the spacecraft although I do know that after such a trip the reactor might need to be replaced.
 
D

DarkenedOne

Guest
pathfinder_01":16bdg36k said:
DarkenedOne":16bdg36k said:
So there are a number of things you are missing here.

First of all, ISP has absolutely nothing to do with mass of the engine itself. It depends on the exhaust velocity of the propellant. The higher the exhaust velocity the more ISP you get regardless of the engine size.

Secondly even if the nuclear powered rocket engine was 10 times are large as its chemical counterpart it would still be significantly better for the high delta-v transfers. Trips to the moon or Mars and back will require significant velocity changes. Higher ISP rockets are going to be useful for these missions.

Thirdly in space who cares about radiation. It already has tonnes of radiation. Thus who cares about radioactive exhaust, or radiation from the reactor. The reactor could just run open core. The only concern is for the crew, which can be solved by doing things like placing the fuel tank between the reactor and the crew compartment just like in regular rockets. Then again the crew has to be protect from the substantial amount of space radiation as well.
NTR are not 10 times better than chemical. More like twice as efficient in terms of ISP but slightly less thrust than chemical.
I know that ISP has nothing to do with the mass of the rocket but two other things do. Thrust to weight ratio and dry mass.

A NTR could in theory take an equal mass to the moon as a chemical one but with about half the propellant. However when you use the rocket equation you have to count the dry mass of the rocket . This is where the performance hit occurs. The mass of shielding and the mass of the reactor are much higher than the mass of the fuel tanks and engines of the chemical rocket.

In the real world this means that the nuclear rocket needs more propellant to account for this mass than a chemical one. This is what I mean by performance hit and this is why lightweight nuclear reactors and shielding is important for both NTR and NEP.
A similar thing happens in the case of chemical rockets. LOX/Hydrogen is in theory gives better performance than LOX/Kerosene and Hypergolics. In reality LoX/Hydrogen is better but not by as much as you would expect by ISP alone. The density of Kerosene and of hypergolic means that a tank that hold an equal amount(in terms of energy) is smaller and masses less than the one needed for hydrogen. Additionally the mass of the insulation needed to keep the Hydrogen cold counts against it.

Thrust to weight ratio is another thing to consider. In the case of NTR it is similar but less than a chemical rocket which causes greater gravity losses than a chemical one. Again requiring a bit more propellant.

In terms of lunar travel, a NTR would take 4 days to make the trip as opposed to a chemical one that would take 3 days due to lower thrust. While not horrific the edge would go to chemical. NTR could be better for large cargo. When it comes to in space travel with people the faster trip time is usually better.

In terms of mars travel an NTR makes more sense. It could get there a month or two faster than a chemical rocket because it could accelerate for a longer period of time.

The other hassle is the radioactive exhaust. While there are trajectories that can be used to prevent radioactive exhaust coming back to earth the fact that you need to worry about stuff like this is an hassle. Not counting the expense of a nuclear reactor and so on.

Honestly when it comes to mars chemical, NTR, and electric propulsion are all valid ways to get there. I prefer NEP because it offers hope that you can learn to reuse the spacecraft although I do know that after such a trip the reactor might need to be replaced.
First of all it is like I said before for high delta-v transfers the higher impulse will always win out. Let just do a few calculations to demonstrate this fact.

For reference the rocket equation is V_final = V_exhaust x ln(mass_initial / mass_final)

Alright lets consider the 3rd stage of the Saturn V rocket. It had a total mass of 120,000 kg and a dry mass of 14700 kg with a 1438 kg J-2 engine. Alright for the sake of the argument lets just assume that the nuclear rocket is 10 times more massive than the J-2. That would make a nuclear powered version of the vehicle have a dry weight of appox. 28000 kg.

Now notice already that despite the fact that the nuclear rocket's mass is 10 times greater than the J-2 it only doubles the dry mass of the spacecraft. Of course its effect on the total mass of the spacecraft is even less. It brings the total mass up to 133,000 kg.

Plugging these number into the rocket equation reveals that the nuclear version would be capable of a delta-v of 13.5 km/s. Compare that to the regular versions 8923 km/s. So we can clearly see that despite its larger size the higher ISP wins out in the end.

Now lets see how massive the nuclear version would have to be to transport the same dry cargo to the chemical versions 8,923 km/s. Using the equation again we find that the nuclear version would have a initial mass of 94,000 kg. So even more lunar travel the nuclear version is significantly smaller despite its much more massive engine.

Of course there is another point you should consider when judging nuclear vs. chemical rockets. Chemical rockets have pretty much reached the end of the line. There are not much room for improvement in this area. The J-2 was capable of of a 425 ISP. The shuttle is capable of around 450 ISP. Beyond that in the last 40 years there has not been any major improvements in specific impulse. They have met their fundamental limitation. The chemical reactions simply cannot provide more energy for greater exhaust velocity. Chemical rockets of the future will probably be lighter, more reliable, more affordable, more powerful, and longer lasting, but physics tells us there will be no significant gains in specific impulse.

On the other hand the first prototypes of nuclear rockets were able to achieve an ISP double that of the best of chemical. That was just the first generation achieved with 1960 technology. We can only imagine what they would be capable of todays engineering, technology, and materials. Of course the fundamental limitations of nuclear power are far higher than chemical. Nuclear power is able to deliver something like 10 million times more energy per unit of mass than chemical. There is immensely more potential in thermal nuclear rockets than in chemical rockets.
 
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