New Mars Forums

Tom Kalbfus

Banned

Registered: 2006-08-16

Posts: 4,401

Re: Ares and Ares

NASA's proposed Ares rocket bears some resemblence to Zubrin's Mars Direct Ares Vehicle proposed in his book the Case for Mars. Just how suitable would NASA's Ares Rocket be in launching a Mars Direct Mission, and also what are the differences between the two vehicles?

GCNRevenger

Member

From: Earth

Registered: 2003-10-14

Posts: 6,056

Re: Ares and Ares

There is little practical difference, they both have much the same capabilities. Zubrin's rocket calls for four SSME engines in a side-mounted pod plus the single-segment ASRM boosters. The upper stage on Zubrin's rocket calls for a single SSME class engine too. The NASA Ares-V uses upgraded five-segment versions of the Shuttle boosters and uses five RS-68 engines on the bottom of a wider 10m tank. The upper stage uses a single less powerful J-2X engine.

Neither rocket is really powerful enough without nuclear engines to go directly to Mars.

---

[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

RobertDyck

Moderator

From: Winnipeg, Canada

Registered: 2002-08-20

Posts: 7,807

Website

Re: Ares and Ares

A nuclear engine is nice, it increases mass delivered to Mars for a given launch vehicle, but it's not required. The Mars Direct architecture calls for a chemical upper stage which when empty acts as a counter weight for artificial gravity.

GCNRevenger

Member

From: Earth

Registered: 2003-10-14

Posts: 6,056

Re: Ares and Ares

Yes, it changes it from "Bob Zubrin is nuts" to "cut off toothbrush handles so we make it off the ground"... which is why I think Zubrin secretly doesn't believe in the chemical option for single-launch direct flight to Mars. He is a nuclear engineer by trade after all.

No reason you can't use a nuclear stage for the artifical gravity counterweight, the separation distance would be sufficent to limit radiation exposure probably.

The trouble is that a nuclear Ares would have to activate the reactor before reaching a stable orbit, which even me the nuclear fan boy (the "N" in GCNR) believe is a bad idea.

---

[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

publiusr

Banned

From: Alabama

Registered: 2005-02-24

Posts: 682

Re: Ares and Ares

Chemical is good.

Some nice images:

http://www.nasa.gov/pdf/151420main_aresV_factsheet.pdf
http://www.astronautix.com/lvs/magnum.htm

other options?
http://forum.nasaspaceflight.com/forums … 5&start=76
http://forum.nasaspaceflight.com/forums … ntid=10222
http://forum.nasaspaceflight.com/forums … entid=9638
http://forum.nasaspaceflight.com/forums … ntid=10621
http://forum.nasaspaceflight.com/forums … ntid=10617
http://forum.nasaspaceflight.com/forums … ntid=10582
http://forum.nasaspaceflight.com/forums … ntid=10583  HLLV paths
http://forum.nasaspaceflight.com/forums … 5&start=61
http://forum.nasaspaceflight.com/forums … 25&start=1
http://forum.nasaspaceflight.com/forums … &start=121
http://forum.nasaspaceflight.com/forums … 37&start=1
http://forum.nasaspaceflight.com/forums … &start=106
http://forum.nasaspaceflight.com/forums … ntid=10708 Missions
http://forum.nasaspaceflight.com/forums … entid=9668
http://forum.nasaspaceflight.com/forums … entid=9778
http://forum.nasaspaceflight.com/forums … 17&start=1
http://forum.nasaspaceflight.com/forums … =5&start=1

From http://forum.nasaspaceflight.com/forums … 45&start=1
http://simcosmos.planetaclix.pt/

Space Vehicles: A History in Patents
http://www.dataviewbooks.com/sapcecover.jpg
http://www.dataviewbooks.com/space-a.jpg
http://www.dataviewbooks.com/space-b.jpg
http://www.dataviewbooks.com/space-c.jpg

Over 260 pages of spacecraft designs from US government patent documents.

http://forum.nasaspaceflight.com/forums … entid=6541
http://forum.nasaspaceflight.com/forums … 6&posts=52

publiusr

Banned

From: Alabama

Registered: 2005-02-24

Posts: 682

Re: Ares and Ares

What the Russians are talking about:

http://www.novosti-kosmonavtiki.ru/cont … 3/30.shtml
http://www.novosti-kosmonavtiki.ru/phpB … &start=990

Buran
http://www.novosti-kosmonavtiki.ru/phpB … &start=825
http://www.buran.ru/htm/os-120.htm

http://www.novosti-kosmonavtiki.ru/
http://www.cosmoworld.ru/eng/nk-online/
http://www.roscosmos.ru/

Tom Kalbfus

Banned

Registered: 2006-08-16

Posts: 4,401

Re: Ares and Ares

Yes, it changes it from "Bob Zubrin is nuts" to "cut off toothbrush handles so we make it off the ground"... which is why I think Zubrin secretly doesn't believe in the chemical option for single-launch direct flight to Mars. He is a nuclear engineer by trade after all.

No reason you can't use a nuclear stage for the artifical gravity counterweight, the separation distance would be sufficent to limit radiation exposure probably.

The trouble is that a nuclear Ares would have to activate the reactor before reaching a stable orbit, which even me the nuclear fan boy (the "N" in GCNR) believe is a bad idea.

Why space is space. Scaled Composites reached space without reaching orbit. What if we had a chemical booster with a nuclear upper stage? The bottom booster could fall back into the atmosphere and be recovered for later use, just like Space Ship One was. The upper nuclear stage can then reach orbit, but the larger more expensive portion of the launch system could be made reusable. The upper nuke stage is only a problem if it fails and doesn't reach orbit, so if we design it properly, it won't fail most of the time. The reaction mass would be hydrogen with a higher specific impulse. If Iran can have nuclear reactors and the World gives its assent to that, which apparenly does, who can object to nuclear rockety which is much safer than an Iranian fanatic with a nuclear weapon?

There are alot of things that damage the environment alot more than a nuclear rocket would. the exhaust from the Shuttles SRBs is not healthy after all, is the reason that its unhealthy being chemical rather than radioactive all that consequential. I hear that doctors used to prescribe mercury to their patients, they'd swallow some mercury and it would go right down their digestive track, well most of it anyway. Compared to that, I think the rocket exhaust of a nuclear rocket released in space is less dangerous than a spoonful of mercury swallowed by a single patient.

dicktice

Member

From: Nova Scotia, Canada

Registered: 2002-11-01

Posts: 1,764

Re: Ares and Ares

Just what, exactly, is this "nuclear rocket" that you are epousing?

Tom Kalbfus

Banned

Registered: 2006-08-16

Posts: 4,401

Re: Ares and Ares

Just what, exactly, is this "nuclear rocket" that you are epousing?

An upper stage rocket that heats hydrogen as a propellant above the Earth's Atmosphere. So long as the thrust is high enough, it can take the space ship the rest of the way to orbit. It goes like this. You have a lower stage that uses some cheap easy to handle rocket fuel to thrust the Vehicle above the atmosphere and then a nuclear Nerva rocket takes over. The real danger is concentrated radioactives, the higher the nuclear engine is when it first goes on, the more dispersesd the propellent is, and were talking about hydrogen here, even the heavier more radioactive isotopes will tend to stay on top of the atmosphere. I'm interested in any way to make space flight cheaper. if someone just has a knee-jerk reaction that "if its nuclear, it must be bad," that is rather unfortunate and it makes people not consider the possibilities or even try to fix the problems they have with the concept, while currently were are doing worse things to Earth's environment than nuclear rockets would have done. There are many ways a substance can be harmful to the environment, radioactivity is just one of them.

GCNRevenger

Member

From: Earth

Registered: 2003-10-14

Posts: 6,056

Re: Ares and Ares

Bob Zubrin knows that his plan is borderline even by his stanards, and so he has proposed a modified version of Ares with a different upper stage, trading the single SSME class engine for a single J-2 sized nuclear rocket. This would make MarsDirect practical and put it over the threshold from "nuts."

The problem is that this has to be a pretty big nuclear engine, and it won't be in orbit before the reactor is brought critical and starts producing radiation & radioactive waste. The exhaust is pretty trivial, but even a small chance that it could come back down is a risk I am not willing to take. It won't fail "most" of the time, but even once is too many, resulting in either a hypersonic radiation bomb that could fall anywhere around the Earth's equator, or a cloud of radioactive fallout of the same scale as Chernobyl. So long as the engine is below orbital or escape velocity, it or its remains will fall back down before the nuclear material decays to safe levels.

The added performance, and the high cost with developing a large nuclear engine is not worth it. The engine that would be equipped would only increase payload by ~50%, so instead it would be better to make the launch vehicle larger. It probably wouldn't cost much more.

"who can object to nuclear rockety which is much safer than an Iranian fanatic with a nuclear weapon?"

This is nonsense babbling, genocidal theocrats in Iran has nothing to do with spaceflight and its risks.

---

[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

John Creighton

Member

From: Nova Scotia, Canada

Registered: 2001-09-04

Posts: 2,401

Website

Re: Ares and Ares

If the rocket fails can you just shut the reactor down? Wasn’t the biggest problem with Chernobyl that it didn’t shut down and still hasn’t. Is there away to limit the amount of radioactive fuel used until escape velocity is reached? Maybe some kind of fuel injection system.

---

Dig into the [url=http://child-civilization.blogspot.com/2006/12/political-grab-bag.html]political grab bag[/url] at [url=http://child-civilization.blogspot.com/]Child Civilization[/url]

Tom Kalbfus

Banned

Registered: 2006-08-16

Posts: 4,401

Re: Ares and Ares

Bob Zubrin knows that his plan is borderline even by his stanards, and so he has proposed a modified version of Ares with a different upper stage, trading the single SSME class engine for a single J-2 sized nuclear rocket. This would make MarsDirect practical and put it over the threshold from "nuts."

The problem is that this has to be a pretty big nuclear engine, and it won't be in orbit before the reactor is brought critical and starts producing radiation & radioactive waste. The exhaust is pretty trivial, but even a small chance that it could come back down is a risk I am not willing to take. It won't fail "most" of the time, but even once is too many, resulting in either a hypersonic radiation bomb that could fall anywhere around the Earth's equator, or a cloud of radioactive fallout of the same scale as Chernobyl. So long as the engine is below orbital or escape velocity, it or its remains will fall back down before the nuclear material decays to safe levels.

The added performance, and the high cost with developing a large nuclear engine is not worth it. The engine that would be equipped would only increase payload by ~50%, so instead it would be better to make the launch vehicle larger. It probably wouldn't cost much more.

"who can object to nuclear rockety which is much safer than an Iranian fanatic with a nuclear weapon?"

This is nonsense babbling, genocidal theocrats in Iran has nothing to do with spaceflight and its risks.

Demanding 100% safety all the time is what keeps us on Earth. Do you want to avoid all nuclear accidents, or do you want to get humans off Earth and spread our risks? I think the risk of nuclear accident is over avoided putting us in danger of other risks such as all of us being wiped out by nuclear war and none of us surviving the attack  as we were too busy trying to avoid nuclear accidents in getting off Earth and so we stayed all on one planet, vulnerable.

Do rockets typically launch over populated areas?

You seem to be assuming that  a failed nuclear rocket would always fall in a densely populated area dropping nice solid chunks of concentrated plutonium so as to make the area uninhabitable and forcing its evacuation. the Pacific ocean is not very populated. The Atlantic is even less so. A nuclear launcher can always be rigged sith exploses so any fallout won't come down in a concentrated mass. Instead of banning nuclear launches to avoid nuclear accidents, why not design the nuclear rockets so that accidents are less likely to happen and if accidents happen plan the flight trajectory so that the rockets don't overfly populated areas.

The best strategy is to launch over an ocean and quickly attain orbital velocity and failing to do this on schedule, blow up the rocket so that it lands in unpopulated areas. Shouldn't be hard to do, we have reliable bombs.

GCNRevenger

Member

From: Earth

Registered: 2003-10-14

Posts: 6,056

Re: Ares and Ares

No, this risk is much more dangerous than you know, that this really would produce fallout comperable to Chernobyl if not worse thanks to the rapid fuel burnup. Even if you sucessfully shut down the reactor, the nuclear waste built up during its operation will remain extremely deadly for some years.

Blowing up the reactor over the Atlantic and dropping it into the ocean is a non-solution, since the remaining radioactive dust will remain in the atmosphere and the winds will blow it all over the place. Nuclear fuel is always a ceramic, which if blown up will shatter. Chernobyl's cloud extended for hundreds of miles, this could be even worse with a high altitude failure.

Strapping bombs to the reactor is not going to work either, the temperature and radiation flux right up against the core pressure vessel will be too severe to trust a chemical explosive. The radiation will fry electronics and actually break down organics (which explosives generally are).

Especially concerning nuclear technology, you must weigh the bennefits versus the risks, in this case you get a trans-atlantic fallout cloud comperable to the worst radiation disaster ever assuming the bombs work, or a radiation missile that could fall anywhere around the globe if they don't, even if the reactor does shut down. And this is assuming that the reactor stays in one piece if it fails, instead of just blowing up anyway, maybe off the coast of Florida.

And the bennefit? About a 50% increase in payload but a much much higher development and per-unit cost due to the relatively large nuclear engine required. 50% with higher rocket costs isn't worth it, forget this, just make a bigger chemical rocket. It probably won't cost any more and you get the same performance. Bob just made his rocket too small to begin with so we could shave a few years and a few billion off the plan, or at least the one he presents to the public, since swapping the Ares chemical upper with a nuclear one would erase the savings.

You see, Bob lied to the public with his MarsDirect plan, it will never work with the chemical engine... but as long as Congress is duped and orders NASA to do it, then the impracticality of the regular chemical Ares will not be addressed until it can't be ignored, which will be some time after the project is started. Then Bob will pretend to be all sorry that he has led NASA astray, but low and behold he has a solution to fix everything! ...The big nuclear engine.

---

[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

RobertDyck

Moderator

From: Winnipeg, Canada

Registered: 2002-08-20

Posts: 7,807

Website

Re: Ares and Ares

NERVA was a nuclear reactor that ran liquid hydrogen through it. Exhaust velocity determines specific impulse, the 1960s NERVA has an Isp of 800 seconds. The space shuttle main engine has 453 seconds; requirements were 455 seconds in vacuum but it never achieved that. In 1974 NERVA achieved 825 seconds, tested at Jackass Flats where nuclear bombs were tested. An upgraded NERVA in the late 1980s would have achieved 925 seconds, but was never built. However, Timberwind had an Isp of 1000 seconds and much lower engine mass. The Air Force worked on it in 1990, but nuclear protestors got the project killed. Timberwind 75 had a thrust of 735,500 kN and engine mass of 2,500 kg, while the last verion of NERVA had 333,400 kN and massed 8,500 kg. That's a dramatic difference but Timberwind could not be restarted. It was a pebble bed reactor and the pebbles would melt together so it was for short thrust duration and non-restartable.

John Creighton

Member

From: Nova Scotia, Canada

Registered: 2001-09-04

Posts: 2,401

Website

Re: Ares and Ares

What are the failure modes in these nuclear rockets? Most launch problems I know of have occurred on or near the launch pad. Can we wait before starting the reactor to make sure the propellant is properly flowing though it? What level of diagnostics can be done before starting the reactor? What level of redundancy is required to avoid a spurious start of the reactor? What are the risks after a proper start? Or is it the main fear of the unknown risks?

---

Dig into the [url=http://child-civilization.blogspot.com/2006/12/political-grab-bag.html]political grab bag[/url] at [url=http://child-civilization.blogspot.com/]Child Civilization[/url]

GCNRevenger

Member

From: Earth

Registered: 2003-10-14

Posts: 6,056

Re: Ares and Ares

What are the failure modes in these nuclear rockets? Most launch problems I know of have occurred on or near the launch pad. Can we wait before starting the reactor to make sure the propellant is properly flowing though it? What level of diagnostics can be done before starting the reactor? What level of redundancy is required to avoid a spurious start of the reactor? What are the risks after a proper start? Or is it the main fear of the unknown risks?

No no, there is no way to make such an engine "safe enough" to be worth the risk and extra cost. Rocket engines, particularly of this type, operate at such extreme conditions that everything done to improve them will be nickle and dime. The engine does improve performance substantially, but not radically, and greatly increases the cost. Small nuclear engines that are easy to develop and fired in orbit only, sure I am fine with those, but not big ones as upper stages.

For goodness sakes, don't fool with a big expensive nuke engine, spend the money on a bigger launch vehicle instead and you get nearly comperable performance without the risks I bet.

---

[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

RobertDyck

Moderator

From: Winnipeg, Canada

Registered: 2002-08-20

Posts: 7,807

Website

Re: Ares and Ares

The reference mission for a nuclear engine is an upper stage to go from Earth orbit to trans-Mars insertion. Radiation from uranium is so low it can be easily dismissed. I keep referring to a video I saw on TVO, TV Ontario, the equivalent to PBS. The video was produced by Ontario Hydro and showed workers loading uranium in fuel rods but stuffing yellow cake (uranium oxide powder) into stainless steel tubes with their fingers. They wore the same plastic gloves you get with oven cleaner, a paper filter mask, shower cap over their hair, and a white lab coat. I saw the video in the late 1980s, and I don't know how old the video was at that time. They probably don't do that today, but the point is simple precautions are all you need with uranium. The catch is that's what it's like before it goes into the reactor, when the fuel rods come out the uranium has been split. Fission fragments are highly radioactive. Ontario Hydro uses a robot to pull fuel rods out of the reactor, the room has concrete walls several feet thick, and the rods are placed into a pool of water. No one is in the same room as the rods when they come out.

So the reference mission launches the reactor cold, it has never been turned on so the radiation is very mild. Nerva embedded uranium in ceramic; it wasn't even a capsule, the uranium was mixed with material for the ceramic before the ceramic was hardened. If a ceramic fuel capsule breaks, you just get a different face of the ceramic. If the rocket fails all you need is someone with the same oven cleaner plastic gloves, a paper filter mask, rubber boots, and a pair of BBQ tongs to pick up the fuel elements. Put them in a plastic garbage bag, just don't pick up too many at once. Enough fuel elements in the same bag could achieve fission, creating radiation. The crash site wouldn't be any more dangerous than an airplane crash. Again the key thing is not turning the reactor on until after safely inserted into orbit.

Once in orbit, radioactive exhaust in space would be like adding a tea spoon of water to the ocean. Radiation from solar wind and cosmic radiation is far more than exhaust from one rocket. Just ensure the hot reactor doesn't crash onto Earth's surface.

If you want to use a nuclear thermal upper stage, the Bush administration is the time to do it. He doesn't care about nuclear activists. Previous presidents wouldn't consider nuclear propulsion, no matter how safe.

John Creighton

Member

From: Nova Scotia, Canada

Registered: 2001-09-04

Posts: 2,401

Website

Re: Ares and Ares

I think GCNRevenger is talking about the scenario where the rocket fails once the reactor is turned on. In which case you can’t use plastic gloves of course not that it matters much if you are going down with the ship. I don’t know enough about these type of rockets to know how likely the scenario is, and what safe guards can be put in place. It is interesting though that GCNReveneger refers to a radio active cloud as big as Chernobyl. I don’t think the space engine would use as much fuel as Chernobyl (just a hunch) but I guess it would burn it hotter. How do the radiation levels compare? I am not sure but if it is burning hotter it should decay faster. I wonder how much the radioactive dust would decay by the time it reached the ground. Also if the radio active material was spread widely enough would it contribute significantly at all to the background radiation? I think the worse case scenario is if the rocket falls in one piece most of the way down but blows up right over a city. I wonder what the odds are of it falling in a major population area. I know 2/3’s of the world is ocean. That has to add somewhat to the factor of safety.

---

Dig into the [url=http://child-civilization.blogspot.com/2006/12/political-grab-bag.html]political grab bag[/url] at [url=http://child-civilization.blogspot.com/]Child Civilization[/url]

GCNRevenger

Member

From: Earth

Registered: 2003-10-14

Posts: 6,056

Re: Ares and Ares

Of course I am talking about only after reactor startup, if the engine would actually fail, the core is about as dangerous as steel drum full of dirt before startup.

Nuclear rockets are designed to "burn" as much of their Uranium fuel as possible in as short a time as possible, to minimize the amount of Uranium and the size of the core you need, producing large amounts of radioactive waste quickly. When Uranium undergoes nuclear fission, it doesn't just vanish, it splits into two smaller atoms. These atoms many orders of magnetude more radioactive than Uranium, and can cause death almost immediatly if you were anywhere near the thing.

These atoms don't go away for months or years, so even if you turned the reactor off sucessfully and stopped the fission chain reaction, the core's contents will still be extremely deadly for a long time.

Edit: to put things in a little more prespective, late model NERVA reactors produced several gigawatts of power, more than even the largest power plant reactors today. Large Timberwind models would have been loaded with 800kg of weapons-grade enriched Uranium, which is of the same scale of power reactors with their low-enriched fuel.

---

[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

Tom Kalbfus

Banned

Registered: 2006-08-16

Posts: 4,401

Re: Ares and Ares

No, this risk is much more dangerous than you know, that this really would produce fallout comperable to Chernobyl if not worse thanks to the rapid fuel burnup. Even if you sucessfully shut down the reactor, the nuclear waste built up during its operation will remain extremely deadly for some years.

Blowing up the reactor over the Atlantic and dropping it into the ocean is a non-solution, since the remaining radioactive dust will remain in the atmosphere and the winds will blow it all over the place. Nuclear fuel is always a ceramic, which if blown up will shatter. Chernobyl's cloud extended for hundreds of miles, this could be even worse with a high altitude failure.

What exactly will be contaminated if it blows up over the ocean? The Ocean?
Chernobyl was on land near a populated area. I think the worst parts of the fallout zone we're where the radioactive fallout wasn't dispersed so much, especially where it rained. Lets suppose it rains over the ocean, causing the fallout to drop out of the air and into the water. Well the water will disperse and dilute the contaminants.

Lets now suppose the winds disperses the radioactive fallout over a wider area, that's less contamination per unit area over the effective area which are mostly thousands of miles of ocean. By the time the remaing fallout reaches land there will be much less of the stuff to go around. Life will go on as usual, and it won't be Doomsday just because of this rocket accident.

I think the attitude toward nuclear rocketry is excessively cautious. What if the Chinese are not as cautious as we are and jump ahead in the space race by building nuclear upper stages to boost their craft into orbit? That's a 50% increase in payload capability is one way of looking at it, but consider this. If the bottom stage is not moving at high velocities when it reeneters the atmosphere, it becomes easier to recover this booster and use it again. The Chinese could build a resuable bottom stage rocket booster whose only job is the lift the nuclear stage above the atmosphere and then fall back to Earth. If that stage has wings or a parachute, the Chinese can recover it and use it for the next launch. The Chinese could develop a safer more reliable bottom stage, it could even be a solid rocket booster with no cryonic propellents at all, and no plumbing, simply ignite the rocket, the rocket delivers its payload, and then the nuclear rocket ignites. The Chinese government is sort of immune to criticism from anti-nuke groups just as they were immune to the pro-democracy protestors in 1989, if they cause too much of a fuss, they end up in jail. Besides if the Chinese were so concerned about the World environment, they wouldn't be helping out the Iranians or letting North Korea get the bomb. Even more dangerous than a nuclear rocket which may fail is a nuclear bomb in the hands of a fanatic, but no one in the Communist government considers these environmental risks, so why should they concern themselves with the effects of nuclear rocketry. Seems like we'd have to build much more massive chemical rockets and spend alot more money in order to compete with a Chinese nuclear rocket program to send men to Mars. Zubrin justs spoke in China. I think China might be willing to take more risks to get ahead than NASA might. Nuclear rocketry is tempting, the consequences of failure for the Chinese are less. Lose a few astronauts, they go on, evacuate a village or town, they go on, no one dares criticise the Chinese government while in China.

GCNRevenger

Member

From: Earth

Registered: 2003-10-14

Posts: 6,056

Re: Ares and Ares

But you can't guarantee that it won't come down or blow up over a populated area, and the Chernobyl cloud did pose a health risk for people dozens or perhaps hundreds of kilometers from the facility due to fine powder dispursed in the wind. Just because it is over water is irrelivent, the world's first nuclear space accident, where an early Plutonium fueled burned up over the Pacific, the fallout persisted for some time. The hyper-radioactive byproducts from nuclear fission are also taken up by living systems to some degree, posing a longer term concern too, on land or water.

No it won't be doomsday, the risk will either be small for a large number of people or high for a small number, but ultimately neither is a good thing. Another thing to consider is proliferation risk, that this thing will be fueled by bomb-grade Uranium. What if the reactor fails to start up and lands intact over a hostile country? There would be more than enough fuel in the engine to build several bombs.

And for what? A 50% increase in payload but at the literal cost of a much more expensive rocket. Why not just make the rocket bigger in the first place? If it were 500% instead of 50% then the nuclear option could be much harder to argue against, but the increase in payload is modest and not revolutionary. Take Ares-V for instance, instead of spending several billion to develop the engine and another several hundred million a copy versus J-2, why not instead add an additional pair of boosters and swap out the five RS-68s for RS-84s or seven expendable SSMEs and the same instead of J-2. It would have similar payload, similar development cost (if not a bit less), and similar per flight cost.

The bennefit of solid-core nuclear engines is not that great for launch vehicles or vehicles that use aerobraking. There is no technical/logistical reason to bother with large nuclear engines for launch vehicles, and then you have the political cost of the controversy that will inevitibly surround it.

Making a vehicle where you just toss a nuclear upper stage above the atmosphere makes little sense: to enter orbit, you need ground speed, not altitude. Altitude, as far as orbital mechanics goes, is totally irrelivent. This is why Shuttle or Saturn nose-over and curve away from vertical as soon as they clear the pad, altitude does not determine if you are in orbit or not, speed is everything. If you had a rocket with infinite thrust and zero drag, you could infact launch horizontally and enter orbit. From a safety standpoint, it matters little if you are at 100,000ft or 200,000ft, so long as the reactor is not at orbital or escape velocity, it is going to come back down.

You can't make the lower stage too small, the thrust of nuclear engines is relatively poor without their size, mass, cost, and risk getting out of hand. Actually the higher the efficiency of a given engine, the harder it is to produce a given amount of thrust. Using a nuclear engine doesn't change the fact you need a powerful first stage.

You also can't make a rocket with a totally dumb first stage, so long as the rocket is pushed from the end it will have to have thrust vectoring and/or verneer thrusters, some sort of guidence system, and power to operate it. If not, when you nose-over to arc around the Earth, the nose will keep getting pulled until you point straight down. Boom.

By the way, did you know that China is moving very fast tward ruining their environment as bad or worse than Stalinist Russia to maintain their economic overload? Or that it is said there were several thousands of protests, perhaps riots, throughout the country last year? Of couse, the Chinese media isn't allowed to report them. China can't ignore their own people forever.

---

[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

dicktice

Member

From: Nova Scotia, Canada

Registered: 2002-11-01

Posts: 1,764

Re: Ares and Ares

Gosh, I'm glad I asked what a nuclear rocket was. Now that I know enough to have an opinion, I wish to remind all and sundry that we're no talking about just one experimental, fail-safe-as-possible rocket launch. Lots and lots of launchings, once space exploration opens up--and not only governmentally regulated ones either.

And, how far up does the atmosphere, not to mention the ionosphere, "end." I can remember when the distribution of radioactive dust (or whatever, I'm too busy to look it up just now) in the upper atmosphere, surprised scientists by how long lasting the damage (to what, communications?) lasted.

On the other hand, must the hydrogen become ionized, since it's only the propulsive medium?

So, just to offer something other than objections, I'll go out on a limb and suggest that a special, reactor-assembly space station be placed up in Medium Earth Orbit where the, until then, relative innocuous components for the booster stage are collected, and then put together (by te be defined methods) to complete the nuclear engine, etc.--which when mated wtih the rest of the Mars expedition vehicle (say) and follow-on expedition vehicles, only would become critical out there beyond any possibility (?) of uncontrolled reentry, prior to reaching Earth escape velocity.

GCNRevenger

Member

From: Earth

Registered: 2003-10-14

Posts: 6,056

Re: Ares and Ares

Oh private industry would never be allowed to use the engine for private uses, or at least very strict government oversight, if for no other reason the requirement for bomb-grade Uranium.

How far up the reactor is if it blows up doesn't change the fact that the remaining bits are going to fall back down. Even at orbital altitude, reentry would occur within minutes or hours most likely if the rocket does not attain orbital velocity. Actually at very high altitudes, the remaining pieces of the core would be more likely, not less, to form the dust since the fragments would burn up. It doesn't matter if the fuel is burned, it will just float around as Oxides instead, still just as radioactive.

The ionization of the Hydrogen is short-lived and not at all a radiation problem. It does, however, corrode almost anything which is why the cores are difficult (and expensive) to build plus restartable ones are quite heavy.

We don't need to assemble reactors in space, on a space station or otherwise, since the fresh Uranium fuel is not appreciably radioactive. Only after the core is started up for the first time does it become dangerous. It is fine by me to launch the completed core into a stable orbit before startup, but by no means until we are sure it is not going to reenter if the rocket fails.

---

[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

Tom Kalbfus

Banned

Registered: 2006-08-16

Posts: 4,401

Re: Ares and Ares

Another possible short cut is Orion. The Chinese have nuclear bombs, they have access to all the declassified materials for the old Orion project in the 1960s and perhaps some classified ones as well. I don't think the Orion spaceship counts as a solid core nuclear rocket. The capabilities of that old Orion design were computed to be quite fantastic. If China wants to jump ahead of us in the race to Mars, they might build an Orion. Would their people object? Perhaps if their was an accident, if not, the Chinese are very patriotic, they'd be happy about China beating the US to Mars. Orions can be lifted above the atmosphere with a lower stage and then the bombs go off underneath it. If the UN objects, then China will simply use its veto and stymie the Security Council just as it has in the past with North Korea and Iran. Yes, China may eventually have to listen to its people, but who knows when that will be. If Chinese people die in a nuclear accident then they will die just like they had in Chernoble. Despite Chernoble, it seems that the Ukraine still has a loyal contingent of Russophiles who were opposed to seperation from Russia and Ukrainian Independence. Large numbers of Ukrainians are opposed to closer ties with NATO despite what Russia did to them. That says alot about a societies ability to recover from a nuclear accident, especially a totalitarian one. They paper over all those cancer deaths with propaganda and most people forget about it, i don't see why China couldn't do the same.

Orion is a bit more controversial and it flouts international law, by exploding atomics in space. International law has yet to stop the North Koreans, or the Iranians. If the UN has no teeth, as China and Russia has pulled them, then we can't dismiss the possibility of China using a nuclear solution to get into space while our public only permits us to use chemical rockets, that means China wins!

John Creighton

Member

From: Nova Scotia, Canada

Registered: 2001-09-04

Posts: 2,401

Website

Re: Ares and Ares

I like Orion better because the performance gains are much more significant. However, it is by no means a short cut. The engineering challenges of building an Orion vehicle of sufficient scale to have a significant economic advantage over chemical rockets is immense.

---

Dig into the [url=http://child-civilization.blogspot.com/2006/12/political-grab-bag.html]political grab bag[/url] at [url=http://child-civilization.blogspot.com/]Child Civilization[/url]