Mars Landings

[amphibulous]

There is a brief reference in Voyage that the nuclear rocket programme predates NASA and was originally intended to produce a nuclear ICBM.

Nuclear rockets give improved ISP at the cost of poor thrust to weight - this is the opposite of what you need for a launcher or ICBM and the problem only gets worse as payload increases.

Ive never come across any other references to it but I assume it was seen as a way of delivering the early and very heavy thermonuclear devices, but once these had become miniaturised to the point where they could be carried on chemical rockets the programme was dropped and then turned over to NASA.

No. The physics wouldn't have been altered for larger payloads.

Of course, this doesn't mean that no one during the Cold War didn't try something stupid...

 

[The Oncoming Storm]

Of course, this doesn't mean that no one during the Cold War didn't try something stupid...

Considering the period of history we're referring to a nuclear ICBM is quite a sane idea!

 

[JamesHunter]

Well the States was massively paronoid at that point people saw communists under the bed, a bomber/ missile gap and Soviet satelites and then men soring over their heads. Of course we know the truth now, that the soviets only had a few missiles and barely any of their most advanced bombers, that they could barely feed their own people and the military budget was already doing their economy all kinds of bad.

Back then though people were scared, and people who are scared do stupid things, like trying to build nuclear ICBM's or for that matter this http://en.wikipedia.org/wiki/Project_Pluto .

After the missile crisis things calmed down a bit, the Americans took the lead in the space race, the soviets became less interested in a direct confrontation, and American had it's own problems with Vietnam. Also post crisis the American people assumed that the soviets had blinked, they didn't know about the deal with the jupiters in turkey, and I think the US government had realised just how deseperate the recent arms race had been making the soviets.

 

[amphibulous]

I found this:

http://large.stanford.edu/courses/2011/ph241/hamerly1/

..My best guess is that people didn't realize the problems with high thrust to weight NTRs and hoped for a lower stage engine. (And a lower stage engine *might* be possible some day - which would be very interesting.)

 

[Workable Goblin]

Yeah, I don't get it either. I assume they thought it would be a lot easier to improve the T/W of NTRs then it turned out to be.

Well, NERVA was only ever intended for in-space usage, so T/W wasn't quite so important as it would have been for a takeoff engine, and of course NERVA was the focus into the 1970s. In theory, injecting oxygen into the exhaust stream, the "LANTR" concept, would increase the T/W quite a bit, but that essentially gives you a hydrolox rocket with a nuclear reactor attached--bit pointless, that.

Really, the only particularly viable usage of an NTR I can see is having a bimodal one, that is one that can also generate electricity, and using it to power electric thrusters. The thermal rocket mode would be used to provide high thrust for certain uses--for instance, boosting into an Earth escape trajectory, where pure electric would require a long spiral-out--but the electric thrusters would be the main thrust mode. Essentially a tradeoff between big thrust but poor efficiency and tiny thrust but very large efficiency. It would also help if you had a hydrogen-electric thruster, but I don't know how viable those are.

 

[amphibulous]

OncomingStorm: Considering the period of history we're referring to a nuclear ICBM is quite a sane idea!

Back then though people were scared, and people who are scared do stupid things, like trying to build nuclear ICBM's or for that matter this http://en.wikipedia.org/wiki/Project_Pluto .

You can laugh at Project Pluto now, but when Cthulhu turns up you'll wish we had the thing.

Also post crisis the American people assumed that the soviets had blinked, they didn't know about the deal with the jupiters in turkey, and I think the US government had realised just how deseperate the recent arms race had been making the soviets.

Most people still don't realize this - and this deal and the false perception it created has placed a huge burden on US foreign policy.

 

[asnys]

Well, NERVA was only ever intended for in-space usage, so T/W wasn't quite so important as it would have been for a takeoff engine, and of course NERVA was the focus into the 1970s. In theory, injecting oxygen into the exhaust stream, the "LANTR" concept, would increase the T/W quite a bit, but that essentially gives you a hydrolox rocket with a nuclear reactor attached--bit pointless, that.

NERVA makes a fair amount of sense to me, if you assume that the US will be going to Mars by 2000 and are a bit optimistic about your technical assumptions for NTRs and a bit pessimistic about electric drives. I meant the whole nuclear-powered ICBM thing, which was by no means limited to ANP's nuclear Atlas - that was just the first pic I had to hand.

I've found some very intriguing documents from the late 80s / early 90s, descendants of TIMBERWIND - I think I've mentioned them to you before - suggesting that the T/W issues of NTRs might have been resolvable if there'd been further development. One version claims to be able to get a 40:1 T/W with a particle-bed reactor and LOX augmentation, and I forget the T/W for non-augmented except that it was more than 1:1 - I want to say 5 or 10:1 but I'm probably misremembering.

That doesn't make it a good idea, of course, and I haven't yet gotten around to really reading through them carefully, so maybe it's bullshit. But atomic rockets are just so cool...

 

[Workable Goblin]

NERVA makes a fair amount of sense to me, if you assume that the US will be going to Mars by 2000 and are a bit optimistic about your technical assumptions for NTRs and a bit pessimistic about electric drives. I meant the whole nuclear-powered ICBM thing, which was by no means limited to ANP's nuclear Atlas - that was just the first pic I had to hand.

I was trying to suggest that the T/W ratio didn't improve as much as they thought it would because the focus was on NERVA, which didn't need an improved T/W ratio. Basically, "you don't work on it, you don't get it". Anyways, as I posted in reality chemical beats out nuclear, except possibly for the special hybrid thermal/electric concept I just mentioned. Hopefully they'll figure that out before they launch.

I've found some very intriguing documents from the late 80s / early 90s, descendants of TIMBERWIND - I think I've mentioned them to you before - suggesting that the T/W issues of NTRs might have been resolvable if there'd been further development. One version claims to be able to get a 40:1 T/W with a particle-bed reactor and LOX augmentation, and I forget the T/W for non-augmented except that it was more than 1:1 - I want to say 5 or 10:1 but I'm probably misremembering.

That doesn't make it a good idea, of course, and I haven't yet gotten around to really reading through them carefully, so maybe it's bullshit. But atomic rockets are just so cool...

I recall having discussed Timberwind with you and e of pi at some point, but I think I had heard about the project already. Of course, there are lots of bizarre ideas for improving the performance of nuclear rockets--gas core rockets, for instance, whether lightbulb or open-core varieties (they're both bizarre, but each in their own ways). I don't know what it is about the intersection of nuclear and space engineering that makes people think of these things...

 

[JamesHunter]

You can laugh at Project Pluto now, but when Cthulhu turns up you'll wish we had the thing.

It the Cthulhu show up we are er.fraked, I doubt Pluto or anything else would do much good.

Most people still don't realize this - and this deal and the false perception it created has placed a huge burden on US foreign policy.

More true than I like to think, but at the same time, after going to the edge over cuba, would the American people accept that Kennedy had done a deal to defuse the crisis? The American public needed to believe that they had won, they didn't want to know that the two sides had done a deal because they were terrified of what was coming. Also this is just before MAD, people didn't quite realise that a nuclear war was a no win scenario, yes America would have won in '62 but it would have been pyric at best.

Back to Mars I still say the best option was to wait until someone came up with Mars Direct, the irony is the cheap probes we've sent to the moon since the '90's have probably told us more about the money than the zillions they spent on Apollo. An Ares style mission would give us 30 days or so of astronauts on Mars for many times the cost of the probes that have spent years disecting the planet. More footprints and flags might look glosy but it won't do much for space science. We need to wait until a trip is both cheaper, and the space program culture is able to acept that any trip will have to be a long duration stay, and probably setting up a permenant colony on day one.

Maybe not Mars to stay in the sense of no return, but maybe no return intended keep a way back but plan for long term career length stays on Mars. If I hadn't gone into history, but stayed with the sciences, was lot fitter and lets face it five years younger, I wouldn't mind moving to another planet in a decade or so.

Mars is fasinating to me I would love to get at it's secrets. Besides lets face it, I don't have many anchors holding me to this planet, and time delay aside, well I'm sure they can upload the latest Doctor who episodes and Comic books once a month or so, so I wouldn't be missing much. Of course posting to AH.com might get a little wierd, since I'd be responding to posts half an hour or so after everybody else (or longer depending on the time of year).

 

[Workable Goblin]

Back to Mars I still say the best option was to wait until someone came up with Mars Direct, the irony is the cheap probes we've sent to the moon since the '90's have probably told us more about the money than the zillions they spent on Apollo.

Hm, not so much. At the very least, the samples returned by Apollo together with the extensive data accompanying them (in terms of where they were collected and how, etc.) have been extremely important for interpreting the finds of Clementine & Lunar Prospector & so on confidently. Ground-level truth, as it's called.

Most of what's known about the interior has been determined by Apollo, too, via the ALSEP seismometer packages, although Ebb & Flow recently changed that somewhat. Of course, Apollo didn't say anything about the poles, but those were suspected of having volatiles since the 1950s (seriously!) at least, so that was more of a "well, something we thought might be the case turned out to, in fact, be the case," which is important but maybe not fundamental.

 

[Michel Van]

Back to Tonic
The UdSSR had several proposal for mannend Mars Mission
Like Mars 1986 http://www.astronautix.com/craft/mars1986.htm
They use nuclear-electric Engine to get there.

On NERVA
It was Design for orbital use, but there were Other study with High thrust.
Like DUMBO, who was Never Build.

 

[Archibald]

NERVA makes a fair amount of sense to me, if you assume that the US will be going to Mars by 2000 and are a bit optimistic about your technical assumptions for NTRs and a bit pessimistic about electric drives. I meant the whole nuclear-powered ICBM thing, which was by no means limited to ANP's nuclear Atlas - that was just the first pic I had to hand.

I've found some very intriguing documents from the late 80s / early 90s, descendants of TIMBERWIND - I think I've mentioned them to you before - suggesting that the T/W issues of NTRs might have been resolvable if there'd been further development. One version claims to be able to get a 40:1 T/W with a particle-bed reactor and LOX augmentation, and I forget the T/W for non-augmented except that it was more than 1:1 - I want to say 5 or 10:1 but I'm probably misremembering.

That doesn't make it a good idea, of course, and I haven't yet gotten around to really reading through them carefully, so maybe it's bullshit. But atomic rockets are just so cool...

Top discussion on the subject here

http://forum.nasaspaceflight.com/index.php?topic=1139.0

General consensus about Timberwind is that it would melt pretty rapidly and in a rather nasty way.
NASA big NTR guy these days is Stanley K. Borowski from the Lewis research center.
NTR discussions usually focuse on four projects
- NERVA
- DUMBO (an improved variant)
- LANTR (classic NTR with an oxygen afterburner, Borowski pet project)
- Timberwind (pebble bed reactor for Reagan SDI)

The Soviet NERVA was called the RD-410 and only elements of it were tested at Semipalatinsk back in the day. Supposedly, they were ceramic pellets able to reach higher temperatures; as such, specific impulse would be higher. NERVA was 825 seconds, the soviet one, 915 or even 940 seconds. But all this is highly speculative.
It happened that Borowski travelled to USSR in September 1992, re-discovered these carbide elements, and was impressed enough to become NASA big NTR advocate (a little forceful at times).

 

[Bahamut-255]

Actually, if this information is correct. Then the only Soviet Nuclear Thermal Engine to ever reach the testing stage, was the Kosberg RD-0410 with a Vacuum Thrust of 3,800 Kg, a Mass of 2,000 Kg, and an Isp of 910 s.

Not bad, but not really usable for a Manned Mars Mission while the 'take everything with you' mindset was in force.

 

[phx1138]

The thinking is to form a crew, get them to Mars with enough materials and supply to start a colony. They will get re-supplied on a continuous basis, but there is no return.

...Will there be people who would like to give it a bash? Obviously, the crew must be enhanced with more and more people, but apparantly even that can be figured out.

...I think a lot could sign up.

I think the first step would need to be a change in emphasis from "astronaut" to "scientist". If the Mars landing is a more/less permanent science station, close in approach to Antarctica, I think you'd still get lots of scientists who'd volunteer.

I read somewhere that building an earth-orbit "warehouse" and start supply runs from there is a bit more smart than trying to go straight earth-mars.

This makes a lot of sense IMO. I also think building a "construction shack" in L4/L5 makes a lot of sense, because it can be used to turn captured asteroids into habitats &/or solar power satellites. Once there are powersats, the prospect of powered in-system flight is very real.

 

[sloreck]

One way around the limitations of the manned mission taking everything with it for a stay on the surface would be to launch several unmanned supply missions to the proposed landing site in advance. If you get 2-3 down in close proximity you have a cushion that allows you to launch, and also you can put a few follow on unmanned supply missions up & on the way along flight paths that require minimal energy. Supply missions can have longer transit times & of course less shielding etc.

A low tech idea is to have some cement equivalent sent and mix this with a high percentage of local soil to make rammed earth structures (as done in desert areas on earth), which are partially buried. Solid, safe and can be easily sealed. Key to any long term stay is use of local materials - soil, atmosphere etc. Small nuke used enroute for power/thrust becomes on ground power plant, solar panels also used although the decreased energy of sunlight on Mars & dusty conditions will mean they cannot be primary power source.

 

[Delta Force]

The majority of the fuel in a chemical rocket is being spent to propel fuel that hasn't been used yet, so the fuel you save from ISP alone is only a low end estimate (you save fuel every time you cut fuel). Atmospheric drag is also such a large issue that rockets actually rise to full throttle during their flight because to take off at full throttle would increase drag and fuel consumption for no real gain. Essentially, whatever you are doing in the atmosphere is never going to be as efficient as what you are doing in space once you are out of the atmosphere and gravity is mostly a non-issue, and you can have terrible thrust to weight ratios and low thrust in general and still slowly move where you want to in space as there is nothing to slow you down. That's how tiny ion engines can propel probes through space while they can't propel aircraft (although ion engines are a case of low total thrust and an inability to properly function in charged atmospheres). Even if the thrust to weight ratios were good enough for them to be used as a lower stage, I doubt they would be used for that as you would either have an inadequately shielded nuclear reactor running on the ground irradiating everything or you would have to fully shield the reactor, which would cost and weigh a lot. If the reactor is only running in space it is much easier to shield as you only have to protect the astronauts and sensitive electronics and you don't have to worry about a nuclear disaster if you have a first stage accident. Dumping unspent reactor fuel on the ground in an accident is obviously far less of an issue than having a meltdown.

On an ion engine related topic, a 1966 NASA study for a 1986 lunar landing would have used both NERVA and ion engines. The study claimed that a mission using NERVA and ion engines would require half as many rockets as NERVA alone, which is quite impressive seeing as NERVA is often cited as requiring half as many rockets a chemical engines alone. Also, here is some information on NERVA from Los Alamos, which worked on the program. It talks about how nuclear thermal rockets were originally developed as the second stage for USAF ballistic missiles until conventional engines caught up with them around 1957. It also mentions how the doubled ISP allows for flights half as long and potentially frees spacecraft from having to use gravity maneuvers to reach their destination.

 

[asnys]

Top discussion on the subject here

http://forum.nasaspaceflight.com/index.php?topic=1139.0

General consensus about Timberwind is that it would melt pretty rapidly and in a rather nasty way.
NASA big NTR guy these days is Stanley K. Borowski from the Lewis research center.
NTR discussions usually focuse on four projects
- NERVA
- DUMBO (an improved variant)
- LANTR (classic NTR with an oxygen afterburner, Borowski pet project)
- Timberwind (pebble bed reactor for Reagan SDI)

The Soviet NERVA was called the RD-410 and only elements of it were tested at Semipalatinsk back in the day. Supposedly, they were ceramic pellets able to reach higher temperatures; as such, specific impulse would be higher. NERVA was 825 seconds, the soviet one, 915 or even 940 seconds. But all this is highly speculative.
It happened that Borowski travelled to USSR in September 1992, re-discovered these carbide elements, and was impressed enough to become NASA big NTR advocate (a little forceful at times).

Thanks, I'm reading through that thread and finding it very interesting.

 

[phx1138]

live in a hole underneath a hostile environment for the rest of their lives!

Have you forgotten the obvious? If it's possible to put them there, it's possible to bring them back, eventually. It's just damned hard to do it in the same mission.

 

[JamesHunter]

Thats an idea, plan say a five year intensive study of the planet, a dozen scientists a set up like antartica. Launch surface habs, automated assembly bots, etc, two years bedore. Next lauch the science team on two or three smallish craft at the next window, then send a retrieval mission at the window four years later, returning home at the next launch window after that.

The team of course gets paid enough money to retire on, and the surface gear can be used by the next team.

 

[Archibald]

Thanks, I'm reading through that thread and finding it very interesting.

I highly recommend you to register there and try to get in touch with Kirk Sorensen. Much like you he is a fan of nuclear matters (with a special affection for the Molten Salt Reactor).