Absurdly inane BBC article

[Matuchkin]

At this point, I'd just like to say: screw Pulitzer.

[KSK]

16 hours ago, Shpaget said:

Oh, one more thing... Has any of you ever been in a Concorde?

I was. And I was really unimpressed. That thing is tiny. In a world where airlines advertise "Extra room", they really are left behind.

Yup - there's one at my local air museum. The airframe is a marvel - it still looks futuristic, forty years (and more) after it was designed and built. The interior - not so much. The one I saw would have been the height of fashion - in the 80s! I understand that everything else would have been as luxurious as they could make it but they couldn't do much about legroom I don't think.

In fairness though, it was a case of form over function and the design constraints imposed by supersonic travel. Again - this is a forty year old plane and the key parts of the design were probably fixed long before that.

Edited July 21, 2016 by KSK

[Nibb31]

The latest ones had their interiors refurbished in the late 90 early 2000 by couture designers.

It's size was driven by it being as a successor to the Comet or the Caravelle (the French design was originally called the Caravelle II), which were commercially successful aircraft.

When comparing with modern aircraft, remember these aircraft were from the same era as the 707 or the DC10. The cockpit is all analog gauges and switches and the flight controls are all mechanical. It used mechanical fuel pumps to move the CoG around depending on the flight regime.

 

Being unimpressed by Concorde is a bit like feeling unimpressed by the Apollo CM when compared to Orion or CST100. It was really a huge accomplishment to make such a complex aircraft with only slide rules and wooden templates and hardly any electronics in sight.

Edited July 21, 2016 by Nibb31

[magnemoe]

55 minutes ago, Nibb31 said:

The latest ones had their interiors refurbished in the late 90 early 2000 by couture designers.

It's size was driven by it being as a successor to the Comet or the Caravelle (the French design was originally called the Caravelle II), which were commercially successful aircraft.

When comparing with modern aircraft, remember these aircraft were from the same era as the 707 or the DC10. The cockpit is all analog gauges and switches and the flight controls are all mechanical. It used mechanical fuel pumps to move the CoG around depending on the flight regime.

Being unimpressed by Concorde is a bit like feeling unimpressed by the Apollo CM when compared to Orion or CST100. It was really a huge accomplishment to make such a complex aircraft with only slide rules and wooden templates and hardly any electronics in sight.

yes, DC9 was only 5 seats wide in economic. you also want an thin fuselage for supersonic too and it was never designed to carry loads of people. 
Are not all pumps mechanical? 

[PB666]

6 hours ago, Nibb31 said:

The latest ones had their interiors refurbished in the late 90 early 2000 by couture designers.

It's size was driven by it being as a successor to the Comet or the Caravelle (the French design was originally called the Caravelle II), which were commercially successful aircraft.

When comparing with modern aircraft, remember these aircraft were from the same era as the 707 or the DC10. The cockpit is all analog gauges and switches and the flight controls are all mechanical. It used mechanical fuel pumps to move the CoG around depending on the flight regime.

 

Being unimpressed by Concorde is a bit like feeling unimpressed by the Apollo CM when compared to Orion or CST100. It was really a huge accomplishment to make such a complex aircraft with only slide rules and wooden templates and hardly any electronics in sight.

Yes, but to be at the pinnacle of commercial technology when completed and yet not go under any major improvements in 40 years? The 747 was followed by 777, and now you have 747-8. All of the commercial aircraft from the 60s and early 70s have had engine-pack replacements (more efficient engines). Take a look at the engines on the 707 and the 737. There were lots of room for both safety and efficiency improvement in the Concorde, but not with the business model in which is operated.

[Shpaget]

Yep, Concorde was left behind.

Concorde has (had) 4 seats in a row, same as, for example an A320. However, in A320 the fuselage is just shy of 4 m wide, in Concorde it's 2,6. Concorde may be fast, but still, a transatlantic trip took around 3,5 hours. 3,5 hours last a lot longer when you have somebody siting in your lap.

Look at his picture of a Concorde next to an old 747 (not sure what generation).

Edited July 21, 2016 by Shpaget

[DDE]

21 hours ago, PB666 said:

Because like VASIMR, they need a GW of electric power and currently no feasible source in space. Solve the electric power problem, and the radiation problem cheaply then you have a choice.

Radiation problem is severely overblown. While I don't quite trust,Zubrin's assessment, data from Curiosity shows that an unshielded pressurized habitat is enough to keep the dose within ESA tolerances on a regular Hohmann.

13 hours ago, pxi said:

Dumb question but, asides from all the technical issues, do we really want to go sticking fission reactors on planes?  What exactly happens when a fission reactor has a high-speed encounter with the ground?

(This may explain why I'm unqualified to write for the BBC.)

If the crash of the Soviet US-A radar sat is of any indication, a local radiation containment situation.

The Soviets had given it thought, though; while the Tu-95LAL/Tu-141 only had a directional shadow shield for its reactor, when designing An-22PLO they decided to try and add a reactor jettison and recovery system. It would be a radiation hazard for some time anyway, but no fallout.

Finally, we have proposals from the heydays of NERVA to just drop the damned thing into the ocean, claiming that no shielding is required for the reactor to reenter and be recovered for reuse because it's already stupidly durable.

Edited July 21, 2016 by DDE

[DDE]

11 hours ago, Matuchkin said:

At this point, I'd just like to say: screw Pulitzer.

Please start with Jessica Valenti's team.

[PB666]

21 minutes ago, DDE said:

Radiation problem is severely overblown. While I don't quite trust,Zubrin's assessment, data from Curiosity shows that an unshielded pressurized habitat is enough to keep the dose within ESA tolerances on a regular Hohmann.

If the crash of the Soviet US-A radar sat is of any indication, a local radiation containment situation.

The Soviets had given it thought, though; while the Tu-95LAL/Tu-141 only had a directional shadow shield for its reactor, when designing An-22PLO they decided to try and add a reactor jettison and recovery system. It would be a radiation hazard for some time anyway, but no fallout.

Finally, we have proposals from the heydays of NERVA to just drop the damned thing into the ocean, claiming that no shielding is required for the reactor to reenter and be recovered for reuse because it's already stupidly durable.

No, the radiation problem is that for any given power supply and any given electric drive system there are inefficiencies that give of heat. Vasmir and ION drives waste about 10%. Solar panels themselves dissipate their own waste, but the transformers and conductors waste heat. Point sources of heat need to be radiated, and panels are far less efficient as radiators than they are as absorbers. The radiators add weight in addition to the weight added by solar panels. The option is fusion power, does not have solar panels but alot more unradiated waste heat is generated. 

These two engineering problems exist before you even think about the payload problem. 

[DaMachinator]

4 hours ago, PB666 said:

Yes, but to be at the pinnacle of commercial technology when completed and yet not go under any major improvements in 40 years? The 747 was followed by 777, and now you have 747-8. All of the commercial aircraft from the 60s and early 70s have had engine-pack replacements (more efficient engines). Take a look at the engines on the 707 and the 737. There were lots of room for both safety and efficiency improvement in the Concorde, but not with the business model in which is operated.

Concorde had no competitors in it's niche, meaning that the companies who owned it probably had the "if it ain't broke, don't fix it" mentality.

 

On the subject of the aircraft in question: It's an electric aircraft powered by a nuclear reactor. It doesn't use nuclear propulsion. 

The fission reactor on the NR-1 could easily fit in any modern airliner. It would need very infrequent refueling - the biggest problem would be heat dissipation.

Whether 5MW (as someone who, without citing their sources, said the power output was) is enough to propel an airliner through the air, and whether the weight of a reactor would significantly disturb the CoM, is something I am not knowledgable enough to speak on.

Edited July 21, 2016 by DaMachinator

[Nibb31]

5 hours ago, PB666 said:

Yes, but to be at the pinnacle of commercial technology when completed and yet not go under any major improvements in 40 years?

 

5 hours ago, PB666 said:

The 747 was followed by 777, and now you have 747-8. All of the commercial aircraft from the 60s and early 70s have had engine-pack replacements (more efficient engines). Take a look at the engines on the 707 and the 737. There were lots of room for both safety and efficiency improvement in the Concorde, but not with the business model in which is operated.

Production was stopped after 14 production aircraft were built between 1975 and 1978. They received upgrades over their lives, but not the sort of redesign updates that you would get between different generations of 747s or 737s. A 747 built in 2016 is a very different aircraft than the original 747 from 1969.

The Concorde airframes that were still flying in 2003 were the original ones built in the 1970s. Most of the 747s from the same era have also been retired, but if you were to visit one, it would not have the latest engines and avionics.

[PB666]

2 hours ago, Shpaget said:

Yep, Concorde was left behind.

Concorde has (had) 4 seats in a row, same as, for example an A320. However, in A320 the fuselage is just shy of 4 m wide, in Concorde it's 2,6. Concorde may be fast, but still, a transatlantic trip took around 3,5 hours. 3,5 hours last a lot longer when you have somebody siting in your lap.

Look at his picture of a Concorde next to an old 747 (not sure what generation).

Branniff went out of business 1982, Concorde started operation in 1976. More than likely it was an earlier 747. Braniff was one of the first customers for 747.

Looks like 747-127/20207 if its N601BN (also known as "Big Orange" in 1978 or 79). Those look like JT9D-3As. Basically the same aircraft as a shuttle carrier without the mods.

The plane was bought by Tower Air and operated until it was rendered unflyable in 2001 and was scraped at JFK. You normally can't track aircraft by they livery but BI gave all the earliest 747 is different paints. The only oddity here with published photos is the bicolor B on the tail. 

http://www.jetphotos.net/showphotos.php?cn=20207&manu=Boeing

 

Note: this aircraft went into service in 1971 (5 years before the concorde) and was 'retired' 2 years before the concorde went out.

 

 

 

 

Edited July 21, 2016 by PB666

[magnemoe]

5 hours ago, PB666 said:

Yes, but to be at the pinnacle of commercial technology when completed and yet not go under any major improvements in 40 years? The 747 was followed by 777, and now you have 747-8. All of the commercial aircraft from the 60s and early 70s have had engine-pack replacements (more efficient engines). Take a look at the engines on the 707 and the 737. There were lots of room for both safety and efficiency improvement in the Concorde, but not with the business model in which is operated.

Engine replacement for Concorde was not an option as it was no other suitable engines, for standard planes it makes sense as its lots of engines out there. 
The problem with Concorde is that its an first class only plane in ticket price so its only relevant on heavy traffic routes, it can only fly supersonic over ocean and it don't have the range for the pacific limiting to even fewer airports. 
An serious problem as if you fly from say berlin to chicago Concorde would not be an option outside of the experience even if money was no issue as you would need to change planes twice, easier to just buy an first class ticket on an direct flight. 
However British Airways found they lost money on the cancellation of the Concorde, many of their Concorde customers would either fly other companies or even fly business class who is cheaper and bring less income. 
An small premium charter and private jet supersonic plane is under work, it escapes all the Concorde issues including flying supersonic over land because of better aerodynamic. 
Any expensive planes will suffer the same issues, A380 has problems as today its more an focus on direct flight, you only have to pass the poophole security once and the company has no issues if on plane is two hour late. 

[Shpaget]

23 minutes ago, PB666 said:

The only oddity here with published photos is the bicolor B on the tail. 

The darker color of the top left part of the "B" is due to the rudder being deflected and in the shadow.

Otherwise, nice info!

[DaMachinator]

18 hours ago, magnemoe said:

Engine replacement for Concorde was not an option as it was no other suitable engines, for standard planes it makes sense as its lots of engines out there. 

One could replace the turbojets with ramjets, which are more efficient at supersonic speeds. Whether this would actually improve efficiency and be at all practical is another matter, although I suspect that it would be. Again, it had no competition, meaning that the kind of people who wanted the aircraft that the Concorde was had no other choice.

Even with it's outdated technology and poor fuel efficiency, the Concorde aircraft did make British Airways a profit.

18 hours ago, magnemoe said:

The problem with Concorde is that its an first class only plane in ticket price so its only relevant on heavy traffic routes, it can only fly supersonic over ocean and it don't have the range for the pacific limiting to even fewer airports.

Any extreme commercial aircraft is going to be suited only for long-range or mid-range high traffic routes. The A380 has the same problem, yet it is used.

Also, planes don't fly straight across the Pacific (or the Atlantic, for that matter). They fly polar great circle routes.

18 hours ago, magnemoe said:

An serious problem as if you fly from say berlin to chicago Concorde would not be an option outside of the experience even if money was no issue as you would need to change planes twice, easier to just buy an first class ticket on an direct flight. 

Or you could refuel the aircraft. The Concorde still would make the trip over twice as fast as any modern subsonic jet.

18 hours ago, magnemoe said:

An small premium charter and private jet supersonic plane is under work, it escapes all the Concorde issues including flying supersonic over land because of better aerodynamic. 

The sonic boom occurs continually as long as an aircraft is moving, but anything moving slower than the aircraft will only hear the characteristic double boom. As best as I can tell, there are four ways to decrease it: 

1. Decrease the lift produced by the wings. The higher the lift, the bigger the sonic boom. This strongly favors small aircraft like fighters and business jets, and is the real reason business jets should be able to supercruise over land.
2. Go faster.
3. Shape the aircraft in such a way that less of the energy of the sonic boom is directed towards the ground.
4. Shape the aircraft in such a way that the sonic boom has less energy to begin with.

19 hours ago, magnemoe said:

Any expensive planes will suffer the same issues, A380 has problems as today its more an focus on direct flight, -snip- and the company has no issues if on plane is two hour late. 

All planes are expensive. The key word here should be "specialized" or "high performance". In other words, any aircraft that does a few things really well will be lacking in other areas, perhaps enough to render it impractical.

It is the nature of people to be upset at things which make them late. There are multiple airlines that operate the A380. If one airline is consistently late, people will not use it.

[fredinno]

On 2016-07-19 at 11:42 PM, Shpaget said:

Are we still talking about the airliner or are we talking about orbital stuff?

VTOL airliners are not going to happen unless we magic up a power source of mind boggling energy density. A fusion reactor of a fraction of the size of current best (paper) designs that somehow doesn't irradiate everything on board, or batteries straight out of a Jedi light saber or Star Trek hand held phaser.

I also don't see airliners using LOX any time soon. For a vehicle to not use the atmospheric oxygen but carry it onboard sounds asinine. Same goes for not using air as reaction mass. Modern turbofan engines rely on air as reaction mass so much that only about 10% of the air that goes through the engine actually goes through the combustion chamber. The other 90% is just pushed around the engine. And we're not talking about small quantities of air either. Rolls Roys Trent XWB engine, for example displaces around 1400kg of air every second. Airbus A350 has two of them.

I was thinking space.b

True, unless you go suborbital. But then that raises the question of if anyone truely needs it.

On 2016-07-20 at 0:41 AM, p1t1o said:

Hmm? We are talking airliners here aren't we? Its not going to have smaller wings if it needs to fly at all, in fact larger wings would capture more ground effect and rebounded exhaust, increasing lift in the VTOL mode. No reason why any craft cant have lifting body characteristics either.

 

Are you talking about an SSTO?

About aborts, this isn't necessarily the case. For example, the concorde apparently had quite benign characteristic even if two engine went out on the same side at Mach 2. This was due to the way air was dumped from beneath the engine, countering the loss of lift and reducing the increase in drag.

I was talking Spaceplanes.

On 2016-07-20 at 0:47 AM, SinBad said:

Even with awesome power densities, for an atmospheric craft aerodynamic lift designs will always be more efficient than VTOL (barring any hoopdedoo future tech antigravioli propulsion devices) just because it takes less energy to generate X amount of lifting force by propelling a wing forward than it does to have the engine provide lift directly. Even helicopters use their powerplants this way, its a rotating aerodynamic lifting surface. Airliners are already a business running tight profit margins, every extra bit of lost efficiency turns into lost profit. Which is why i am of the opinion that vtol will not be used in a commercial transport role where it can be avoided. (The company next door to my old job was a helo operator that mostly serviced oil rigs, hard to htol on those)

Oh, I thought you were talking about space VTOL.

 

On 2016-07-20 at 4:38 AM, PB666 said:

Concorde 1.9 was expensive to develope and was not safe tontake off,mit would have been more expensive to make it safe, there were only four flights. It was a very space age idea, but it was not fully developed. 

There was a a Concorde 1.9?

I thought there was only 1?!?!

And 4 flights? Really?

 

I would think a military/elite supersonic airliner would find a market. Military for getting things across enemy land with minimal chance of getting shot due to speed (but the sonic boom would complicate things), or Elite for politicians, buisnessmen, or other rich fuks who need to get to a negotiational meeting ASAP.

On 2016-07-20 at 8:19 AM, DDE said:

VASIMR is not an ion thruster, it's a wholly different family, electromagnetic (pondermotive, to be precise) as opposed to electrostatic. No, the magnets aren't the element accelerating remass in a Hall-effect thruster. Therefore your appeal to Dawn is invalid.

Efficiency is always a big deal, because the requirement for a reactor results in your propulsion system mass bloating; sure, you can have high ISP, but the hit to the ship's mass ratio still results in your dV tanking, pun intended.

No, there appears to be no way to power a VASIMR with solar panels; or, if there is, it is even heavier than a reactor.

They are the stuff directing the ION flow out. They are sill very powerful, and very reliable.
 Not 100% invalid.

 

There is a way to power VASMIR/ION with solar- that's the primary NASA baseline for mars missions right now for SLS (not DRM 5.0, it's a post-DRM 5.0 baseline made long after Constellation).

It is heavier than a reactor. Not that NASA has a choice.

On 2016-07-20 at 8:33 AM, magnemoe said:

As I understand it was thoughts of installing an vasmir on the IIS for the lifting burns and to prove the technology, this was canceled but would have used the stations solar panels for power
And yes they are heavy. If you could scale vasmir down to something more fitting on an probe rater than an manned interplanetary ship power demands would be lower but its probably an lower limit on power it will need. 

You probably could, but NASA already has ION thrusters for that (NeXT), so reasearch is concentrating on bigger thrusters

On 2016-07-20 at 9:08 AM, Shpaget said:

Oh, one more thing... Has any of you ever been in a Concorde?

I was. And I was really unimpressed. That thing is tiny. In a world where airlines advertise "Extra room", they really are left behind.

Wow. Really? I thought it was a luxury liner... You'd think all the seats would be 1st class style.

On 2016-07-20 at 10:50 AM, DDE said:

Yeah, but I haven't seen good info on how well it scales down. There are very few reasons to use it over current electrostatic thrusters. I mean, do you really want to deal with liquid hydrogen or liquid lithium when compressed xenon does the job well enough? Not to mention the ISPs can be forced through the roof (~12000 sec).

Also, VASIMR isn't being developed for probes. It's touted as a manned interplanetary craft engine, possibly because it overcomes the inherent thrust limitations of ion thrusters (although it's not fully clear why an array of a few thousand of them is off the table).

VASMIR uses Argon as a base, as far as I know. Xenon would be better if they wanted the extra thrust, and lower ISP, but right now, it's Argon.

 

And there are reasons to use it over current thrusters. Such as turning the ISP up during transit to speed up transit, but down when trying to go into and out of Mars. (assuming a mars spacecraft).

 

And you just described why VASMIR is a big contender (conventional ION is also on the table, but big ION thrusters have not really gone far in development, aside from the ESA one that had way too high ISP for a sane amount of solar cells, giving VASMIR a huge advantage.)

Having a few thusters is A LOT less complex than a few thousand. At the low flight rates of Mars misssions, development costs trump per flight costs. (and even then, fewer engines tend to be better in rocketry/space due to the very low amounts of missions launched).

It's a similar reason to why SLS is being made instead of propellant depots and EELVs. The R+D costs are lower (even more so, since SLS Block I is an uprated inline shuttle stack with a ICPS)

On 2016-07-20 at 1:43 PM, PB666 said:

Because like VASIMR, they need a GW of electric power and currently no feasible source in space. Solve the electric power problem, and the radiation problem cheaply then you have a choice.

You can reduce ISP on VASMIR for less electric power used.

Really, that's why it's better than normal ION- it uses a lot less power overall, but is less efficient.

 

NTRs would be even better, but come to them from the wrong side..... 

And let's not discuss public perception of nuclear power.

On 2016-07-20 at 9:59 PM, pxi said:

Dumb question but, asides from all the technical issues, do we really want to go sticking fission reactors on planes?  What exactly happens when a fission reactor has a high-speed encounter with the ground?

(This may explain why I'm unqualified to write for the BBC.)

You're right. Let's have nuclear space probes first....at least those would be actually useful and be possible.

For example, an SLS Block IB launched Kuiper-Belt or Centaur DAWN-style mission.

 

Or a mission to sedna/interstellar space (or Planet 9 if it's real).

 

If that happens, there will be too much excitement in this thread to be contained, and the KSP forums will crash...

On 2016-07-21 at 1:56 PM, magnemoe said:

An small premium charter and private jet supersonic plane is under work, it escapes all the Concorde issues including flying supersonic over land because of better aerodynamic. 

Source?

[fredinno]

On 2016-07-22 at 9:08 AM, DaMachinator said:

One could replace the turbojets with ramjets, which are more efficient at supersonic speeds. Whether this would actually improve efficiency and be at all practical is another matter, although I suspect that it would be. Again, it had no competition, meaning that the kind of people who wanted the aircraft that the Concorde was had no other choice.

I doubt there are off-the-shelf ramjets available.

On 2016-07-21 at 10:55 AM, DDE said:

Radiation problem is severely overblown. While I don't quite trust,Zubrin's assessment, data from Curiosity shows that an unshielded pressurized habitat is enough to keep the dose within ESA tolerances on a regular Hohmann.

Finally, we have proposals from the heydays of NERVA to just drop the damned thing into the ocean, claiming that no shielding is required for the reactor to reenter and be recovered for reuse because it's already stupidly durable.

You got that from Zubrin?

Take it with a *big* grain of Salt.

NASA has already been proven to double whatever Zubrin states is possible, so expect at least some water-based shielding on your inflatable HAB.

Quote

Finally, we have proposals from the heydays of NERVA to just drop the damned thing into the ocean, claiming that no shielding is required for the reactor to reenter and be recovered for reuse because it's already stupidly durable.

Ah, the good old days of spaceflight. Not happening today. It would make the Cassini protests look like peanuts.

 

[Andem]

Sorry mods pls dont ban

--EDIT--

The above is referencing only the article, and not the entire thread.

Edited July 24, 2016 by Andem

[Emperor of the Titan Squid]

Its fine that there looking into how it would work if we did have the technology. Even NASA does that. But is does not need a BBC article, especially not one saying it could be the first nuclear powered airliner. Because it really couldn't be.

[purpleivan]

For straight forward news the BBC website is very good, but in my experience the "magazine" sections of the website including BBC future are often complete drivel.

[DaMachinator]

On 7/23/2016 at 10:56 PM, fredinno said:

I doubt there are off-the-shelf ramjets available.

If there are, they are military designs and therefore probably classified. You would have to design one from scratch. Which you would have to do anyways, because replacing engines on a precisely designed aircraft is no simple task. It might not be possible at all.

On 7/23/2016 at 10:46 PM, fredinno said:

Or a mission to sedna/interstellar space (or Planet 9 if it's real).

Voyager/Voyager 2
 

On 7/23/2016 at 10:46 PM, fredinno said:

Source?

http://www.aerionsupersonic.com/ is probably the one. Note my above comment that the noise of the sonic boom is proportional to the lift generated by the wings, heavily favoring business jets for supercruise capabilities.

On 7/23/2016 at 10:46 PM, fredinno said:

NTRs would be even better, but come to them from the wrong side..... 

Unless it's a closed-cycle design, like a nuclear lightbulb (closed-cycle gas core reactor rocket) Which so happens to be even more efficient than a solid core NTR.

Even better would be nuclear pulse propulsion, which has the side effect of frying unshielded electronics on the same side of the Earth as it when you use it because of the EMP from a nuclear explosion.

[DaMachinator]

On 7/23/2016 at 10:46 PM, fredinno said:

Oh, I thought you were talking about space VTOL.

See also: NEXUS, DC-Y concept, North American Air Augmented VTOVL, and others. 

[KerikBalm]

On 7/25/2016 at 9:29 PM, DaMachinator said:

Unless it's a closed-cycle design, like a nuclear lightbulb (closed-cycle gas core reactor rocket) Which so happens to be even more efficient than a solid core NTR.

closed cycle or open cycle isn't relevant to what he was talking about (I think). While an open cycle design spews radioactive exhuast, and a closed cycle doesn, this doesn't solve the issue.

The issue is that the reactor itself is a radiation emitter (please not the difference between radiation, and radioactivity). Due to mass constraints, the reactor would only have a "shadow shield". The radiation emitterd by the reactor, even when powered down* would be deadly, and the only safe way to approach the reactor would be in the radiation "shadow" from the shielded direction.

 

* once its been used - a pristine never been used reactor full of enriched Uranium isn't so bad at all, its not until the reactor runs and Uranium starts getting split ... natural uranium, even U235, has extremely long half lives.. meaning its mostly stable and it rarely decomposes and emits any radiation)

[magnemoe]

1 hour ago, KerikBalm said:

closed cycle or open cycle isn't relevant to what he was talking about (I think). While an open cycle design spews radioactive exhuast, and a closed cycle doesn, this doesn't solve the issue.

The issue is that the reactor itself is a radiation emitter (please not the difference between radiation, and radioactivity). Due to mass constraints, the reactor would only have a "shadow shield". The radiation emitterd by the reactor, even when powered down* would be deadly, and the only safe way to approach the reactor would be in the radiation "shadow" from the shielded direction.

 

* once its been used - a pristine never been used reactor full of enriched Uranium isn't so bad at all, its not until the reactor runs and Uranium starts getting split ... natural uranium, even U235, has extremely long half lives.. meaning its mostly stable and it rarely decomposes and emits any radiation)

yes, this is an issue with nerva, however in space this is quite managable, you can put engine in the back of an long ship and only approach from front. 
On ground in an airplane its another issue, not without reason USSR dropped the idea for military planes, they was not much concerned with radiation either. 

[KerikBalm]

"you can put engine in the back of an long ship and only approach from front. "

Yes, that's the whole point, because this started with someone saying "NTRs would be even better, but come to them from the wrong side...." followed by someone implying that closed vs open cycle was relevant... ie they quote that and responded with "Unless it's a closed-cycle design,"

So in summary: you need to approach from behind the shadow shield, there won't be 360 degree shielding because Mass. Open vs closed cycle doesn't matter, you need to be behind the shadow shield