Project Orion Revisited. - Why not an Earth Launch?

archiebald · 2003-03-17 08:31:03

Question For John_Frazer (Fraz right??)

Apologies if this has been dealt with elsewhere...

Saw something on this tread about the radiation hazard to the crew.
They placed the crew at the top of the stack, with all the mass f the ship in between them and the blasts. Fallout isn't a problem when you're going away from the blast site at high speed.

What about arrival when you want to decelerate, aerobraking would not be feasible I guess, and turning the ship around and decelerating into your own radioactive plume is going to be an issue. Or would you propose a shield zone within the structure for this maneuver

nebob2 · 2003-03-17 14:51:55

Aerobraking would be possible only if the dV is low enough, but could be done for extreamly high payload mass cargo missions.

EPPP is only inefficient in realation to the total energy involved, with a fission system and a 10m size the Isp can be currently as high as 5000s (SCNTR max out at about 1000s) with a thrust level of 4 MN. While this is not as high as many electric engines, the thrust levels are far higher.

In reality the best bet for EPPP politically is using antiproton ignition systems with fission/fusion pellets rather then supercritical devices. With such systens (like ICAN) the Isp is about 13000s while the thrust levels are lower at 180 kN for a 10m ship. They are not availible now but will likely be ready before controled fusion rockets.

Defects can exist in any system, cracked pusher plates/thrust shell, exploding turbopumps, cracked fuel tanks, defective magnetic nozzels. In fact turbopumps for liquid fueled rockets are pobably more likely to fail due to their high stresses, and a failure is just as likely to ruin your day.

As for the plume while decelerating, in either form the debrei cloud is being accelerated away from the ship so I don't see the problem.

dicktice · 2003-03-17 19:12:33

Radioactive plumes and exhusts on Earth and/or within our atmosphere...? I still remember when Dyson tossed out all those whacko ideas back in the 1950s. With crazies like you guys--who needs terrorist planners?

soph · 2003-03-17 19:17:29

dicktice, NTR engines could be clean in the atmosphere. But I don't support Orion because I just cant see it being safe from Earth->orbit.

dicktice · 2003-03-17 20:12:42

Okay Soph, I'll back off...but those other two guys--whew!

nebob2 · 2003-03-18 18:27:32

I have no problem with starting up that sort of engine from Earth orbit, but not a ground launch. The antiproton catilized engines should have a lot less political fallout as they don't use bombs, have better performanc as well. I don't see a bomb driven Orion being built in reality.

Gennaro · 2003-03-28 19:31:07

I'm no expert but strangely I've come to exactly the opposite conclusion. Ground launch, in fact, I think is the actual ra?son d'etre for nuclear pulse propulsion. As such it could also have enormous implications for nearby industrial ventures.
Speaking from the interested public side of the fence, what really made me appreciate the idea of resuscitating the Orion are the incredible thrust levels involved. Almost makes me feel like digging up the treasures of a lost civilization. According to http://www.islandone.org/APC/ it had a T/W ratio of about 4, as far as I can tell making it optimal for carrying heavy payloads into space.

Provided fall out levels can be minimized as outlined by Nuclear Space and discussed in this thread, the immediate use for an updated Orion would thus be for Earth launch as a heavy lifter.

Why do I think that's decisive?

Well, when going to Mars for example, going there as fast as possible isn't the primary concern (although you'll do that as well), arriving there in one piece and good health is. That requires things like heavy shielding for protection against coronal mass ejections (if lead, I've read 50 cm, which is probably pretty heavy) plus an adequate system for providing artificial gravity. Minimum requirements for the latter suggests a cylinder 44 m in diameter and as far as I've understood it, even then 0,3 g will be about the level reached if the cylinder is not to revolve too fast to be comfortable.

With the Orion we could put all this bulk on top and stuff the equipment needed for setting up a substantial martian base in just one trip. The entire hab section can be lined for protection so we won't need to rely on hopefully accurate reports on space weather and storm shelters. There'll be no need for consecutive launches from Earth by chemical rockets, dockings and final assembly in LEO just to get the spacecraft together. I suspect the latter can be more complicated than expected and by any rate prone to mistakes. Instead, just launch it from Earth as one complete package and go! So long as there's no orbital infrastructure, I find a direct launch much more appealing (not to mention that I can think of no better way of getting this into place).
In transit, forget about complicated tethers and cramped living quarters. Accomodations could be provided to make Flash Gordon envious.

Whatever couldn't nuclear pulse propulsion do to boost the Mars Direct plan? The spaceship could remain in Mars orbit, dock with the ascend viechle and be used for the return trip. Sounds like one critical sequence in the entire mission apparatus. While remaining in orbit it could prove vital as a means of premature evac if something went wrong on the surface, it could even be equipped with several landers. Bigger payloads means room for contigency plans and thus increased security. Big is bold, practical and generous. Thus, big is beautiful.

If however, a launch from orbit is callled for, I see no decisive need for using the Orion concept. NTR or hybrid NTR/NEP would be sufficient, at least since industrial expansion and scale economics is not on the agenda but merely a humble mission to Mars. Too bad I guess, the most meaningful use of the Orion concept is precisely the one everyone fears: a ground launch.
One more thing that caught my eye. It seems to follow from the pulse propulsion concept (total number of bomblets/pulse interval) that accelerating/deaccelerating is done within a rather limited time frame at the start and end of each journey. That means there's a long segment of cruise speed in between, which I believe is well suited to artificial gravity since none will be generated in the wrong direction.

soph · 2003-03-28 20:01:27

Like I said before, any type of NTR launch is more desirable from the ground. GCNRs could be designed to be heavy lift vehicles, or even SSTOs for planetary or orbital travel. They could be clean, manuverable, efficient, and powerful.

Plus, they give you a reactor for your ship, which Orion doesn't, and they allow much more design flexibility. You don't have a huge plate that serves as basic dead weight.

If we have a pulse every second, let's calculate how many pulses you need to get to Mars and back. Are you going to store that many nuclear devices on board?

It would only take a few dozen kg of uranium/plutonium, at most, for a NERVA based Mars mission. Less if we used liquid core NTRs, and even less if we used GCNRs.

I understand what you mean about heavy lift, Earth->orbit/space, and I once thought the same way. But it just isn't worth the political hassle, and there are more attractive and flexbile alternatives.

dicktice · 2003-03-29 10:01:35

Soph et al.: I'd just love to debate with "youse guys" but until you define your acronyms at least once per post, you're simply talking to the converted. Who the heck's got time to (a) look up what you mean by them, and (b) memorize the damn things in the first place. Give us, as-yet-unconverted types a break (who nevertheless aspire to discussing how to get to Mars, etc.). I say: Grr-r to every- and anyone who hide/s behind acronyms they/you don't define first!

soph · 2003-03-29 11:39:06

NERVA->Nuclear Engine for Rocket Vehicle Applications

NTR-> Nuclear Thermal Rocket/Reactor (depending on who you ask)

SSTO-> Single Stage To Orbit

GCNR-> Gas Core Nuclear Rocket/Reactor

Better?

Josh Cryer · 2003-04-05 14:58:45

Feel free to add those to the Mars Wiki, soph.

dicktice · 2003-04-06 09:33:14

Soph: Much obliged...but don't stop there in future, please.

soph · 2003-04-06 10:40:01

What others do you need?

Gennaro · 2003-04-07 18:40:36

Soph, I guess we could argue about this forever and you are much more informed about these matters than I am, that's for sure. Just felt like replying anyhow.

Like I said before, any type of NTR launch is more desirable from the ground. GCNRs could be designed to be heavy lift vehicles, or even SSTOs for planetary or orbital travel. They could be clean, manuverable, efficient, and powerful.

- Some people say gas core nuclear rockets cannot yet be built (a heat resistance issue?) and there seems to be some divided opinons on how good nuclear thermal reactors would be for a ground launch. I used to believe NTR's had an awful lot of thrust to weight power, but Nuclear Space seems to imply that's not the case. Could we get some clarification on this point from the assembled experts? Sure, they must be superior to chemical rockets at least?
Just to point it out, I'm not against NTR's, I would love to see one built and I agree the clean system is a major advantage.

Plus, they give you a reactor for your ship, which Orion doesn't, and they allow much more design flexibility. You don't have a huge plate that serves as basic dead weight.

- That could not be a major problem. The original nuclear pulse propulsed space ship was designed to carry 150 people. Surely, we could trade some of that for a small nuclear reactor plus 50 m + of hab space cylinder and heavy shielding etc, etc.
The pusher plate is not "dead weight" by the way, but an essential part of the propulsion system. Just like the (heavy) nuclear reactor on an NTR.

If we have a pulse every second, let's calculate how many pulses you need to get to Mars and back. Are you going to store that many nuclear devices on board?

- I think it was about 2000 bomblets to make it to Mars and back. What's the problem?

It would only take a few dozen kg of uranium/plutonium, at most, for a NERVA based Mars mission. Less if we used liquid core NTRs, and even less if we used GCNRs.

- Okay, you have a point there. Still, don't you think the sheer lifting power of an Orion would out perform the benefits of reduced fuel costs?

I understand what you mean about heavy lift, Earth->orbit/space, and I once thought the same way. But it just isn't worth the political hassle, and there are more attractive and flexbile alternatives.

- I guess you are right. In America at least. Maybe in the end, someone else will turn up and make it fly?

soph · 2003-04-07 20:03:43

The pusher plate means that the Orion craft is at least 4,000 tonnes. This is 4,000,000 kg, or about twice the total liftoff weight of the Shuttle, orbiter, stack and all. This is the minimum, and least efficient weight.

Out of that, you get 1,000 tonnes of steel, and 3,000 tonnes of structure, payload, etc. You're already down to 75%. And you dont have power, yet.

The NERVA engine weighed 10 tonnes. And gave a good deal of power. Yes, Orion outperforms the thrust of NERVA, however, due to the weight of the pusher plate, mathematically, it would only take about 12 NERVA engines to lift the payload equivalent of an Orion launch--120 tonnes of reactor, 10% of the mass of the pusher plate.

They are far superior to chemical rockets-even the lowliest NTR has twice the isp and better thrust conversion than the best chemical engines.

There are gas core designs that employ active reactor wall cooling, which allow Isps of up to 7,000 seconds. These reactors would be large, but 7,000 seconds is a tremendous Isp. They could also get at least 6x the thrust of a solid core engine. Not too shabby.

And before I have to go, one quick last point. Orion is blocked by the Test Ban Treaty, which bans firing nuclear weapons in space. Orion's bomblets classify as nuclear weapons.

dicktice · 2003-04-08 08:09:04

What others do you need?

Soph: How about once each post, similar to the following:
"... This term a Stimulated Motor Instructional Learning Education (SMILE) course is being introduced. SMILE will provide hands-on physical disability therapy training ..."
(Note: Even the instructors with SMILE silk-screened on the front of their T-shirts couldn't remember what the acronym meant--nor the students--the first time I saw it and asked them out of curiosity!)

clark · 2003-04-08 11:41:55

http://www.spaceref.com/news/viewpr.html?pid=11185

Go this link if you are at all interested in faster trips to Mars!

Andrews Space & Technology (AS&T) successfully demonstrated the fundamental operating principles of a propulsion system that could dramatically affect interplanetary space travel, shortening round trips to Mars from two years to six months and making future trips to Jupiter and back a two-year affair.

The Mini-Mag Orion system, short for Miniature Magnetic Orion, is a scaled down but more efficient version of the 1958 Orion interplanetary propulsion concept.

Looks like Project Orion HAS been updated!

Josh, I think I may have come just a wee bit closer to collecting....

soph · 2003-04-08 15:38:21

Eh, using a NERVA engine, it would be a 12 week round trip to Mars. If you want me to do the math, I can. It's pretty simple, really.

In any case, this really doesn't help Orion. In fact, Project Prometheus is more likely to help NTRs, because it is more legally and politically viable. Orion is still strapped by the Test Ban Treaty, and it still doesn't have much of an advantage overall (if at all) technically over NERVA.

John_Frazer · 2003-04-21 18:18:57

dicktice Mar. 17 2003
> Radioactive plumes and exhusts on Earth and/or within our atmosphere...? I still remember when Dyson tossed out all those whacko ideas back in the 1950s. With crazies like you guys--who needs terrorist planners?

Get over it. I never talked about wildly proposing a ground launch, and to hell with any arguments. I don't like the idea, unless it's possible to guarantee no fallout.
I also talk extensively about multinational controls & cooperation. How is this conducive to terrorists? I don't think Al-Queda or the IRA or PLO has a UN delegation.

OTOH, I steadfastly maintain that there is no good reason to not use it in space above LEO. None at all.
If you know about Dyson's thinking then, then you should also be familiar with the 10 and 20 meter designs.
How about big Orion interplanetary ships like the "Super" built, fueled, and used in space? If we ever get long term off-planet human presences around trhe solar system, there'll be large scale industries, and every reason to use old-fashioned fission bomb Orion in them. (Will antimatter ever be as cheap as an A-bomb?)

Contrary to many others, I don't see NPR (Nuclear Pulse Rockets) main strength being ground launch. It takes only 8km/sec to get into LEO, but another ~50km/sec to get to Mars in 6 weeks.
Many things get us into orbit, but interplanetary space is where Orion really is needed.

soph April 08 2003
> using a NERVA engine, it would be a 12 week round trip to Mars. If you want me to do the math, I can. It's pretty simple, really.

Please do. Show also that it's done with ~45% of the starting mass in HEO being cargo delivered to the destination.
Show that, contrary to all the design studies to date, it can have above 10,000 second isp, and high thrust, with technology readily understood in the '60s, and improved upon today. No contained/controlled plasma, no high temp superconductors in close proximity to plasma.

April 07 2003
> Orion is blocked by the Test Ban Treaty, which bans firing nuclear weapons in space. Orion's bomblets classify as nuclear weapons.

Ever notice that the treaties are able to be modified by the signatories, or any signatory can pull out at will? That's what treaties are for. If there's ever a need for the capabilities conferred by Orion-style NPRs, there'll be political clout too.

As to protests about details like magazine capacity, power generation, etc, look over the old designs and try to find something they've overlooked.

soph · 2003-04-21 18:37:40

Please do. Show also that it's done with ~45% of the starting mass in HEO being cargo delivered to the destination.
Show that, contrary to all the design studies to date, it can have above 10,000 second isp, and high thrust, with technology readily understood in the '60s, and improved upon today. No contained/controlled plasma, no high temp superconductors in close proximity to plasma.

When did I ever say 10,000 seconds of isp? And when did I say it needed plasma?

250,000 lbs of thrust is, what, peanuts?

The Earth escape velocity from orbit is ~5 km/s. So, let's check our rocket equation:

1-(e^(5000/9800)^1/x)

The payload ratio that is left is slightly above 40%.

With an exhaust velocity of 9800 m/s, you can expect speeds of about 18,000-20,000 m/s (or 1.8-2 km/s). This equates to a 6 week travel time to Mars.

Mars_B4_Moon · 2024-03-24 12:55:15

an old project and an idea now considered to dangerous by many

Project Orion Nuclear Pulse Rocket

https://www.youtube.com/watch?v=be2-bHDjsww

Last edited by Mars_B4_Moon (2024-03-24 12:55:47)

GW Johnson · 2024-03-25 10:07:16

The radiation from air bursts of fractional KT devices is not that much per launch of a nominal 5000 ton ship. It's roughly equal to one air burst of a megaton-range weapon. Not zero, but not a very large threat. However, it would not be wise to launch hundreds or thousands of these things from Earth.

The other risk is EMP damage on the ground below the flight path, from the explosions. This is a very real effect, as demonstrated by telephone and grid failures in Hawaii caused by the in-space Starfish Prime nuclear test (some 200 miles up) of 1962, some 900 miles away at Johnston Island in the Pacific. You really probably would want to launch these things from the moon.

GW

Last edited by GW Johnson (2024-03-25 10:08:17)

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#76 2003-03-17 08:31:03

Re: Project Orion Revisited. - Why not an Earth Launch?

#77 2003-03-17 14:51:55

Re: Project Orion Revisited. - Why not an Earth Launch?

#78 2003-03-17 19:12:33

Re: Project Orion Revisited. - Why not an Earth Launch?

#79 2003-03-17 19:17:29

Re: Project Orion Revisited. - Why not an Earth Launch?

#80 2003-03-17 20:12:42

Re: Project Orion Revisited. - Why not an Earth Launch?

#81 2003-03-18 18:27:32

Re: Project Orion Revisited. - Why not an Earth Launch?

#82 2003-03-28 19:31:07

Re: Project Orion Revisited. - Why not an Earth Launch?

#83 2003-03-28 20:01:27

Re: Project Orion Revisited. - Why not an Earth Launch?

#84 2003-03-29 10:01:35

Re: Project Orion Revisited. - Why not an Earth Launch?

#85 2003-03-29 11:39:06

Re: Project Orion Revisited. - Why not an Earth Launch?

#86 2003-04-05 14:58:45

Re: Project Orion Revisited. - Why not an Earth Launch?

#87 2003-04-06 09:33:14

Re: Project Orion Revisited. - Why not an Earth Launch?

#88 2003-04-06 10:40:01

Re: Project Orion Revisited. - Why not an Earth Launch?

#89 2003-04-07 18:40:36

Re: Project Orion Revisited. - Why not an Earth Launch?

#90 2003-04-07 20:03:43

Re: Project Orion Revisited. - Why not an Earth Launch?

#91 2003-04-08 08:09:04

Re: Project Orion Revisited. - Why not an Earth Launch?

#92 2003-04-08 11:41:55

Re: Project Orion Revisited. - Why not an Earth Launch?

#93 2003-04-08 15:38:21

Re: Project Orion Revisited. - Why not an Earth Launch?

#94 2003-04-21 18:18:57

Re: Project Orion Revisited. - Why not an Earth Launch?

#95 2003-04-21 18:37:40

Re: Project Orion Revisited. - Why not an Earth Launch?

#96 2024-03-24 12:55:15

Re: Project Orion Revisited. - Why not an Earth Launch?

#97 2024-03-25 10:07:16

Re: Project Orion Revisited. - Why not an Earth Launch?

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