One Month to Mars -- Methods for Very Fast Settler Transit

[lamontagne]

Fusion Microexplosion Propulsion

This method gives a theoretical Isp of up to ~ 1 million s (Schmidt et al. 2000).

Winterberg's 2004 "Mini Fission-Fusion-Fission Explosion" design specifies 10 kg of high explosives to start the nuclear sequence.  Methalox might serve here; LCH4 is miscible in LOX, forming a uniform methane / oxygen mixture (MOX).  (image)

MOX has been shown to be a high explosive with a TNT equivalence greater than that of C-4.

Here MOX surrounds Winterberg's container, which is < 20 cm in diameter, holding shells of aluminum, beryllium, U238 / Th232, and D-T gas around < 1 gram of fissile core.  In use, fusion delivers to the MOX:

...a gain of ∼ 10^3, releasing an energy equivalent to a few tons of TNT...

Corresponding Isp is around 13,000 s (trading high native fusion Isp for high thrust).

The design could utilize methalox ISRU, with LOX harvested from Earth's thermosphere and LCH4 possibly from Deimos.  Also, fusion tankers could transfer Deimos LCH4 to Earth orbit.  In this way, the crew tugs' most massive consumable (MOX) is stocked efficiently where needed.  In effect, notional on-orbit ISRU methalox infrastructure is now integrated and repurposed within a newer fusion transport system.

Proven fusion tech is of course another point in favor.

Comparisons?

Refs.

Blackwood, J.M., Skinner, T., Harrison, S.J., Whitworth, B., Hays, M.J. and Wilde, P., 2023, May. An Interim Set of TNT Curves for LOX/LNG Explosions. In 12th International Association for the Advancement of Space Safety (IAASS) Conference.

Schmidt, G., Bonometti, J. and Morton, P., 2000. Nuclear Pulse Propulsion - Orion and Beyond. In 36th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit (p. 3856).

Winterberg, F., 2004. Mini fission-fusion-fission explosions (mini-nukes). A third way towards the controlled release of nuclear energy by fission and fusion. Zeitschrift für Naturforschung A, 59(6), pp.325-336.

How would the device hold together if its was made of liquid oxygen and methane? Some kind of tank is required.  And how would you get explosive symetry? 

[LMT]

Fusion Microexplosion Propulsion

Winterberg's 2004 "Mini Fission-Fusion-Fission Explosion" design specifies 10 kg of high explosives to start the nuclear sequence.  Methalox might serve here; LCH4 is miscible in LOX, forming a uniform methane / oxygen mixture (MOX)...

How would the device hold together if its was made of liquid oxygen and methane? Some kind of tank is required.  And how would you get explosive symetry?

Posters grok spherical containers.

You still have a skeptical 3F thermonuclear analysis to finish, or start.  Regardless, physicists don't see issues with 3F; the methods aren't controversial or new.  If you can't calculate any issue yourself, you should say so. 

[lamontagne]

Fusion Microexplosion Propulsion

Winterberg's 2004 "Mini Fission-Fusion-Fission Explosion" design specifies 10 kg of high explosives to start the nuclear sequence.  Methalox might serve here; LCH4 is miscible in LOX, forming a uniform methane / oxygen mixture (MOX)...

How would the device hold together if its was made of liquid oxygen and methane? Some kind of tank is required.  And how would you get explosive symetry?

Posters grok spherical containers.

You still have a skeptical 3F thermonuclear analysis to finish, or start.  Regardless, physicists don't see issues with 3F; the methods aren't controversial or new.  If you can't calculate any issue yourself, you should say so.

It's not a calculation.  It's just that I wonder how you can effectively mix the oxygen and methane.  It's a practical problem, not a math problem. 

[LMT]

Fusion Microexplosion Propulsion

Winterberg's 2004 "Mini Fission-Fusion-Fission Explosion" design specifies 10 kg of high explosives to start the nuclear sequence.  Methalox might serve here; LCH4 is miscible in LOX, forming a uniform methane / oxygen mixture (MOX)...

How would the device hold together if its was made of liquid oxygen and methane? Some kind of tank is required.  And how would you get explosive symetry?

Posters grok spherical containers.

You still have a skeptical 3F thermonuclear analysis to finish, or start.  Regardless, physicists don't see issues with 3F; the methods aren't controversial or new.  If you can't calculate any issue yourself, you should say so.

It's not a calculation.  It's just that I wonder how you can effectively mix the oxygen and methane.  It's a practical problem, not a math problem.

Again, that's the definition of miscible.  They pour it, as in Blackwood et al. 2023, shown previously with photos. 

As for the nuclear calculation, Winterberg 2004 provided that in appendices.  You didn't calculate a 3F issue, no.

[Twark_Main]

Fusion Microexplosion Propulsion

Winterberg's 2004 "Mini Fission-Fusion-Fission Explosion" design specifies 10 kg of high explosives to start the nuclear sequence.  Methalox might serve here; LCH4 is miscible in LOX, forming a uniform methane / oxygen mixture (MOX)...

How would the device hold together if its was made of liquid oxygen and methane? Some kind of tank is required.  And how would you get explosive symetry?

Posters grok spherical containers.

To borrow a certain charming demeanor...

you still have embarrassingly failed to answer the original question: how would you get explosive symmetry? do you even "grok" explosive lenses? or are you unable to comprehend fundamental facts about the subject?

Winterberg's diagram shows a symmetrical implosion, not an explosion. you now demonstrate that you can't use even basic terminology correctly.

you still have yet to answer the explosive symmetry question. your analysis is incomplete, or nonexistent






I really wish you could realize — someday, somehow  — how your writing improves dramatically without the blue crap     Just go back and delete it as you're about to click [Post].  You won't regret it.

[LMT]

Fusion Microexplosion Propulsion

Winterberg's 2004 "Mini Fission-Fusion-Fission Explosion" design specifies 10 kg of high explosives to start the nuclear sequence.  Methalox might serve here; LCH4 is miscible in LOX, forming a uniform methane / oxygen mixture (MOX)...

How would the device hold together if its was made of liquid oxygen and methane? Some kind of tank is required.  And how would you get explosive symetry?

Posters grok spherical containers.

To borrow a certain charming demeanor...

you still have embarrassingly failed to answer the original question: how would you get explosive symmetry? do you even "grok" explosive lenses? or are you unable to comprehend fundamental facts about the subject?

Winterberg's diagram shows a symmetrical implosion, not an explosion. you now demonstrate that you can't use even basic terminology correctly.

you still have yet to answer the explosive symmetry question. your analysis is incomplete, or nonexistent

I really wish you could realize — someday, somehow  — how your writing improves dramatically without the blue crap     Just go back and delete it as you're about to click [Post].  You won't regret it.

Checkpoint:

The 3F approach to high-speed Mars transit hasn't raised any red flags, physically or technically.  Oddly, negative emotions still run high with some, two months after introduction of Winterberg's surprisingly relevant paper on "mini fission-fusion-fission explosions". 

At this point, do any posters have positive thoughts on the 3F approach?  Are there any potential benefits to highlight, or improvements to explore?

[LMT]

do you even "grok" explosive lenses? or are you unable to comprehend fundamental facts about the subject?

The simple sphere works, amazingly.  Notice that.

If lensing were needed for max gain, it's a simple addition.  I presented Rafique 2023 for design reference, with focusing theory and options.  Did he miss something important?

[LMT]

MOX

Some methods for safely preparing and handling MOX:

Method and apparatus for the preparation and usage of a cryogenic propellant or explosive system

...a method and apparatus for remotely forming a mixture of liquid oxygen (“LOX”) and liquid methane (“LNG”), with the mixture commonly referred to as MOX, such that the LOX and LNG never contact each other until inside the container in which the mixture will be used. The method disallows contact between the LOX and the LNG in order to prevent the premature or inadvertent explosive combustion that can occur in a variety of ways. The method provides a way to deactivate the MOX mixture, even after the MOX mixture has been formed. The invention also contemplates various apparatuses that will allow the method to be practiced...

By using knowledge of the various known properties of LOX, LNG and MOX mixtures, various embodiments of the present invention also include methods to remotely and safely control (1) the composition of the MOX mixtures, (2) the holding time for stable MOX mixtures and (3) the non-explosive termination of the MOX mixture. The present invention further includes means for remotely and safely forming a controllable mixture of MOX in a container at the final location of its desired application.

Method for making and storing cryogenic monopropellant

...the present invention provides methods and assemblies for producing and storing liquid methane and liquid oxygen at a temperature and pressure which are in thermal equilibrium so that heat is not introduced when these components are mixed to form a monopropellant or explosive, i.e., a cryogenic mixture of liquid methane and liquid oxygen, and therefore vaporization does not occur. In this manner, MOX can be safely stored and used without any substantial loss thereof.

Those familiar with the workings of Stage Zero and cryogenic depots could probably list improvements and microgravity adaptations suitable for fusion-drive tug operations.  One month to Mars, safely.

Image:  "FIG. 9 shows a schematic side view of a possible container for the remote mixing of MOX which has a means for aborting the mixture."  Flynn and Watson 2003.

Image:  "FIG. 13 achieves the objective of producing MOX as a single-phase, storage liquid without boiling or vapor bubbles forming and thus without venting or loss of MOX."  Flynn 1998.

Refs.

Flynn, T. and Watson, J., Cryoco Inc, 2003. Method and apparatus for the preparation and usage of a cryogenic propellant or explosive system. U.S. Patent Application 09/988,698.

Flynn, T.M., Cryoco Inc, 1998. Method for making and storing cryogenic monopropellant. U.S. Patent 5,804,760.

[LMT]

Drive Miniaturization

Miniaturization would improve metrics on most any fusion drive system.  Dimensions might shrink with improvements in:

1.  Magnetic mirror:

Some new HTS tapes have engineering and critical current densities much higher than the initial space-rated HTS coming from Faraday, e.g. Kim et al. 2021, Wang et al. 2022.  It's a near-term prospect for smaller HTS cables or smaller magnetic mirrors, after Ewig 2003.

2.  Reflector reinforcement:

Type-II glassy carbon (type-II GC) has strength to manage pressures beyond 10 GPa.  Zhao et al. 2015.  If structured optimally, it could improve on the notional 1 GPa reflector previous.

Conceptually:

Miniaturize a drive with notional engineering current density of 4 kA/mm2 and blast pressure of 5 GPa.  The changes:

a.  Nozzle: 

Reflector diameter is now roughly 3 m, approaching SpaceX RVac nozzle dimensions (with 3F, at ~ 1000x the specific energy, or thrust per kg propellant).

b.  Cables: 

Characteristic HTS cable current is 150 MA, at ~ 22 cm diameter.  (Ultimately, strength and direction of the cables' compressing multi-Tesla magnetic field overlaps will factor into current and pressure limits.)

c.  Breeding: 

If the drive breeds tritium, reduced reflector surface area increases transmutation heat flux.  To compensate, thermally conductive type-II GC structure might be lengthened by some meters, giving a longer radiator.  Lengthening a notional low-density auxetic section (7) would also give a more robust GC / EM regenerative shock absorber system.

Refs.

Ewig 2003.  Mini-MagOrion Program Document:  Final Report.

Kim, G., Ha, H., Kim, H., Oh, S., Lee, J. and Moon, S., 2021. Fabrication of 6-superconducting layered HTS wire for high engineering critical current density. Progress in Superconductivity and Cryogenics, 23(4), pp.10-13.

Wang, K., Dong, H., Huang, D., Shang, H., Xie, B., Zou, Q., Zhang, L., Feng, C., Gu, H. and Ding, F., 2022. Advances in second-generation high-temperature superconducting tapes and their applications in high-field magnets. Soft Science, 2, p.12.

Zhao, Z., Wang, E.F., Yan, H., Kono, Y., Wen, B., Bai, L., Shi, F., Zhang, J., Kenney-Benson, C., Park, C. and Wang, Y., 2015. Nanoarchitectured materials composed of fullerene-like spheroids and disordered graphene layers with tunable mechanical properties. Nature communications, 6(1), p.6212.

[LMT]

Focusing Without Lenses

do you even "grok" explosive lenses? or are you unable to comprehend fundamental facts about the subject?

The simple sphere works, amazingly.  Notice that.

If lensing were needed for max gain, it's a simple addition.  I presented Rafique 2023 for design reference, with focusing theory and options.  Did he miss something important?

Remarkably, spherical implosions are known to "self-focus" with Mach stems.  These merged, high-density shock waves form between the detonation points.  As the implosion progresses, Mach stems accelerate and spread out along the collapsing shock front.  The result is a focusing effect which smooths the front. 

Image:  The effect is seen in the simulation of Qiu and Eliasson 2016, reproduced in Almustafa and Nehdi 2023.  In (a), 10 charges form a semicircle around T1.  In (b), 9 Mach stems focus / smooth the semicircular shock front of the 10 coalescing blasts.  In (c), the front converges on T1.

Refs.

Almustafa, M.K. and Nehdi, M.L., 2023. Fundamental review on collision of blast waves. Physics of Fluids, 35(3).

Qiu, S., & Eliasson, V. (2016). Interaction and coalescence of multiple simultaneous and non-simultaneous blast waves. Shock Waves, 26(3), 287-297.

[Twark_Main]

Having some non-zero amount of "self-focusing" effect isn't enough. The mere fact that you saw the words "self-focusing" somewhere doesn't save you, therefore.

For a nuclear implosion you need nothing less than perfect sphericality and uniformity, otherwise the core will just "blorp" out the side.   Yes that is the technical term. 

[LMT]

For a nuclear implosion you need nothing less than perfect sphericality and uniformity, otherwise the core will just "blorp" out the side.   Yes that is the technical term. 

Imagine such text in a letter to Dr. Winterberg himself.  Oho.

-

Of course, Winterberg 3F works with simply "uniform and homogenous" high explosive, which a MOX sphere surely is.  His radius sizings prevent Rayleigh-Taylor implosion instability, yes?  Have other fusion-drive concepts struggled with instability?

And we see how Mach stems perfect focus, simply with spaced detonations.  Do you suppose Winterberg knows this trick?    Maybe posters can find more examples.

[lamontagne]

For a nuclear implosion you need nothing less than perfect sphericality and uniformity, otherwise the core will just "blorp" out the side.   Yes that is the technical term. 

Imagine such text in a letter to Dr. Winterberg himself.  Oho.

-

Of course, Winterberg 3F works with simply "uniform and homogenous" high explosive, which a MOX sphere surely is.  His radius sizings prevent Rayleigh-Taylor implosion instability, yes?  Have other fusion-drive concepts struggled with instability?

And we see how Mach stems perfect focus, simply with spaced detonations.  Do you suppose Winterberg knows this trick?    Maybe posters can find more examples.

I think everyone struggles with fusion instabilities.  NIF certainly does:

https://iopscience.iop.org/article/10.1088/1361-6587/ab49f4/meta#artAbst
https://lasers.llnl.gov/news/improving-understanding-of-nif-implosion-instabilities

General Fusion also struggles with stability.
https://generalfusion.com/wp-content/uploads/2022/04/aps-2018-magnetized-target-fusion-overview.pdf

Unfortunately, the military applications of these technologies have limited the available information.  Or perhaps fortunately, depending on your point of view.

[LMT]

For a nuclear implosion you need nothing less than perfect sphericality and uniformity, otherwise the core will just "blorp" out the side.   Yes that is the technical term. 

Imagine such text in a letter to Dr. Winterberg himself.  Oho.

-

Of course, Winterberg 3F works with simply "uniform and homogenous" high explosive, which a MOX sphere surely is.  His radius sizings prevent Rayleigh-Taylor implosion instability, yes?  Have other fusion-drive concepts struggled with instability?

And we see how Mach stems perfect focus, simply with spaced detonations.  Do you suppose Winterberg knows this trick?    Maybe posters can find more examples.

I think everyone struggles with fusion instabilities.  NIF certainly does:

https://iopscience.iop.org/article/10.1088/1361-6587/ab49f4/meta#artAbst
https://lasers.llnl.gov/news/improving-understanding-of-nif-implosion-instabilities

General Fusion also struggles with stability.
https://generalfusion.com/wp-content/uploads/2022/04/aps-2018-magnetized-target-fusion-overview.pdf

Unfortunately, the military applications of these technologies have limited the available information.  Or perhaps fortunately, depending on your point of view.

More on Rayleigh-Taylor instability there, yes.  Winterberg explained why 3F avoids that, and we see above that Mach stem implosion can avoid that.

What can you say, factually, about Winterberg's overlooked instability statement?  You didn't calculate any 3F issue, correct?  Some fact-check is needed there.

Image:  simulated Rayleigh-Taylor instability, LLNL.

[lamontagne]

For a nuclear implosion you need nothing less than perfect sphericality and uniformity, otherwise the core will just "blorp" out the side.   Yes that is the technical term. 

Imagine such text in a letter to Dr. Winterberg himself.  Oho.

-

Of course, Winterberg 3F works with simply "uniform and homogenous" high explosive, which a MOX sphere surely is.  His radius sizings prevent Rayleigh-Taylor implosion instability, yes?  Have other fusion-drive concepts struggled with instability?

And we see how Mach stems perfect focus, simply with spaced detonations.  Do you suppose Winterberg knows this trick?    Maybe posters can find more examples.

I think everyone struggles with fusion instabilities.  NIF certainly does:

https://iopscience.iop.org/article/10.1088/1361-6587/ab49f4/meta#artAbst
https://lasers.llnl.gov/news/improving-understanding-of-nif-implosion-instabilities

General Fusion also struggles with stability.
https://generalfusion.com/wp-content/uploads/2022/04/aps-2018-magnetized-target-fusion-overview.pdf

Unfortunately, the military applications of these technologies have limited the available information.  Or perhaps fortunately, depending on your point of view.

More on Rayleigh-Taylor instability there, yes.  Winterberg explained why 3F avoids that, and we see above that Mach stem implosion can avoid that.

What can you say, factually, about Winterberg's overlooked instability statement?  You didn't calculate any 3F issue, correct?  Some fact-check is needed there.

Image:  simulated Rayleigh-Taylor instability, LLNL.

I can't really comment on it, as I am neither a nuclear physicist or a weapons designer.  I can notice that there are no mini nukes around, despite the fact that these might be a handy weapon.  I also notice that no one seems to be pursuing this as a power source, despite  the fact that it would be a useful process to generate heat, at a much smaller scale that what was studied in the past.  A gain of 250 is nothing to sneeze at.

From the principle of mediocrity, my assumption would be that it doesn't work, or else someone would have done it by now. An interesting question is why doesn't it work.  Unfortunately, I don't have the tools to answer that.

[LMT]

I can't really comment on it, as I am neither a nuclear physicist or a weapons designer.  I can notice that there are no mini nukes around, despite the fact that these might be a handy weapon.  I also notice that no one seems to be pursuing this as a power source, despite  the fact that it would be a useful process to generate heat, at a much smaller scale that what was studied in the past.  A gain of 250 is nothing to sneeze at.

From the principle of mediocrity, my assumption would be that it doesn't work, or else someone would have done it by now. An interesting question is why doesn't it work.  Unfortunately, I don't have the tools to answer that.

3F was a surprise.  When the Soviets saw it, they certainly did consider weaponization, as Winterberg himself noted.  But prospective commercial value is for fast fleets; a novel need, thanks to SpaceX. 

The company that perfects safe and cheap 3F mass-production could have some real IP.  Who makes, say, precision cryogenic plastics?

[zubenelgenubi]

I can't really comment on it, as I am neither a nuclear physicist or a weapons designer.  I can notice that there are no mini nukes around, despite the fact that these might be a handy weapon.  I also notice that no one seems to be pursuing this as a power source, despite  the fact that it would be a useful process to generate heat, at a much smaller scale that what was studied in the past.  A gain of 250 is nothing to sneeze at.

From the principle of mediocrity, my assumption would be that it doesn't work, or else someone would have done it by now. An interesting question is why doesn't it work.  Unfortunately, I don't have the tools to answer that.

You "can't really comment", or calculate an issue, or show contradicting research, but...

No.  3F just surprised you.

Moderator:
LMT, you had an opportunity to engage in constructive discussion, and maybe teach us as well.

But, you chose to <blank> on a fellow member.  Again. 

[lamontagne]

I can't really comment on it, as I am neither a nuclear physicist or a weapons designer.  I can notice that there are no mini nukes around, despite the fact that these might be a handy weapon.  I also notice that no one seems to be pursuing this as a power source, despite  the fact that it would be a useful process to generate heat, at a much smaller scale that what was studied in the past.  A gain of 250 is nothing to sneeze at.

From the principle of mediocrity, my assumption would be that it doesn't work, or else someone would have done it by now. An interesting question is why doesn't it work.  Unfortunately, I don't have the tools to answer that.

3F was a surprise.  When the Soviets saw it, they certainly did consider weaponization, as Winterberg himself noted.  But prospective commercial value is for fast fleets; a novel need, thanks to SpaceX. 

The company that perfects safe and cheap 3F mass-production could have some real IP.  Who makes, say, precision cryogenic plastics?

When you mention 3F, is it a generally recognised name, or something your coined? Can you unpack the acronym?  Winterberg used Mini-nuke, is it the same thing?
Rather than going straight to a methane oxygen mixture and higher explosivity, wouldn't it be simpler to start with explosives, and forget the cryogenic part?

[LMT]

Torque

Near Earth, a fusion drive's magnetic mirror would torque in the geomagnetic field, rotating the system about its end diameter.

Notionally, for a returning tug with:

- 200 t mass
- 4 x 150 MA HTS 3-m mirror cable loops
- 1.5 s pulse interval

rotation rate increases by < 0.2 deg/sec between pulses, but this compounds if torque isn't countered with RCS or other means. 

An opposing HTS loop dipole could be mounted in a cryogenic tank to cancel the mirror's torque.  See Thomas et al. 2020, Thomas and Paluszek 2020.

Also, orthogonal dipoles might manage residual geomagnetic and pulse torques as in Alger de Ruiter 2022, Esit et al. 2022.

Image:  Thomas et al. 2020, "Fig. 10.  Direct Fusion Drive transport" with reversed engine dipoles for torque cancellation.  Note:  Here each DFD D-3He engine's thrust is < 100 N.  Do posters see why the DFD concept wouldn't serve OP purpose?

Image:  Esit et al. 2022, "Fig. 1.  Overall Attitude Determination and Control Algorithm"

Refs.

Alger, M. and de Ruiter, A., 2022. Magnetic spacecraft attitude stabilization with two torquers. Acta Astronautica, 192, pp.157-167.

Esit, M., Soken, H.E. and Hajiyev, C., 2022. A Model Predictive Control Based Magnetorquer-only Attitude Control Approach for a Small Satellite.

Thomas, S.J., Paluszek, M.A. and Swanson, C., 2020. Fast human missions to mars using direct fusion drive with a nuclear thermal stage. In ASCEND 2020 (p. 4080).

Thomas, S. and Paluszek, M.A., PRINCETON SATELLITE SYSTEMS Inc, 2020. Magnetic dipole cancellation. U.S. Patent 10,752,385.

[LMT]

re: fusion tug device mass-production

Plastic devices can be machined with 2-micron tolerance (image ref).  That tolerance constituted "high-precision machining" in the 1950s, when spherical implosion devices were perfected.  So perhaps a cryogenic plastic really could serve in 3F / MOX mass-production, for a fusion tug.

Have any posters manufactured structural plastics with such tolerances?