A better engine is what is needed to get to the moon and the planets in the system

[richfororbit]

Hi,

I saw a film about Pluto the other day, and it took many years for a probe to get to the planet, New Horizons, I've forgotten the mission profile and all that now.

But with the challenge of traveling to the planets in the solar system, some sort of research is needed to increase the time to get to them sooner.

To begin with, instead of three days to the moon using the Orion capsule, it should be a day.

And for Mars is half a year? Three months could be better, but of course getting back is still nine months or something.

While propulsion is a hard game, NASA should be challenged to do this. It make not make money for the NASA's communities, but it still could.

 

[GLS]

Is "Neptune and back in 6 minutes" good enough? :lol:
[ame="https://www.youtube.com/watch?v=5kZ-M8LsFwo"]https://www.youtube.com/watch?v=5kZ-M8LsFwo[/ame]

 

[Tycho]

In theory, yes. Trouble is, the time it would take to develop said "better engine" would necessarily entail trading away the sort of experience and know-how that's only attainable via piecemeal developmental steps in lieu of doing it all at once. To say nothing of the necessity of that very experience and know-how in effecting that development.

Edit: @GLS: not as good as Thirty Seconds to Mars... wait, let me do the math...

 

[Linguofreak]

The problem is that the issues are economic and political, not technological.

First of all, we could probably do quite a bit better just with current engines if we had appropriately placed stations around e.g, the Moon and Earth and had a lunar shuttle that could just go between the two without ever landing on either. Such a vehicle could dispense with the weight of heat shields and landing legs, and could use an engine optimized for ISP rather than thrust, with dedicated vehicles for launch and landing at either end. But that would require considerable investment in infrastructure that is just not going to happen unless there's something that can be mined or manufactured on the Moon that can't be mined or manufactured on Earth, and that has a very high value per unit weight.

 

[GLS]

The problem is that the issues are economic and political, not technological.

First of all, we could probably do quite a bit better just with current engines if we had appropriately placed stations around e.g, the Moon and Earth and had a lunar shuttle that could just go between the two without ever landing on either. Such a vehicle could dispense with the weight of heat shields and landing legs, and could use an engine optimized for ISP rather than thrust, with dedicated vehicles for launch and landing at either end. But that would require considerable investment in infrastructure that is just not going to happen unless there's something that can be mined or manufactured on the Moon that can't be mined or manufactured on Earth, and that has a very high value per unit weight.

I've reached the same conclusion: specialized vehicles for specific tasks.
The base shuttle vehicle would have all that is needed (prop, engines, computers, etc), and on top a manned module or payload pallet would be attached (configurable at the stations). To save prop mass, an inflatable or deployable "drag-device" could be used to increase the surface area of the vehicle for aerobraking on Earth.
It would end up taking maybe 4 or 5 days between orbital stations, but actually it would reduce the time between "lunar trips".

Btw: same for Mars with Aldrin Cyclers.

Edit: @GLS: not as good as Thirty Seconds to Mars... wait, let me do the math...

I think the Enterprise is much faster... :lol:

 

[Urwumpe]

I think the Enterprise is much faster... :lol:

Just 4 seconds to Mars on a good day and Warp 6...

 

[Linguofreak]

The second thing, which I ran out of steam to say earlier, is that nuclear propulsion could do even better, and is well within 1960s technological capabilities, but it's likely to be hobbled by NIMBYism for the foreseeable future. Some of that NIMBYism is (IMHO) quite unreasonable (nuclear thermal rockets), and some is quite reasonable (Orion, in which case it's more "NWITVAB" (Not WithIn The Van-Allen Belts) than "not in my back yard").

 

[Moach]

If you read enough Robert Heinlein (forgot exactly which of his books this comes up in as a major issue*) you should inevitably also figure that there's another problem for after "how to build such an engine" becomes a trivial concern...

thing is, with an "Infinity Engine" aboard, your travels are still limited by the "how many Gs are you willing to put up with and for how long" problem.

Wanna travel to the stars? No worries, just wait several years to reach near relativistic speed at 1g, while everyone you left behind dies of relativistic old age.

Or if you don't mind getting there in a liquid form, (Dan Simmons has written some good Sci-fi where that specifically happens) you can shorten the trip to something more manageable...

In either case, never mind making any local appointments for after your trip. It's not like you'd run into anyone you know when you get back...

And most likely, the civilization that has risen to replace yours in the several Einstein-Abridged eons you were away probably won't accept whatever currency you've used to build up your umptillionary fortune of relativistically accumulated interest....


Tough gig going out there, ain't it? Something to think about next time at the airport when they make you wait a bit at the gate.


Physics is the worst airline....




*edit:

It was actually Larry Niven's "World of Ptaavs" that had the high-acceleration trip to Neptune (or the other blue ball in that general 'hood) featured quite prominently.

It also presented a very curious thing you can do when you have a "TorchShip" (Inifinite or near-enough engine aboard) - Namely: You can put yourself in a comfortable 1G environment, in space, mind you, by entering a Forced Orbit.

Basically you're forcing your ship to orbit somewhat faster than normal for your given altitude, this is achieved by pointing the nose straight at the ground and gunning your engines towards zenith. If you get your angles just right, the idea is that you force yourself to remain at the periapsis of an elliptical orbit which rotates along the center body along with you.

Not fuel efficient perhaps, but who cares about that? We got an Infinity Engine! Weeeeeee!

 

[richfororbit]

Well, while getting to the Moon in three days isn't that long, but you know, certainly that could be a goal that NASA could work on, sending the Orion there in one day.

 

[Linguofreak]

The point is, we can probably do it with current tech, even 1960s tech, but lack a reason to actually do it.

"Because it's there" is barely enough to get Congress to cough up the money for the slow trip. The fast trip is right out.

 

[Urwumpe]

The second thing, which I ran out of steam to say earlier, is that nuclear propulsion could do even better, and is well within 1960s technological capabilities

I doubt that it is that easy. Nuclear thermal engine research also took place in the 1980s and 1990s, all with promising results in terms of feasibility but still with MANY unsolved problems to actually build and operate one such engine.



How many reactors do you know, that can operate at the chamber temperature of a SSME? While getting rid of the oxygen in the exhaust means 3 times the specific impulse alone, reducing the temperature in the chamber to what nuclear fuel elements for existing high temperature reactors can take also reduces it again, resulting in a only slightly higher performance in the end.


Nuclear magnetic engines sound like the more promising technology right now in terms of what we can already build, but the "To Mars in 90 days" scenario means strapping a 100 MWe reactor into a spacecraft - with approximate 600 MW thermal power.



Maybe we can create expendable nuclear reactor cores for maximum performance, but that would essentially translate to sitting on a nuclear bomb instead of a chemical bomb....

 

[MaxBuzz]

or leave the engines as is. but the man himself will be in the form of sperm and egg cells in the apparatus of the artificial womb and a robot babysitter

 

[Urwumpe]

or leave the engines as is. but the man himself will be in the form of sperm and egg cells in the apparatus of the artificial womb and a robot babysitter

What could possibly go wrong?

 

[JonnyBGoode]

Just 4 seconds to Mars on a good day and Warp 6...

[ame="https://www.youtube.com/watch?v=5kZ-M8LsFwo"]YouTube[/ame]

 

[Linguofreak]

I doubt that it is that easy. Nuclear thermal engine research also took place in the 1980s and 1990s, all with promising results in terms of feasibility but still with MANY unsolved problems to actually build and operate one such engine.



How many reactors do you know, that can operate at the chamber temperature of a SSME? While getting rid of the oxygen in the exhaust means 3 times the specific impulse alone, reducing the temperature in the chamber to what nuclear fuel elements for existing high temperature reactors can take also reduces it again, resulting in a only slightly higher performance in the end.

No, the problem of building an NTR with significantly better performance than hydrolox *was solved* in the 1960s.

The NERVA project built engines that were actually fired on the test stand, all of which performed at over 800 seconds vacuum ISP (nearly *twice* that of the SSME) and gigawatt power levels, for thrust on the order of 250 kN, with chamber temperatures on the order of 2200 K. One was fired at full power for 15 minutes, and then restarted for another 14, another did a burn lasting a full hour, and the final one tested was deemed ready for spacecraft integration. In the end, Nixon killed the project despite a specific stipulation by Congress in that year's appropriation for NASA that funds were not to be diverted away from NERVA.

[Rant]I was aware NERVA hadn't actually flown, but what Nixon did to it I only just now read while gathering exact details. The killed a flight-ready NTR, and abandoned Apollo/Saturn in favor of the Shuttle boondoggle. We've only just now regained a man-ratable booster/capsule (the Shuttle may have gotten the "man-rated" stamp, but it certainly never *should* have), and a replacement flight-ready NTR is still a ways off, if it ever happens. Nixon set the US space program back at *least* half a century.[/rant]

The more recent 80s and 90s project you refer to (Timberwind) was, AFAIK, a paper design, which, if feasible, as you say, would have offered ISP in the 1000 second range.

The 2019 federal budget funds development of an NTR with plans to flight test it by 2024. I'm not horribly optimistic about that, between the likelihood of a change of administration in November and the fact that it would be starting from scratch, but if they kept their goals modest (design conservatively rather than bleeding-edge, don't try to get better performance than NERVA) it might well be doable. But I figure it's fairly likely that they'll try to match or exceed Timberwind, in which case they'll be going into uncharted territory. I *know* 800 seconds is 60s tech. Since I haven't heard of any Timberwind engines being built or fired, I have no idea if 1000 is 80s tech, or 2000s tech, or 2020s tech, or 2080s tech.

 

[MaxBuzz]

What could possibly go wrong?

I wanted to joke and propose the most incredible scenario of colonization. it turned out i repeated the most realistic model at the moment Sleeper ship (Embryo space colonization)


about the engine NERVA Do not forget that the USSR also failed RD-0410 a year ago the engine failed TEM (nuclear propulsion)

 

[Urwumpe]

[Rant]I was aware NERVA hadn't actually flown,

It was also still far away from a flight-prototype. It was still pretty much a massive open-cycle gas-cooled nuclear reactor. Timberwind tried to solve a lot of the problems discovered with NERVA regarding the fuel elements and the optimal engine cycle.



And it still failed to achieve the necessary parameters, additionally to the poor political climate at that time for nuclear technology. Project Pluto also should be stated there, since it tried to solve the same problems. (And just decided to accept the problem of fracturing fuel elements as somebody elses problem...)

 

[Thinker55]

I'm sure I don't have to point out to people well-versed in orbital mechanics that it takes 3 days to get to the moon because if you want to cut that time, you have to waste fuel boosting to an orbit that loops well beyond the moon, then waste more fuel braking into lunar orbit... Even breaking it up into specialized chunks doesn't fix that. Personnel and cargo transfers in LEO and possibly LLO would ADD time...

 

[GLS]

Even breaking it up into specialized chunks doesn't fix that. Personnel and cargo transfers in LEO and possibly LLO would ADD time...

Yes, but you probably end up doing more flights if you don't have to launch EVERYTHING from the ground each time. I'd rather have a system that connects a station around the Moon with another around the Earth twice a month with a trip lasting about 1 week, than a trip once a month that takes 3 days. :shrug:

 

[Urwumpe]

I'm sure I don't have to point out to people well-versed in orbital mechanics that it takes 3 days to get to the moon because if you want to cut that time, you have to waste fuel boosting to an orbit that loops well beyond the moon, then waste more fuel braking into lunar orbit... Even breaking it up into specialized chunks doesn't fix that. Personnel and cargo transfers in LEO and possibly LLO would ADD time...

Well, except that for those who are well-versed in orbital mechanics know, that time is a resource. 3 days is not the shortest time to the moon and not the longest time to the moon. It is also not the most fuel-efficient way to the moon.



A hohmann transfer is just a very good compromise between time, fuel and available launch windows.