DerekL1963

If you have to keep making your engine more complex and heavier (and costing performance as the individual nozzles aren't as efficient as a single aerospike type combustor) in order to magically overcome real engineering concerns... that's usually prima facie evidence that you're headed off in the wrong direction entirely if your first goal was to increase efficiency. Not to mention that (multiple swiveling motors) engine will have even worse heating problems and will still have plume recirculation issues. And also not to mention, airflow is also a function of speed and altitude, not just of the gimbal position of the internal motors. Um... No, no matter what airflow you choose, you're going to have massive heating problems. Airflow alone won't cool those nozzles, nor cool the exhaust sufficiently that you won't cook the downstream portion of your shroud - you'll need active cooling. Especially for the period when you'll have insufficient or zero airflow, E.G. once you're at sufficiently high altitude or in vacuum. Umm... no. A few cm of cork or foam is sufficient for launch, but will be a feather in a windstorm during re-entry. (Not to mention, one of the reasons the DC-Y wasn't followed up on was the impact the TPS would have on the design, and concerns about weight and structural strength during the dive-and-swoop maneuver.)

If the "may" isn't enough, the [citation needed] should tell you why there has been so little research. That such ramjets are actually air augmented rockets is pure unsupported speculation on that part of whoever wrote that line. That's the HL in "HTHL" - Horizontal Takeoff Horizontal Landing. (Though my original post is in error, it should have said "HTHL (which is silly) or VTHL".)

So long as you're not going for a reuseable - because on landing the airflow is in precisely the wrong direction. (Unless you're going for a HTHL RLV, in which case you need professional help.) And either way the second engine, the high bypass one, is going to have some very serious cooling issues to deal with... and once it gets to altitude some very, very serious plume expansion/recirculation problems without some heavy, complicated, and very heat resistant mechanism for sealing off the inlet. As usual the devil, and why this hasn't actually been done, lies in the details.

Great mod! Much better than MJ's... Looking forward to the 'auto-learn' function, because I do tend to re-use a lot of designs. Question though, will it learn and remember even if you revert back to the launch pad?

If you have enough space travel to have space battles - you're also likely to have space traffic control and people looking for things that are behaving oddly. (Or, to put it another way, you've made the classic intellectual error of the armchair admiral - you've assigned all the advantages to the side you've chose, and have failed to consider even briefly the likely outcome of the scenario you posit and the behavior of the Other Side.)

How well do these play with Modular Fuel Tanks?

I used to have a link to a Google Docs spreadsheet that would calculate the required amounts of life support for a given time (very handy for use with MFT), but somewhere along the line I lost the link... Anyone have the link?

No, I'm not acting like the US is the entire story here. I'm demonstrating *why* they got outcompeted, with the caveat that the idiot "everything will ride on Shuttle" policy decision back in the early 80's is also a factor in that. (As is Eurocentrism and fall of the Soviet Union.) It's a complicated picture with roots that run back half a century and more. And the US is part of the international market too, and changes to US launch providers *will* have international repercussions. So, don't play the Eurocentric card, because it's bull. The problem I'm having with Nibb's response has nothing to do with our nationalities and everything to do with people trying to reduce complex situations into simplified and rote answers.

Commercial space flight has existed for 40 years now. The reason prices haven't gone down is due to low demand, not lack of offering. In fact, the commercial launch market is pretty saturated, between Atlas, Delta, Ariane, Soyouz, Proton, etc... for a market of less than 100 launches per year. *sigh* I didn't say commercial space flight - I said commercial launchers. The two things don't mean the same thing, not even (censored) close. Low demand is one factor, but that demand is low also in part because of the factors keeping the prices up. Chief among these is the fact that US launchers (with rare exceptions) were developed under government contracts for government purposes, and even when flown commercially are tied to the immense standing army and standing bureaucracy demanded by the government. And so long as people are willing to step up and pay the freight, none of the existing launch providers have had any impetus to reduce costs even fractionally. This is not, as you and so many others treat it, a law of nature - it's an accident of history. SpaceX's growing order book, and the responses of the established launch providers say otherwise. For the first time in history there's real competition between launch providers - and the game is already very visibly changing.

*deleted* Found my screwup.

Yes, it does matter whether it's private or public - because government developed launchers* have precisely zero impetus to bring costs down. (Which is why space access has remained so freaking expensive for so long.) Commercial launchers have every reason to bring the price down, because it attracts business. (Private and public. There's a reason why ULA et al fought so hard against SpaceX getting certified.) And even though launch costs are only a fraction of the cost to bring a comsat on stream - it's still a huge line item. No business is going to turn down the opportunity to reduce costs. And if the trend is to make them smaller and lighter (and less capable and more expensive), then reducing launch costs will serve to flatten or reverse that trend. (Again, something that no business will turn down.) Space access isn't immune to the laws of economics and the normal forces of business, and the status quo isn't a law of nature. * E.G. the Atlas and Delta EELV's.

Apples and the thing least like apples you can imagine. SLS-HLV (and Energia) is a government launcher (and to a large extent so are the other US offerings) - Falcon is a whole new ball of wax, a truly commercial launcher.

I'm not. Robert Zubrin has always been... hazy about the difference between theoretical concepts, laboratory scale proofs of concept, prototypes, and developed flight hardware. Much (most) of what he treats as the last is actually one of the other three.

That is, assuming that a NSWR rocket even works in the first place. Zubrin's paper on it is different from a bar napkin calculation only in that it's written up as a paper. It's never been the subject of anything but the most simplistic and handwaving of analyses.

Presuming you also ship the raw stock to feed those machines. And remember to stock the consumables (cutting fluid) they'll require. And spare tools to replace the ones that wear out (as well as spare parts for the machines themselves - and all the tools and equipment needed for said maintenance). Etc.. etc... Supporting a machine shop remotely gets complicated very quickly. That's what I keep pointing out - you guys keep forgetting there are a lot of links to the chain. Stuff that's not obvious until you stop hand waving and actually think. And no Kaos, I didn't avoid your question - words have meaning, and I answered in clear and unequivocal terms. (And stone age colonies are irrelevant. We aren't building stone age colonies in space.)

Precisely what it says on the tin and what it's commonly assumed to mean; A colony that requires no significant inputs in order to maintain viability. Again, you've forgotten one of the benefits of trade is to obtain goods or materials that we cannot produce ourselves, or which would be extraordinarily difficult to produce economically in sufficient quantities, or which are just flat out cheaper to import. A key example would be titanium - which the US has virtually none of AFAIK. You've missed practically everything - because you've created the industry to "build up water cleaners and recyclers" out of thin air. In the real world, the tools and materials for doing so would consume a significant quantity of the 100 tons... and that's just for the "water industry". Even back in the 15-1700's (the great age of colonization) nobody tried to build self sufficient colonies because even then you needed too much machinery (everything from looms to paint mills) and too many people to operate them and too many farmers to feed them... (And I haven't even mentioned the specialists needed to build the machinery.) We don't need quite so many people nowadays, but the equipment required is much more complex and difficult to build. The basic problem is that it's turtles all the way down, no process is independent, they all require infrastructure and bodies to support them. (And, as juanml82 correctly points out, there's a lot of processes that don't scale down well at all.) Nobody is debating whether or not Mars colonies are possible, but whether or not self sustaining colonies are possible.

No, the reason we cannot build a self sustaining colony (here on Earth, or elsewhere) is that we simply cannot - there's no place that has all the needed inputs (materials) and even if there were, the number of specialties and the amount of infrastructure needed is simply overwhelming. (And that presumes we can solve the known unknowns, which is by no means a given and doesn't address the unknowns we're certain to encounter.) I know "try your best and you'll always succeed" is what they teach kids nowadays, but that's just not how the real world works.

It's a design patent, which is a very different kettle of fish than a technology patent.

We can't.

I'm always reminded of a quote by Admiral Rickover on the difference between paper and reality; An academic reactor or reactor plant almost always has the following basic characteristics: (1) It is simple. (2) It is small. (3) It is cheap. (4) It is light. (5) It can be built very quickly. (6) It is very flexible in purpose (“omnibus reactorâ€Â). (7) Very little development is required. It will use mostly “off-the-shelf†components. (8) The reactor is in the study phases. It is not being built now. On the other hand, a practical reactor plant can be distinguished by the following characteristics: (1) It is being built now. (2) It is behind schedule. (3) It is requiring an immense amount of development on apparently trivial items. Corrosion, in particular, is a problem. (4) It is very expensive. (5) It takes a long time to build because of the engineering development problems. (6) It is large. (7) It is heavy. (8) It is complicated. Having studied various forms of engineering and design from my armchair over the years - he hits it pretty much spot on.

In terms of weather/climate - there's a barrier of sorts of ocean currents and atmospheric flow between Antarctica and the rest of the world, Antarctica is also (on average) at a higher elevation that the Arctic, and the Earth is at aphelion in July (Antarctic winter), and the Earth is at perihelion in January Antarctic summer). All these things make it difficult to compare the two (Arctic and Antarctic) directly.

Precisely 00.00000000000000000000000000000000000000000000000

*Sigh*. Everything thinks that since you can shut down liquids, you have to shut down solids. Nothing could be further from the truth. You don't have to shut them down - you just have to be producing zero (or very small positive) net thrust. The technology for doing so (venting the case) is old and well proven. (It was first deployed in the 1950's.) Now that brings up the obvious question, "why didn't they try this with the Shuttle?". The answer to that is, "the ET was a huge problem". See, during first stage flight the SRB's were essentially dragging the ET behind them. When thrust was terminated, the changing loads would tear the ET apart tossing the Orbiter in the airstream where it would be torn apart by aerodynamic forces. (This is essentially what happened to Challenger.) For the same reason, they couldn't simply blow the attachments and let the SRB's go on their own merry way. The answer to this was a solid fueled escape rocket to power the Shuttle clear - but the escape rocket required was too big and too heavy, even if it was subsequently used (after ET jettison) as a "third stage". (First stage being SRB+SSME, second stage being SSME's only.) A capsule doesn't suffer these problems. It's lighter, and rather than being "beside" the booster it's on top of the booster and leaving it behind as the booster slows down and the escape rocket accelerates the capsule which further reduces the size of the escape rocket required.

At any speed faster than a few m/s, difference in density between peat, water, and soil is essentially moot.

While there ends up being some advantages (as well as some disadvantages) to having multiple small engines, one of the key reasons Falcon has multiple small(er) engines is that small simple engines are cheaper, simpler, and faster to develop and manufacture. A properly designed modern engine fails very rarely. (And having multiple engines actually *increases* your chances of having a single engine fail.) Multiple engines also require more complex piping, a heavier and more complex thrust structure, more effort (read, $$) to install and checkout.... Some of that can be recouped through economy of scale, yes, but that doesn't mean the issues aren't there. Engineering is always about tradeoffs, and while SpaceX has chosen a route different than that generally followed by the other players (which tend towards fewer, larger, engines) - that doesn't make their approach intrinsically better or right, just different.