(Speculative) historical circumstances for space exploration

[Ajidica]

Reinitiate Reagan's plan to destroy our enemies with frickin' laser beams.

But then the laser beams aren't mounted on sharks....

Link to video.

 

[Crezth]

Well, how to put it... okay, what has happened to NASA has nothing to do with the amount of money that is available. Its budget is three or four times that of ESA, the second largest space agency in the world. NASA's budget wasn't even cut - which is the real tragedy. It *should* have been cut. It should have been cut 50% or more, because according to what the politicians legislate, its new mission is to boldly go nowhere and spend ridiculous amounts of money doing it. At least if the budget was cut profoundly, all the fat and the dead meat would fall off and the agency would become more effective again.

I am being sarcastic here, of course. What I really mean is that the problem isn't just funding, it's organization or the lack of it within the agency and the political system which governs it. Obama cancelled the existing programme, throwing NASA into complete disarray, but the Congress is trying to resurrect it bit by bit through various bills it keeps passing. It's a ridiculous - no, criminal - waste of money. As a result, you'll waste 10 years developing your new Big Rocket, only to see it cancelled in 2-4 years time, and then you'll be back at square one.

Until you guys can teach your politicians to leave NASA alone and let it set its own goals based on what makes sense scientifically, not politically, your space programme won't go anywhere. In fact, eventually people will get so pi**ed off at how much money NASA is spending without results, that they'll close it down entirely.

Well, yeah. I don't see this as a problem with the principles of cooperation, but with the political system that isn't interested in doing Stuff. The general trend is towards more politics and less governing.

You make a good point about political meddling causing disarray within NASA, however; that is certainly a major factor.

Space exploration is, most likely, to be handled almost exclusively by Corporations looking to make a profit. The first step I see is the mining of the asteroid belt: on average, a single asteroid has 30 million tons of nickel, 1.5 million tons of metal cobalt and 7,500 tons of platinum; the platinum alone would earn the Corporation $150 billion.

Complete fantasy. The tech isn't there yet, and will continue to not be there until it is developed, which won't happen unless bodies which are not interested in profit cultivate it (there's no profit in going to the moon nor in going to Mars, both are tasks that must be completable before we can get to the asteroid belt - you can see where I'm going with this).

I remain skeptical that corporations can even land on the moon (with aid from NASA I guess it's theoretically possible); to expect them to go beyond? Unrealistic in the extreme.

\/\/\/ Read that article.

 

[tokala]

It's not going to happen, for economic reasons.
For scientific purposes, those robotic probes will probably keep getting launched for a while.

That nasty physics once again shattering high flying dreams ...

 

[innonimatu]

1) Educated population.
2) International competition
3) A system of effective long term planning

Coming around to miss the USSR, are you?

In Europe, long-term planning is easier to do, but at a terrible cost (nobody is willing to commit to truly bold projects, so our long-term plan is to do nothing).

Excuse me? Easier to do? No one is willing to pony up the money! Governments can't even agree on how to salvage their cherished political union project!

The only reason European governments still fund fundamental research reasonably well is the incestuous relationship between politicians and universities. Which is better, I guess, that having primarily incestuous relations between politicians and business like in the US, but doesn't guarantee that the funding goes to the most interesting (scientifically) projects.

Just complaining also, not that I can thing of any solution for that.

 

[Winner]

Coming around to miss the USSR, are you?

I miss their "enthusiasm" for space, but realistically speaking, even if there was the USSR around still, not much would be happening.

Excuse me? Easier to do? No one is willing to pony up the money! Governments can't even agree on how to salvage their cherished political union project!

Read the whole of what I said. It's comparatively easier because nobody is willing to pay very much. ESA has sent some great stuff in space (probes, landers, telescopes), but it usually took it quite a long time to do these projects. The truly ambitious projects usually don't get off the ground, and if they do, they rarely survive.

The problem is partially that ESA's structure is a... relic of a previous era of European integration. It's very intergovernmental in nature, meaning very bureaucratic and very prone to deadlock over serious issue. It would probably be better if the EU took over the agency, reformed it, and infused some more money into it. The last thing is already happening, but not on the scale I'd like to see.

The only reason European governments still fund fundamental research reasonably well is the incestuous relationship between politicians and universities. Which is better, I guess, that having primarily incestuous relations between politicians and business like in the US, but doesn't guarantee that the funding goes to the most interesting (scientifically) projects.

That's way too pessimistic. The EU actually does fund fundamental research, and the scientists are quite happy with it: BBC article. Of course, I'd be the first one to approve reducing agricultural subsidies by ~90% and pouring all the money in research and innovation (that way, we'd see at least some of it turn to something other than manure and rotten fruit).

---

But we also need more organization in our space efforts. I'd like us to set up achievable goals, have a timetable of sorts - what do we want to do in what timeframe and how much will it cost.

Right now, I want

a) fully utilize the ISS. It's not the best station we could have built, but we have it and it would be foolish not to take advantage of it. Let's test the stuff we need for deep space human spaceflight there: life support systems, radiation shielding, artificial gravity, etc.

b) work on reducing the recurring costs of getting to the low Earth orbit (LEO). More than half of the costs are due to bad management and organization. There is no *technological* justification for the insanely high launch costs. Let commercial companies send tourists to space, let them operate commercial space stations, subsidize their programmes, buy their products. The more "ordinary" people will fly to space, the more people will care about what happens on the space front.

c) a robust planetary/lunar exploration programme. We should be making space probes like sausages (to quote a certain Soviet premier) - has a design been successful? Fine, let's make more of them. NASA has built two very successful rovers, so why not build more? Now when they know how, it would be much cheaper to "mass produce" them. Say, four rovers to Mars at every launch opportunity (+- 2 years), every time with a slightly different set of instruments to do as much science on Mars as possible.

d) renew serious work on nuclear thermal rockets and other advanced methods of in-space propulsion. Test these on robotic missions - a Mars sample return mission would be nice.

Then we can think about sending humans somewhere - the Moon (again), the asteroids, Mars, you name it. None of what I mention should be unaffordable. Yes, it's not exactly cheap, but it would cost us much less than one of these Greek bailouts. Also, it would help to prepare and educate people - the constant stream of exciting news from space would generate more support for the latter more ambitious missions.

 

[Crezth]

b) work on reducing the recurring costs of getting to the low Earth orbit (LEO). More than half of the costs are due to bad management and organization. There is no *technological* justification for the insanely high launch costs. Let commercial companies send tourists to space, let them operate commercial space stations, subsidize their programmes, buy their products. The more "ordinary" people will fly to space, the more people will care about what happens on the space front.

I like everything else you say (really!) but we keep coming back to this one.

It is literally not possible to get to space in just one rocket stage with the fuels we have now. I mean it that it can't be done. You need at least two stages and three is optimal for most cases (five will work if you're insane and also German). So perhaps launch costs can be cut down, but I am skeptical they will ever be truly low, and there are two reasons I say this:

1) Multi-stage rockets are an engineering nightmare. They are all the problems of a single rocket times n where n is the number of stages the rockets have and is proportionally linked to your insanity. They are expensive not only because the expertise required to produce them is special, but

2) they are prone to failure. Multi-stage rockets have a high risk of destroying themselves in some catastrophic way due to structural instability and all the iniquities of the multi-stage system, and a single look at NASA's early days and even at SpaceX in the modern day is all it takes to realize that you will need to make many rockets before you get it right. Rockets can and will fail on you, and each time they do, you're just adding to your bill.

These two problems are the biggest obstacles right now (in my opinion). However, recent advances in hypersonic jet technology are promising in terms of getting to LEO effectively/efficiently, and a more advanced type of rocket fuel could get to space in just one stage, which by itself would make space an incredibly, incredibly achievable thing.

 

[aelf]

b) work on reducing the recurring costs of getting to the low Earth orbit (LEO). More than half of the costs are due to bad management and organization. There is no *technological* justification for the insanely high launch costs. Let commercial companies send tourists to space, let them operate commercial space stations, subsidize their programmes, buy their products. The more "ordinary" people will fly to space, the more people will care about what happens on the space front.

These two problems are the biggest obstacles right now (in my opinion). However, recent advances in hypersonic jet technology are promising in terms of getting to LEO effectively/efficiently, and a more advanced type of rocket fuel could get to space in just one stage, which by itself would make space an incredibly, incredibly achievable thing.

Going by what Winner said about the benefits of subsidising private enterprise, am I right to say that, today, more effective launch rockets, which would give space exploration a much-needed boost (heh), would have to be developed more-or-less commercially?

 

[gangleri2001]

The only thing that will lead us to space exploration is overcoming the only problem that keeps us from doing so: the achievement of an artificial magnetic field technology that would protect us from the radiation.

 

[Winner]

I like everything else you say (really!) but we keep coming back to this one.

It is literally not possible to get to space in just one rocket stage with the fuels we have now. I mean it that it can't be done. You need at least two stages and three is optimal for most cases (five will work if you're insane and also German). So perhaps launch costs can be cut down, but I am skeptical they will ever be truly low, and there are two reasons I say this:

I disagree. It is perfectly possible to build a simple dumb single-stage-to-orbit booster. It will just be next to useless, because it will have to be quite big to lift a tiny payload.

Take for example the Saturn-V second stage, S-II: it had a dry mass (engines, fuel tanks, outer shell, paint, etc.) of 36 tonnes. Fully loaded with liquid oxygen/liquid hydrogen propellant, it weighed about 480 tonnes. The specific impulse its engines were capable of delivering was 421 seconds. If used as a standalone rocket, it would be able of achieving a delta-v of about 10.6 km/s - theoretically enough to get to orbit (which is 7.8 km/s plus, say, 2 km/s to compensate for air drag and gravity losses) and then some. If you traded this "excess" delta-v for payload mass, you'd get something between 4-8 tonnes to orbit.

Now I understand that this is a gross simplification, and most of this margin would probably be lost due to other things (lower specific impulse in the early ascent phase, for instance), but you can see where I am heading with it. If you're willing to build a big booster to get a tiny payload to space without the use of staging, it is possible. It's just so hugely impractical that we use staged rockets instead.

1) Multi-stage rockets are an engineering nightmare. They are all the problems of a single rocket times n where n is the number of stages the rockets have and is proportionally linked to your insanity. They are expensive not only because the expertise required to produce them is special, but

You're exaggerating it. Rockets are complicated machines, yes, but in comparison to a modern airliner (say, A380), they're actually quite simple. Their expandability means many dirty and cheap engineering solutions are possible - you don't have to care if the machine will work for years, you need it to work for 8 minutes or so, and then you're done with it.

You're right that more stages increase complexity, but two or three stages (depending on whether you consider things like laterally attached solid rocket boosters a separate stage or not) are quite easy to do, and we have half a century of experience with them. There is absolutely no reason such a machine should cost ~100 million Euros per piece, NONE whatsoever.

From what I read on the subject, the insane prices are a result of an extraordinary distortion of normal economic mechanisms which has resulted from the strategic importance of an independent, government-controlled access to space. There are other factors - the ICBM legacy (most space launchers are in one way or another evolved from missiles), the crazy feedback loop between high launch prices -- satellite complexity -- costs, and so on and so forth.

2) they are prone to failure. Multi-stage rockets have a high risk of destroying themselves in some catastrophic way due to structural instability and all the iniquities of the multi-stage system, and a single look at NASA's early days and even at SpaceX in the modern day is all it takes to realize that you will need to make many rockets before you get it right. Rockets can and will fail on you, and each time they do, you're just adding to your bill.

Again, we're getting better at this. It is possible to reach very high reliability figures (for a rocket, it has to be said that rockets will NEVER be as reliable as aircraft or cars, because much higher energies are involved in their line of work). Soyuz-FG used in the Russian manned programme has so far had 100% reliability. Europe's Ariane-5 started off with a rather spectacular failure, but has since only suffered one other failure (two partial involving the upper stage, one of them when the new cryogenic upper stage was introduced). That makes it 96% reliable, but it hasn't experienced another failure since 2003.

Some rockets will blow up, so what? It's no reason to make them 900% more expensive than they should be.

These two problems are the biggest obstacles right now (in my opinion). However, recent advances in hypersonic jet technology are promising in terms of getting to LEO effectively/efficiently, and a more advanced type of rocket fuel could get to space in just one stage, which by itself would make space an incredibly, incredibly achievable thing.

I agree that air-breathing engines are promising. We're now approaching the tech level to actually build them. As for other fuels, what do you mean, exactly? Except exotic materials like metastable metallic hydrogen or other forms of unobtainium ( ), the oxygen/hydrogen mixture is the best there is - at least if we're still speaking about chemical rockets.

---

I say, stop treating space launch business as a sacred ritual only a select few are allowed to take part in (after receiving the modern equivalent of a special dispensation from the Pope) and treat it more as... well, business. Foster competition, be intolerant of cost overruns, dump contractors if they can't push down prices, be prepared to allow foreign competitors into your country, etc. etc. etc. The prices are being reduced as we speak, and it just proves that if there was a will to run the whole thing properly, we could be sending stuff to space 5 to 10 times cheaper than today. That alone would enable us to do far more in terms of robotic exploration, if not human spaceflight.

---

The only thing that will lead us to space exploration is overcoming the only problem that keeps us from doing so: the achievement of an artificial magnetic field technology that would protect us from the radiation.

That's bull. It would be a nice thing to have, but it is by no means critical for the kind of missions we want to do now (Moon, Mars, asteroids).

 

[gangleri2001]

That's bull. It would be a nice thing to have, but it is by no means critical for the kind of mission we want to do now (Moon, Mars, asteroids).

I was answering to the OP. If you want an interstelar empire, you totaly need that. And for a Mars mission is also necessary because getting there means spending months in the interplanetary space, where there's lots of radiation.

 

[Winner]

I was answering to the OP. If you want an interstelar empire, you totaly need that. And for a Mars mission is also necessary because getting there means spending months in the interplanetary space, where there's lots of radiation.

You can't shield against the really hard stuff (cosmic rays, you won't stop them with any reasonably imaginable portable magnetic shield - even the Sun's magnetosphere can't block them out), and you can shield against the soft stuff (solar particles) with far simpler measures.

I am not in any way opposed to research/development of this kind of shielding technology, I am merely saying that it isn't really something we need to have to do stuff in space beyond low Earth orbit.

 

[Tee Kay]

Either someone invents this:

Or finds a way to do this:

Or this:

 

[Winner]

I shall keep bumping this up, since I am interested in space so much that I feel an irrational urge to discuss these issues with other people

Anyway, some people are seriously proposing that we "scour the Moon" for traces of alien civilizations. No, this has nothing to do with the Apollo 18 film. The idea is that since the lunar environment changes very very little over the eons (so much so that the footprints left by the Apollo astronauts will still be recognizable in millions of years, until the steady micrometeoroid bombardment erases them), if some alien civilization had visited the Earth-Moon system in the past, we might still find some traces of their visit on the Moon.

We should scour the moon for ancient traces of aliens, say scientists
Online volunteers could be set task of spotting alien technology, evidence of mining and rubbish heaps in moon images

Hundreds of thousands of pictures of the moon will be examined for telltale signs that aliens once visited our cosmic neighbourhood if plans put forward by scientists go ahead.

Passing extraterrestrials might have left messages, scientific instruments, heaps of rubbish or evidence of mining on the dusty lunar surface that could be spotted by human telescopes and orbiting spacecraft.

Though the chances of finding the handiwork of long-gone aliens are exceptionally remote, scientists argue that a computerised search of lunar images, or a crowd-sourced analysis by amateur enthusiasts, would be cheap enough to justify given the importance of a potential discovery.

(the rest of the article)

I say it's about time we found the bloody big black monolith that Clarke once prophesied I think there is also a novel which deals with this, although there the "alien" ruins are in fact ruins left by a previous Earth-born sentient species.

And if we find nothing, I propose building pyramids or some other visibly artificial structures there, and fill them with some of our artefacts and DNA samples, so that when we finally destroy ourselves, someone else might one day find out that we were here. It would be an act of cosmic vanity, admittedly, but one that'd be entirely forgiveable

 

[Crezth]

I disagree. It is perfectly possible to build a simple dumb single-stage-to-orbit booster. It will just be next to useless, because it will have to be quite big to lift a tiny payload.

Take for example the Saturn-V second stage, S-II: it had a dry mass (engines, fuel tanks, outer shell, paint, etc.) of 36 tonnes. Fully loaded with liquid oxygen/liquid hydrogen propellant, it weighed about 480 tonnes. The specific impulse its engines were capable of delivering was 421 seconds. If used as a standalone rocket, it would be able of achieving a delta-v of about 10.6 km/s - theoretically enough to get to orbit (which is 7.8 km/s plus, say, 2 km/s to compensate for air drag and gravity losses) and then some. If you traded this "excess" delta-v for payload mass, you'd get something between 4-8 tonnes to orbit.

Now I understand that this is a gross simplification, and most of this margin would probably be lost due to other things (lower specific impulse in the early ascent phase, for instance), but you can see where I am heading with it. If you're willing to build a big booster to get a tiny payload to space without the use of staging, it is possible. It's just so hugely impractical that we use staged rockets instead.

I recall at one point in the past you remarked how afraid you were that I would start blathering about "delta-v" and all that. Well, it looks like we're at that stage.

To clarify, because I was non-specific earlier sad I mean that it is not possible to escape Earth's gravity - ever - with a one-stage rocket. I'll go off the assumption that this is what we're discussing because you bring up the Saturn V which was certainly a rocket intended to escape Earth's gravity.

We can measure the ability of a rocket to get to space by its capacity to generate the required delta-v. Now then, you bring up the specific impulse of the rocket fuel, which is on the right track but you seem to be arriving at an erroneous conclusion, which I will illuminate presently.

Let's give our hypothetical rocket of virtually any mass fuel of specific impulse 450 seconds, which is not generous and in fact the norm for liquid fuel these days (Isp=450 sec). Let's assume one stage (N=1) and a payload mass of 1 kilogram (m*=1 kg). Let's say our required delta-v is 10.5 km/s.

Since we only have one stage, we can only measure the delta-v produced by that one stage, which as I will reveal shortly will be insufficient, no matter what.

Math spoilered, only un-spoiler if you want to check my work or find out how delta-v works.

Spoiler math :

We can obtain values for exhaust velocity from the specific impulse:

Ve=Isp*g0 (where g0 is the gravitational acceleration constant for Earth at the Earth's surface). If you're calculating along at home, using SI units, this value is 4410 m/s.

We can obtain a coefficient for the structural ratio as well, we'll call it Epsilon:

Epsilon=ms/(ms+mp) (where ms is the mass of the rocket and mp is the mass of the fuel). Normally, the structural ratio is somewhere between 0.15 and 0.2, and optimizing this variable is difficult. We'll assume 0.15.

Finally, we obtain the payload ratio (called Pi) from:

Pi^N=(m*+ms)/m0 (where m0 is the starting mass). We're solving for Pi because we need to find out how much mass we have to start with to obtain the goal conditions.

So, all of this is important because the delta-v you can get is defined by:

delta-v=-N*Ve*ln(Epsilon+(1-Epsilon)*Pi)

A variation on the Tsiolkovsky equation. We plug in our needed delta-v (10.5 km/s), our N (1), our Ve (4410 m/s), our Epsilon (0.15) and then solve for Pi. We get:

Pi=-0.0677

So then we try to find our starting mass..

m0=m*/Pi=-14.773 kg

And it should be self-evident that a negative mass is unattainable.

Through the use of math-magic we can determine that the only two variables you can really change for better values of Pi (and, therefore, m0) are epsilon and Isp. Your Saturn V rocket (the S-II stage, specifically) example, then, is extraordinarily interesting because that particular rocket has an epsilon of 0.075, about half of the traditionally accepted lower value for epsilon. So that's interesting - at first glance it seems perfectly viable.

Unfortunately, it's an extremely lightweight rocket, and being a rocket stage is not a complete launch vehicle in and of itself, and throughout its development cycle was known to suffer from failure due to structural insufficiencies. But yes, I suppose it demonstrates that you can get to orbit in a single stage, albeit with a small payload mass. The trouble is that the S-II rocket stage is so lacking in so many features necessary in a rocket expected to undergo takeoff that it's not really a convincing argument in my book, and if you want I will elaborate further.

You're exaggerating it. Rockets are complicated machines, yes, but in comparison to a modern airliner (say, A380), they're actually quite simple. Their expandability means many dirty and cheap engineering solutions are possible - you don't have to care if the machine will work for years, you need it to work for 8 minutes or so, and then you're done with it.

You also need people to not die and the rocket to not explode during those eight minutes, which is a lot harder than it sounds.

You're right that more stages increase complexity, but two or three stages (depending on whether you consider things like laterally attached solid rocket boosters a separate stage or not) are quite easy to do, and we have half a century of experience with them. There is absolutely no reason such a machine should cost ~100 million Euros per piece, NONE whatsoever.

For virtually any rocket going past geosynchronous orbit, the the stages exit the realm of triviality a la the space shuttles and enter the realm of the very difficult.

Yes, the capability is certainly there, but I wouldn't call it reliable by a long shot.

From what I read on the subject, the insane prices are a result of an extraordinary distortion of normal economic mechanisms which has resulted from the strategic importance of an independent, government-controlled access to space. There are other factors - the ICBM legacy (most space launchers are in one way or another evolved from missiles), the crazy feedback loop between high launch prices -- satellite complexity -- costs, and so on and so forth.

An interesting claim I can neither verify nor wholly refute, except to say that the technological obstacles are larger than you claim.

Again, we're getting better at this. It is possible to reach very high reliability figures (for a rocket, it has to be said that rockets will NEVER be as reliable as aircraft or cars, because much higher energies are involved in their line of work). Soyuz-FG used in the Russian manned programme has so far had 100% reliability. Europe's Ariane-5 started off with a rather spectacular failure, but has since only suffered one other failure (two partial involving the upper stage, one of them when the new cryogenic upper stage was introduced). That makes it 96% reliable, but it hasn't experienced another failure since 2003.

Part of the reason they're so reliable is because they're so expensive.

Some rockets will blow up, so what? It's no reason to make them 900% more expensive than they should be.

No, making them not blow up is a large part of the cost.

I agree that air-breathing engines are promising. We're now approaching the tech level to actually build them. As for other fuels, what do you mean, exactly? Except exotic materials like metastable metallic hydrogen or other forms of unobtainium ( ), the oxygen/hydrogen mixture is the best there is - at least if we're still speaking about chemical rockets.

I was thinking of Vasimir, but of course that's really pie-in-the-sky so take that however you will. Liquid-fuel rockets are still the way to go, but so long as they are we have to cope with the troubles of high structure ratios in order to get to space.

I say, stop treating space launch business as a sacred ritual only a select few are allowed to take part in (after receiving the modern equivalent of a special dispensation from the Pope) and treat it more as... well, business. Foster competition, be intolerant of cost overruns, dump contractors if they can't push down prices, be prepared to allow foreign competitors into your country, etc. etc. etc. The prices are being reduced as we speak, and it just proves that if there was a will to run the whole thing properly, we could be sending stuff to space 5 to 10 times cheaper than today. That alone would enable us to do far more in terms of robotic exploration, if not human spaceflight.

I think the competition is there, and currently burgeoning, but its failure to launch demonstrates its real lack of long-term viability.

 

[Winner]

I recall at one point in the past you remarked how afraid you were that I would start blathering about "delta-v" and all that. Well, it looks like we're at that stage.

Ah, I didn't mean I wouldn't understand, I just kind of expected it. You probably don't do it in order not to scare people

I realized a long time ago that one can't have a serious discussion about space without at least a basic understanding of the math that is involved, so I made an effort to obtain it

To clarify, because I was non-specific earlier sad I mean that it is not possible to escape Earth's gravity - ever - with a one-stage rocket. I'll go off the assumption that this is what we're discussing because you bring up the Saturn V which was certainly a rocket intended to escape Earth's gravity.

(snip)

Through the use of math-magic we can determine that the only two variables you can really change for better values of Pi (and, therefore, m0) are epsilon and Isp. Your Saturn V rocket (the S-II stage, specifically) example, then, is extraordinarily interesting because that particular rocket has an epsilon of 0.075, about half of the traditionally accepted lower value for epsilon. So that's interesting - at first glance it seems perfectly viable.

Unfortunately, it's an extremely lightweight rocket, and being a rocket stage is not a complete launch vehicle in and of itself, and throughout its development cycle was known to suffer from failure due to structural insufficiencies. But yes, I suppose it demonstrates that you can get to orbit in a single stage, albeit with a small payload mass. The trouble is that the S-II rocket stage is so lacking in so many features necessary in a rocket expected to undergo takeoff that it's not really a convincing argument in my book, and if you want I will elaborate further.

No need, actually, I am perfectly aware of that. I think you're generally overestimating the minimum dry mass fraction of a rocket, but I also admit this is a very contentious point (especially to people who want to develop reusable SSTOs and are consistently frustrated by the fact that heat shielding, landing gear and other stuff eat their mass margins). What I am saying is that I don't think it is impossible to build expendable SSTOs for low Earth orbit operations. I don't think it would be a good idea, but it's doable. IIRC the US had a rocket that essentially was an SSTO (ok, it jettisoned some of its engines during the flight, but there was no staging per se involved), though I don't recall its name - wasn't it one of the early Atlases?

You also need people to not die and the rocket to not explode during those eight minutes, which is a lot harder than it sounds.

I was talking more about unmanned launches. I'll get back to it later.

For virtually any rocket going past geosynchronous orbit, the the stages exit the realm of triviality a la the space shuttles and enter the realm of the very difficult.

But we don't want to go beyond GEO with single-launch-from-earth rockets anyway. Deep space operations will always have to involve in-orbit assembly.

An interesting claim I can neither verify nor wholly refute, except to say that the technological obstacles are larger than you claim.

Part of the reason they're so reliable is because they're so expensive.

No, making them not blow up is a large part of the cost.

Now we're getting to the point I alluded to the last time. It's a vicious circle that goes roughly like this:

- rockets are expensive
- because rockets are expensive, we need to make our payloads (satellites) very light and reliable (everything is triple redundant, very finely made so that it can work for decades)
- that makes our payloads more expensive
- because our payloads are so damn expensive, we need the rockets to be more reliable
- extra reliability means they are now even more expensive
- because they're even more expensive now, our payloads need to be more reliable and lighter

and so on, and so forth. Of course, the more expensive everything gets, the less it is being used, which kills any economies of scale you might have taken advantage of otherwise. It doesn't help that contracts to build these rockets are given to preferred aerospace contractors who aren't bound by fixed cost contracts (basically, they can charge you for whatever the hell they want, and you pay and pay and pay). No wonder you end up with rockets that cost 100 million dollars to launch.

At some point, a minute increase in reliability costs a disproportional amount of money. Most rockets we use today are terribly over-engineered - and still it's not enough to some people. They probably don't realize that a 100% reliable rocket would be infinitely complex and thus infinitely expensive In this the Russian approach to rocketry - if done *right*, that is, not by Russians - is superior to the Western one. You build something that is not terribly complicated, and you launch it often. Eventually you will work out the flaws and end up with a solid design. I think that is how SpaceX plans to build competitive launch vehicles, so we'll see about that.

I was thinking of Vasimir, but of course that's really pie-in-the-sky so take that however you will. Liquid-fuel rockets are still the way to go, but so long as they are we have to cope with the troubles of high structure ratios in order to get to space.

Uh, I don't get this VASIMR is an electric thruster, it cannot be used for launch from Earth to LEO. And in any case, it's next to useless for manned mission in space anyway due to the fact it requires a magical nuclear power source which we don't have and which is probably impossible.

(I recently listened to Steven Howe on the Space Show programme who was talking about his work on nuclear thermal rockets. His take on nuclear-electric propulsion is that it makes little sense due to its inherent inefficiency. Nuclear reactors in space require huge radiator assemblies to work and produce electricity, but the whole process is only about 30% efficient. Nuclear thermal rockets (simply put, you heat a core which heats your propellant that is then expelled through a nozzle) are nearly 90% efficient, meaning 90% of the energy produced by the reactor is actually turned into thrust. This difference in efficiency more than compensates for the higher Isp of the nuclear-electric propulsion systems. Nuclear thermal rockets we could relatively easily build now would have Isp of about 900 seconds, if hydrogen was used as propellant [less if you used something else, ammonia is the next best thing]).

I think the competition is there, and currently burgeoning, but its failure to launch demonstrates its real lack of long-term viability.

We're currently in the egg-chicken phase. We need a larger market to really create a competitive environment that would drive down costs, but this market is unlikely to emerge without cheaper access to space. This is where I think governments need to intervene to get us over this phase.

 

[Crezth]

Well, you clearly know what you're talking about, so I'm willing to admit that a lot of these suppositions can be filed in the category of "speculation."

Talking about SSTOs specifically, you're right on-target with the fact that the mass-fractions often get botched by a need for your variety of necessities, and that this has effectively marginalized the real push to minimize those mass margins as opposed to, say, obtaining a higher-energy fuel. This is really what I mean when talking about the practicality of the matter, and a fuel of specific impulse on par with that of VASIMR (which I know was a bad example, I brought it up because I was trying to think of a high-Isp propulsion system without referring anything) or even some non-trivial fraction thereof would open up our margins for really sustainable, quick, and easy space flight moreso than a craft that's 90% fuel with necessities stripped to the bare bones. And the US rocket you're thinking of was not a true SSTO, although it was technically single-stage.

Anyway, I don't see access to space cheapening up in a hurry without some means of guaranteeing those investments vis-a-vis reliable rockets. You could say part of the problem is a bad, distorted market, and you'd have a good point (great point, actually), but what it really is is a lack of general capital for pursuing optimization in that regard. So giving NASA (for example) the flexibility (through autonomy), the ability (through funding), and the general directive (through public support) to start making lots of rockets and launch them often would be one of the things you have to do, but that's not something government is really interested in doing (same reasoning applies for developing rockets according to the "Western" approach). The method, in fact, isn't even the problem - but encouraging a change in the way NASA conducts is business like that requires a change of inertia. Since that's a problem that could be solved with more funding (and less political meddling), that's why I really think the major problem is NASA being underfunded.

But US government doesn't seem able nor willing to do such a thing, so NASA is in limbo. I have mused behind closed doors to my colleagues how I think it will be either the Chinese or the Europeans who blaze us forward into the space age, since America's eggs are all in the NASA basket, and it is a basket that has been consistently mistreated and ignored.

edit: I don't make it clear, either because of some vain obfuscation or a desire to be mysterious and nebulous, but this post should be read as agreeing with you.

 

[Valka D'Ur]

I shall keep bumping this up, since I am interested in space so much that I feel an irrational urge to discuss these issues with other people

Anyway, some people are seriously proposing that we "scour the Moon" for traces of alien civilizations. No, this has nothing to do with the Apollo 18 film. The idea is that since the lunar environment changes very very little over the eons (so much so that the footprints left by the Apollo astronauts will still be recognizable in millions of years, until the steady micrometeoroid bombardment erases them), if some alien civilization had visited the Earth-Moon system in the past, we might still find some traces of their visit on the Moon.



I say it's about time we found the bloody big black monolith that Clarke once prophesied I think there is also a novel which deals with this, although there the "alien" ruins are in fact ruins left by a previous Earth-born sentient species.

And if we find nothing, I propose building pyramids or some other visibly artificial structures there, and fill them with some of our artefacts and DNA samples, so that when we finally destroy ourselves, someone else might one day find out that we were here. It would be an act of cosmic vanity, admittedly, but one that'd be entirely forgiveable

I don't recall either the title or author, but I read a short story where the first Mars expedition finds and excavates the ruins of a building constructed by an intelligent species... and they're totally floored when they find out that humans were on Mars... several tens of thousands of years ago. The author was basically saying, what makes us so special that we think we're doing everything technological for the first time in our species? Considering how far we can go in a century, twenty or fifty or a hundred thousand years is plenty of time for a civilization to rise from stone age to space age, fall back to stone age, and rise again... more than once. And just because we haven't found evidence for that in RL doesn't mean there's no evidence to be found - it just means we don't know how or where to look for it (or don't have the current technology to be able to look for it).

Note that while the story I'm referencing would be nice if it were true, I am firmly in the camp of Carl Sagan: Extraordinary claims require extraordinary evidence. It's a nice dream, but my personal jury's out until there is hard evidence to back it up.

Putting artifacts on the Moon (objects? a gene bank? historical database?) would be a good idea. Yes, it's vanity. It's also a way for our species to be remembered a bit longer than we might otherwise manage. Of course, it'll all be vaporized in a few billion years, so we should make it worth the effort for an alien species to take along with them when they leave this vicinity!

Speculation and dreams are nice... but honestly, I just want SOMEBODY to get off this planet and go to the Moon, Mars, the asteroids... make Ben Bova's "Grand Tour" novels a reality as far as the exploration goes. When it's the whole species we're talking about, does it really matter which countries are the first? Just as long as it gets done. In my lifetime, preferably, because I want to live long enough to see for myself that humans have gone to Mars.

 

[BasketCase]

Uh-oh. Aelf is an alien spy! He's trying to get us Earthlings to betray our plans!!!

I think we can all agree that the world is not currently making much progress in that regard.

It's more about mindset than anything else. A few decades ago we humans were a lot more curious about outer space. I think our mindset shows pretty clearly in television and movies; science fiction used to be where it was at, but recently, entertainment has taken a turn away from sci fi. To the point where "Avatar" got pwnt by "The Hurt Locker" at the Academy Awards. There's an automatic bias against sci fi these days.

Imagine a future Terran 'empire' spread out across the solar system and maybe nearby star systems. What kind of situation could have led to the spread of human beings to other planets and systems to begin with?

Would it be something like a Cold War-style space race between global superpowers or economic blocs? The existence of a bureaucratic or technocratic world government with the ability to channel global resources as it sees fit? A Stalinist world government or hegemonic world power?

Since communication would be limited to the speed of light, any kind of bureaucracy would be extremely difficult to control; the regional governors would have direct control over their territories...... :tarkin:

 

[Winner]

Well, you clearly know what you're talking about, so I'm willing to admit that a lot of these suppositions can be filed in the category of "speculation."

Talking about SSTOs specifically, you're right on-target with the fact that the mass-fractions often get botched by a need for your variety of necessities, and that this has effectively marginalized the real push to minimize those mass margins as opposed to, say, obtaining a higher-energy fuel. This is really what I mean when talking about the practicality of the matter, and a fuel of specific impulse on par with that of VASIMR (which I know was a bad example, I brought it up because I was trying to think of a high-Isp propulsion system without referring anything) or even some non-trivial fraction thereof would open up our margins for really sustainable, quick, and easy space flight moreso than a craft that's 90% fuel with necessities stripped to the bare bones. And the US rocket you're thinking of was not a true SSTO, although it was technically single-stage.

Well, it used 1960s technology. You can see in the videos that the engines aren't really effectively burning the fuel. I read somewhere that if we used modern kerosene-LOX engines on the early Atlases, we wouldn't need to jettison anything and have a true SSTO It doesn't matter though, it wouldn't change things that much.

Anyway, I refer you again to the (slightly dated) analysis concerning the launch costs: LEO on the Cheap: Methods for Achieving Drastic Reductions in Space Launch Costs by JOHN R. LONDON. It should be available somewhere on the internet, for free (legally ). It's pretty illuminating as to what causes the high launch costs and what can be done to reduce them. It kind of proves that we know what's wrong, but can't bring ourselves to do anything about it.

Anyway, I don't see access to space cheapening up in a hurry without some means of guaranteeing those investments vis-a-vis reliable rockets. You could say part of the problem is a bad, distorted market, and you'd have a good point (great point, actually), but what it really is is a lack of general capital for pursuing optimization in that regard. So giving NASA (for example) the flexibility (through autonomy), the ability (through funding), and the general directive (through public support) to start making lots of rockets and launch them often would be one of the things you have to do, but that's not something government is really interested in doing (same reasoning applies for developing rockets according to the "Western" approach). The method, in fact, isn't even the problem - but encouraging a change in the way NASA conducts is business like that requires a change of inertia. Since that's a problem that could be solved with more funding (and less political meddling), that's why I really think the major problem is NASA being underfunded.

I can agree with that. More money wouldn't hurt, and compared to the other expenses Western countries are making, providing a few dozen billions more for space wouldn't even hurt the national budgets.

But US government doesn't seem able nor willing to do such a thing, so NASA is in limbo. I have mused behind closed doors to my colleagues how I think it will be either the Chinese or the Europeans who blaze us forward into the space age, since America's eggs are all in the NASA basket, and it is a basket that has been consistently mistreated and ignored.

Well, I don't see much hope for the European space programme, unless we totally change the way our politicians think about space (and pretty much everything, they're a bunch of cowards who only do what they absolutely have to, there is no vision, no willingness to lead people through inspiration and example). China... nobody knows what China will do. I hope they decide at some point to send humans to the Moon, if for nothing else than to troll the West. Maybe that will make us rethink our lethargic efforts on this front.

edit: I don't make it clear, either because of some vain obfuscation or a desire to be mysterious and nebulous, but this post should be read as agreeing with you.

BTW:

Sadly, even the Nazis aren't what they used to be. I can't imagine the skinheads would be able to build a good rocket...

 

[Winner]

Speculation and dreams are nice... but honestly, I just want SOMEBODY to get off this planet and go to the Moon, Mars, the asteroids... make Ben Bova's "Grand Tour" novels a reality as far as the exploration goes. When it's the whole species we're talking about, does it really matter which countries are the first? Just as long as it gets done. In my lifetime, preferably, because I want to live long enough to see for myself that humans have gone to Mars.

A Mars mission is always about 30 years in the future

It's not really a matter of not knowing how. We know that pretty darn well. In other words, we know the unknowns, and we believe we can come up with solutions. I am by no means an expert, but what's being discussed now is:

1) radiation shielding - how much is needed to reasonably reduce the risk
2) zero-g health effects mitigation techniques - either medical solutions, or simulated gravity
3) propulsion - only chemical and nuclear-thermal seem practical, with the latter being much better of the two
4) power - again, we need small nuclear power sources
5) ISRU - how much stuff are we going to produce on Mars (oxygen? water? propellant?)
6) landing techniques - right now we don't have an idea how to land heavy stuff on Mars, it's pretty difficult and it would require actual testing
7) life support - can we build close-loop life support systems that will reliably work for years?
8) transit trajectory - do we want a short surface stay, or a long one? That is, a conjunction or an opposition-class mission?

I probably forgot a few, but these are some of the things that are contentious.