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Old 06-11-2011, 03:35 PM   #106
RGClark
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Originally Posted by T.Neo View Post
 STS was also designed to cut costs to LEO by a great amount.

It doesn't matter what they say about the vehicle, or what legitimate advantages it would actually have compared to STS. Spaceflight is extremely difficult to achieve and it's extremely expensive, and thus one should be skeptical about any "magic numbers". Refurbishment of a spacecraft is an intensive process.
Furthermore increasing the payload capacity of the Venture Star will not help (in part due to the fact that the vehicle as it was designed could not carry such a large amount of payload assuming your average payload density).
This will come as quite a shock to most people on this forum but getting to space is not THAT hard. It's not at the scientific or technical difficulty level of nuclear physics.
The cost for a private individual to purchase a flight to orbit has been at the range of 10's of millions of dollars. But if you look at the energy cost for say 100kg to be given orbital velocity it's only in the price range of $100.
Peter Diamandis of the X-Prize has noted this extreme discrepancy and has argued for using beamed energy such as lasers to supply the energy all the way to orbit. He intends to promote another prize to further support the development of beamed energy propulsion.

For doing it with chemical propulsion, I'm estimating it can be done at the price range of $100/kg. If you have an SSTO you of course don't have the expensive to refurbish SRB's or the one use ET of the shuttle.
The VentureStar's metallic shingle TPS was specifically designed to require minimal maintenance between flights. In ground tests they worked as expected. The advanced ceramics of the X-37B also were intended to reduce maintenance costs for the TPS and also apparently have been successful. And the PICA-X ablative heat shield for the Dragon capsule worked so well for the Dragon reentry that Elon Musk said it could be reused for hundreds of uses.
As for the engines, noted space historian Henry Spencer has said with upgrades the maintenance costs on the SSME's could be reduced to only $750,000 per flight, rather than the ten's of millions it is now:

Engine reusability (Henry Spencer)
http://yarchive.net/space/rocket/eng...usability.html



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Old 06-11-2011, 03:50 PM   #107
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 But if you look at the energy cost for say 100kg to be given orbital velocity it's only in the price range of $100.
That is pretty much correct - if the system would be electric and it would not cost money to convert electricity into kinetic energy.

But that last part is actually the problem. The fuel for a rocket is actually one of the smallest items in the launch budget. But without engines, this fuel is just sitting around in its tanks without doing actual work.

And the engines of a rocket are the most expensive parts. And will always be. It isn't cheap to have such a high power as a rocket engine has. A tiny rocket engine of just 3 m diameter produces every second more energy as a typical nuclear reactor.

PS: The SSME costs could be reduced, but at a price. The biggest reduction comes from lowering the performance.
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Old 06-11-2011, 05:45 PM   #108
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Yeah, the difficulty is in applying that energy. The SSMEs on the Shuttle put out over 10 gigawatts, that's more than an entire municipal powerplant.

Split up the kinetic energy of a kilogram at 9500 km/s over 8 minutes, and that's 94 kilowatts of power. To consume that amount of energy at a rate of about 1 kilowatt would take over 12 hours. That's how intensive spaceflight is.

The Sun can deliver to a patch of desert many times the energy delivered by a nuclear weapon, but only over the course of months and years, etc.

I did a (admittedly very simplistic) 'cost assessment' for my Orbital Propellant Tanker, and admittedly may have actually under-represented the cost of some things (such as related facilities to operate the launchers), but what I found was that most of the cost comes from the price of the engines and the vehicle structure. The cost of the engines alone for the OPT was in the range of $70 million, and that is for 5 relatively 'cheap' RS-68 engines.

Propellant costs made up a very small amount of the total cost (didn't even get into the millions of USD).

Now, in my limited experience in engineering, I know that some things can be reduced in cost, and other things just need to be expensive to work. And that entails stuff that is highly intensive, like spaceflight. It's not impossible to reduce those costs, but it is very difficult, and it can only come after a lot of experience in attempting to perfect these sort of technologies.

OPT 'only' got down to $3400-4400, and it's supposed to be an SSTO- the SSTO bit didn't really help. Of course, you can try to reuse your vehicle, but reuse is not cheap either.

I believe Urwumpe came up with a short formula that compares the economic performance of a reusable vehicle with an expendable one, depending on various attributes.

EDIT:

Beamed energy does not solve the problem. Not only do you still have to supply a huge amount of power, but you have to channel that power through a set of huge lasers, that also happen to be war-waging superweapons.

Last edited by T.Neo; 06-11-2011 at 07:04 PM.
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Old 06-12-2011, 12:00 PM   #109
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  Reusable SSTO's can majorly cut launch costs if done in the right way. I have argued that you can get multiple times more payload using a hydrocarbon fueld SSTO compared to a similar sized hydrogen one.
Estimates for the price to orbit for a hydrogen fueled SSTO such as the VentureStar put it at $1,000/kg. I calculated that with fixing the propellant tank overweight problems of the VentureStar and switching to kerosene fueled you could increase the payload by a factor of six. This would bring the cost to orbit to $160/kg. Pretty good for a first level SSTO. More advanced versions could improve on this further...
Hobbyspace.com has a news item about Boeing investigating a SSTO version of the X-37B. I discuss it on the An SSTO as "God and Robert Heinlein intended" thread.


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Old 06-12-2011, 02:48 PM   #110
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I forgot to say that in 100 years I would expect suborbital soldier transport and orbital bombardment...

Last edited by fsci123; 06-12-2011 at 05:12 PM.
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Old 06-12-2011, 05:05 PM   #111
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Orbital bombradment?

Suborbital troop transport, just like suborbital or orbital anything, takes a lot of energy, and is very intensive.

There's a reason overseas bases and aircraft carriers exist. Having a company of marines onboard an aircraft carrier and then sending them to the target in something like a Black Hawk is far cheaper, far safer, and far stealthier than suborbital transport.

It could happen, but there are factors working against it.

And we already have suborbital bombradment devices. They're called ICBMs.
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Old 06-12-2011, 05:11 PM   #112
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 I forgot to say that in 100 years I would expect suborbital soldier transport and orbital bombradment...
Poor guys sitting and waiting inside their ICBMs.

And what do you expect to hit with a bomb that's in orbit?
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Old 06-12-2011, 05:51 PM   #113
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Originally Posted by T.Neo View Post
 Orbital bombradment?

Suborbital troop transport, just like suborbital or orbital anything, takes a lot of energy, and is very intensive.

There's a reason overseas bases and aircraft carriers exist. Having a company of marines onboard an aircraft carrier and then sending them to the target in something like a Black Hawk is far cheaper, far safer, and far stealthier than suborbital transport.

It could happen, but there are factors working against it.

And we already have suborbital bombradment devices. They're called ICBMs.


http://www.popsci.com/military-aviat...-marines-space

I found this 5 years ago and only recently I reunited with it...
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Old 06-12-2011, 06:20 PM   #114
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And if you want to be really stealthy, you use a submarine for deploying the troops.

Orbital bombardment might one day come, FOBS already exists. Suborbital bombardment is normal artillery, but there is also the long range version already by replacing the nuclear warheads of a trident by inert warheads, that simply use kinetic energy for destroying the target (at the impact speed, a 250 kg warhead has the energy equivalent of 1000 kg TNT).

In 100 years, I expect the change to IPV6 being finally done.

But otherwise... I don't think we will see dramatic changes. Most good ideas from today will just become reality, but I can't really imagine another revolution like we did see around 1900. The evolution of what we have today though, might be impressive.

Last edited by Urwumpe; 06-12-2011 at 06:23 PM.
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Old 06-12-2011, 07:23 PM   #115
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Much of the pessimism I've seen here seems to stem from thinking that the mobs of uninterested people have a say in what happens. They don't. Most of our advancement, technological or otherwise, has resulted from the efforts of a small number of passionate, talented individuals. Everyone else is dragged along kicking and screaming.

Elon Musk, founder of SpaceX, has stated that his goal is going to Mars. Given their current rate of progress, I wouldn't be a bit surprised if that happens in less than 15 years. (His goal is 10.) I'll let you do the Web searches to find what he's said. And if you don't know what his company has done already, I'm surprised you're even reading this.
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Old 06-12-2011, 07:29 PM   #116
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I don't think Musk will go that far. If his company runs half-way good in the geostationary business, he will sell it.
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Old 06-12-2011, 07:31 PM   #117
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Mobs of uninterested people do have a say in what happens.

- The public is a mob of uninterested people. Sadly most people think the universe ends at the altitude jetliners fly, and that space is a gigantic hologram in the sky, figuratvely speaking of course.

- Governments are mobs of uninterested people. Like the US Congress, for example. Uninterested in spaceflight progress, that is- they're very interested in their own politics.

If Musk gets to Mars in 15, 20 years, then that's good for him. But it would be such a costly endeavour, that he would only be able to pay for it using satellite launch profits.

And if there isn't any viable economic reason for it, it won't be a very long-lived operation. It'll be flags and footprints, just like Apollo.

There is still no Manned Spaceflight Killer App.
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Old 06-12-2011, 11:11 PM   #118
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 Orbital bombardment might one day come,
As I understand orbital mechanics, an orbital bomb will miss the entire planet.
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Old 06-12-2011, 11:13 PM   #119
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 Mobs of uninterested people do have a say in what happens.
- The public is a mob of uninterested people..
Well that is very true. And the public will, somehow, be sure that funds are spent elsewhere instead of manned spaceflight.

Let me put it to you this way, if you are voting on a stash of $500,000,000 what will you do with it? You are a member of a governing body and must cast a vote. You must also justify your decision. You get a big bonus if your vote is cast on the winning side. Now, what will you do?

1- Spend it to develop a new semiconductor material for a manned spacecraft navigation computer.

2- Feed and clothe the babies of a lesser-educated populace.

Everyone is going to go with #2. Unless this manned spacecraft is gonna be superluminal and leaving Earth on a scouting mission to find a new home for humanity out of necessity because a big bad GRB is ready to fry the planet.


Now all that aside, consider this:
Unmanned probes have a better chance of getting funded than anything manned. Not because they are cheaper, not because they are less risk to life.. But because artists and researchers and promoters are able to put a better spin on the final results. They are also more easily able to translate the research results into something that can be done here on Earth..like more research! Fodder for academia!

Look, $5 billion can inspire more imaginations through the popular mass media and artsy fartsy graphics *IF* it is put into unmanned probes and satellites and telescopes. Ooodles upon oodles (I'm gonna make me some noodles!) more than it can by launching a handful of men on orbital trajectories for a few days.


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 - Governments are mobs of uninterested people. Like the US Congress, for example. Uninterested in spaceflight progress, that is- they're very interested in their own politics.
Well yes, it *IS* what matters to them. I would rather control and manage some thing that makes a real world difference to me in a tangible way. Spaceflight doesn't do that. And it it a hopeless case when you have oversexed male politicians with brain chemical imbalances running the country.

Manned spaceflight is for "flower-power idealists", dreamers, sci-fi authors. That sort of thing, you know. It doesn't benefit the real world in a timely fashion. Spinoffs take too long and are prone to being diverted. There is no immediate capitalism-style control over the technologies developed.


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 There is still no Manned Spaceflight Killer App.
There won't be one either. Not until we have a Killer Asteroid hanging out in LEO. That could be a trigger to run full-tilt on manned spaceflight development. Maybe. Just maybe. Till then, we must be patient and sit back and enjoy the spoils and toils of proposals and project cancellations. A seemingly endless train of startup companies that fall by the wayside when it comes down to it. Whatever "it" may be.

Anything humans (and their debilitating politics) need to accomplish can be done right here, right now, below 40,000 ft. We may send a few machines as high LEO or GEO, but that's to very-specifically enhance the long-established and entrenched toiling and suffering already in progress below the stratosphere.

Allow me to add in one more thing, Humans are too wrapped up in their sickeningly slovenly pleasures and celebrity worshiping american-idol-istic tabloid entertainment activities to think about spaceflight. It is a simple fact of nature, and you CANNOT stop nature. No matter how hard you try. The best we can hope for is for evolution to take a different turn.

But imagine for an instant that you could cut out the tiny nerve circuit that controls the impulsive reward-seeking tendancies in every human. The need for pr0n, the oversexing, the delightfully deliriously hedonistic tendencies. Humans would then develop the clarity of thought needed to pursue long-term betterment of themselves. And I have no doubt manned and unmanned spaceflight would literally explode off the planet.

It is this EVIL and ABOMINATION, a scar, a blight, that has a vice grip on the long term progress of humanity.

A quick calculation indicates that you could collect this offending bio-mass in a container no bigger than a bathtub or two. IMAGINE that!?! 450 kilograms of biological materials, 4500 litres of neurons are what is truly holding the universe from fully discovering itself and re-programming itself! What a frakking pity with humanity being a failed experiment and dead end.

Last edited by Keatah; 06-13-2011 at 12:11 AM.
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Old 06-13-2011, 12:48 AM   #120
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Not until we have a Killer Asteroid hanging out in LEO. That could be a trigger to run full-tilt on manned spaceflight development. Maybe. Just maybe.
If we have a Killer Asteroid hanging out in LEO, we'll just have a new moon...

...albeit one prone to deorbit onto a city due to air drag.

But seriously, how often do these sorts of things come around? Not that often- on the order of millions of years, hundreds of thousands of years, those kind of timescales.

And you can deflect an asteroid with a precise nuclear device, or a gravity tug, or a sun-sail... why would it bolster manned spaceflight?

Quote:
But imagine for an instant that you could cut out the tiny nerve circuit that controls the impulsive reward-seeking tendancies in every human. The need for pr0n, the oversexing, the delightfully deliriously hedonistic tendencies. Humans would then develop the clarity of thought needed to pursue long-term betterment of themselves. And I have no doubt manned and unmanned spaceflight would literally explode off the planet.
I think that nerve-circuit that you malign so much is what prevents humans from being apathetic zombies.

Look, as easy as it is to get all misanthropic here and complain about the Failure! That! Is! Humanity!, it isn't about that at all. It isn't about failures, it isn't about people being disinterested when they should actually be interested in.

It's a very valid opinion. There isn't anything to do in space. For our long term survival, sure, we have to move off of Earth, but why should our civilisation, in there here and in the now care? We are too busy, legitimately, trying to ensure our short-term survival. We have problems of conflict and resource management and environmental depletion. None of which have a space-based solution.

Maybe, just maybe, spaceflight is too darn difficult. Maybe most civilisations in the galaxy- where they arise- stay on their homeworlds, perhaps for millions, even billions of years, but they never leave, they never expand to the stars, they never build Dyson Spheres or other such absurdly gigantic structures to clutter the galaxy with intelligence and blare their existence to our radio telescopes.

Because they don't need to. They have everything they need on their homeworld, and there's no need to expend absurd amounts of energy going anywhere else. They're perfectly happy where they are. If they need to deflect an asteroid, they send out an automated spacecraft. If they want to get a closer look at the stars, they send simplified, rugged, and effective probes.

And maybe that explains the Fermi Paradox- at least partially. But maybe there are another group of civilisations, maybe we would have been one of them if the early opinions of Venus and Mars had held true- civilisations for whom other worlds are not mere slight chances of supposed places an unimaginable distance away, but for whom habitable worlds are beacons in the night, close enough to sniff at.

Civilisations who have a reason- despite the difficulties- to become spacefaring civilisations.

Not like us.





Last edited by T.Neo; 06-13-2011 at 12:54 AM.
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