Atlantis has landed

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Trantor
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Re: Atlantis has landed

Post by Trantor »

Arioch wrote:
Trantor wrote: Yeah. With broken deadlines, exploding costs, tax(payer) funded bailouts, cutting corners and subsequent fatalities...
This would be different from the NASA-run program how? ;)
Gah. I was talking about the 60ies and 70ies, when NASA was led by men with passion and honor.


*sigh*. I get the point. These times are gone forever.
sapere aude.

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Trantor
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Re: Atlantis has landed

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Alexandr Koori wrote:Air Launch is not so complicated and dangerous,
Depends on the scale.
A small rocket like the Pegasus is no problem, but a big rocket for interplanetary probes is not possible with this kind of tech due to structural limits and a million other problems.
The german Sänger-project for example sounded too good in theory, but then they found out that it is impossible to separate the stages at high speeds (mach 5 and beyond @around 50km altitude) due to aerodynamic problems. It would have taken too much structural weight again to solve the issues.
And weight eats up payload: http://en.wikipedia.org/wiki/Tsiolkovsk ... t_equation
;)
Alexandr Koori wrote:don't need the infrastructure and the space launching base.
They´re not that expensive.
sapere aude.

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Trantor
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Re: Atlantis has landed

Post by Trantor »

bunnyboy wrote:I heard once that most succesfully designed part of the shuttle were the boostrockets on its side.
They were about 10% more fuel efficient than calculated.
True engineering gems are the SSME´s. With their staged combustion cycle technology, a specific impulse of 4480m/s² in Vacuum, a thrust-range of 55 to 109% in the 2000 KN-range and last but not least their man-rating they´re at 99% of the theoretical technological maximum.
They should make more of them. ;)
sapere aude.

LegioCI
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Re: Atlantis has landed

Post by LegioCI »

Since I'm a bit contrary, I'm going to say that I'm glad to see the shuttle go.

For more than thirty years, the space shuttle has been a symbol of mediocrity in space exploration; the equivalent of Louis and Clark crossing the Mississippi, shuffling around on the other side and writing a few letters to school children about how if they eat their veggies and do their homework maybe they'll be the first person to go to the Rocky mountains.

I've been waiting for them to can the Shuttle program for years so NASA could get away from wasting time in LEO and start getting their asses back to the moon, or, God forbid, Mars, like they've been promising for decades. (The Mars mission has been a constant carrot on a stick for me, always just a decade or so away but oddly, it never gets any sooner!)

Of course, now we're ditching the shuttle program and instead of taking the next step we're out-sourcing our spaceflight to the Russians. Right now I'm seeing the future of space flight being a private and corporate endeavor rather than one undertook by governments.
"But notice how the Human thinks. 'Interesting... how can I use this as a weapon?'" - Arioch

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Mjolnir
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Re: Atlantis has landed

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NOMAD wrote:Thought manned fleet will be more expensive in the long run and unmanned mission are doing great,
With the notable exception of JWST.

I really wanted that telescope, but given the severity of its mismanagement...cost rising to $6.8 billion from the originally estimated $1.6 billion, originally to launch this year, but now uncertain if it'd launch before 2020...it really did need to be canceled. Maybe a revival under different management will get us the JWST eventually, without eating up the rest of space science to do it. With it canceled, maybe we can launch a Hubble replacement sooner.

Alexandr Koori wrote:Air Launch is not so complicated and dangerous, don't need the infrastructure and the space launching base. I do not know about other projects, but in Russia are being developed lung MiG-31-Ishim, were the development of secondary carrier to start with the IL-76, and a relatively heavy - MAKS-Molnia. Clipper project, alas, closed.
Air launch is more complicated and dangerous. You have to have all of the same infrastructure apart from the pad itself, but instead of putting it at an isolated launch pad, you have to put it at at an airport instead. And instead of just rolling out to a pad, you have to load a massive vehicle full of rocket fuel onto a very large airplane and take off with it. For any reasonable orbital flight, you can't do with just any runway, you need one specially reinforced to carry the weight...that's going to cost a lot more than a simple pad. You're also going to be working with huge quantities of rocket fuel, solid rockets, and extremely pricey payloads...safety and security concerns are going to make it a lot more difficult and costly to base operations out of an existing airport. What makes you think a custom, single-use airport and a special-built superheavy cargo plane adapted to air launch a rocket is cheaper than a launch pad?

Rockets usually use cryogenic fuels that must be topped off as they evaporate. You're talking about a carrier plane with its own LOX and LH2 tanks, piping fuel into the rocket slung underneath and trailing boiled-off oxygen and hydrogen as it taxies onto the runway. If you're not using cryogenic fuels, you're using hypergolics that are extremely toxic and corrosive, raising even greater safety issues when operating out of an airport and hauling around in a launch vehicle slung underneath an airplane. And then there's the fact that you can't light up and test engines before launch. You're not coming back after an abort with a rocket full of fuel.

And even with the biggest carrier aircraft imagined, you're terribly limited in payload. Try air-launching one of these: http://en.wikipedia.org/wiki/File:Delta ... ch_pad.jpg

That's 70 meters tall, as long as a 747, just over 15 meters wide, and it masses 733 metric tons at launch. The Antonov An-225 can carry 200 metric tons on top. Your IL-76 can only carry about 45 metric tons. And no, air launch is not going to make that notably lower.

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Mjolnir
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Re: Atlantis has landed

Post by Mjolnir »

bunnyboy wrote:I heard once that most succesfully designed part of the shuttle were the boostrockets on its side.
They were about 10% more fuel efficient than calculated.
They're glorified fireworks chosen for political reasons, and they destroyed one vehicle and killed seven astronauts. And a solid that's 10% more fuel efficient still isn't very impressive. Liquid rocket boosters such as those used by Energia would have had far better performance, and could have served as the first stage of smaller launchers, as the Zenits (the launcher with the current lowest cost per kg to orbit) did.

LegioCI wrote:I've been waiting for them to can the Shuttle program for years so NASA could get away from wasting time in LEO and start getting their asses back to the moon, or, God forbid, Mars, like they've been promising for decades. (The Mars mission has been a constant carrot on a stick for me, always just a decade or so away but oddly, it never gets any sooner!)
Phobos and Deimos are more interesting to me. They're easier to get to and from than the moon in terms of delta-v, due to their position in the gravity well of Mars. You can even use Mars for an aerobraking assist to reach them. And their own gravity wells are tiny, so you're not stuck when you get there. They appear to most likely be captured main-belt asteroids, so they may have sizable amounts of volatile resources, and you can get solar power in their vicinity without the planet turning you away from the sun half the time and covering your solar panels with dust.

Start up orbital propellant depots with propellant obtained from orbital sources, and you can send manned missions effectively anywhere in the system using simple chemical propellant rockets or NTRs. Build a vehicle in orbit with a mass ratio similar to or better than that of a vehicle that has to support itself on the ground and launch through the atmosphere, and make use of powered flyby maneuvers, and you can go places.

LegioCI wrote:Of course, now we're ditching the shuttle program and instead of taking the next step we're out-sourcing our spaceflight to the Russians. Right now I'm seeing the future of space flight being a private and corporate endeavor rather than one undertook by governments.
Fortunately, there actually appears to be interest in such things among the companies with the capabilities needed to do the job.

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icekatze
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Re: Atlantis has landed

Post by icekatze »

hi hi

Personally, I'm waiting for someone to build a Lofstrom Loop...

I understand where you're coming from Mjolnir. Yes the space shuttle was far less efficient than other possible designs. But you're thinking like a scientist and not like a politician. From a political point of view, we were lucky to have the shuttle at all. I don't think that the absence of the shuttle would have freed up an equal amount of political capitol for other space ventures.

Also: I'm going to continue to do my best to not turn this into a flame war, so I accept ahead of time that I could be wrong.

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Trantor
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Re: Atlantis has landed

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icekatze wrote:hi hi

Personally, I'm waiting for someone to build a Lofstrom Loop...
Nice! Thx for the link, never saw sth like this before.
Looks way better than those impractical ugly space elevators.
icekatze wrote:I understand where you're coming from Mjolnir. Yes the space shuttle was far less efficient than other possible designs. But you're thinking like a scientist and not like a politician. From a political point of view, we were lucky to have the shuttle at all. I don't think that the absence of the shuttle would have freed up an equal amount of political capitol for other space ventures.
The Idea was great. The Shuttle despite all it´s downsides was also great for it´s time.
I´d really like to see a next-gen shuttle, smaller, easier to maintain, and more versatile (eg unmanned/automated flight possible).
We should NOT repeat the mistake, and let all the knowledge go byebye as it was with Saturn.
We should learn from the mistakes and build a better one.
sapere aude.

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Trantor
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Re: Atlantis has landed

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Mjolnir wrote:For any reasonable orbital flight, you can't do with just any runway, you need one specially reinforced to carry the weight...that's going to cost a lot more than a simple pad.
I agree 100% to the rest, but it is not that bad with the runways. You´ll have to have matching or lower ACN to PCN*, and as military planes usually have very low ACN due to their undercarriage this is not an issue. More weight? Just add wheels.
You also need to land on other airports, too, so you always design transporters to do so.


* runway strengh is measured in PCN, eg EDDH (Hamburg) has a PCN of 65 with parameters F / A / W / T; "F" means Flexible surface (the other one would be "R" for Rigid, like concrete), "A" means highest category of underconstruction, "W" means highest category for tyre pressure and "T" means that "65" was tested, not calculated (can be expensive sometimes, if the pavement fails...).

Then ACN, eg: Antonov 225: fully loaded it has an ACN of "63" at airports with surface and underconstruction characters "F / A" (the first and the second character).
Tyrepressure is 1.13, which means it needs at least the second highest category of tyrepressure in PCN (the third character, here it would be "X" instead of "W").
"T", the fourth character, is not of importance here.

So Hamburg (EDDH) is able to serve a fully loaded (!) An-225, at least in suitable weather (a hot day would result in a too long take-off run, so it would have to start in the night)

A 777-300 eg is worse to runways (it was temporarily banned from Le Bourget and other Airports), and the numbers would be: "76" @ "F /A", and a tyrepressure of 1,48, just short of the highest category. So a fully loaded 773 couldn´t take off in Hamburg (aside from other problems like tyrespeed-limits, but these are not related to ACN/PCN).

You´ll find PCNs in the NOTAMs, and some ACNs here (Pdf, 37kB).
sapere aude.

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bunnyboy
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Re: Atlantis has landed

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bunnyboy wrote:I heard once that most succesfully designed part of the shuttle were the boostrockets on its side.
They were about 10% more fuel efficient than calculated.
Maybe I was busy, because I forgot say that they were only part, what worked as well as was hoped.
I'm not sure about this, but if they didn't have extra juice on them, some of the missions would have been imbossible to do.
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Alexandr Koori
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Re: Atlantis has landed

Post by Alexandr Koori »

I'm not saying that the air start, even with IL-76 could lift a man into space, but for satellites it looks competitive. Are you concerned about an excess of fuel on board? Think about tanker aircraft like KC-10. "Molnia" includes programs included a non-toxic blended fuel "Kerosene-hydrogen-oxygen". Outlying military airfield will solve the problem of security.

It is also interesting is the system "Parom", the main element of which will be the interorbital module that will "pull over" with loads from low hights to the working orbits, making it even SpaceShip2 or M-21 a real transport ship.

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Mjolnir
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Re: Atlantis has landed

Post by Mjolnir »

Trantor wrote:I agree 100% to the rest, but it is not that bad with the runways. You´ll have to have matching or lower ACN to PCN*, and as military planes usually have very low ACN due to their undercarriage this is not an issue. More weight? Just add wheels.
You also need to land on other airports, too, so you always design transporters to do so.
It's admittedly not that severe a problem with plain old air-launch rockets. It's a bigger problem for over-complex monstrosities like Skylon, which has an undercarriage capable of supporting its fully-fueled weight, which it carries all the way into orbit and back. Keep in mind that the moment Skylon leaves the runway (assuming the thing ever flies), that heavy-duty undercarriage is dead weight that will not be needed to support that load again until the next launch. Landing must be done with empty fuel tanks, giving them much less weight to support.

Alexandr Koori wrote:I'm not saying that the air start, even with IL-76 could lift a man into space, but for satellites it looks competitive.
Did you miss the part about Pegasus being the most expensive launcher in existence?
You're not making things cheaper by adding air launch to the equation. You only move infrastructure around and replace a simple pad with a big, expensive carrier airplane that ends up with most of a launch pad built into it, except more expensive because it has to work while flying on a plane.

Alexandr Koori wrote:Are you concerned about an excess of fuel on board? Think about tanker aircraft like KC-10. "Molnia" includes programs included a non-toxic blended fuel "Kerosene-hydrogen-oxygen".
Yes, I'm concerned about the fuel. Why do you think rockets launch where they do?
If you're carrying cryogenic hydrogen, you're venting hydrogen. LOX/RP-1 is safer to work with, but carrying large amounts of LOX along with it still makes it far more dangerous than a plain old fuel tanker. Plus, the KC-10 only carries 160 tonnes of fuel, which makes for a pretty small rocket...the Falcon 9 carries about 300 tonnes of LOX/RP-1, the Atlas V about 284 tonnes of LOX/RP-1 and another 21 tonnes of LOX/LH2. These aren't even heavy lift rockets.

Alexandr Koori wrote:Outlying military airfield will solve the problem of security.
Oh, really? Run civilian launches out of a military airfield because it's too dangerous to do out of a civilian airport, they won't mind at all?

Alexandr Koori wrote:It is also interesting is the system "Parom", the main element of which will be the interorbital module that will "pull over" with loads from low hights to the working orbits, making it even SpaceShip2 or M-21 a real transport ship.
No, it makes them barely adequate and unusually expensive transport ships. For small launches, the cost of involving another spacecraft that must be supplied with fuel, moved to the right orbit, scheduled together with your launch, etc will be exorbitant. It's something that's more useful the larger your launches are, which is why Parom was sized to handle cargo containers larger than the payloads lifted by the Shuttle or Proton. Just the scheduling issue and consequences of a delay will make this impractical to use for routine small satellite launches.

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Trantor
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Re: Atlantis has landed

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Mjolnir wrote:It's admittedly not that severe a problem with plain old air-launch rockets. It's a bigger problem for over-complex monstrosities like Skylon, which has an undercarriage capable of supporting its fully-fueled weight, which it carries all the way into orbit and back. Keep in mind that the moment Skylon leaves the runway (assuming the thing ever flies), that heavy-duty undercarriage is dead weight that will not be needed to support that load again until the next launch.
345 tons is not impossible. And maybe they start on a sled...

Just kidding. That thing will not fly. Not with our todays´ tech. We won´t see SSTO until we have somewhat reliable hypersonic planes.
sapere aude.

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Mjolnir
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Re: Atlantis has landed

Post by Mjolnir »

Trantor wrote:Just kidding. That thing will not fly. Not with our todays´ tech. We won´t see SSTO until we have somewhat reliable hypersonic planes.
SSTO's easier without air-breathing, as air-breathing mandates an inefficient high-drag trajectory and requires you to carry extra equipment into orbit. We can do it now (several vehicles have exceeded the needed mass fractions), we don't and won't see SSTO because staging isn't actually that difficult, because it makes things vastly more efficient, because it makes vehicles more flexible and easier to develop and improve, and so on. It also makes reuse much easier...the first stage, the big expensive one with the most/largest engines, gets dropped on a suborbital trajectory and needs much less heat shielding to be recovered intact, and that shielding doesn't have to be carried into orbit, so it subtracts less from the payload mass.

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Mjolnir
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Re: Atlantis has landed

Post by Mjolnir »

icekatze wrote:Personally, I'm waiting for someone to build a Lofstrom Loop...
I don't think the dynamics of a full Lofstrom Loop are at all manageable. When the spacecraft starts dragging on that loop, it's going to buck and whip all over, if you can get it stable in the first place. It also makes for a poor match between the spacecraft velocity and the loop velocity...spacecraft acceleration will drop a lot as its velocity relative to the loop drops. Plus there's the practical issues of how to start the thing up and shut it down, and how to handle a catastrophic failure.

A string of small loops positioned along a linear mass driver track avoids the stability problems, lets you rotate later loops faster to keep acceleration constant, etc, and still avoids the need for equipment that can release high energy pulses of electrical power with precise timing and rise/fall characteristics...the energy is stored mechanically in the loops themselves and coupled electromagnetically from there directly to the payload, a quite elegant solution.

But unlike the full Lofstrom Loop, you kind of need a negligible atmosphere for this to be much use, and in that case a tether sling is probably simpler and more flexible.

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Trantor
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Re: Atlantis has landed

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Mjolnir wrote:we don't and won't see SSTO because staging isn't actually that difficult, because it makes things vastly more efficient, because it makes vehicles more flexible and easier to develop and improve, and so on. It also makes reuse much easier...the first stage, the big expensive one with the most/largest engines, gets dropped on a suborbital trajectory and needs much less heat shielding to be recovered intact, and that shielding doesn't have to be carried into orbit, so it subtracts less from the payload mass.
That too.
2 stages plus boosters for any earthorbit, 3 stages plus boosters for anything beyond.

I once made an excel-sheet based on Tsiolkowskis´ plan to play around with different designs of rockets, types of fuel and stages; if i find it again i´ll post a link to it.
sapere aude.

Yevette
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Re: Atlantis has landed

Post by Yevette »

I'm glad the landing was successful!n This is so breathtaking!

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