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Getting to space without violating the Proscriptions

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Re: Getting to space without violating the Proscriptions
Post by SWM   » Tue Jul 14, 2015 4:09 pm

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Dilandu wrote:
SWM wrote:Dilandu, it's not nearly as hard as you think. Getting to a specific orbit and approaching a specific point in space at a specific time is not that hard. It does not require microsecond timing. It can definitely be done by precision mechanical equipment. In fact, quite a bit of equipment on historical space probes was mechanical, not electronic.


Well, i consulted some my friends that knew rocketry and mechanic pretty good. And he prove to me that this is possible, indeed... after couple of thousand tries.

Yes, it theory this is pretty easy. On practice - and there is always this practice, that ruined so much pretty good in theory ideas... like artillery shells with wheels (c) - the rocket motors that could be build on pre-electrical level wouldn't be reliable, and wouldn't work perfectly. In fact, they would fluctuate pretty hard. And because you haven't got any datalink with rocket, you couldn't correct the trajectory if the motor would start to fluctuate.

Simply: the mechanical system would not be able to actually determine how much speed the rocket did not gain, or how much the trajectory is erroneous because the rocket burning is erractic due to the fuel quality. It would be impossible to correct on purely mechanical system.

Please understood me: i'm not doubting that the pure mechanical system is possible. I doubt that it would be even slightly effective. Yes, you could achieve the parameters eventually - after thousands of launches.

It's not nearly as bad as you think. Rockets did not start having ways of correcting their trajectories in flight until relatively recently. Hundreds of satellites have been put into orbit without the ability to correct the launch trajectory. Solid rockets can be quite reliable.
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Re: Getting to space without violating the Proscriptions
Post by Silverwall   » Wed Jul 15, 2015 5:57 am

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SWM wrote:It's not nearly as bad as you think. Rockets did not start having ways of correcting their trajectories in flight until relatively recently. Hundreds of satellites have been put into orbit without the ability to correct the launch trajectory. Solid rockets can be quite reliable.


However I believe we have established earlier in the thread that solid rockets are non-viable due to lack of power. That leaves us with the much more finiky liquid fueled variety. If you believe there is a solid rocket fuel that can be manufactured in industrial quantities I would love to hear about it because everything I know is that without electricity you can't make a decent solid rocket fuel and the whole point of the thread is the viability of a rocket that can be launced without violating the proscriptions.
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Re: Getting to space without violating the Proscriptions
Post by SWM   » Wed Jul 15, 2015 8:06 am

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Silverwall wrote:
SWM wrote:It's not nearly as bad as you think. Rockets did not start having ways of correcting their trajectories in flight until relatively recently. Hundreds of satellites have been put into orbit without the ability to correct the launch trajectory. Solid rockets can be quite reliable.


However I believe we have established earlier in the thread that solid rockets are non-viable due to lack of power. That leaves us with the much more finiky liquid fueled variety. If you believe there is a solid rocket fuel that can be manufactured in industrial quantities I would love to hear about it because everything I know is that without electricity you can't make a decent solid rocket fuel and the whole point of the thread is the viability of a rocket that can be launced without violating the proscriptions.

That may be. I was only responding to the claim that mechanical guidance was not sufficient. I believe it can be good enough, even with liquid fuel.
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Re: Getting to space without violating the Proscriptions
Post by cralkhi   » Thu Jul 16, 2015 3:18 am

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I don't see why solid rockets are not viable.

Remember we don't need to reach orbit - only get the projectiles to OBS altitude. So propellants do not need to be the best possible performance. Ammonium perchlorate composite propellant probably isn't workable without electricty, but I think there are nitrocellulose/nitroglycerin based ones with decent performance.

Trying to do it with liquid propellants, I agree would be too complex/nonviable.

I was envisioning this post-war, with a vast explosives industry built up for the war now being turned to rockets...
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Re: Getting to space without violating the Proscriptions
Post by cralkhi   » Thu Jul 16, 2015 3:24 am

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As for why a low orbit: the OBS should orbit fast enough that it isn't practical to just turn off your "proscribed" equipment when it's over the horizon.

Also, the only disadvantage* is the need for re-boost due to air drag, and with reactionless engines, that disadvantage goes away.

*Well, beyond vulnerability to this sort of attack, but I really doubt they ever considered this sort of low-tech trick.
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Re: Getting to space without violating the Proscriptions
Post by Silverwall   » Thu Jul 16, 2015 4:50 am

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cralkhi wrote:I don't see why solid rockets are not viable.

Remember we don't need to reach orbit - only get the projectiles to OBS altitude. So propellants do not need to be the best possible performance. Ammonium perchlorate composite propellant probably isn't workable without electricty, but I think there are nitrocellulose/nitroglycerin based ones with decent performance.

Trying to do it with liquid propellants, I agree would be too complex/nonviable.

I was envisioning this post-war, with a vast explosives industry built up for the war now being turned to rockets...


Perchlorate based propellants as perchlorate requires anodic oxidation which requires electricity. Here is the page on Wikipedia on rocket propelants and none of the nitro ones look viable to me.
https://en.wikipedia.org/wiki/Solid-fue ... ropellants

To help see the problems of solid rockets look at the specific impulse numbers and thrust per kilo of exhaust.

https://en.wikipedia.org/wiki/Specific_impulse.

There is a reason all the early rockets and most of the current gen heavy lifters use liquid fuel. Given the no electricty requirement I estimate the power differential to be over 20 times more thrust/kg in favour of liquid fuels.

The big advantage of solid rockets is simpler manufacture and long term stability, epsecially important in applications such as ICBMs.
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Re: Getting to space without violating the Proscriptions
Post by SWM   » Thu Jul 16, 2015 8:54 am

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cralkhi wrote:I don't see why solid rockets are not viable.

Remember we don't need to reach orbit - only get the projectiles to OBS altitude. So propellants do not need to be the best possible performance.

If you can reach the orbit of the OBS, you can probably get into orbit. The velocity differential is not that great.
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Re: Getting to space without violating the Proscriptions
Post by MTO   » Thu Jul 16, 2015 10:42 am

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SWM wrote:If you can reach the orbit of the OBS, you can probably get into orbit. The velocity differential is not that great.


No this is absolutely not true.you need to hit 7.8km/s to get into LEO, but the delta-v's required is about 9km/s. So getting to orbital height is about 10% of the effort.
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Re: Getting to space without violating the Proscriptions
Post by SWM   » Thu Jul 16, 2015 12:02 pm

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MTO wrote:
SWM wrote:If you can reach the orbit of the OBS, you can probably get into orbit. The velocity differential is not that great.


No this is absolutely not true.you need to hit 7.8km/s to get into LEO, but the delta-v's required is about 9km/s. So getting to orbital height is about 10% of the effort.

That is indeed more than I remembered off the top of my head. But it does not completely invalidate the premise that if you can build a ship to reach orbital height, you probably can build a ship to reach orbital velocity.
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Re: Getting to space without violating the Proscriptions
Post by Dilandu   » Thu Jul 16, 2015 12:25 pm

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SWM wrote:
That is indeed more than I remembered off the top of my head. But it does not completely invalidate the premise that if you can build a ship to reach orbital height, you probably can build a ship to reach orbital velocity.


Only in theory. The first rockets were send to orbital height in 1946, but it took almost 11 years and a lot of resources to send sattelite into space. And to achieve the orbit that isn't send you into the planet surface, you would need at least some guidance and active maneuvering capability AFTER launch.
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