Author Topic: Basic Rocket Science Q & A  (Read 271960 times)

Offline gloomygod

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Re: Basic Rocket Science Q & A
« Reply #340 on: 10/13/2009 07:42 AM »
Hi there,

I'm looking some sites, and it seems that the space shuttle travels at aprox 17500 mph while orbiting the earth.
That would be roughly 8km/sec.

I guess other non geostationary satellites would travel at similar speeds in order to maintain orbit.

But, which is really the maximum speed at which one of those bodies could travel in open space (while traveling to other planets)? Would it be possible to increase speed to let's say, 1000km/s?

In the vacuum, increasing speed should be "cheap", and just a matter of time. Would these speeds be achievable by a common shuttle/satellite?

Thanks a lot for your answers.

Update: Edited some mistakes. Sorry for my poor english.
« Last Edit: 10/13/2009 08:01 AM by gloomygod »

Offline khallow

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Re: Basic Rocket Science Q & A
« Reply #341 on: 10/13/2009 04:17 PM »
The theoretical upper limit is the speed of light. But in current practice, you'll be moving at the orbital speed for moving around the Sun at that radius plus a little extra. At Earth, that'd be 36 km/s plus a few km/s. For current proposed interstellar missions using electric propulsion (like VASIMR) and radiothermal generators (RTGs), one might be able to obtain speeds of 100-200 km/s.

If we can obtain a high thrust, high isp nuclear powered propulsion system, we should be able to achieve much higher speeds. But I'm not knowledgeable enough to guess how fast that would be.
Karl Hallowell

Offline Analyst

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Re: Basic Rocket Science Q & A
« Reply #342 on: 10/13/2009 05:35 PM »
One question to ask is speed relative to what? The Galileo entry probe for example has been very fast relative to Jupiter, just by being pulled by Jupiters gravity.

Analyst

Offline AlexInOklahoma

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Re: Basic Rocket Science Q & A
« Reply #343 on: 10/13/2009 07:11 PM »
One question to ask is speed relative to what?
Analyst

And does this thing need to stop (or enter an orbit) at its destination?  Or just blaze on by it meaninglessly?  Can really make a difference overall (form -v- function)   ;)

Alex

Offline Nomadd

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Re: Basic Rocket Science Q & A
« Reply #344 on: 10/13/2009 07:40 PM »
Not counting Galileo at Jupiter entry (108,000mph) I believe the fastest travelling away from the sun is Voyager I at 38,600 mph. Dawn might have the greatest change in velocity. Just not all in one direction, since it will have to orbit two different bodies.
« Last Edit: 10/13/2009 07:40 PM by Nomadd »

Offline edkyle99

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Re: Basic Rocket Science Q & A
« Reply #345 on: 10/13/2009 07:58 PM »
Hi there,

I'm looking some sites, and it seems that the space shuttle travels at aprox 17500 mph while orbiting the earth.
That would be roughly 8km/sec.

I guess other non geostationary satellites would travel at similar speeds in order to maintain orbit.

But, which is really the maximum speed at which one of those bodies could travel in open space (while traveling to other planets)? Would it be possible to increase speed to let's say, 1000km/s?

I believe that NASA's Pluto New Horizons, launched by an Atlas V 551 on January 19, 2006, was given the largest initial velocity of any human-made object to date.  It left Earth at 16.26 km/sec (Earth-relative), or about 36,373 mph.  It took only 9 hours to pass lunar distance, 13 months to fly past Jupiter, and less than 2.5 years to pass Saturn's orbit.  Even at that blistering pace it won't reach Pluto until 2015.

 - Ed Kyle
« Last Edit: 10/13/2009 07:58 PM by edkyle99 »

Offline Pheogh

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Re: Basic Rocket Science Q & A
« Reply #346 on: 10/13/2009 08:09 PM »
So hopefully this isn't to far out but under the following conditions (below) what fraction of the speed of light would you guess we could achieve?

- NASA's "entire" current exploration budget to 2020
- Nuclear restrictions removed
- Using known technology or technology that appears likely to mature within that time scale
-Spacecraft in the New Horizon's weight class

*Oh and describe it please!

Basically what I am asking is if for one reason or another we HAD to accelerate a spacecraft in the New Horizon's Class how fast could we get it going by 2020?
« Last Edit: 10/13/2009 08:09 PM by Pheogh »

Offline Nomadd

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Re: Basic Rocket Science Q & A
« Reply #347 on: 10/13/2009 08:14 PM »
 I think one of the Helios probes will hit close to 150,000 mph at it's closest approach to the sun.
 New Horizons didn't have time for the normal inner planet dosey-do since it was trying to get to Pluto before the atmosphere froze out.

Offline Antares

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Re: Basic Rocket Science Q & A
« Reply #348 on: 10/13/2009 09:16 PM »
So hopefully this isn't to far out but under the following conditions (below) what fraction of the speed of light would you guess we could achieve?

- NASA's "entire" current exploration budget to 2020
- Nuclear restrictions removed
- Using known technology or technology that appears likely to mature within that time scale
-Spacecraft in the New Horizon's weight class

*Oh and describe it please!

Basically what I am asking is if for one reason or another we HAD to accelerate a spacecraft in the New Horizon's Class how fast could we get it going by 2020?

Need more constraints, like a reliability number.  You could pick the lowest cost per kilo existing stage (I'll assume Atlas CCB) and start stamping them out like mad and strap them together asparagus cluster and wedding cake style.  You'd end up with ~150 of them.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline gloomygod

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Re: Basic Rocket Science Q & A
« Reply #349 on: 10/13/2009 09:20 PM »
Hi there,

Thx moderator for moving the post to the right section.

One question to ask is speed relative to what?
Analyst

And does this thing need to stop (or enter an orbit) at its destination?  Or just blaze on by it meaninglessly?  Can really make a difference overall (form -v- function)   ;)

Alex

That's exactly the question. Yes, it needs to stop, and the speed relatively faster than the target moon/planet/body. Let me ellaborate, although this would almost certainly absurd and impossible.

I was wondering, if it's possible to accelerate a body(satellite) to a speed faster to the rotation speed for example of our moon (~1000 kms/s). If that was possible, would it be feasible to intercept the orbit of the moon at such speed, that the gravity of the moon would decelerate the satellite, until they collide at really slow speeds?

Imagine that we put our satellite going very fast right into the moon's path. The moon continues it's path, and eventually its gravity starts "braking" out satellite. The moon would get closer and closer, and eventually it will catch our satellite.

So I was wondering if it would be possible to calculate and reach such speed, so the collision would transate into a light landing:D

I haven't done the equations, and probably such speed would be orders of magnitude greater than the target moon speed, but I was just curious if that would be possible theoretically.


Offline Jorge

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Re: Basic Rocket Science Q & A
« Reply #350 on: 10/13/2009 10:04 PM »
Hi there,

Thx moderator for moving the post to the right section.

One question to ask is speed relative to what?
Analyst

And does this thing need to stop (or enter an orbit) at its destination?  Or just blaze on by it meaninglessly?  Can really make a difference overall (form -v- function)   ;)

Alex

That's exactly the question. Yes, it needs to stop, and the speed relatively faster than the target moon/planet/body. Let me ellaborate, although this would almost certainly absurd and impossible.

I was wondering, if it's possible to accelerate a body(satellite) to a speed faster to the rotation speed for example of our moon (~1000 kms/s). If that was possible, would it be feasible to intercept the orbit of the moon at such speed, that the gravity of the moon would decelerate the satellite, until they collide at really slow speeds?

Imagine that we put our satellite going very fast right into the moon's path. The moon continues it's path, and eventually its gravity starts "braking" out satellite. The moon would get closer and closer, and eventually it will catch our satellite.

So I was wondering if it would be possible to calculate and reach such speed, so the collision would transate into a light landing:D

I haven't done the equations, and probably such speed would be orders of magnitude greater than the target moon speed, but I was just curious if that would be possible theoretically.



It's not possible. The proper way to work the problem is to take the initial states of the spacecraft and the moon and compute the *relative* state between the spacecraft and the moon. Then work the problem in moon-centered coordinates.

You'll see that, because the problem started out with the spacecraft outside the moon's sphere of influence, it will always approach the moon along a hyperbolic path, and will *always* accelerate *toward* the moon as distance decreases. So when the spacecraft strikes the moon, it'll always be going faster than when it started out. That rules out this method of attempting a "free" soft-landing.
JRF

Offline Danny Dot

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Re: Basic Rocket Science Q & A
« Reply #351 on: 10/13/2009 10:39 PM »
Hi there,

I'm looking some sites, and it seems that the space shuttle travels at aprox 17500 mph while orbiting the earth.
That would be roughly 8km/sec.

I guess other non geostationary satellites would travel at similar speeds in order to maintain orbit.

But, which is really the maximum speed at which one of those bodies could travel in open space (while traveling to other planets)? Would it be possible to increase speed to let's say, 1000km/s?

I believe that NASA's Pluto New Horizons, launched by an Atlas V 551 on January 19, 2006, was given the largest initial velocity of any human-made object to date.  It left Earth at 16.26 km/sec (Earth-relative), or about 36,373 mph.  It took only 9 hours to pass lunar distance, 13 months to fly past Jupiter, and less than 2.5 years to pass Saturn's orbit.  Even at that blistering pace it won't reach Pluto until 2015.

 - Ed Kyle

Did I do my math right?  I come up with a whopping 53,300 ft/sec  :o

Any gravity assists on this mission?

Are they going to orbit or fly-by?

Danny Deger
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Offline zeke01

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Re: Basic Rocket Science Q & A
« Reply #352 on: 10/13/2009 10:59 PM »
There was an assist from Jupiter.  New Horizons spacecraft will not be captured by Pluto.  It will go onward to investigate any additional Kuiper objects within its small delta-v capability after visiting the Pluto system.

zeke

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Re: Basic Rocket Science Q & A
« Reply #353 on: 10/14/2009 01:03 AM »
I believe that NASA's Pluto New Horizons, launched by an Atlas V 551 on January 19, 2006, was given the largest initial velocity of any human-made object to date.  It left Earth at 16.26 km/sec (Earth-relative), or about 36,373 mph.
But thanks to gravity assists, not the fastest spacecraft. According to http://www.heavens-above.com/solar-escape.asp that honor belongs to Voyager 1

Offline Antares

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Re: Basic Rocket Science Q & A
« Reply #354 on: 10/31/2009 04:10 PM »
Quote
Quote
Quote
Quote
Hypothesis:  There was no recontact, but the first stage disrupted the upper stage simulator *aerodynamically* and caused it to tumble when it's upper end exited the slipstream of the upper stage simulator.
Lee Jay, I suspect you might be right, especially after checking out klausd's video above.
I like the attempt at a higher-order physical explanation, but this is literally impossible at supersonic speeds.  Such disturbances can only flow upstream at sonic speed (exactly) no matter the speed of the vehicle.  So the USS could not have been disturbed by the flow of the FS since they were somewhere M~4.
Aren't bow shocks generated in front of an object traveling supersonically? I.e. a higher pressure region *some distance* in front of the front end of the SRB? If so, what if one side of the USS aft end dipped into this region? Don't know much about fluid dynamics, just wondering if that's possible here.

Not enough to matter.  The blunt forward end of the separated SRM would have a small bow shock, probably detached by just a few inches from the solid surface.  It would be a minimal detachment distance due to the high supersonic (i.e. not hypersonic) flow regime.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline littlepagan

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Re: Basic Rocket Science Q & A
« Reply #355 on: 11/01/2009 01:21 AM »
hey, what senseations do astornauts experience when in outer space and on takeoff, mostly on takoff

Offline Antares

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Re: Basic Rocket Science Q & A
« Reply #356 on: 11/04/2009 05:47 AM »
Read any of the astronaut autobiographies for really good descriptions of this.  I'm not copping out.  I just like to see more off-line reading.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline mmeijeri

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Re: Basic Rocket Science Q & A
« Reply #357 on: 11/08/2009 05:01 AM »
Experts on this forum have said Titan IIs used for launching early space missions did not need an escape tower because the propellants are hypergolic and will deflagrate instead of detonating. Further googling reveals that this 'barely' enabled the use of ejection seats.

In another thread I wondered if this would apply to catalysed kerosene/peroxide launchers such as the ones Beal Aerospace intended to develop. On reflection this seemed unlikely to me since I imagined the peroxide could decompose if heated. But I was surprised to learn hydrogen peroxide could be used for regenerative cooling, so maybe things are not as bad as I imagined.

So, would you need an escape tower for a kerosene/peroxide launcher or would ejection seats be enough?
« Last Edit: 11/08/2009 05:01 AM by mmeijeri »
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Offline MKremer

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Re: Basic Rocket Science Q & A
« Reply #358 on: 11/08/2009 07:24 AM »
IMO, the Gemini ejection seat was a Dumb Idea, and was mostly a result of mass restrictions, plus R&D time and costs to find an effective LAS tower.

Using ejection seats to me is a Dumb Idea in general, if for nothing else than having multiple flammable/explosive ordinance devices as permanent parts within a pressurized crew cabin.

IMO, if your booster can't handle the additional mass of an effective crew LAS, then you need a bigger rocket.

Offline clongton

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Re: Basic Rocket Science Q & A
« Reply #359 on: 11/08/2009 11:44 AM »
Quote
Using ejection seats to me is a Dumb Idea in general, if for nothing else than having multiple flammable/explosive ordinance devices as permanent parts within a pressurized crew cabin.

*ALL* our military fighter aircraft, indeed *all* modern military fighter aircraft around the entire planet, use this system. To the best of my knowledge in all those years there has never been an accidental ignition of one. It takes a very deliberate, conscious action on the part of the crewman to activate. Don't forget that those astronauts were on loan to NASA from the military. They were all military pilots and they were very, very comfortable with them, as are ALL military pilots to this day.

Gemini was very popular with the pilots in part because it "felt" familiar. The astronauts asked for the ejection seats in the design phase. The spacecraft has been described as a "pilot's dream". It was designed around the pilots and what they wanted in it and everyone who flew in them loved the design. The ejection seat was part of that.

Ejection seats are not a dumb idea. They are a very good idea, are very safe inside the pressurized cabin and are an extremely efficient way to quickly exit a destructing vehicle. While the ignition process has been simplified to facilitate quick activation, it has been designed to be exceptionally safe; they cannot be accidentally activated; it has to be deliberately done. After Challenger, they were the top runner for a safety change to Shuttle but couldn't be incorporated into the STS design without a MAJOR complete redesign of the crew cabin. That's the main reason they are not on Shuttle today.

Ejection seats would likely have saved most of Challenger's crew as it has been reliably reported that they were alive, and probably conscious, inside the descending crew cabin which had survived the explosion intact, all the way down to ocean impact. If I recall correctly, in spite of additional wounds they may have received caused by the breakup of the Shuttle's airframe, the cause of death for the crewmembers was blunt force trauma caused by the cabin's impact with the ocean surface. If they had had ejection seats they could have ejected and most of them would likely have survived. But there was, sadly, no way to incorporate ejection seats into Shuttle after-the-fact.
« Last Edit: 11/08/2009 02:30 PM by clongton »
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