Why Rocket Ships

This has been puzzling me since before I was in kindergarten. When we take people into space, we use a rocket ship, a very huge, and long vehicle. But many rockets don't take off due to mechanical failures, weather conditions, and many other factors.

But I've always seen a problem, always. And that problem is: Why Rocket Ships. The whole idea of a rocket ship in my opinion is ridiculous. Its vehicle itself is too long for its base. Making it way unbalanced. Even though the base is absolutely huge, it still can be very unbalanced during take-off and flight.

Have you ever watched a rocket ship take off? If so, have you ever noticed that they sometimes start to tilt, and begin to fly at an angle? When I see that, I go straight back to my question...WHY?

The whole idea is ridiculous. But finally, about 2, maybe 3 years ago, one man did something smart. If I recall correctly, this happened in California. A man, built his own plane, specially built to fly in space, and then took it into the highest atmosphere layer. And then he successfully flew back down and landed.

So, why are we trying to balance a toothpick, while we can be insuring our astronauts a safe, and a more fuel efficient transportation into space with an actual plane. Now, I didn't say that this plane had to be small, but why aren't we doing that. To many things can go wrong with rockets to begin with, rockets ships should be considered a dead science in my opinion.

Plus, with an actual plane-like structure, it will be easier to deploy satellites, and to control the space craft. Its just that rocket ships in general are unsafe, its about a 50 50 chance, that you'll make it back, or if you'll even make it out of the atmosphere alive...

Do you agree with me, or am I just a lone ranger?

umm...

Have you not seen the space shuttle? It looks like a plane to me. Or are you just refering to the take off method?

reply to post by Ramzus


I understand what your saying. I understand that there is an escape velocity that must be reached. Why is it that the capsule or shuttle heat up during reentry but not when exiting the atmosphere? I understand friction, but I don't understand why it doesn't do this on the way out only back in?

Its vehicle itself is too long for its base. Making it way unbalanced. Even though the base is absolutely huge, it still can be very unbalanced during take-off and flight.

A fatter object would create far more drag.

An Air & Space plane may not be such a good idea. NASA persued it in the past but it didn't really get anywhere.

en.wikipedia.org...

en.wikipedia.org...

Have you ever watched a rocket ship take off? If so, have you ever noticed that they sometimes start to tilt, and begin to fly at an angle? When I see that, I go straight back to my question...WHY?

The fly off at an angle so they can get into orbit... if they just went straight up.... then they'd just come hurtling back down again.

If I recall correctly, this happened in California. A man, built his own plane, specially built to fly in space, and then took it into the highest atmosphere layer. And then he successfully flew back down and landed.

All Space Ship One did was fly up into space and come back down. It did NOT go into orbit, it did NOT carry any payload, & really did NOT have any real useful applications in the real world.

Plus, with an actual plane-like structure, it will be easier to deploy satellites, and to control the space craft. Its just that rocket ships in general are unsafe, its about a 50 50 chance, that you'll make it back, or if you'll even make it out of the atmosphere alive...

100% of proper launches go to plan, the only time when they do not is due to negligence and faults. For example, Challenger should never of been launched. Columbia should of had repairing techniques for the insulation & possibly would of happened to an aircraft too.

But I agree with you that alternate ways to get satalites in orbit should be persued. A Rocket is overkill for smaller Satellites.

en.wikipedia.org...

Why is it that the capsule or shuttle heat up during reentry but not when exiting the atmosphere?

Much of the orbital velocity required is reached once already in space, while on re-entry it must be lost through friction with the air.

Hope this helps.

[edit on 11/8/2008 by C0bzz]

reply to post by letthereaderunderstand


A plane couldn't be used because the escape velocity needed is far more than what a jet engine currently allows. Gravity would act against the plane and make it impossible to get to the speed needed for orbit.

The reason the heat is greater on reentry is because orbit speed is far greater than the speed at which the shuttle leaves the atmosphere. On the way out, it accelerates to a speed that allows orbit to be achieved after leaving the atmosphere.

[edit on 11-8-2008 by fiftyfifty]

A plane couldn't be used because the escape velocity needed is far more than what a jet engine currently allows. Gravity would act against the plane and make it impossible to get to the speed needed for orbit.

Just to add:

If SCRAMJETS were used, then the problem with that is most of the orbital energy would have to be attained WITHIN the atmosphere, creating massive heat, which would have to be endured AGAIN on re-entry.

I think the future lies with conventional boosters, but also Plane / Rocket comboes such as Pegasus rocket.

reply to post by Ramzus


As C0bzz points out, SpaceShip One - which seems to be the craft you are referring to; in the future please provide a link - didn't go into orbit. It didn't even come close. And it DID use a rocket engine to reach the goal altitude of ~100 kilometers. The carrier aircraft, called White Knight, carried Spaceship One to an altitude of ~47,000 feet (this varied from test to test; test logs are available here) using jet engines before the rocket took over for the remainder of the flight.

Wings are only useful on a spacecraft if you intend to land your craft like an airplane, and the shuttle there are significant drawbacks to this mode of re-entry - the thermal protection system (TPS) of your vehicle is exposed for the entire flight, you have to maintain a great deal of seldom-used downmass capacity in your re-entry vehicle (the shuttle seldom returns with a significant portion of its cargo bay occupied).

The biggest drawback of having wings on a spacecraft is that they are completely useless until you re-enter the atmosphere. You have to carry the mass of the wings up with you into space - which, on a spacecraft like the shuttle requires a great deal of fuel/oxidizer - and you have to factor in the mass of the wings when calculating the amount of fuel you burn for orbital maneuvering (moving to retrieve satellites, space station reboost, etc.).

reply to post by Ramzus


You don't really understand the problem.

Firstly in order to go into orbit, you have to travel so fast sideways that the curvature of the earth falls away as fast as you fall down. That is why you see rockets tilting sideways after launch, to get that horizontal velocity of around 17,000 mph.

In fact the reason why they go up at all is only to get above the drag of the atmosphere which is only a few tens of miles thick, after that it is all sideways.

As for their shape it is a compromise between mass and drag. Spherical tanks would weigh less for the same volume than cylindrical tanks but the drag low in the atmosphere would be very high.

Final it is actually easier to balance an object the longer it is, try balancing a pen or a yard broom on your hand.

Originally posted by fiftyfifty
reply to post by letthereaderunderstand

 

A plane couldn't be used because the escape velocity needed is far more than what a jet engine currently allows. Gravity would act against the plane and make it impossible to get to the speed needed for orbit.

The reason the heat is greater on reentry is because orbit speed is far greater than the speed at which the shuttle leaves the atmosphere. On the way out, it accelerates to a speed that allows orbit to be achieved after leaving the atmosphere.

[edit on 11-8-2008 by fiftyfifty]

Thank you for your help, yet I'm still not understanding this. Won't the object fall at terminal velocity? Surely they are traveling much faster on the way out then in, since they just nudge out of orbit and fall back to earth. I know orbit is achieved by vertical distance (in regards to the earth floor) and horizontal speed correct? If this is the case you would just need slow down your horizontal speed to exit orbit since there is 99% Gravity still working. Please help...Thanks

[edit on 11-8-2008 by letthereaderunderstand]

reply to post by letthereaderunderstand


Rockets have so much momentum that they're still going UP once IN space, and the rocket is obviously still burning at this point. This is where they slowly angle down towards the horizon, which gains much of the orbital velocity required.

www.youtube.com...

Simply put - the majority of energy gained is aquired once in space. The reason why it doesn't fall back down to the ground when gaining the energy is because it has lots of kenetic energy which keeps pulling it upwawrd...

The de-orbit burn is typically just enough to get it to skim the atmosphere where 99% of the energy is dissapated through friction...

Originally posted by C0bzz
reply to post by letthereaderunderstand

 

Rockets have so much momentum that they're still going UP once IN space, and the rocket is obviously still burning at this point. This is where they slowly angle down towards the horizon, which gains much of the orbital velocity required.

Simply put - the majority of energy gained is aquired once in space. The reason why it doesn't fall back down to the ground when gaining the energy is because it has lots of kenetic energy which keeps pulling it upwawrd...

The de-orbit burn is typically just enough to get it to skim the atmosphere where 99% of the energy is dissapated through friction...

Doesn't it seem that there should be friction going up as well, especially in the lower atmosphere where the air is denser. Doesn't the shuttle go like mach 10 or something? I have no idea except that it is fast, but none the less, unless it is burning on the way down it will hit terminal velocity not to mention the drag. Isn't there a layer of atmosphere where stuff will just burn up in that layer? I can't remember.

Another thing, I've seen in the Saturn 5 footage as well as the footage of the shuttle, how are the rockets still burning in space since there is no oxygen? With the shuttle they blow the boosters but are still lit. The Saturn's would loose the bottom rings and it is way obvious in any footage from those that a burn is still occuring in space.

Also, why is the footage always from a fish eye lens? Do you know of any "Transit" rocket footage that isn't? I understand that it is possibly to get a better look at more area of the rocket, but with that comes the illusion of a curved earth surface through the lens?

Better yet, have you ever seen footage from inside the shuttle during take off? I find it very strange how easy it is for the astronauts to move there arms, to hold up mirrors, flip switches, when I thought they were experiencing super high G-Forces. I know you will black out past a certain amount, but in the Atlantis cabin view launch that I saw The female astronaut was holding up and away in front of her a mirror almost the whole time and the pilots moved with no problem. I also find it weird that there is so much light coming in the windows that you can't see out of them in the video. Shouldn't it be blue then darker blue then black, but it is like they are heading into the sun. Thanks for all your help. I feel like a dork not knowing this stuff, yet I have a hunch that things aren't always what we see on t.v....Peace and thank you again

letthereaderunderstand

Originally posted by letthereaderunderstand

Doesn't it seem that there should be friction going up as well, especially in the lower atmosphere where the air is denser. Doesn't the shuttle go like mach 10 or something? I have no idea except that it is fast, but none the less, unless it is burning on the way down it will hit terminal velocity not to mention the drag. Isn't there a layer of atmosphere where stuff will just burn up in that layer? I can't remember.

Yes, the Shuttle and other launch vehicles have to be very careful with regard to how fast they go - which is why at one point soon after actual lift off the Shuttle actually throttles back as it goes through the maximum air density threshold. After that, it throttles back up to 104% or so (100% is the original rated thrust of the engines, which has been increased since then) because the atmosphere is thinning the farther it goes up.

Another thing, I've seen in the Saturn 5 footage as well as the footage of the shuttle, how are the rockets still burning in space since there is no oxygen? With the shuttle they blow the boosters but are still lit. The Saturn's would loose the bottom rings and it is way obvious in any footage from those that a burn is still occuring in space.

Rockets carry their own oxidiser, as well as the actual fuel - the big reddish brown tank on the Shuttles belly contains two tanks inside it, one for the liquid oxygen and one for the liquid hydrogen.

Also, why is the footage always from a fish eye lens? Do you know of any "Transit" rocket footage that isn't? I understand that it is possibly to get a better look at more area of the rocket, but with that comes the illusion of a curved earth surface through the lens?

The footage isnt done for your enjoyment, its done for reasons linked to the launch - better view of the vehicle is more important than making it look good for spectators.

I also find it weird that there is so much light coming in the windows that you can't see out of them in the video. Shouldn't it be blue then darker blue then black, but it is like they are heading into the sun.

Its lighter outside because the light level inside the cabin is so much lower - the camera taking the footage is set to the exposure level for the light level inside the cabin, and thus the much brighter outside light will overwhelm it.

[edit on 12/8/2008 by RichardPrice]

Thanks for your responses, didn't mean to derail the topic if I did, but I always have questions. On topic, what do you guys think about the new Virgin space vehicle? Thanks again, Peace

Originally posted by letthereaderunderstand
Thanks for your responses, didn't mean to derail the topic if I did, but I always have questions. On topic, what do you guys think about the new Virgin space vehicle? Thanks again, Peace

The new Virgin space vehicle? Its a sub-orbital pimp mobile - its the sort of thing tourists hire to drive around Florida in, you see thousands of these parked outside Disney World.

Originally posted by RichardPrice

Originally posted by letthereaderunderstand
Thanks for your responses, didn't mean to derail the topic if I did, but I always have questions. On topic, what do you guys think about the new Virgin space vehicle? Thanks again, Peace

The new Virgin space vehicle? Its a sub-orbital pimp mobile - its the sort of thing tourists hire to drive around Florida in, you see thousands of these parked outside Disney World.

The Branson Pimp mobile...that gave me a good laugh...no you can join the 200 mile high club. Rad...peace

reply to post by Ramzus


"Why rocket ships?" you say?

You can try to have it both ways with a Single Stage to Orbit (SSTO) launch vehicle. GOOGLizing the word or acyronym should give anyone enough information to form an opinion.

My opinion is that a lot of R&D money would be required to being such a vehicle into production, along with certain technological improvements---engine specific impulse, for instance---before this becomes feasible.

It's all a good idea because avionics, engines and fuselage components are exceedingly expensive and if you can get back your invested equipment to reuse, it costs less in tne long run.

A rocket is aerodynamic and moves through the atmosphere with as little resistance as can be engineered into it. A rocket is pure Newtonian physics at work: An equal and opposite reaction less all of the usual losses to drag, weight, etc.

One of the key problems with any journey into space is the weight of the fuel. A rocket is big because it has to carry all of the fuel required to get reach escape velocity in order to get its payload into space. Here is a simplified example has been used elsewhere: Imagine if you had to drive nonstop from L.A. to New York City and were only allowed one tank of gas. You would need a big vehicle to carry a crew and its food. An empty Class A RV weighs about 14,500 pounds and gets about 10 miles per gallon when fully loaded. That means we need 270 gallons of gas to go 2700 miles. Gas weighs 6.25 pounds per gallon, so now we have 16,875 pounds of gas to haul in order to go from LA to NYC. So the vehicle and gasoline weigh 31,375 pounds. Add in crew and food, and we are up over 36,000 pounds. We have to make sure that the tires and suspension can handle the weight. We have to distribute the weight evenly and burn fuel form the tanks in a way that maintains the weight distribution. If we don't correctly manage the weight, the vehicle could tip over in high winds or on a sharp curve.

The Space Shuttle needs giant external tanks for the ride up into orbit. A spaceplane's wings and fuselage simply cannot carry enough fuel for a ride into space. Even if you made giant wings for a giant shuttle so that the shuttle itself would not need external boosters, the wings would tear off the fuselage due to sheer weight. The Nazi's "Amerika Bomber" program revealed many of the problems of building gigantic planes for normal travel in the atmosphere. Add in the problem of making a plane than can withstand escape velocity it is not feasible at present. A giant shuttle that carried all of its fuel would tear itself apart at launch, assuming it did not collapse during fueling.

Round tubes are inherently strong as containers of liquid. That is why we use round water tanks and circular rocket boosters. Put a nosecone on a stack of tubes, and you can get a rocket into space. Science wants simplicity and rockets are elegant and simple. The Space Shuttle is a very strong glider. It is made to strap onto those giant tanks and separate from them as it rides into space. Once in space, the shuttle has glide back to Earth. In doing so, its tiles trade speed for heat. Aerobraking is the hardest part of making a spaceplane. Re-entry is profoundly challenging.

The X-15 was a close as we ever got to a true spaceplane.

Interorbital Systems of Mojave, CA (interorbital.com is working on inexpensive launch vehicles (rockets). Reducing the costs of a government bureaucracy is one way to make space flight far less expensive.

[edit on 16-6-2009 by Sadhu]

[edit on 16-6-2009 by Sadhu]

I think all of your questions can be answered simply by understanding what Delta-V is:

When designing a trajectory, delta-v is used as an indicator of how much propellant will be required. Propellant usage is an exponential function of delta-v in accordance with the rocket equation.

For example, most spacecraft are launched in an orbit with inclination fairly near to the latitude at the launch site, to take advantage of the earth's rotational surface speed. If it is necessary, for mission-based reasons, to put the spacecraft in an orbit of different inclination, a substantial delta-v is required, though the specific kinetic and potential energies in the final orbit and the initial orbit are equal.

The rockets “tip” so they can take advantage of the rotation of the earth and increase their speed relative to the earth by going in the opposite direction. That is why they always “tip” and head East. As others have touched on, it is not possible to carry enough fuel to overcome gravity and reach escape velocity directly (straight up). So what we do is a number of tricks to achieve orbit, including dumping empty weight (stages, boosters) on ascent, and the "tipping" mentioned above. All of this comes down to the Delta-V, the fuel/energy required to reach a trajectory, and the weight of that fuel on the spacecraft.

Though they never seemed to catch on to this fact, Delta-V is also the reason why “certain individuals on this website”'s theory of a secret space station is not feasible. The Shuttle, for example does not have enough Delta-V to go from station to station, and it barely has enough to get the ISS. This is why it has to be launched in such a precise window when it docks with the ISS.

I supposed I should also add that in the upper atmosphere, the air is so thin, it lacks the ability to generate lift under an airfoil surface, rendering wings useless. The lack of Oxygen makes it impossible to use traditional, combustion, turbine engines. The Shuttle uses LOX/LH2 (Liquid oxygen/Liquid hydrogen) so it basically is providing its own oxygen allowing it to burn in a vacuum.

[edit on 6/16/2009 by defcon5]

Time to cut the bull and get right to the heart of the matter:

Rockets are used because of their ability to generate large amounts of thrust and are not "air breathing" - they do not require the Earth's atmosphere to function.

That's pretty much it.

Reaching a higher altitude effectively increases your velocity, which reduces the "escape velocity" necessary. Escape velocity is - atmosphere aside, the speed at which an object must be moving away from the center of mass (and surface of the mass) to 'escape' to a self-sustaining orbit. Escape velocity, in and out of itself, has very little relevance to whether or not a craft can go into orbit.

You can put yourself into orbit by climbing up a ladder, if you really wanted to. It would be no different than blasting you up there with a rocket.

Now - why not use an airplane, then?

Well, regardless of what has been said previously - rockets are horribly inefficient by comparison to even the most inefficient aircraft. You can talk aerodynamics all you want to - flying the empire state building around with jet engines is more efficient than shooting it around with rockets.

The reason why aircraft are not used is due to the engineering challenges associated with placing a payload-carrying, trans-atmospheric vehicle into the outer fringes of our atmosphere. You're looking at the largest winged craft ever built - it would make a B-52 look like a toy Micro Machine. You would need a runway that stretched across Texas to help the thing take off - much less land.

More recently, the concept of using magnetically coupled catapult systems (similar to the systems used in roller-coasters and maglev trains) in the mountains to accelerate a craft designed for hypersonic, trans-atmospheric flight to supersonic (or higher) velocities on the ground before ski-jumping it skywards. Sustaining rockets and/or engines will bring the craft into orbit.

It's a far more practical approach than even the ridiculous space-elevator concepts. Though it requires an initial investment overhead that will not be taken by any private firms any time soon, and will certainly not be approved by the present administration (and congress) with regards to government spending.

It's also questionable just how suitable such methods will be for transporting organic materials (people). That ski-jump is likely to exact some very high G-forces.... though they will be momentary - so shock-absorbing systems will likely help ease some of the trauma risks.

As for in-space maneuvering, it's highly likely that "plasma jets" (forget what they are actually called) will become the new favorite toy. Most of their power comes from electricity - which can be converted from solar radiation, as well as nuclear decay and nuclear fission and fusion. It has much more power-density than chemical rockets - and the "plasma jets" only require a small amount of reaction mass - which can be provided by waste fluids and materials. Their exospheric performance is vastly superior to chemical rockets, and their nature allows them to be actively-electronically-'scanned' (AESA Jet engines - the future of 3d thrust-vectoring) - or... 'steered' in three directions - which greatly improves the versatility of said engines.

Eventually - they may even be powerful enough to operate in an atmosphere and simply use the atmosphere, itself, as a reaction mass (though none of the prototypes in existence are anywhere near capable of this).

Originally posted by Aim64C
Time to cut the bull and get right to the heart of the matter:

You can put yourself into orbit by climbing up a ladder, if you really wanted to. It would be no different than blasting you up there with a rocket.

While I admit that I am no expert on physics, doubly so on astrophysics, I am about 99% sure that this statement is incorrect. The reason being that orbit is achieved and sustained through forward momentum. When you launch something into orbit, you need to attain a speed greater then the pull of gravity for that orbit altitude, if you do not reach that speed the object falls directly back into the atmosphere. Orbit is really nothing more then putting something into an arch that is long enough that so when gravity pulls it down, it misses the surface of the Earth, and continues to miss the earth until its speed begins to dissipate. When the speed dissipates, the orbit decays, and the objects orbit will tighten until the arch intersects the planet and the object reenters. This is why they refer to the weightlessness experienced as “Freefall”, because essentially that is what it is. The people on the spacecraft are in continuous freefall, as long as the periapsis of the orbit remains above the surface of the earth. The whole thing is controlled by velocity, hence the fact that neither a space elevator, or your ladder suggestion would work. The Earthen end of the elevator/rope/ladder would be flying around the planet at tremendous speed, and would burn up due to air friction.

When a spacecraft goes into orbit its periapsis is low and will bring it back into the earth within a single orbit, requiring additional pro-grade burns to make the eccentricity less elliptical and bring the periapsis off the surface of the planet. When a spacecraft wishes to reenter, it performs a retro-grade burn, slowing its velocity, and bringing the pariapsis down to where it will enter the earths atmosphere at a specific entry location.

If you are intereseted in playing with this concept, may I suggest a freeware program called Orbiter, and the guide Go Play In Space…

Have fun!

[edit on 6/17/2009 by defcon5]