[graham.d]

Of course every little helps but there is no complete solution. You need to achieve around 17,000 mph and, even if this could be achieved at a low altitude there would be a need for some impressive (and probably weighty) heat shields and sufficient (i.e. a lot more) extra speed to allow for the considerable drag from air resistance. It would generally be best to launch from as near the equator as politically acceptable to the nation involved and to launch in an easterly direction (which is what most do). This gives over 1,000mph free because of the earth's rotation. There is some significant gain from an altitude launch; this has not much to do with the tiny gain in height (remembering that you have to get to about 400 miles if you want to stay in orbit - even a low one), but would gain from the forward speed of the launch vehicle (say another 600 mph) and probably much more from the thinner atmosphere providing much less drag. Despite all this complication there is still a lot of thrust required from the craft itself to attain an orbit.

[wolfekeeper]

Given no friction and say 2 miles of tube, does anyone know how fast it is possible to theoretically accelerate a one ton object? Lets say your using magnets as the "accelerant"?

Supermagnets and magnetically soft iron can achieve an acceleration of 1000g

[CliffordK]

you have to get to about 400 miles if you want to stay in orbit - even a low one),

The Hubble is at about 559 km (347 mi) speed 7,500 m/s
The ISS is at about 402 km (250 mi), speed: 7,706.6 m/s (27,743.8 km/h, 17,239.2 mph) but notes indicate that the orbit is currently decaying at about 2km / month.
speed: 7,706.6 m/s (27,743.8 km/h, 17,239.2 mph)

Geostationary orbit is at  35,786 kilometres (22,236 mi)

Anyway, one could likely save fuel and resources by building a short range, reusable heavy lift mach 4 supersonic jet for the first stage.  But, the engineering cost might be extreme, and it still could be limited in capacity.

I am still a bit puzzled on why Pegasus is considered more expensive than other launch methods, but it must have to do with the custom work for a one-time use rocket with a small payload.

Since volume increases by the cube of the length, but surface area by the square, potentially larger rockets are also more efficient than smaller ones.

[CliffordK]

Given no friction and say 2 miles of tube, does anyone know how fast it is possible to theoretically accelerate a one ton object? Lets say your using magnets as the "accelerant"?

Supermagnets and magnetically soft iron can achieve an acceleration of 1000g

People become puddles of goo at 1000g.
Or, at least looking more like bugs on a windshield.

Wind friction and heat generation would be high from an extreme velocity, low altitude launch, but it might get one up a few miles of vertical displacment.

At 10,000 m/s², in one second, one would get about 5km, and 10,000 m/s, or about 36,000 kph.

Earth's escape velocity (without wind resistance?) is listed as 11,190 km/s.

[Airthumbs (OP)]

As I thought then, it can be done quite easily.  We have the technology already.  In fact it's fair to say I think that the potential speeds an object could reach would well exceed orbital levels.  At the very least you could use a normal rocket fired from a ground launch system to maintain velocity.  Is it coincidence that there is current research underway to produce circuitry that can withstand 1000g impacts? 

If the highest landmass on Earth was used to site a launch system then I would expect the air resistance would be considerably less and given much higher velocity such as 100,000kph, or even 500,000kph, maybe heat shields could be incorporated into an outer protective shell, during initial launch.

If breaking the sound barrier is a problem then maybe it could be done inside a vacuum environment although I would expect the shock wave to be massive when it hits even the thinner air at high altitude?  Maybe the shock wave could be reduced by shooting up supersonic jets of air into the area the capsule will come into contact with the air when it exists then vacuum sealed accelerator.

I think the "U" tube launch idea for a magnetic system is fantastic, as done inside a vacuum, Gravity can do a very large part of the work.

[CliffordK]

Note the change of units for the calculated mag gun above at 36,000 kph, and the escape velocity of 11,190 kps.  [xx(]

With the U above, using gravity alone, one would get high speed at the bottom of the U, but not at the top, so it would be ineffective of aiding the launch. 

However, the level, then curve up might be effective as it would be easier to create a long path allowing slow acceleration, and the elevation change from start to release might be less than a a vertical acceleration pathway.

[wolfekeeper]

A pure gravity U shaped track would essentially give no significant benefit over a static launch.

That's actually wrong. There's a (somewhat) significant advantage.

When you turn a rocket engine on, pointing downwards, you gain speed from the gravity and the rocket.

And then when you're moving, the rocket engine acts over the distance; generating work, so the faster you're moving the more energy you make.

The net upshot is that the rocket gains speed from turning on at the top of the U, going downwards and back up again.

[CliffordK]

Ok,
So, if you drilled a hole 5 miles deep for the launch, then you would have 5 miles of extra gravity to contend with, reducing the velocity by 9.8 m/s² for every second until one gets back up to ground level.

If you launched horizontally, then turned up, you would not have to contend with the extra gravity during the initial acceleration phase.

Interesting thinking about the U-shaped launch.
So, if the time is greater for the downward path, and shorter for the upward path.
Then the effect of gravity may not in fact be symmetrical, and one may get and extra boost from the gravity.

The same would be true if you bored a hole through the center of the moon for some kind of a magnetic accelerator.  One would spend more time travelling towards the center of moon than away from the center of the moon.  And, thus would get an extra boost from the moon's gravity, albeit weak.

This time effect of gravity may also explain why there is a benefit of a nearly vertical launch of a wingless rocket vs launching at an angle, say 45 degrees.  One wants a launch that gets to as high of an altitude as possible, as quickly as possible.

[wolfekeeper]

The same would be true if you bored a hole through the center of the moon for some kind of a magnetic accelerator.  One would spend more time travelling towards the center of moon than away from the center of the moon.  And, thus would get an extra boost from the moon's gravity, albeit weak.

Oh, no, not weak at all, that would be a MASSIVE win!

You would wait till you reached very nearly the middle before turning on the rocket engine. You should always use rockets when you're going as fast as possible.

edit: Mmm come to think of it, you should light the rocket at the bottom of the U for the same reason.

This time effect of gravity may also explain why there is a benefit of a nearly vertical launch of a wingless rocket vs launching at an angle, say 45 degrees.  One wants a launch that gets to as high of an altitude as possible, as quickly as possible.

I think that that's just the Earth's atmosphere. In the absence of atmosphere you would launch very nearly horizontally, with the rocket angled to support its own weight, and to give as much sideways thrust as possible, although that would vary somewhat if you are trying to achieve a particular orbit, then you would launch more steeply upwards and then lean over.

The "time effect of gravity" is more normally called 'gravity losses' and are a thing though.

[Airthumbs (OP)]

Did anyone see the successful test of the British inventors space rocket recently?  I did refer to him earlier on in the discussion and am very excited about it's development.  It uses air drawn into the rocket externally to power combustion.  I may have heard that it makes a 50% weight loss for the same performance as a normal rocket.  Interesting prospect for a combo Airthumbs solution

Read what I wrote previously about a British Inventor and carefully read this article if you dare!! 

http://www.bbc.co.uk/news/science-environment-20510112

[CliffordK]

I'm glad to see work on Jet/rocket hybrids.

Do they count the extra weight for carrying liquid helium coolant?  Or, would the liquid hydrogen used for fuel be enough for the precooling?

Of course, helium has a much lower density than hydrogen.

[Airthumbs (OP)]

Hi Clifford K, I think the information you might be interested in can be found here... http://www.reactionengines.co.uk/sabre.html 

The engine is called Sabre.   

If this was used in conjunction with a ground launch system as discussed then I do not see how it would not work.  I have not seen any of the people at NASA, ESA or any of the private space companies give this a good look over yet but I hope they do as it would be great to get some feedback from the people who have all the experience.

I have e-mailed the company and asked them for some input into my idea so watch this space........ exciting times.