Traveling to space

[fredreload]

So uh, let's say I take a jet pack and I fly slowly into space in a space suit in auto pilot mode close to 5m/h upward(This is just the upward speed, it has nothing to do with the orbital speed). What is my orbital velocity when I reach space? My speed at that height relative to the earth's orbit speed? Actually the helium balloon idea is good, I can just jet pack to space after I reach that distance

[Strange]

8 minutes ago, fredreload said:

So uh, let's say I take a jet pack and I fly slowly into space in a space suit in auto pilot mode close to 5m/h upward(This is just the upward speed, it has nothing to do with the orbital speed). What is my orbital velocity when I reach space? My speed at that height relative to the earth's orbit speed? 

Not sure what you mean. But if you only change your vertical speed, then the speed you are orbiting at will be the speed your are moving at the surface  of the Earth.

Orbital speed, [math]v = \sqrt{\frac{G M}{r}}[/math]

So, the distance is given by [math]r = \frac{G M}{v^2}[/math]

If you take off from the equator your "sideways" (orbital) speed will be about 1,000 mph. This means the distance you would need to be in order to orbit at this speed is about 1.2 million miles: https://www.wolframalpha.com/input/?i=(G+*+mass+of+Earth)+%2F+(1000+mph)^2+in+miles

 

[mathematic]

"reach space" is not well defined.  As you increase altitude, the atmosphere thins out, but there is no sharp transition point.

[fredreload]

7 hours ago, Strange said:

Not sure what you mean. But if you only change your vertical speed, then the speed you are orbiting at will be the speed your are moving at the surface  of the Earth.

Orbital speed, v=GMr−−−√

So, the distance is given by r=GMv2

If you take off from the equator your "sideways" (orbital) speed will be about 1,000 mph. This means the distance you would need to be in order to orbit at this speed is about 1.2 million miles: https://www.wolframalpha.com/input/?i=(G+*+mass+of+Earth)+%2F+(1000+mph)^2+in+miles

 

Yes, since I am moving so slow, I would be moving counter to earth's orbit at -3km/s

[Janus]

3 hours ago, fredreload said:

Yes, since I am moving so slow, I would be moving counter to earth's orbit at -3km/s

Do you mean Earth's orbital speed with respect to the Sun?  (Which is ~30km/s)

In which case,  let's assume that you are lifting off from the North pole so you don't have to take the Earth's rotation into account.

When you start off, both you and the Earth share the same velocity with respect to the Sun.  As you climb, you don't lose that shared velocity, so you would be orbiting the Sun just like the Earth is even though you are no longer in contact with the Earth.

[fredreload]

10 minutes ago, Janus said:

Do you mean Earth's orbital speed with respect to the Sun?  (Which is ~30km/s)

In which case,  let's assume that you are lifting off from the North pole so you don't have to take the Earth's rotation into account.

When you start off, both you and the Earth share the same velocity with respect to the Sun.  As you climb, you don't lose that shared velocity, so you would be orbiting the Sun just like the Earth is even though you are no longer in contact with the Earth.

That is a good idea that I haven't thought of, thing is something needs to be there in space where I can stay in, like a burger stand lol. Yes it seems jet packing into space seems rather realistic, but having a place to stay in, now that's the hard part. If you are to follow the earth's orbit you'll need to be at 3~30km/s. If you build a stationary structure in the middle of nowhere, you better be prepared to travel long miles. It sounds like a cool idea, but colonization into space is still a bit of a problem. For one there is no oxygen, and everything needs to be vacuum sealed. Personally I'd choose the Elysium idea

[Strange]

8 hours ago, fredreload said:

Yes, since I am moving so slow, I would be moving counter to earth's orbit at -3km/s

No you would be moving along with Earth's orbit (around the Sun). Even if your initial direction was "backwards" along the Earth's orbit, because you are going around the Earth after 12 hours you would be going "forwards" along the Earth's orbit.

4 hours ago, fredreload said:

Yes it seems jet packing into space seems rather realistic

Apart from the amount of fuel you would need!

4 hours ago, fredreload said:

but having a place to stay in, now that's the hard part.

There is the ISS you could call in on. But it would be rushing past at about 17,000 mph so that might be a bit tricky. (That is the problem with going straight up and not trying to change your lateral speed.)

Quote

 If you build a stationary structure in the middle of nowhere

Stationary relative to what? 

This might be helpful: https://what-if.xkcd.com/58/

Quote

Could a (small) rocket (with payload) be lifted to a high point in the atmosphere where it would only need a small rocket to get to escape velocity?

...

 getting to space is easy. The problem is staying there.

...

Only a fraction of a rocket's energy is used to lift up out of the atmosphere; the vast majority of it is used to gain orbital (sideways) speed.

 

[fredreload]

5 hours ago, Strange said:

Stationary relative to what? 

This might be helpful: https://what-if.xkcd.com/58/

Uh, between earth and the moon? Like Elysium?

[Strange]

15 minutes ago, fredreload said:

Uh, between earth and the moon? Like Elysium?

The moon goes round the earth about once a month. Something between the earth and moon would go round faster. So not really stationary. 

Maybe you are thinking of something like this: https://en.m.wikipedia.org/wiki/Geostationary_orbit

Edited October 29, 2018 by Strange

[Janus]

2 hours ago, fredreload said:

Uh, between earth and the moon? Like Elysium?

If you mean like the movie, you are talking about an object that is in orbit around the Earth. From this image:

Elysium is in what is typically known as a Low Earth Orbit (LEO).  While is it hard to judge from just this picture ( I'm not sure if the film gives an orbital altitude),  it can't be orbiting too much further out than the ISS is ( and certainly not anywhere near geosynchronous orbit distance.)  

Let's put it out at 500 km.  At this altitude, it would orbit with a period of  ~94 min 36 sec.  if it orbited in the plane of the equator and in the same direction as the Earth, it would pass over the same point of the Earth's surface every 101 min 15 sec.

There is only one place where an object could orbit between Earth and The Moon and maintain this relative position.  This is the L1 Lagrange point which is ~58,000 km short of the Moon (the Moon is 384,000 km away).   But even this point isn't entirely stable and something put there would need occasional correctional nudges to keep it from drifting away and into its own independent orbit around the Earth (There are two Lagrange points that are stable, L4 and L5, which are located 60 degrees ahead of and behind the Moon in it orbit. These are often mentioned as good places to put space colonies)

[et pet]

On 10/28/2018 at 1:56 PM, fredreload said:

So uh, let's say I take a jet pack and I fly slowly into space in a space suit in auto pilot mode close to 5m/h upward(This is just the upward speed, it has nothing to do with the orbital speed). What is my orbital velocity when I reach space? My speed at that height relative to the earth's orbit speed? Actually the helium balloon idea is good, I can just jet pack to space after I reach that distance

   Hey, fredreload,

      I will most likely be told that I am wrong about this, but a "jet pack" will most likely have a Maximum Operational Ceiling because it needs oxygen to Operate.

     I am fairly certain that no just plain "jet pack" will allow you to or enable you to actually reach "space".

     Some 20 or so years ago, I heard reports that a Soviet Pilot had flown a Soviet Jet aircraft to somewhere around 120,000 -125,000 feet. I believe that it was reported to be one of the Soviet Mig series of Fighter Jets. This information was and is totally anecdotal - I was neither involved in the Flight, nor did I have direct access to any telemetry to verify the Flight.

      I am fairly certain, fredreload, some other Members will soon come along to either correct or further expound this information.

     Interesting idea, by the way!

[Janus]

1 hour ago, et pet said:

   Hey, fredreload,

      I will most likely be told that I am wrong about this, but a "jet pack" will most likely have a Maximum Operational Ceiling because it needs oxygen to Operate.

     I am fairly certain that no just plain "jet pack" will allow you to or enable you to actually reach "space".

     Some 20 or so years ago, I heard reports that a Soviet Pilot had flown a Soviet Jet aircraft to somewhere around 120,000 -125,000 feet. I believe that it was reported to be one of the Soviet Mig series of Fighter Jets. This information was and is totally anecdotal - I was neither involved in the Flight, nor did I have direct access to any telemetry to verify the Flight.

      I am fairly certain, fredreload, some other Members will soon come along to either correct or further expound this information.

     Interesting idea, by the way!

The lack of oxygen isn't the real problem with this idea. (your jet pack could be fitted with its own oxygenator supply. )

The real problem come from trying to climb upward at such a slow speed.  If we put our target altitude at 300 km (187.5 mi) at 5 mph, it would take 37.5 hrs to climb to that altitude. Earth's gravity will not have fallen off by much (to about 91% of earth surface value), so your jet pack will have to be thrusting against nearly 1 g of gravity the whole time.  So even if we use the 91% value for the whole trip, it would have to produce the same amount of energy as it would to accelerate itself up to 8.94 m/sec² x 135000 sec = ~1207 km/sec.

On the other hand, if you got up to a high enough speed while still near the surface of the Earth such that inertia alone (without an further firing of your engine) would lift to to 300 km, you would only have to accelerate up to 2.7 km/sec. 

And its even worse than that.  If you accelerate quickly, you use up your fuel while you are still near the Earth. Fuel used up near the Earth is fuel you don't have to lift any higher.

If you try to climb slowly, you have to lift more of your fuel to a higher altitude. But lifting fuel to burn later means burning more fuel now, which means that you needed even more fuel earlier to lift the fuel you are burning now...   This compounds very quickly, and the amount of total fuel needed increases immensely 

Earth launched rockets have to compromise.  They want to get up to speed at as low of an altitude as possible to reduce fuel requirements, but they can't get up to full speed too low in the atmosphere or they would burn up from air friction. 

Then there is the fact that it isn't enough to just get to 300 km above the Earth, in order to stay there, you have to be moving at least orbital speed, which is ~ 7.7 km/sec at that altitude.

 

[et pet]

2 hours ago, Janus said:

The lack of oxygen isn't the real problem with this idea. (your jet pack could be fitted with its own oxygenator supply. )

The real problem come from trying to climb upward at such a slow speed.  If we put our target altitude at 300 km (187.5 mi) at 5 mph, it would take 37.5 hrs to climb to that altitude. Earth's gravity will not have fallen off by much (to about 91% of earth surface value), so your jet pack will have to be thrusting against nearly 1 g of gravity the whole time.  So even if we use the 91% value for the whole trip, it would have to produce the same amount of energy as it would to accelerate itself up to 8.94 m/sec² x 135000 sec = ~1207 km/sec.

On the other hand, if you got up to a high enough speed while still near the surface of the Earth such that inertia alone (without an further firing of your engine) would lift to to 300 km, you would only have to accelerate up to 2.7 km/sec. 

And its even worse than that.  If you accelerate quickly, you use up your fuel while you are still near the Earth. Fuel used up near the Earth is fuel you don't have to lift any higher.

If you try to climb slowly, you have to lift more of your fuel to a higher altitude. But lifting fuel to burn later means burning more fuel now, which means that you needed even more fuel earlier to lift the fuel you are burning now...   This compounds very quickly, and the amount of total fuel needed increases immensely 

Earth launched rockets have to compromise.  They want to get up to speed at as low of an altitude as possible to reduce fuel requirements, but they can't get up to full speed too low in the atmosphere or they would burn up from air friction. 

Then there is the fact that it isn't enough to just get to 300 km above the Earth, in order to stay there, you have to be moving at least orbital speed, which is ~ 7.7 km/sec at that altitude.

 

   I thought that you had more or less covered the Orbital Mechanics (?) side of the coin quite commendably, Janus.

 

   I was focusing more on this : "Actually the helium balloon idea is good, I can just jet pack to space after I reach that distance "

   Some years back I remember some talk of having to switch from Jet engines to actual Rockets to get above a certain altitude.

   Maybe somewhere around  40 miles, 200,000 ft ? 

   In your previous Post about the fictional "Elysium" in (LEO), you had "put it out at 500 km".  ~ 300 miles?

   I guess I am guilty of more or less accepting and agreeing with the previous Posts and was simply addressing that one small aspect that had NOT been broached yet.

    Is any kind of Jet engine operational out to 100 miles...200 miles...300 miles?

    

[Janus]

15 hours ago, et pet said:

   I thought that you had more or less covered the Orbital Mechanics (?) side of the coin quite commendably, Janus.

 

   I was focusing more on this : "Actually the helium balloon idea is good, I can just jet pack to space after I reach that distance " 

I think you are focusing too much on the word "jet" in jet pack.   A jet pack is a general use term for a single person propulsion system based on the rocket principle.  In fact, nothing that we have now which is called a "jet pack" uses an air-breathing jet engine.  They all use rockets with a self-contained oxygenator supply.

[fredreload]

16 hours ago, Janus said:

I think you are focusing too much on the word "jet" in jet pack.   A jet pack is a general use term for a single person propulsion system based on the rocket principle.  In fact, nothing that we have now which is called a  "jet pack" uses an air-breathing jet engine.  They all use rockets with a self-contained oxygenator supply.

You are right, this is more of a single person traveling idea than to move something heavy into space. My idea comes from the idea of a space elevator. It was a big idea then about traveling to space using carbon nanotube as an anchor, but no existing structure can withstand such amount of pressure connecting an object in space to the ground. Then I thought about the tallest structure, one that would connect space to earth to allow an actual elevator to reach the sky, then again the integrity of such a structure would be in question. So my recent post is on the idea of using photonic light to propel a an object into space(no anchor). This comes from the top 5 ideas in traveling to space in which you use a laser to create compressed air beneath the rocket to push it into space. The idea is that the entry and re-entry from space is kept at a slow speed and with no strings, so the space suit would not get burned from the atmospheric pressure. Then the idea of a water fountain pushing an object up. And finally, the jet pack, the type that is used in space to move the ISS to avoid debris.

So what do you do once you reaches space? Beats me, I've seen the Geostorm space station. If you could fly to a stationary(not orbiting) spot in space and build a structure there, sure that would be cool. Or you could build a structure that is in geo synchronous orbit to the same place you lifted. Without gravity to keep air in place surely everything needs to be vacuum sealed.

P.S. I'll probably jet pack a remote drones or dummies up to build the structure first , I dunno if you can jet pack something that weighs one ton

P.S. We could literally have a steel cone controlled by jet pack on each side controlled by a computer. That's in the movie First Man, and that's how they improved the computer electronics that leads to the fire in the shuttle.

Edited October 31, 2018 by fredreload

[fredreload]

Never mind, I looked into jet packs as there is no viable way of (holding gas) and expel gas for more than 10 minutes duration. Best count on the laser photonic light disperse thruster that is still in the laboratory stage

[Janus]

6 hours ago, fredreload said:

You are right, this is more of a single person traveling idea than to move something heavy into space. My idea comes from the idea of a space elevator. It was a big idea then about traveling to space using carbon nanotube as an anchor, but no existing structure can withstand such amount of pressure connecting an object in space to the ground. Then I thought about the tallest structure, one that would connect space to earth to allow an actual elevator to reach the sky, then again the integrity of such a structure would be in question.

A space elevator is an entirely different matter.   With the slow moving rocket, the vast amount of energy required is due to the fact that the rocket must provide the thrust just to support the weight of the Rocket. With a space elevator, the cable supports the weight, so you only have to provide the energy needed to lift the payload to altitude and their is the extra advantage of not having to carry that energy as fuel in the capsule.

Structurally,  A space elevator is suspended from orbit and not supported by the ground.   The basic idea is to put a counter-mass at the end which is at some point further than geostationary orbit distance.   This mass then acts something like a rock tied on the end of a string and then swung around in circles, it pulls the string taught.  This makes the material requirements less stringent. (though still beyond out present capabilities)

Even with a ground-based laser system, a slow climb and ascent adds tremendously to the energy required. The iaser still has to provided the energy needed to support the payload's weight against gravity.  The less time spent getting your payload up to orbital speed, the better.