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Getting to space without rockets

by Mfo
Tags: rockets, space
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Nov18-13, 09:18 AM
P: 2
Hi guys,
Wacky idea,
Could we use a combination of balloons and spacecraft to place objects into orbit?

A balloon could be used to attain altitude and reduce air resistance but the problem faced is that we need to reach a high velocity to escape the earths gravitational field. The problem is velocity, a source of velocity is needed to impart on our platform at a high altitude.
Could we use something from space to impart the velocity to our object?

Why can't we use the moons slingshot to impart a large increase in velocity on any spacecraft which can then be used to pick up our platform at a high altitude and give it the necessary escape velocity?

This piggy back craft could be re used and slingshot around the moon again to increase the velocity for another.

Is this a stupid idea?
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Nov18-13, 08:54 PM
PF Gold
P: 866
The idea of lifting stuff into orbit has lots of appeal, but slingshotting a spacecraft down into the atmosphere to pick up an object seems impractical. The maximum altitude of balloons is about 20-25miles, still well within the atmosphere, so the pickup vehicle would be wrapped in plasma from air friction, which makes it tough for it to find the target or to steer to it. Even more difficult, an object coming back from the moon would be moving at about 25,000 mph at the time of encounter, which makes for a very jerky pickup.
There has been some conceptual designs involving tethers (think space elevator) that involve geostationary tethers that dangle down into the upper atmosphere. The idea is that a rocket payload can be attached as the rocket is reaching its peak altitude, when there is minimal relative motion between the payload and the tether.
It is energetically much cheaper to just reach an altitude than to also speed up to orbital velocity.
Nov18-13, 10:20 PM
P: 5‎
this site is one of many you may find cool.

Nov22-13, 03:27 AM
P: 31
Getting to space without rockets

There's work being done on an "Airship to Orbit" in Rancho Cordova, California by a group called JP Aerospace. They are planning on using a ion/hybrid rocket motor mashup to provide propulsion. If it works, it'd be a quantum leap in capability. MY only question is how they intend to run a hybrid motor at any power level for the 5 days they estimate it would take to make the orbital insertion. A small liquid fuel rocket? Sure, just use a highly reliable fuel pump and a large fuel supply. The hybrid motor's got me scratching my head over how they plan on getting the required endurance.

There's a LOT of ideas on how to make it to orbit without a rocket; it's just that the cost is usually higher than the cost of continuing the existing "legacy" technology of expendable launch vehicles. If someone can come up with a way to break that cycle, the aerospace industry will beat a highway to their door. :)
Nov22-13, 05:16 AM
P: 2
Why your idea of balloons wouldn't work is because the physical property that makes a ballon go up in the air is density. So the density of the system you are trying to float up through the atmosphere must simply be lower than that of the atmosphere. It wouldn't work because the air density decreases with altitude.

and second because most probably a system that we are interested in putting in the atmosphere is surely denser.
Now what they do is heat the air inside the balloon to reach a lower density. but if we want to reach the stratosphere for example, the amount of heat you would have to add to the air control volume in your balloon wouldn't seem so efficient I suppose, in addition to having to find a material to withstand a high temperature.
Nov22-13, 07:32 PM
PF Gold
P: 866
The JP Aerospace concept seems ambitious in the extreme, think of a vehicle bigger than the Disney Magic cruise ship, much much lighter than air and driven to hypersonic speed at 200-400,000 ft altitude. Truly a project to push the state of the art for materials and structures, not to mention propulsion. My guess is that that kind of material would make a conventional reusable single stage to orbit vehicle quite practical, bypassing the need for balloons.

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