Discussion
Some big names in Aerospace are getting together to create an air launched booster with capability to deliver 13 tonnes to Low Earth Orbit.
http://www.youtube.com/watch?feature=player_embedd...
Scaled Composites are providing the carrier plane, Spacex the booster and Microsoft cofounder Paul Allen seems to be supplying a lot of the money.
More info here: http://spaceflightnow.com/news/n1112/13stratolaunc...
http://www.youtube.com/watch?feature=player_embedd...
Scaled Composites are providing the carrier plane, Spacex the booster and Microsoft cofounder Paul Allen seems to be supplying a lot of the money.
More info here: http://spaceflightnow.com/news/n1112/13stratolaunc...
Caruso said:
Some big names in Aerospace are getting together to create an air launched booster with capability to deliver 13 tonnes to Low Earth Orbit.
http://www.youtube.com/watch?feature=player_embedd...
Scaled Composites are providing the carrier plane, Spacex the booster and Microsoft cofounder Paul Allen seems to be supplying a lot of the money.
More info here: http://spaceflightnow.com/news/n1112/13stratolaunc...
Does it mean we're going back to the Moon anytime soon?http://www.youtube.com/watch?feature=player_embedd...
Scaled Composites are providing the carrier plane, Spacex the booster and Microsoft cofounder Paul Allen seems to be supplying a lot of the money.
More info here: http://spaceflightnow.com/news/n1112/13stratolaunc...
I've always wondered what the advantages of air launching an orbital spacecraft would be. My thoughts were that there were very few.
To achieve earth orbit, a spacecraft MUST reach 17,500 mph at an altitude of at least 500,000 feet.
Lifting a spacecraft to 40,000 feet or so under a lifting aircraft is hardly going to make a big difference to its struggle to 500,000 feet.
Also, the lifting aircraft will only give the spacecraft a 500 mph bonus starting speed in its race to 17,500 mph. So again, the effort of lifting it up into the air first hardlly helps much.
Finally, a really useful large spacecraft needs a huge amount of fuel to accelerate it to the altitude and speeds required for orbit. Since the lift to 40,000 feet and 500 mph is only a small farction of the speed and altitude required, the spacecraft will still need at least 90% of the fuel load of a pad launched spacecraft. Hauling all that fuel and weight to 40,000 feet requires a very big aircraft.
The only advantages I can see are that the fact that the spacecraft is attached to an aeroplane means that the launching pioint can be above and away from any nasty weather in and around the launch site and there may be some additional safety for a manned spacecrft in that possibly the crew might have time to get out if things went wrong just after launch.
The only air launched orbital system that has been used so far, as far as I am aware, is the Pegasus launcher.
In fact, the Scaled spacecraft looks very like a bigger version of Pegasus.
To achieve earth orbit, a spacecraft MUST reach 17,500 mph at an altitude of at least 500,000 feet.
Lifting a spacecraft to 40,000 feet or so under a lifting aircraft is hardly going to make a big difference to its struggle to 500,000 feet.
Also, the lifting aircraft will only give the spacecraft a 500 mph bonus starting speed in its race to 17,500 mph. So again, the effort of lifting it up into the air first hardlly helps much.
Finally, a really useful large spacecraft needs a huge amount of fuel to accelerate it to the altitude and speeds required for orbit. Since the lift to 40,000 feet and 500 mph is only a small farction of the speed and altitude required, the spacecraft will still need at least 90% of the fuel load of a pad launched spacecraft. Hauling all that fuel and weight to 40,000 feet requires a very big aircraft.
The only advantages I can see are that the fact that the spacecraft is attached to an aeroplane means that the launching pioint can be above and away from any nasty weather in and around the launch site and there may be some additional safety for a manned spacecrft in that possibly the crew might have time to get out if things went wrong just after launch.
The only air launched orbital system that has been used so far, as far as I am aware, is the Pegasus launcher.
In fact, the Scaled spacecraft looks very like a bigger version of Pegasus.
Eric Mc said:
To achieve earth orbit, a spacecraft MUST reach 17,500 mph at an altitude of at least 500,000 feet.
Lifting a spacecraft to 40,000 feet or so under a lifting aircraft is hardly going to make a big difference to its struggle to 500,000 feet.
Why MUST the spacecraft reach 17,500mph??Lifting a spacecraft to 40,000 feet or so under a lifting aircraft is hardly going to make a big difference to its struggle to 500,000 feet.
Ive heard the speed mentioned on the few space launches I've seen. What it significant about that speed?
Always struck me as a speed someone plucked from thin air.
tvradict said:
Eric Mc said:
To achieve earth orbit, a spacecraft MUST reach 17,500 mph at an altitude of at least 500,000 feet.
Lifting a spacecraft to 40,000 feet or so under a lifting aircraft is hardly going to make a big difference to its struggle to 500,000 feet.
Why MUST the spacecraft reach 17,500mph??Lifting a spacecraft to 40,000 feet or so under a lifting aircraft is hardly going to make a big difference to its struggle to 500,000 feet.
Ive heard the speed mentioned on the few space launches I've seen. What it significant about that speed?
Always struck me as a speed someone plucked from thin air.
Every planetary body has a selection of "orbital speeds". In other words, if an object wants to orbit that planetary body, a distinct speed MUST be achieved or else the object will either fall back to the ground - or head off into space. The orbital speed is determined by a number of different factors -
how high above the planetary surface the object wishes to orbit
the mass of the planetary body
the mass of the orbiting spacecraft - although in comparison to a planet this is so small that it can be virtually ignored
the diameter of teh planetary body
whether the planetary body has an atmosphere or not
Most satellites are launched into orbits above 100 miles. This means they are clear of the atmosphere. At these altitudes 17,500 mph is the required orbital speed.
Orbit of the earth has to be above the atmosphere as otherwise frictional atmospheric heating will burn up the spacecraft/satellite and/or drag it back down to earth (referred to as orbital decay).
On the moon there is no atmosphere. Therefore, stable orbits can be achieved at any height above the surface as long as the orbit is high enough to clear the tallest mountains. A stable lunar orbit can be achieved as low as 6 miles or so. The Apollo spacecraft orbited the moon at around 60 miles.
Because the moon is so much smaller and less massive than the earth. a 60 mile altitude orbit is usually set at around 4,500 mph.
XB70 said:
While not designed to launch it, but merely to carry it (like the 747 which was eventually used), this is very similar to the twin C-5 Galaxy mockup where the Shuttle would be carried under the central wing section joining the two aircraft.
Now THAT would have been a big aircraft
Now THAT would have been a big aircraft
Really is quite an interesting approach.
Eric Mc said:
I've always wondered what the advantages of air launching an orbital spacecraft would be. My thoughts were that there were very few.
To achieve earth orbit, a spacecraft MUST reach 17,500 mph at an altitude of at least 500,000 feet.
Lifting a spacecraft to 40,000 feet or so under a lifting aircraft is hardly going to make a big difference to its struggle to 500,000 feet.
Also, the lifting aircraft will only give the spacecraft a 500 mph bonus starting speed in its race to 17,500 mph. So again, the effort of lifting it up into the air first hardlly helps much.
Finally, a really useful large spacecraft needs a huge amount of fuel to accelerate it to the altitude and speeds required for orbit. Since the lift to 40,000 feet and 500 mph is only a small farction of the speed and altitude required, the spacecraft will still need at least 90% of the fuel load of a pad launched spacecraft. Hauling all that fuel and weight to 40,000 feet requires a very big aircraft.
The only advantages I can see are that the fact that the spacecraft is attached to an aeroplane means that the launching pioint can be above and away from any nasty weather in and around the launch site and there may be some additional safety for a manned spacecrft in that possibly the crew might have time to get out if things went wrong just after launch.
The only air launched orbital system that has been used so far, as far as I am aware, is the Pegasus launcher.
In fact, the Scaled spacecraft looks very like a bigger version of Pegasus.
If you read the website, it seems that they're pushing the 'any orbit' bit as the big deal. The design of the rocket nozzle can be optimised for lower air densities, and of course there's less drag at higher altitudes, so the rocket doesn't have to overcome that. I'd have thought the fuel and expense of getting to altitude by being carried by a massive aircraft outweighs any benefits there though, so that's why they're left with the 'any orbit' facility.To achieve earth orbit, a spacecraft MUST reach 17,500 mph at an altitude of at least 500,000 feet.
Lifting a spacecraft to 40,000 feet or so under a lifting aircraft is hardly going to make a big difference to its struggle to 500,000 feet.
Also, the lifting aircraft will only give the spacecraft a 500 mph bonus starting speed in its race to 17,500 mph. So again, the effort of lifting it up into the air first hardlly helps much.
Finally, a really useful large spacecraft needs a huge amount of fuel to accelerate it to the altitude and speeds required for orbit. Since the lift to 40,000 feet and 500 mph is only a small farction of the speed and altitude required, the spacecraft will still need at least 90% of the fuel load of a pad launched spacecraft. Hauling all that fuel and weight to 40,000 feet requires a very big aircraft.
The only advantages I can see are that the fact that the spacecraft is attached to an aeroplane means that the launching pioint can be above and away from any nasty weather in and around the launch site and there may be some additional safety for a manned spacecrft in that possibly the crew might have time to get out if things went wrong just after launch.
The only air launched orbital system that has been used so far, as far as I am aware, is the Pegasus launcher.
In fact, the Scaled spacecraft looks very like a bigger version of Pegasus.
tvradict said:
Eric Mc said:
To achieve earth orbit, a spacecraft MUST reach 17,500 mph at an altitude of at least 500,000 feet.
Lifting a spacecraft to 40,000 feet or so under a lifting aircraft is hardly going to make a big difference to its struggle to 500,000 feet.
Why MUST the spacecraft reach 17,500mph??Lifting a spacecraft to 40,000 feet or so under a lifting aircraft is hardly going to make a big difference to its struggle to 500,000 feet.
Ive heard the speed mentioned on the few space launches I've seen. What it significant about that speed?
Always struck me as a speed someone plucked from thin air.
But the imnportant thing is that, if they only achieved a speed of (say) 17,000, the spacecraft would only travel about 90% of the way around the earth before it fell back to earth.
So, the 17,500 is not an arbitary figure, it is the absolute MINIMUM speed that an object must achieve to achieve a low earth orbit.
And don't forget that, even though an orbit further out can be stable at lower speeds, a correspondingly higher amount of energy (i.e. fuel) must be spent to reach that distance from earth.
So, the 17,500 is not an arbitary figure, it is the absolute MINIMUM speed that an object must achieve to achieve a low earth orbit.
And don't forget that, even though an orbit further out can be stable at lower speeds, a correspondingly higher amount of energy (i.e. fuel) must be spent to reach that distance from earth.
Eric Mc said:
I've always wondered what the advantages of air launching an orbital spacecraft would be. My thoughts were that there were very few.
Essentially it is because at that altitude 90% of the atmosphere is below you, so lower drag. After all the only reason rockets go straight up when launched is to get above the atmosphere before pitching down to accelerate parallel to the earth surface to achieve orbital velocity ( I know, this is much simplified compared to an actual rocket trajectory ).Eric Mc said:
dr_gn said:
Eric Mc said:
So, the 17,500 is not an arbitary figure, it is the absolute MINIMUM speed that an object must achieve to achieve a low earth orbit.
That's what I said 
davepoth said:
Every kilo of fuel not needed to start with means there's less mass to move - which helps as well.
Great - apart form the combined mass of approx 2 747's and the fuel needed to get the whole lot up to x0,000ft. Can't see a big advantage there in terms of fuel saved...or cost.
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