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Vilkata
2007-Oct-12, 01:40 AM
A Cubesat can be a fairly sophisticated spacecraft, all things considered. Yet, they're traditionally launched as secondary payloads on giant conventional heavy rockets.

A Cubesat weights 1kg or less!

How come some company can't make a basic sounding rocket specifically designed to orbit cubesats?

The big Black Brandt sounding rockets can have a payload of over 60 kg, and maximum flight height of 225 km.

Naturally, they're rather sophisticated large rockets, but my point is that it seems like one could design a rocket with a useful payload of just a few Kg, specifically for Cubesats, and the entire thing might end up being so cheap it would replace the current method of launching cube sats.

What's the smallest rocket that could orbit a 1kg sattelite, and what is the guestimated cost of such a launch system?

Thanks in advance!

---Vil.

Cugel
2007-Oct-12, 12:19 PM
Sounding rockets, by definition, will fly parabolic trajectories with near vertical uplegs and downlegs. In other words, it goes straight up and down, and so it won't orbit anything. Not even a cubesat. They also have very short mission times, a few minutes, which means they don't need sophisticated tracking and/or telemetry systems. This is why sounding rockets are so cheap.

What you need is a booster that can deliver a cubesat in orbit. That means it needs multiple engine burns, probably two stages and full blown communication systems. It is something very different from a sounding rocket.
The cheapest thing you can get might be the Falcon-I, I believe it comes for something like 10 million dollars. But it could deliver quite a few cubesats in a single launch. Building a booster that can launch a single cubesat would not be a lot cheaper I would think.

BTW. There is an application for a booster that can launch a single cubesat. It's not on Earth. It's the booster that will launch a sample return cannister from the surface of Mars. So, in this context your question is actually quite a good one!

Larry Jacks
2007-Oct-12, 01:15 PM
Putting something in orbit is much more difficult than a sounding rocket mission. A sounding rocket simply flies straight up as high as it can go. It doesn't need an elaborate guidance system. To put something in orbit, you not only need to get above the atmosphere vertically, you need to be moving very fast horizontally (~8 KM/Sec). Your orientation has to be very precise to get you into the desired orbit. This requires a good guidance system. They tend to be fairly expensive. You also need a telemetry system with range enough to be tracked and range safety equipment (self-destruct package) if things go wrong.

Looking back, the Vanguard satellites (http://www.astronautix.com/craft/vanuard1.htm) had a mass of 1-2 KG. The Vanguard rocket (http://www.astronautix.com/lvs/vanguard.htm) had a rated payload of 9 KG to a 200 KM orbit. Does this represent the smallest and cheapest liquid fueled rocket capable of launching a CubeSat? Not necessarily. Using more modern technology for things like materials and guidance system, it should be possible to build a somewhat smaller rocket if all you want to do is put 1 KG into orbit.

Liquid fueled rockets are more efficient from a propulsion standpoint but they're also more complicated and expensive than a solid fueled rocket. One of the smallest orbital boosters that I know about was the Scout X-1 (http://www.astronautix.com/lvs/scoutx1.htm). It was built in 1960 and had a payload of 59 KG to a 185 KM orbit. Like the Vanguard, it should be possible to build a somewhat smaller rocket than the Scout X-1 using more modern materials and avionics. I'm not talking about a huge reduction in size or cost, maybe something on the order of 10% or so.

While it is possible to design an orbital booster with a payload of 1 KG, it would be cost prohibitive to do so. That 1 KG payload would have to bear the entire cost of the mission, so it'd be much more expensive than simply being a secondary payload on another launch.

mugaliens
2007-Oct-12, 03:55 PM
The big Black Brandt sounding rockets can have a payload of over 60 kg, and maximum flight height of 225 km.

With that payload, you could mount your cubesat on a micro second stage weight 50 kg and get it to a significantly higher orbit.

NEOWatcher
2007-Oct-12, 04:18 PM
With that payload, you could mount your cubesat on a micro second stage weight 50 kg and get it to a significantly higher orbit.
Do you have any numbers that show what the max speed of a sounding rocket are, and if a 50kg rocket can push the sat from that speed up to orbital speed?

I actually looked for numbers and didn't find any, but I did come across this page from NASA (http://rscience.gsfc.nasa.gov/srrov.html) talking about their sounding rocket program and other differences between that and orbital.

cjl
2007-Oct-12, 04:30 PM
With that payload, you could mount your cubesat on a micro second stage weight 50 kg and get it to a significantly higher orbit.
Not significantly. As stated before, the black brant rockets have no ability whatsoever to orbit anything - it is a purely suborbital lob. A 50kg upper stage would need to give the cubesat around 8km/s of sideways velocity in order to orbit it, something which is basically impossible based on some quick, back of the napkin calculations.