Future Robot Space Explorers, Technological Developments Options

[Tom Tamlyn]

I see they don't think that the rocker-bogie system is the best, but Im not going to be the one to tell them.

I've read that JPL patented the rocker bogie system which it uses for the Mars rovers. I wonder what JPL's licensing policy is?

TTT

[ljk4-1]

ENERGY TECH

- Researchers Focus On Spacecraft Power Storage

http://www.spacedaily.com/reports/Research...er_Storage.html

Kirtland AFB NM (SPX) May 02, 2006 - By the summer of 2007, a team of eight
personnel serving at the Air Force Research Laboratory's Space Vehicles
Directorate, Kirtland Air Force Base, N.M., believe their experiment consisting
of three flywheels, spinning between 16,000 and 40,000 revolutions per minute,
will demonstrate the innovative technology of combined attitude control and
energy storage on a satellite.

[tasp]

{I have no special training in radar}

However, I have wondered if illuminating a celestial object with a spacecraft onboard radio transmitter and analyzing the reflections on earth with the VLA would be useful. Might characterize surface properties, compositions, textures better than visible light.

I assume the power requirements would be largish and a technique like this, if practical, would be more suited to a Prometheus type craft.

[djellison]

Or better, the craft called 'earth'. Radar observations of NEO's, the moon and even, I believe, Mercury have been done from Earth using dishes like Arecibo and the DSN.

Doug

[The Messenger]

ENERGY TECH

- Researchers Focus On Spacecraft Power Storage

http://www.spacedaily.com/reports/Research...er_Storage.html

Kirtland AFB NM (SPX) May 02, 2006 - By the summer of 2007, a team of eight
personnel serving at the Air Force Research Laboratory's Space Vehicles
Directorate, Kirtland Air Force Base, N.M., believe their experiment consisting
of three flywheels, spinning between 16,000 and 40,000 revolutions per minute,
will demonstrate the innovative technology of combined attitude control and
energy storage on a satellite.

"Once it is proven that flywheels can store and convert energy into electricity while simultaneously controlling satellite orientation, they will eliminate the need for heavy, chemical batteries on many satellite systems, thus significantly reducing spacecraft weight," he noted.

That is a tall order, because you are basically substituting a fixed rotational inertia with a variable one, and predicting small changes in position on the bases of known changes in load - known, according to some accurate measure of current. The navigational accuracy would be slightly less than the combined temperature compensation and radiational shielding of the system. Lots of variables here.

[helvick]

That is a tall order, because you are basically substituting a fixed rotational inertia with a variable one, and predicting small changes in position on the bases of known changes in load - known, according to some accurate measure of current.

Interesting idea but I also can't see that it would be possible to accurately manage orientation\roll rates with just three such flywheels. It would be simpler with 6 (2 contra rotating flywheels for each axis). And then there is the question of redundancy.
Possibly I've missed out on some stunning advances in mechanical engineering over the past few years but I suspect that this is something that really is only at a proof of concept level and a long way from being practical for long term\range missions.

[dvandorn]

Hmmm... well, if you used a common transmission for all three flywheels, or if you can manage to add energy to all three of them in exactly the same increments at exactly the same time, then you're really operating as if you had three constant-speed CMGs, I would think.

-the other Doug

[helvick]

Hmmm... well, if you used a common transmission for all three flywheels, or if you can manage to add energy to all three of them in exactly the same increments at exactly the same time, then you're really operating as if you had three constant-speed CMGs, I would think.

That would just give you net rotation in the 3 axes. You need to be able to add energy into the system without adding any net angular momentum - the simplest way of doing that that I can think of is to have two contra rotating flywheels on each axis that are driven in such a way that energy inputs and outputs accelerate\decelerate contra-ratating pairs. In gyro pointing\rotation control mode they would be driven asymmetrically.

So the simple problem is managing the changing angular momentum imparted by storing or bleeding off energy, or at least figuring out what the net change is that needs to be managed. With two contra rotating flywheels on each axis it should be theoretically straightforward to add\bleed energy in response to changing charge\load conditions without imparting any net additional angular momentum to the main body. The hard problem that I see arises when attempting to manage the angular momentum transferred to and from the flywheels (acting as gyros) with the sort of precision that would be needed to manage the pointing of the craft. The hardest problem for me is figuring out how to add or remove energy from a contrarotating pair when they have been put in an asymmetric state.

Now it must be said that it's almost 20 years since I did any mecanical engineering work so I could be way off on this but my gut reaction is that a flywheel capable of storing a few hundred watts of power just can't be handled with that sort of delicacy. Also I never worked with any aerospace rated stuff and 20 years is a long time so maybe it is possible.