### Author Topic: Dragonlab artificial gravity experiment.  (Read 7736 times)

#### baldusi

• Senior Member
• Posts: 7437
• Buenos Aires, Argentina
• Liked: 1446
• Likes Given: 4499
##### Dragonlab artificial gravity experiment.
« on: 08/23/2011 11:46 PM »
If the Dragonlab could do a couple of months on space while carrying a few small rodents, a very interesting artificial gravity experiment could be made.
The maximum inner diameter of the Dragon is 3.1m. Let's say 3m. At 17.5rpm would give 0.5g. It's fast, but if a normal rodent is 5cm tall, and a human 1.70m, then it would be equivalent to a 50m radius for a human.
And, you could put not one ring, but three rings. The outer most doing 0.5g, the middle one 0.375g (Mar's) and the innermost 0.165g (Moon's).
If the Dragon could support them for two months, we'd have a very interesting datapoint on artificial gravity and a first approach about Mar and the Moon.
Since the rodent's would have limited resource usage, and assuming a trunk full of oxygen and water, it wouldn't seem like too difficult a mission. Besides, the fact that most of the mission would have gravity, might make the feeding and cleaning easier. If they could also send some pregnant rodents, some extra data could be gathered about bone and muscle development.
What do you think? Should this go on Advanced Science?

#### docmordrid

• Senior Member
• Posts: 5043
• Michigan
• Liked: 2172
• Likes Given: 1
##### Re: Dragonlab artificial gravity experiment.
« Reply #1 on: 08/24/2011 12:38 AM »
I would worry about the mounts and structural integrity of the solar panels holding up during spin-up and spin-down. Also, if you're producing .5G in that small of a radius then the tips of those arrays, being a much larger distance from the c/l, should be under some multiple of 1G. Can they take it?
DM

#### Lars_J

• Senior Member
• Posts: 6161
• California
• Liked: 665
• Likes Given: 195
##### Re: Dragonlab artificial gravity experiment.
« Reply #2 on: 08/24/2011 12:52 AM »
I don't think that idea would work. A more gentle approach might be to tether a DragonLab to an F9 upper stage as counter-weight, and spin. But there is still the problem will solar tracking. And communications.

I don't think Dragon(Lab) is a good platform for artificial gravity research.
« Last Edit: 08/24/2011 12:52 AM by Lars_J »

#### rickyramjet

• Member
• Posts: 94
• Killeen, TX
• Liked: 58
• Likes Given: 25
##### Re: Dragonlab artificial gravity experiment.
« Reply #3 on: 08/24/2011 01:29 AM »
Don't spin the Dragon.  Build a rotating ring inside that holds the rat cages.

#### DaveH62

• Full Member
• Posts: 297
• Liked: 19
• Likes Given: 53
##### Re: Dragonlab artificial gravity experiment.
« Reply #4 on: 08/24/2011 02:39 AM »
Don't spin the Dragon.  Build a rotating ring inside that holds the rat cages.
I was hoping to reply first, but I think you have the proper option. You could build the larger ring at the base of the Dragon, with smaller rings at the smaller circumference at the top of the capsule for mars and moon gravities.
Regarding the topic, it is a brilliant idea to create a micro environment to replicate a larger scale human option. If it did work, then tethering two capsules fifty meters apart for a human experiment would work. Maybe keep a dragon ISS supply capsule up after a mission and then a human rated dragon to follow. Use the supply module as an anchor on one side and have astronauts on the ISS man the capsule and run a two week test near the ISS and see if the occupants have regained any muscle mass.

If any volunteers are needed I call shotgun.

#### Lars_J

• Senior Member
• Posts: 6161
• California
• Liked: 665
• Likes Given: 195
##### Re: Dragonlab artificial gravity experiment.
« Reply #5 on: 08/24/2011 03:29 AM »
Unfortunately small centrifuges are of much more limited use than one might think - especially for humans. You just cannot reliably test how wall a person or an animal handles different G levels if the Coriolis effect (if rpm is above a certain point) is significant.
« Last Edit: 08/24/2011 03:29 AM by Lars_J »

#### Danderman

• Extreme Veteran
• Senior Member
• Posts: 9637
• Liked: 371
• Likes Given: 465
##### Re: Dragonlab artificial gravity experiment.
« Reply #6 on: 08/24/2011 03:47 AM »
Regarding the topic, it is a brilliant idea to create a micro environment to replicate a larger scale human option. If it did work, then tethering two capsules fifty meters apart for a human experiment would work. Maybe keep a dragon ISS supply capsule up after a mission and then a human rated dragon to follow. Use the supply module as an anchor on one side and have astronauts on the ISS man the capsule and run a two week test near the ISS and see if the occupants have regained any muscle mass.

The rotational velocity of the objects at the ends of the tether would probably exceed the velocity required for re-entry, which means that when the tether breaks (they all break eventually), there is a chance that one of the end masses will find itself in an orbit with a perigee at sea level.

#### DaveH62

• Full Member
• Posts: 297
• Liked: 19
• Likes Given: 53
##### Re: Dragonlab artificial gravity experiment.
« Reply #7 on: 08/24/2011 04:25 AM »
Regarding the topic, it is a brilliant idea to create a micro environment to replicate a larger scale human option. If it did work, then tethering two capsules fifty meters apart for a human experiment would work. Maybe keep a dragon ISS supply capsule up after a mission and then a human rated dragon to follow. Use the supply module as an anchor on one side and have astronauts on the ISS man the capsule and run a two week test near the ISS and see if the occupants have regained any muscle mass.

The rotational velocity of the objects at the ends of the tether would probably exceed the velocity required for re-entry, which means that when the tether breaks (they all break eventually), there is a chance that one of the end masses will find itself in an orbit with a perigee at sea level.

That would be an unfortunate result.

#### Comga

• Senior Member
• Posts: 4338
• Liked: 1570
• Likes Given: 1313
##### Re: Dragonlab artificial gravity experiment.
« Reply #8 on: 08/24/2011 06:43 AM »
Mice in a spinning recoverable orbital habitat. A decent idea, if not an original one:
http://web.mit.edu/aeroastro/marsgravity/mission.html
You will find that their budget is only a fraction of a DragonLab.

PS We have seen a Dragon solar panel hanging from the rafters in Hawthorne.  If the Dragon spin to generate 0.38 G's, the tips of the solar arrays shouldn't be under much more than 1 G.  But that's a small detail.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

#### happyflower

• Full Member
• Posts: 176
• Earth
• Liked: 22
• Likes Given: 16
##### Re: Dragonlab artificial gravity experiment.
« Reply #9 on: 08/24/2011 07:51 AM »
If you use rings inside the capsule to spin gravity, then you can also have a control group weightless.

Not to go too off topic, I think a dragonlab mission to L1 would be much better suited for a solar radiation mitigation experiment.

#### kevin-rf

• Elite Veteran
• Senior Member
• Posts: 8652
• Overlooking the path Mary's little Lamb took..
• Liked: 1124
• Likes Given: 243
##### Re: Dragonlab artificial gravity experiment.
« Reply #10 on: 08/24/2011 01:26 PM »
If you use rings inside the capsule to spin gravity, then you can also have a control group weightless.

Not to go too off topic, I think a dragonlab mission to L1 would be much better suited for a solar radiation mitigation experiment.

You can also have different rings to simulate lunar, mars, and earth gravity.
If you're happy and you know it,

#### baldusi

• Senior Member
• Posts: 7437
• Buenos Aires, Argentina
• Liked: 1446
• Likes Given: 4499
##### Re: Dragonlab artificial gravity experiment.
« Reply #11 on: 08/24/2011 02:34 PM »
Unfortunately small centrifuges are of much more limited use than one might think - especially for humans. You just cannot reliably test how wall a person or an animal handles different G levels if the Coriolis effect (if rpm is above a certain point) is significant.
Which was why I was thinking of an experiment only using mice. As I stated, if mice are 34 times shorter than humans (in height), 1.5m radius would mean 51m radius equivalency for human. That doesn't quite solve the coriolis problem, though. But I don't care so much if the rats are uncomfortable. I care if we can get some datapoints on different gravity levels.
More than enough. The difference between 0.5g and 0.375g is 17.2rpm and 15rpm. Those are minimum differences. What could be an interesting experiment, would then be to have three different diameter ring experiments. One experiment could be to test different gravities. Other, could be same gravity at different rpm.

Mice in a spinning recoverable orbital habitat. A decent idea, if not an original one:
http://web.mit.edu/aeroastro/marsgravity/mission.html
I was aware of them, and actually got inspired. But as I understand it, they are are closed down. Besides, whatever the budget, I'm sure it would be cheaper to use an already existing capsule, specially an already used one, like the DragonLab.

If you use rings inside the capsule to spin gravity, then you can also have a control group weightless.
There have been extensive work on microgravity on the Shuttle and ISS. From having rats, having rats born in space and even tadpoles. So there's a lot of information on zero gravity.

More in general, I think that the whole experiment should include higher gravities (like 1.33g and 2g). Those experiments can perfectly be done on Earth, and might give a good idea about the "other side" of the health/gravity curve. In the case of a dragonlab mission, having more than one ring could be used to test if exposure to microgravity can be offset by conditioning with higher gravity before and after the exposure.
Let's say that we find that 0.375g is no better than 0g. Can we offset some of the problems by conditioning with 1.5g for a week before?
I really don't know about the dragonlab rotational limitations. But I though that if you spin it while pointing the trunk at the sun (and the solar panels too), it would act like a gyroscope, and keep pointing that way. Having an insulating back would make environmental control a simple matter of heating, not cooling. Also, if the whole craft rotates, the ECLSS and all the care needed for the lab rats would be easier to implement.
I've even wondered if you could make the Vomit Comet do a different parabola to simulate low gravity (like 0.375g). It should be even longer than the current free fall 30s. Between that an a lab prototype, most of the technological risks could be mitigated.
If the only solution would be a series of rotating rings, the technological problems are bigger. But you could install a couple of rings on a Cargo Dragon, and let the ISS crew take care of most of the rat's necessities. Depending on how long the dragon stays on ISS, they could do a couple of experiments and actually analyze the rats on the station. The only problem I can see with that is if the Dragon and CBM can take the forces of the centrifuge. Being only for rats, it should be orders of magnitude less than a human centrifuge. I just wonder about the gyroscopic forces while the station move. And if it would behave like a reaction wheel.

#### A_M_Swallow

• Elite Veteran
• Senior Member
• Posts: 8504
• South coast of England
• Liked: 353
• Likes Given: 154
##### Re: Dragonlab artificial gravity experiment.
« Reply #12 on: 08/24/2011 08:25 PM »
If you have rings moving in one direction a mass can rotate in the opposite direction to counteract the effects of the torque.

#### baldusi

• Senior Member
• Posts: 7437
• Buenos Aires, Argentina
• Liked: 1446
• Likes Given: 4499
##### Re: Dragonlab artificial gravity experiment.
« Reply #13 on: 08/24/2011 08:29 PM »
If you have rings moving in one direction a mass can rotate in the opposite direction to counteract the effects of the torque.
Yes, but as any gyro would offer a lot or resistance to non axial rotations.

#### A_M_Swallow

• Elite Veteran
• Senior Member
• Posts: 8504
• South coast of England
• Liked: 353
• Likes Given: 154
##### Re: Dragonlab artificial gravity experiment.
« Reply #14 on: 08/24/2011 08:40 PM »
If you have rings moving in one direction a mass can rotate in the opposite direction to counteract the effects of the torque.
Yes, but as any gyro would offer a lot or resistance to non axial rotations.

That is the problem with artificial gravity by rotation.

• Senior Member
• Posts: 3301
• Boca Chica, Texas
• Liked: 5593
• Likes Given: 353
##### Re: Dragonlab artificial gravity experiment.
« Reply #15 on: 08/24/2011 08:53 PM »
I think small centrifuges might be undervalued and misunderstood. I know a metallurgist who thought the CAM being cancelled was the most shortsighted move in the history of science. It's purpose wasn't just to make gravity, but to make varying levels of gravity. The data gained from creating alloys at hundreds of different combinations of gravity, temperatures and rates of cooling would have been priceless. He thought that module would have lead to materials with custom tailored characteristics that would have been the greatest revolution in metallurgy since fire.

If you're looking at materials research, small, variable centrifuges are what you need.
Finding that gravitational sweet spot for creating a super-material would take a lot spinning.

Tags: