undefined | Better HN

0 pointsergothus7y ago0 comments

I'm skeptical -

You've shown a proposal, not a reality. (and the proposal didn't even mention a "shield" that I saw, but I may have skimmed past it). I didn't see a price tag, nor a timeline. Money can boost research speed, but not remove the need entirely.

Second, If the cross section of the earth is 1.2x10^14 m^2, one of these would...well, we don't know, because the link mentioned volumes and length (the 10k km is a potential "span length" and wasn't tied to being "one" of anything). I failed to find the cargo volume for a Falcon 9 or other rocket (everything is in mass) but I think it's safe to say that you're talking a lot of launches which clearly aren't trivial to do.

Third, and most importantly, you've just decreased the amount of energy coming to earth. You've not solved the problem, you've changed it.

I love tech, but I think it's worth noticing the ratio of times someone says "It's [just] an engineering problem" versus the number of issues that have been actually been solved in this way (seeing the problem, spending a boatload of money, seeing problem solved). Most of our industries are based on the fact that we KNOW they can grow into more, but figuring out how and the complications thereof are literally the work of countless lifetimes.

0 comments

Tuna-Fish7y ago

> Third, and most importantly, you've just decreased the amount of energy coming to earth. You've not solved the problem, you've changed it.

Probably the most important advantage sunshades have over other kinds of geoengineering megaprojects is that they can be trivially (compared to their construction costs, that is...) turned off. If they turn out to be very harmful in some previously unforeseen way, we can choose to not have them anymore.

That is not so for, for example, seeding lots of nutrients for algae over the continental shelf.

philipkglass7y ago

As others have noted, solar radiation management doesn't do anything to counteract ocean acidification. I still think that SRM of some sort may be necessary to stop runaway feedback loops like loss of soil carbon from thawing permafrost.

The sunshade approach to SRM looks like it may have been devised like other big speculative space projects: "start by assuming that big projects in space are the solution, then find a problem to motivate that solution." (See also: mining helium 3 from the Moon.)

Solar radiation management with reflective aerosols instead of space sunshades looks simpler and easier to me. Most importantly, SRM based on aerosols is incrementally scalable from small low initial investment/scope. The sunshade approach, like many envisioned large space projects, appears to require large "lumpy" investments before delivering any detectable benefit.

singingboyo7y ago

On the other hand, we've got a pretty bad track history with adding gases to the atmosphere.

And, as mentioned, it's pretty easy to 'turn off' (fold or destroy) a sunshade. Not so easy to remove a bunch of aerosol in the stratosphere. I'd prefer more expensive but reversible action, personally.

On the other hand, a slow approach may negate that aspect, and just about anything is better than the nothing we've got now.

philipkglass7y ago

Depending on how high in the atmosphere the aerosols are added, they remain aloft for a few weeks to a few years. It's not a long-term commitment to altering the atmosphere's composition like burning fossils has been. This is in fact one of the arguments raised against solar radiation management: that the temperature rebound could be terrifyingly rapid if SRM is stopped. But that danger applies to space sunshades too.

jpfed7y ago

>Third, and most importantly, you've just decreased the amount of energy coming to earth. You've not solved the problem, you've changed it.

There's a lot of EM that neither chlorophyll nor existing PV can use. Hopefully a sunshade would be chosen that selectively works on those less-useful bands. I hope that someone is looking into aerogels for this purpose; they can cover a lot of area per unit mass and have tunable optical properties.

j / k navigate · click thread line to collapse

0 comments

Tuna-Fish7y ago

> Third, and most importantly, you've just decreased the amount of energy coming to earth. You've not solved the problem, you've changed it.

That is not so for, for example, seeding lots of nutrients for algae over the continental shelf.

philipkglass7y ago

singingboyo7y ago

On the other hand, we've got a pretty bad track history with adding gases to the atmosphere.

On the other hand, a slow approach may negate that aspect, and just about anything is better than the nothing we've got now.

philipkglass7y ago

jpfed7y ago

>Third, and most importantly, you've just decreased the amount of energy coming to earth. You've not solved the problem, you've changed it.

j / k navigate · click thread line to collapse