I'm not rocket scientist, but it seems like the author is calculating a decreasing spiral into the sun rather than an impact. Why not slingshot around a planet and barrel into the sun with all of the orbital velocity still intact.
Let me put it another way. If it is comparatively cheap to get to any of the other planets. Couldn't we just go to Neptune and stop our orbital velocity from there where it's only 5kms?
How about exiting planetary orbits retrograde? It seems like larger planets would have escape velocities that are larger than their orbital velocity. Why couldn't our space barge leave Jupiter's orbit on a trajectory that would intersect with the sun?
> Couldn't we just go to Neptune and stop our orbital velocity from there where it's only 5kms?
Yes. This is a bi-elliptic transfer, it's a standard technique, and another thread claims it would save about 40% of the required dV.
> How about exiting planetary orbits retrograde? It seems like larger planets would have escape velocities that are larger than their orbital velocity. Why couldn't our space barge leave Jupiter's orbit on a trajectory that would intersect with the sun?
It could. That's a gravity assist, and it's the only practical way to go just about anywhere with current technology (all our interplanetary probes do that).
(There are arguments against using either with nuclear waste, but I don't think the page is seriously talking about that)
If you're interested in this stuff, definitely play Kerbal Space Program.
Because if the orbital velocity is intact you will perputally miss hitting the sun. The only way you can hit a thing you are orbiting is to remove all the orbital velocity (well, remove enough of the orbital velocity such that your orbit drops low enough to scrape the surface anyway).
While the solar wind gets stronger closer to the sun, it's an r-square law that balances the r-squared force of gravity. Fun fact: If a solar sail could be in a fixed position at Mercury orbit then it could also be in fixed position a Neptune orbit.
The Orion space capsule is ~25 sq meters. I'll round that up to 100 sq meters (I'm being generous), giving a breaking force of 5/64 N on the waste barge.
The capsule mass is 20 tons. Assuming the waste barge were the same mass (I'm being generous) gives a solar gravitational force in Earth orbit of 120 newtons. This far exceeds the push from solar wind, even with wildly optimistic numbers. (Note: there's some 50,000 tons of high-level nuclear waste in the US.)
So no, you couldn't lose a lot of velocity just braking against the solar wind. Not unless you've also developed effective solar sail technology.
Your calculations seem sensible, but you're only talking about radial forces, ie. countering the "downward" force of gravity with "upward" thrust of a solar sail.
But space flight maneuvers typically use tangential or almost tangential thrust. Slowing down or accelerating the orbital motion will cause the altitude to vary, preserving the orbital energy and angular momentum. Placing a solar sail in a 45 degree angle from the sun will change the orbit slowly but surely, as there will be a little tangential and radial thrust.
I still don't think it's viable for throwing anything into the sun, though.
The actual time will be smaller because you only need to hit the sun, and solar wind will get stronger. So, 350 years? As a wild-ass guess.
That same page points out that sails don't work much inside of 0.25 AU, because the temperature can exceed the material properties of the sail. Though I think if the apogee is inside of 0.20 AU it's good enough.
To make it worse, the solar wind fluctuates, so unless there's active control on the rocket, its orbit will be unpredictable over the centuries. When it's still near Earth orbit, or when it approaches Venus orbit, what are the chances of a gravitational assist leading to an Earth-return?
With 50,000 tons of high-level waste, and 15 tons per rocket => 3,333 rockets in uncertain orbits, the chances become much higher.
its not the only way, its just one way... there are other ways to increase the eccentricity of an orbit - increasing the orbital velocity at the right time, and in a direction that is not radial is less efficient but since the earth's orbit is nearly circular, its not by much.
this is essentially the brute force approach or the bielliptic transfers mentioned in other comments.
he is describing making it fall into the sun directly (if the 'burn' is instantaneous), or if you like, starting to spiral but then just falling in a straight line.
a slingshot changes orbital velocity... thats the whole point. you are right that it is possible to slingshot into an ellipse intersecting the sun... although setting up that manoeuvre itself would be pretty expensive.
But that's is expending a whole lot of energy to "remove" earth's orbital velocity. Why remove it when you can just deflect the rocket by the gravity of Venus and redirect the rocket directly towards the sun? Or are we missing something more fundamental?
Gravity assists are helpful but they're not all-powerful. There's a hard constraint: your orbit is deflected more as you make your point of closest approach lower, but you can't make it too low without hitting the atmosphere. (Unless you actually want to crash into Venus instead of the sun; in which case, knock yourself out, but the moon is closer.)
Math time: a Hohmann transfer orbit from Earth to Venus will have 2.7km/sec of excess velocity when it reaches Venus. That means your orbit has a 44000km semi-major axis. With a closest approach of 6100km, that gives you a minimum eccentricity of 1.137; if I'm doing my trigonometry right, the most orbital speed you could lose in a single flyby is 4.2km/sec, or about 11% of your speed relative to the sun.
> Why remove it when you can just deflect the rocket by the gravity of Venus and redirect the rocket directly towards the sun?
The fundamental thing you are missing is that to point the rocket directly at the sun required removing all of the orbital velocity. If you were to just point a rocket directly at the sun ignoring its relative motion and burn you would never actually hit the sun. You would just burn forever and never make any progress.
> "Gravitational assists can help, but they can also help you get other places."
Without gravitational assists, you need ~30km/s to drop into the sun, and far less to go other places. With gravitational assists both can be easier, but going to the sun will still be one of the harder places to go.
That aside, if you are going to loop it around Venus, why not just hit Venus? I'm sure Venus wouldn't mind.
Yes, I did read that. But what I didn't understand is why you were disregarding what seems to be a key part of interplanetary travel. The point that johngalt and I are making is that "falling" isn't the only way to get there.
Now, the real point seems to be that the Sun's gravity doesn't help you get there — in fact it works against you! You must rely on very precise calculations and instrumentation to target yourself there. So why not dive straight into another planet instead of using it for a gravity assist. That I can understand.
If it isn't a bubble now, what criteria would make it a bubble?
The opening paragraph creates an infallible criteria. It's true that many people thought instagram wasn't worth $1billion. Does that mean $35 billion is less indicative of a bubble, or more? Simply saying 'hah! Bubble predictions were wrong in 2012 because valuations are still rising, so they must be wrong now too.' This sort of thinking would never predict a bubble.
> you won't be kicking yourself a few months down the line as you baby your custom storage solution. Normally i'm the guy building stuff like this, but sometimes I would rather just sleep at night...
"Even Southwest doesn't build their own airplanes." I have this argument with myself all the time. If you don't have an IT pro who works on storage every day, then buy something from someone who does work on storage every day. Their time is worth the price. Your time is worth it too.
I've taken this from where I replied to a comment on my blog:
4 hour on site response offered from vendors is not good enough for us and to improve on that is expensive. With using more standard components we are able to be on site at either our primary or secondary datacenter within 30 minutes with spare parts in hand if required.
Choosing one vendor as an example, the support we've received from HP has been atrocious - they've caused more outages than they've be able to fix. The engineers they send to smaller organisations are generally relatively incompetent and they have certainly shown that they don't care about your uptime.
Proprietary storage systems offered by HP, DELL and EMC are not only expensive to purchase and license but they're very time consuming to manage as they're essentially a 'snowflake' in your infrastructure. It's hard to make them integrate with modern automation tools such as Puppet and CI requirements and they all use their own management tools that are specific to the vendor or range of product - usually this involves having a Windows VM running Java or some equally frustrating technology to manage the system. Performing updates on proprietary systems can often be painful as hardware vendors generally are not very good at designing software.
It's very hard to outsource quality and it comes at a large cost.
You have hit the nail on the head for why most "enterprise" gear is basically overpriced junk. That doesn't mean there isn't quality hardware out there, just that you have to be more selective. AKA do your own research and don't be dazed by the feature lists. Some of those features shouldn't actually be used.
I personally tend to like the KISS arrays that don't have dedupe/replication/etc built in, and are web manageable. The extra bonus is that there are a metric boatload of tier 2 array vendors (imation's nexan for example) that provide rock solid hardware for a small fraction of the prices of EMC/etc. Its quite possible to get native capacity for less than a company like EMC charges for deduped capacity (aka 100TB from a tier two company can cost less than the 10TB deduped to 100TB from EMC). Raw RAID is pretty simple/understood in comparison to deduped solutions, and I think that has a significant affect on reliability. AKA more features, more latent bugs...
Finally, get a bunch of demo units, and if the configuration UI is a mess of esoteric proprietary command line junk, or it is only configurable with a 32-bit java app that won't run on a 64-bit windows (yah I've seen that) then send the unit back. Be clear about why it won't work for you. The only way to convince these companies to behave is to show them lost sales.
I got voted down yesterday for linking this kind behaviour to the Salem Witch Trials... but I stand by my point: Fear of what they're ignorant about and starting witch hunts to eradicate it is part of American history... you may cast it to the annals of history, but with the undertones of Islamophobia, xenophobia and racism that constantly play out in the media demonstrate that it's still alive and kicking in the halls of politics. This is just another form of the same thing - fear of their own ignorance.
> That Manning was convicted of computer fraud seems to suggest that using wget on a U.S. government computer to download large numbers of files can be considered the digital equivalent of trespassing – even if it's on turf you're otherwise allowed to access.
Get a job at the DOD and I'm sure they'd be glad to share it with you.
Is it really that unbelievable that the Department of Defense would have a strict set of software that's allowed to utilize their network, for a variety of reasons, including Manning's usecase or just simple security concerns?
Is your employer comfortable with you sharing encryption keys via post-it notes stuck on your monitor?
Should the DOD be comfortable with people accessing classified filesystems with any software they please?
This is simply a non-argument. I think it's a tacked-on charge meant to take down a maybe-legitimate whistleblower, but it's not like you can say it's actually unreasonable/unrealistic.
About 10-11 years ago, I was contacted by an employee at NOAA who needed sha1 checksums of open-source software I released. He needed it so that it could go on their whitelist of usable software, but he couldn't generate them himself due to policy.
Whitelisting acceptable software really isn't a bad idea, especially for organizations that care about safety and security of data. The next step is to lock down the platforms to only execute whitelisted software (similar to how Apple tries to lock down iPhones, iPods, and iPads).
Could it be done with a non-DOD site? If not, why not?
Could I make a website that immediately drops you onto a landing page that says "The rest of this website may only be accessed using Safari. Use of Firefox, Chrome, or any other software constitutes unauthorized access."?
Yes, you could make such a website, but I doubt that it would mean anything in court.
Manning was active-duty military, accessing classified military systems. There are all sorts of duties, laws, and regulations that apply to that situation that don't apply to a civilian accessing some random website on the web.
If cars become more useful, they will be used more often and car companies will sell more cars not less. Obviously automakers that end up on the wrong side of this trend might struggle, but overall the industry will be larger.