Why all the failures to natural disasters?

Well, obviously, hold your breath when you hide under beds. You can't be too safe these days!

John

It is our business to know, if you are offering opinions on the military. Have you been (dis)honorary discharged from the military?

I have not served in the military, but I have hanged around the military.

e a

rd

Probably not.

Why not?

I would rather have a soldier next to me, then you. I will be within

30 miles of Ground Zero.

Just no idea in general.

Speaking of "Think about it", John, think about the effects of conservation of momentum and Newton's third law.

I previously mentioned the reaction momentum issue (see copy above) as another reason why rockets make so much more sense than rail guns.

John

His kind excites him.

To boost ISS' orbit, silly. ;-) ...or maybe to bomb Kadaffi, or some such.

Aren't we supposed to duct-tape the doors and windows to hermetically seal our houses from chemical gasses?

--
Beware of bugs in the above code; I have only proved it correct, not 
tried it. -- Donald E. Knuth

If we dumped the ISS on Tripoli, at least we would have found a use for it.

John

In , Greegor wrote (and I edited it for space):

Just getting a payload from Earth's gravity puts it in an orbit around the sun similar to Earth's orbit around the sun. To get it to fall into the sun from there needs a delta v matching the orbital velocity, or at least the orbital velocity at the orbit's apohelion.

Earth's orbital velocity around the sun is about 29 km/sec. Square root of sum of squares of that and Earth's 11 km/sec escvape velocity is about

31 km/sec - for some oversimplified optimistic figure.

But for an object orbiting the sun around Earth's orbit to be accelerated to escape the solar system instead, it would only need to be accelerated to circular orbit velocity times sqr(2), meaning 41.4% delta of its ~29 km/sec velocity, or about 12 km/sec. Square root of sum of 12 squared and 11 squared is about 16.3 km/sec for an oversimplified estimate of velocity that an object near Earth needs to be accelerated to in order to escape the solar system.

There is a 3rd option, a way to achieve the 1st by doing something more like the 2nd: Have the payload nearly escape the solar system, in a long, eccentric orbit around the sun. That sounds like just a bit under the roughly 16.3 km/sec solar system escape figure while it is near Earth. Once the payload is at apohelion of its long, eccentric orbit, it is moving very slowly with respect to the sun. Just a little nudge will stop it there, and then it will fall into the sun. It may need another little nudge for course correction once it has come back to around the orbit of Mars or so.

--
 - Don Klipstein (don@misty.com)

Will the payload be moving slowly enough while near Venus for the gravity of Venus to be able to divert the payload onto a course falling straight into the sun? Or nearly enough so for a little nudge by Mercury on the payload (moving very fast at that point) to get diverted into the sun? I doubt it. On an eccentric orbit with apohelion near Earth's orbit and perihelion near the orbit of Venus, velocity near the orbit of Venus is greater than Venus's orbital velocity around the sun (which is 35 km/sec). Venus has its own escape velocity around 10 km/sec, so I doubt it will do the job.

On the other hand, it sounds to me that maybe around 15.5 or almost 16 km/sec for an object near Earth is sufficient to get it, at the right time, in an eccentric orbit around the sun in a way for Jupiter to alter its course to straight towards the sun.

Maybe a Venus slingshot could be used to get a minor reduction in delta v requirement to get an eccentric orbit that approaches Jupiter. Some of the delta v will need to be done while the payload's velocity with respect to the sun is around its maximum, while the payload is well within the gravitational field of Venus. The total delta v requirement will still need to exceed that needed to get a payload to Venus, and that is somewhere between the roughly 11 km/sec to escape Earth's gravity from near Earth and the roughly 16.3-16.5 km/sec (in the right direction) to escape the solar system from near Earth. My guesstimate at this point is 15 or possibly as low as 14.5 km/sec delta-v can get something from Earth to falling into the sun with slingshotting around multiple planets including Venus and Jupiter. A bit of this delta-v needs to be done where v with respect to the sun is greatest. But also, achieving v with respect to Earth maybe around or a little over 13 km/sec sounds to me necessary to get something "at low Earth orbit altitude" to send something on a course that approaches Mars or Venus.

How do we keep a rogue nation or possible future terrorist group with space technology from retrieving it? Security, defense and warfare? Or counting on such adversaries finding it easier to get similar goods from Earth?

Then again, I think 3 km down a borehole plugged with 2 km of concrete needs little security guard activity. Just a little monitoring and reconnaissance will catch anyone making the effort to get through 2 km of rock or concrete, and then we rain all kinds of hell on whoever is trying to retrieve the stuff without authorization.

--
 - Don Klipstein (don@misty.com)

It's silly to launch nuclear waste into space, but if you did, why try to hit the sun? All you need to do is use the minimal energy that will put it into an orbit that can never intersect the earth, or can't reasonably do so for a few million years.

John

How about a properly placed and timed eccentric orbit with perigee in "low Earth orbit" area, and apogee at 40,000 km - just past a popular orbital altitude that is popular for having its time to do one orbit matching the time it takes Earth to accomplish one rotation?

There are many geosynchronous satellites. Those tend to be deployed by

1st achieving an eccentric orbit with perigee close to Earth and apogee at the geosynchronous orbit altitude of roughly 36 km. The 2nd step is "apogee kick", as in a delta-v at apogee of the eccentric orbit to get the satellite in a circular orbit at the higher altitude.

That has been done so many hundreds or thousands of times already...

And to get a bomb to geosynchronous altitude does not require "apogee kick".

Detonate the bomb where it blasts the forward side of a satellite, and the result is "reverse of apogee kick". The satellite fragments will be decellerated into eccentric orbits with perigees much lower than geosynchronous altitude, maybe some of them with perigees within Earth's atmosphere or within the planet (on direct collision course).

It took me merely 2 minutes to think of this, so I doubt that Al Q'aeda or enemy nations have nobody thinking about this before now. I feel better about dumping nuclear waste where a mere rocket less than one necessary to launch a geosynchronous satellite won't accomplish detonation of "a dirty bomb".

As in either into the sun, or where a km or 2 of rock or concrete are in the way from every angle, or under heavyweight security.

--
 - Don Klipstein (don@misty.com)

You replied to a dolt that has no brains about orbital mechanics. D'oh!

Mentions lack of actual usage so far of SSTO that does not jettison any hardware.

Multistage rockets have the advantage of not needing to accelerate all of their non-fuel mass to final velocity.

However, I have heard of an Atlas rocket achieving orbital velocity from a single stage, though I don't remember whether or not it jettisoned any hardware along the way.

--
 - Don Klipstein (don@misty.com)

No. That is what you use to make your square CO2 scrubber fit into a round CO2 scrubber duct.

We should use your carcass as the holder device for all the nuke rods. Then we could send you to the Sun as well.

Might be even more fun to send you that way live, and pipe the video of your death throes back.

Disagree.

Whilst you cannot bleed off the velocity using Venus, you should be able to point the waste at the Sun by picking a close enough hyperbolic orbit. The intent of the slingshot is not to change speed, but to change direction.

Any nation capable of retrieving nuclear waste from an orbit at 40,000 kms (currently well beyond what the Americans can do or be likely to do in the next 20 years) is more than capable of making its own nuclear waste.

Particularly in the Australian outback. Visitors are unusual and commented on. Visitors with giant drilling rigs, turbans, beards and Middle Eastern accents hanging around nuclear waste dumps even more so.

Hell, Venus or Mercury would do as well!

It isn't like we would be contaminating a place where life could ever be.

Shooting from trailing edge, parallel to circular orbit, with delta-v less than twice the ISS orbital velocity, results in an eccentric orbit with apogee same as where the object was shot from, and perigee lower.

Is not ISS at something essentially "low Earth orbit"? That makes me think that a backwards shot would put the projectile into an eccentric orbit whose perigee is within Earth's atmosphere or within the planet (on collision course with the surface, even neglecting atmospheric decelleration).

Also, firing any gun attached to ISS in a way that has any projectiles leaving ISS for good or even for long, regardless of direction of firing, will change the orbit of ISS. Effort will have to be made to repair the orbital change. (Easiest to have 2 guns firing simultaneously in opposite directions?)

Do you have any other or further ideas?

--
 - Don Klipstein (don@misty.com)