Should we send interstellar probe to Alpha Centauri?

That is why I try to concentrate on today's technology like hydrogen bombs (I am almost 100% sure that H-bombs work).

Landing is usually the most difficult part of a probe mission.

I am not very impressed by statements like "could be solved within 30 years". I recently read an article about rail-gun development from the 1980s (when Reagan's SDI had renewed interest in this things). In this review a paper from the early 1940s was cited, where a german scientist had been quite optimistic about rail-gun development if only the 3rd Reich would give him enough ressources for his research. Then, again in the 1980s article, much optimism for the next decades. Now we have 2008 and the only operational rail-gun I ever saw was in an Arnold Schwarzenegger movie ! (I know some guys built various prototypes in their labs, but the predictions were about operational guns.) So much for "can be solved within x0 years".

There could be a Earth-like planet in the Alpha Centauri system.

Based on theoretical computer simulations, other planetary astronomers consider that any potential terrestrial planets that did once orbit near the stars' habitable zones are now likely no longer located there. The loss several billion years ago of these small bodies probably happened during the system's formation. All may have since been ejected by significant disruptions caused by strong gravitational or perturbation effects generated between the two main stellar components.

I wonder how we would react to a probe coming in
that was useing H-bombs

According to Wiki, only 3 out of 27 (~10%) doomed Mars probes failed on landing. 16 (~60%) failed somewhere between Earth orbit and Mars orbit. The other 8 failed on launch (~30%).

It is called the Mars Curse.

I count at least six landing failures amongst the vehicles that were supposed to land.

1. Mars 2. "Crash landed on surface of Mars".
2. Mars 3. "Success (First successful landing)". That mission was a failure. It ceased transmission seconds after landing. The mission did not do any of the planned surface science, including use of its rovers, and only managed to transmit part of one rather useless picture of the Marse surface (low resolution and very low illumination).
3. Mars 6. "Partial success". Partial success my ***. The Mars 6 lander mission ended with "direct proximity to the surface" at 61 m/s. Stripping away the bureaucrateze, Mars 6 ended with a crash landing.
4. Mars Polar Lander. The most likely cause of the MPL failure was software interprations of vibrations that made the engines cut out 40 meters above the Martian surface.
5. Deep Space 2. "The probes reached Mars apparently without incident, but communication was never established after landing."
6. Beagle 2. "Lost contact while landing; Assumed to have crash landed".

I count 15 lander missions. Of those,

• Two failed in the vicinity of Earth (Sputnik 24 and Mars 96).
• One failed on route to Mars (Phobos 1).
• One failed at Mars orbit insertion (Mars 7).
• One failed at Mars entry (Phobos 2).
• Six failed shortly before, at, or very shortly after landing (above).
• Four succeeded (Viking 1, Viking 2, Pathfinder, Phoenix).

Landing failures accounts for six (seven if you count Phobos 2) out of the eleven failed lander missions.

OK, you've interpreted them differently and divided them up differently. For example: MPL "lost contact before arriving". In my books, that's an "en route" failure, not a "landing" failure. It failed before successfully achieving orbit.

The MPL's three landing legs were kept in a stowed position during launch and the spacecraft s journey to Mars. They were designed to deploy into position for landing when the MPL had descended to 1,500 meters above the surface of Mars. Each leg had a magnetic sensor to detect when it touched the planet s surface. When the sensors detected touchdown, the flight software would send a signal to shut down the MPL s thrusters. During MPL development, tests of the landing legs found that the magnetic sensors usually generated a false touchdown signal when the legs were deployed. To solve the problem, MPL systems requirements stated that all touchdown signals generated before the spacecraft descended to 40 meters above the surface should be ignored. However, the flight software requirements did not properly implement this system requirement. The result was that when the spacecraft descended to 40 meters above the surface, the touchdown signal from leg deployment was still in the system, causing the engine to shut off. At Mars, this would have resulted in the MPL hitting the surface at approximately 22 meters per second (50 mph), causing the loss of the spacecraft. Review teams have determined that this was the most probable cause of the loss of the MPL.

Regardless, your results miss the point: you're only counting lander attempts.

I am trying to point out that landing is a minor problem in the scope of long missions. The bigger problem is just getting there in the first place.

You're missing my point. Vehicles that aren't designed to land can't have landing failures.

I've ignored the stuff about a mission to Alpha Centauri because, to be blunt, the concept is entirely ludicrous. A lander, doubly so.

Or put another way: If 98 out of 100 men died crossing the desert, and one of the two remaining died by drinking from a poisoned well, would you be claiming that 50% of the failed desert crossings were due to poisoned water?

Off topic. I also know you think I am crazy.

Ok. I just calculated that about 99.78% of the mass of the probe will be fuel ...That's a big fraction of fuel, I know...

if assuming [tex]\Delta v = 29979245.8 + 29979245.8 = 59958491.6[/tex] m/s and maximum exhaust velocity of hydrogen nuke Orion of [tex]v_{e} = 9800000[/tex] m/s.

How did you calculate that? Are you assuming full thrust for the duration of the trip?

I wonder how we would react to a probe coming in
that was useing H-bombs to slow down

I saw operational railguns 20+ years ago (with muzzle velocities of 3 km/s), and the Navy is now testing one for naval artillery.

Here's a Popular Mechanics article on the BAE system delievered to the US Navy.
http://www.popularmechanics.com/tech...w/4231461.html

Whether you are impressed or not, you have to realize that being technically able to do something means nothing in reality. There is a lot of other things that have to happen. This is where 99% of failed ventures get tripped up. We went to the moon not only because we had a lot of talented technical people, but mostly because Kennedy set the government on the path that it would be done and gave NASA the support they needed.

I don't know how long a time the accelerating takes exactly. If a = 10g = 98,1 m/s², then accelerating to 0.1c takes about 85 hours.