Antimatter Catalysed Nuclear Pulse Propulsion: Directed blast or not?

[SunJumper]

If one had an ACNP drive, would it be better isp and money wise to have the blast directed wholly at the plate, and the rest of the bomb move off at fast velocities, or just have the bomb blow in all directions, leading to less than 50% of the blast being usable?

[MBobrik]

or just have the bomb blow in all directions, leading to less than 50% of the blast being usable?

You can have a shaped charge. then 80 % of the blast is converted to thrust.

[nyrath]

Like MBobrik said, it is better to have the blast directed at the plate. Assuming the plate is strong enough to handle the blast without being damaged.

The point is that every single kilogram boosted into orbit costs like crazy in terms of propellant. So you want to get as close as you can to 100% utilization from whatever unit you are boosting. Having less than 50% of the blast being usable is wasteful.

Rocketcat sez: Every Gram Counts

http://www.projectrho.com/public_html/rocket/basicdesign.php#id--Every_Gram_Counts

Edited May 15, 2013 by nyrath

[NASAFanboy]

Considering that one anti-matter bomb is 100% more efficient at converting mass into energy than an atomic bomb, even if it went out in all directions, the energy on the pressure plate would still be much, much larger than an atomic bomb. However, it may be in the best interest of money to direct the blast, as then, it may take an mere 10 grams of anti-matter to reach Mars, and around a dozen tons for Alpha Centauri. These fuel ranges are easily within reach of our HLLV's, and so if we use anti-matter as a fuel, we will easily be able to send inter-stellar probes and take humans to Mars with less fuel, freeing up room for supplies and life support systems.

This, might mean we can possibly do MUCH more than previously expected.

[drakesdoom]

Though the fuel is much more efficient if you want to bring people along you are going to need so much hard radiation shielding I think a fusion pulse drive would be better suited for interplanetary distance. Not to mention we already are building a prototype for that and it is magnitudes cheaper. If I can afford 10 rockets to your 1 does it matter yours carries 10 times as much cargo?

[DerekL1963]

If I can afford 10 rockets to your 1 does it matter yours carries 10 times as much cargo?

For an interplanetary vessel, surprisingly enough, it does - there's only so many launch windows. The windows are wider than with chemical, granted, but they're still there. Absent free fuel and massless life support, there's still going to be push to use the most optimum trajectory available.