Prospecting the Solar System

[Diche Bach]

15 minutes ago, Scotius said:

On paper it looks awesome. But in my country we have a saying: "Paper will take anything." We also tried pulse jet engines in the past - because they seemed to be simpler and cheaper than regular ones, while offering good performance. Guess what - it didn't pan out. Only broader application for them were V-1 flying bombs. And that's about it. Why? Imagine welding an anvil to the back of your car, and propelling it forward by repeatedly hitting it with a wrecking ball. Your car wouldn't like it. Planes (which have to be light to fly well) didn't like it. A rocket (and her crew) wouldn't like being hit repeatedly by a nuclear explosion either.

Hmmmm. You damn skeptics and realists . . . So what IS the most likely technology that the Kim dynasty will use to conquest space?

[Bill Phil]

5 hours ago, Scotius said:

On paper it looks awesome. But in my country we have a saying: "Paper will take anything." We also tried pulse jet engines in the past - because they seemed to be simpler and cheaper than regular ones, while offering good performance. Guess what - it didn't pan out. Only broader application for them were V-1 flying bombs. And that's about it. Why? Imagine welding an anvil to the back of your car, and propelling it forward by repeatedly hitting it with a wrecking ball. Your car wouldn't like it. Planes (which have to be light to fly well) didn't like it. A rocket (and her crew) wouldn't like being hit repeatedly by a nuclear explosion either.

The issue with Pulse Jets was the vibrations, not getting hit by a large force, at least for the Argus models used in the V-1 and the other aircraft they tried to build with them. And that was operating at 43 hertz, whereas an Orion would operate at 1 or less hertz, a Medusa even less, with the impulse being spread over a much larger time by a large system of shock absorbers or just letting a tether out and slowly reeling it back in. At least, that was the idea. We really don't know whether or not it will work. But it would be good to know...

[wumpus]

13 hours ago, Bill Phil said:

The issue with Pulse Jets was the vibrations, not getting hit by a large force, at least for the Argus models used in the V-1 and the other aircraft they tried to build with them. And that was operating at 43 hertz, whereas an Orion would operate at 1 or less hertz, a Medusa even less, with the impulse being spread over a much larger time by a large system of shock absorbers or just letting a tether out and slowly reeling it back in. At least, that was the idea. We really don't know whether or not it will work. But it would be good to know...

I'm fairly sure that fuel use on a V1 was extremely poor (although as an airbreather, it almost certainly had to be better than a V2).  It was probably worse than a true jet, which are pretty much only used for supersonic military jets now (everything else are [high bypass, if recent] turbofans).

Back in the 1990s, there were various attempts to build air-breathers that detonated the fuel, rather than combusted it (Ve should be higher that way).  This of course led to severe noise issues for any potential crew/passengers, but it never seemed to work well for even uncrewed launches.  I don't think I've heard of detonation-based takeoff for at least a decade.

As far as I know, a scaled down Orion worked with conventional explosives, but the real thing would deal with much more extreme stresses.

[Scotius]

^This.

If we are going to build a big, expensive, re-useable spaceship capable of ferrying people and cargo across the Solar System, we want something reliable. Multiple, repeated shocks generated by kilotons of nuclear explosions aren't healthy - both for squishy human bodies and for our tech. Sure - we can build very sturdy rocket able to withstand the stress. But it will be very, very expensive. Also, consider this - during the prolonged use of Orion craft, something inevitably will go wrong. In the case of more conventional rocket, such accident is catastrophic. With an Orion, fully loaded with nuclear devices? It would be apocalyptic. Imagine something like this happening in LEO...

No, i don't believe it will ever be built and will fly.

[_Augustus_]

2 minutes ago, Scotius said:

^This.

If we are going to build a big, expensive, re-useable spaceship capable of ferrying people and cargo across the Solar System, we want something reliable. Multiple, repeated shocks generated by kilotons of nuclear explosions aren't healthy - both for squishy human bodies and for our tech. Sure - we can build very sturdy rocket able to withstand the stress. But it will be very, very expensive. Also, consider this - during the prolonged use of Orion craft, something inevitably will go wrong. In the case of more conventional rocket, such accident is catastrophic. With an Orion, fully loaded with nuclear devices? It would be apocalyptic. Imagine something like this happening in LEO...

No, i don't believe it will ever be built and will fly.

I think that it will be built eventually outside of Earth orbit for trips to the Oort cloud and maybe cargo to Alpha/Proxima Centauri and other nearby stars.

[Diche Bach]

Recently got hold of "Children of a Dead Earth." Good stuff! Highly recommend if any of you guys are on the fence

Actually wound up bopping in here because I am building a Helium-propellant driven Nuclear Thermal Reactor powered spacecraft and supplementing this very high exhaust velocity but relatively low thrust "Cruising" system with a much higher thrust Lox/Methane system (high dV and when needed, flip on the overdrive for maneuvers that require high acceleration). Did a search on the proper ratio of Lox to Methane and that google hit was actually THIS thread!

I seem to be going in circles!