That's the analogy to think about with this. When is it best to use the artillery approach, and when is it best to use an airplane approach. An airplane approach implies refueling and re-use. You can amortize investments to improve capabilities over time. Artillery is all about cheap getting payload up there.

If you really want to get pure mass to LEO cheaply - it's hard to beat big artillery with a rocket stage. It has a few issues though.
Your payload has to be able to handle the G's from firing. The payload is probably fairly small unless you build a really big gun. If you are interested - google Gerald Bull.

Another cheapish way to get lots of mass to orbit that is mostly politically acceptable would be *really* big rockets. Some of the plans for humungous solid rocket boosters etc. Big diameter solid rockets are hard to beat for cost if you are going to throw it all away.

The truth is it's a continuum. You can plot this stuff on a graph and it's very informative. You discover the above. Artillery to LEO is very cheap - but limits you to tiny payloads. Massive throw away solids are cheap too, but if the launch vehicle fails you lose a lot. For things you value a lot (like people) you may not want to use a huge solid.

If you want to launch truly huge amounts of stuff to orbit it's very difficult to beat Orion and nuclear pulse propulsion. Politically the only way you'd see that happen would be to save the planet.

Those were really interesting points. I was actually thinking of a fission fragment rocket or stuff like nuclear electric.

OK - totally agree. I was trying to make it easy because I figured even pulling off a ship that could accelerate constantly (say a week or month or year) at about 1/100 of a g was a "significant" engineering feat. More is even better.

I'm pretty sure most people would understand what that means when I said 1/100g engine in the context of the article and ship. That means a ship that can be accelerated at 1/100g via some kind of a propulsion system (engine). The featured article was about nuclear-thermal rocket ships.

Since any useful ship will be composed of matter - it will have mass. If you know the mass, and you know the acceleration then you can figure out all the other boxes.

Constant acceleration ships have been built. Deep Space-1. So you clearly are either totally clueless, or purposely ignoring the fact w built a constant acceleration ship. It was part of the mission. You can google it and find all kinds of fascinating (OK I find it fascinating) stuff like the mass of it, or the thrust of the ion-drive.

BTW - If I am genuinely making you angry I apologize. I am assuming you are just messing with me now, because you seem smart, and must have heard of deep space 1 and fission fragment rockets, and I'm pretty sure you understand what I meant by a 1/100g engine ship. The only reason I keep responding is because I am so sick and tired of the crazies who say stuff like 'We could never do that!" or the almost-worse "Oh no nobody ever went to the moon". It drives me batshit crazy. I have no personal idea if we could build a 1/100g fission-fragment rocket. If someone wanted to try I'd applaud them. Assuming they didn't fire it up in my back-yard.

I'm thinking of things with very high ISP for all the reasons you are citing. The point I'm trying to make is that if we could build a 1/100g drive then we could do a hell of a lot, and low acceleration drives can accomplish lots.

So I didn't think your analogy was fair at all. It seemed, to be honest, the same kind of analogy used to prove that putting humans on the moon is impossible. It's like people saying the rocket equation directly proved that we couldn't possibly build a single-stage rocket that would take a person to the moon and back with any existing engineering.

We all know we got people to the moon, and back again multiple times, safely. Staging was used, and LOR. I'm not suggesting the EmDrive or breaking the laws of physics.

Nobody is suggesting that our constant-g rocket will run forever. That is obviously impossible. But it may well run for long enough to be useful, and better than a chemical or nuclear-thermal rocket.

Your argument about ignoring conservation of momentum is also wrong, as is your comment about the rocket equation. It's because of those two facts that we need really high ISP. That means nuclear. It probably means something like a fission-fragment rocket to get high enough ISP.

So go ahead, take the cheap-shot, make the pun, but honestly - your response sounded to me dumber than the vast majority of the prior posts.

It depends on the ISP of the Tug right? If the tug ISP is 10x that of the alternative for the fuel mass you climbed out of the gravity well with then it would be a win to use the tug right before you start up you light the candle on your *really* dirty *really* high ISP engine.

Explaining more and following up on MachineShedFred point. It's a given that you won't use a 1/100g constant drive as a booster toiget to LEO from Earth.

You are right - a 0.01g constant acceleration drive will take a while to get out of LEO. But it's still about 3 months to Mars. If we had a way to do 0.1g for a while that would be great. I just don't see it happening unless you use a nuclear-thermal or a chemical booster, in which-case your specific-impulse sucks. Maybe VASIMR, but even at the high end I don't think its ISP is enough.

Can you explain what you are trying to say more? It seems clear that you wouldn't use a 0.01G drive as a booster to LEO. The whole subject was Nuclear. If you tie the words Nuclear and constant acceleration drive - you pretty much mean things that are radiologically dirty. In Space (above LEO) it doesn't really matter. Space is big and has lots of hard-radiation anyway.

  Is there a propulsion technology you are thinking of? I'm thinking of stuff that are as dirty as a fission-fragment rocket for the constant-g ship.

The only -single design drive I can think of that would satisfy booster and flight would be Orion. Technically doable but environmentally in-feasible unless it's an emergency to get significant mass to LEO or we all die. Nuclear thermal is OK for a booster maybe, but ISP is way too low to realistically use for a constant-g drive.

Do you mean - We need better propulsion technology for boosters to get all this nuclear stuff to LEO?
   

The better propulsion is implicit if you want a constant g ship (for any meaningful distance), so I think we are agreeing. I didn't make it explicit because it is implicit once you run the calculations that a chemical or nuclear-thermal rocket won't cut it due to fuel mass. To be more explicit, I'd love a propulsion system that can do better than 1/100g for months, but I doubt we will get there soon. A propulsion system that could do 1/100g is much more achievable with existing technology and a worthy goal. We could start with 1/1000g ship.

The ideal ship (for humans) would obviously be a 1g drive. Once you throw relativity in the mix that buys you pretty much everywhere. It gets you to Mars in a couple of days too.

Better propulsion I'm all for, but it's hard to beat a constant drive for long distances with a burst of acceleration. Every day the constant-g ship with a measly 1/100g is adding the equivalent of 8.6g for about 100 seconds. Or 1g for 864 seconds. The delta-v just keeps adding up.

A 0.01g constant acceleration ship gives you the Solar System.

A ship capable of a constant 0.01g acceleration would be a game-changer. Break the steps down as X-prizes. Build a 0.001g ship. Scale it up to a 0.005g ship. Next step is get it to 0.01g and you can reach Mars in three months and anywhere out to Pluto in just less than a year. First place to go? Prospecting the asteroid belt would be my vote. Find useful stuff, use it to build more useful stuff.

Agreed - the Blackbird is obsolete for its original purpose, drones provide a better solution in many cases. My main point was the Blackbird and X-15 weren't just useless "ego projects". The technologies were valuable, and missions performed by the Blackbirds had significant national security value at the time they were deployed.

Let's not forget the Blackbirds were brought back out of retirement at considerable cost too.

Characterizing a platform which provided a way to de-escalate conflict through timely intelligence an "ego project" is crazy. It's the kind of thinking that results in minimizing the very capabilities that you need to avoid ending up in a hot war.

There is no publicly acknowledged air-vehicle with the flight envelope of either the X-15 or the SR-71 in routine operation. Period. There are other platforms that can perform SOME of the operational capabilities of the Blackbird.

I agree 100% on the air-breathing, hypersonic air-breathing being hard - but if we had continued working on air-vehicles like the X-7 "Flying stove pipe" who knows where we would be now.

I'm not quite sure what you mean by "ego projects". Many projects that critics would throw those terms at gave us useful everyday technologies. The X-15 was an early example of fly-by-wire. High temperature ceramics and plastics have many uses too.

I myself wouldn't call the Blackbird and OXCART an ego related exercise at all. The entire aim was to provide a survivable rapidly re-targettable (faster than spy birds) recon platform. Knowing what the other guy has is valuable. It's especially valuable if that guy detonated the largest hydrogen-bomb ever in the atmosphere and has an ideology based around crushing you and your allies.

I'd end by saying there is no acknowledged replacement for OXCART. The black budget is big. Secrets can be kept. If there's a successor to OXCART that's fine by me. I hope they keep it secret too, and I hope it provides intelligence that could allow the deployment of assets to dissuade any potential parties from rolling tanks into countries -"To save their ethnic countrymen" possibly triggering a wider conflict with potentially horrendous consequences.

Frankly I wish relations were better with Russia, but that's another story/post.

Maybe we could use a name hack to come up with a new name for people who "maker" things?

X10 controlled ponies, programmed in postscript on a NeWS system.

That's an article for /.