Quote from: jongoff on 01/27/2017 05:49 pmQuote from: TrevorMonty on 01/27/2017 04:57 pmSpace tourism would be the high flight rate market that would justify RLV. Seat price is critical, this where larger is better. See aeroplane industry.At $10m seat F9/Dragon might be viable at $70m launch. With NG a 20 seat vehicle should be possible at $200m launch. I think flight rate of the vehicle is a bigger driver for seat price than vehicle scale. But agree that space tourism is one of the potential RLV markets (along with propellant, provisions, raw materials for orbital construction, etc).~JonBut this really depends, doesn't it?Is 50 flights of Pegasus cheaper per pound than 15 flights of Falcon 9?Scale is super important, as is flight rate. Scale is most important on the low end. You probably start getting diminishing returns as you go bigger.
Quote from: TrevorMonty on 01/27/2017 04:57 pmSpace tourism would be the high flight rate market that would justify RLV. Seat price is critical, this where larger is better. See aeroplane industry.At $10m seat F9/Dragon might be viable at $70m launch. With NG a 20 seat vehicle should be possible at $200m launch. I think flight rate of the vehicle is a bigger driver for seat price than vehicle scale. But agree that space tourism is one of the potential RLV markets (along with propellant, provisions, raw materials for orbital construction, etc).~Jon
Space tourism would be the high flight rate market that would justify RLV. Seat price is critical, this where larger is better. See aeroplane industry.At $10m seat F9/Dragon might be viable at $70m launch. With NG a 20 seat vehicle should be possible at $200m launch.
Quote from: AncientU on 01/27/2017 10:56 amAren't you assuming that the only things we will be doing in space are the things we have been doing?Nope. RLVs of any size only make sense if we're doing new things that require a lot higher flight rate.Next question?~Jon
Aren't you assuming that the only things we will be doing in space are the things we have been doing?
Quote from: jongoff on 01/27/2017 05:44 pmQuote from: AncientU on 01/27/2017 10:56 amAren't you assuming that the only things we will be doing in space are the things we have been doing?Nope. RLVs of any size only make sense if we're doing new things that require a lot higher flight rate.Next question?~JonSo, if we're doing new things, how can you be certain that small RLVs make sense while large ones don't?
Flight rate and payload per flight are two parameters in the space that pertain to launch cost($/kg to orbit). Where this optimizes is highly dependent on what the new things are... some could be beyond the capability of a 1t launcher entirely(like space tourism).
Others that are infinitely divisible like propellants will achieve an optimum between the two parameters; depending on quantities of propellants needed, orbit(s), etc.
I don't think we need to be doing new things to justify any kind of RLV. Existing things with existing modest growth rates is enough to justify F9 partly reusable.
Quote from: Robotbeat on 01/27/2017 07:04 pmI don't think we need to be doing new things to justify any kind of RLV. Existing things with existing modest growth rates is enough to justify F9 partly reusable.Partial reusability is justified with current markets, I agree. But fully-reusable vehicles flying often enough to get into the RLV price ranges people talk about are going to require much bigger markets, or new ways of doing things.Dave Salt actually made an interesting case that with a ~5mT to LEO full RLV, you could support most GEO launches using distributed launch. And even if you only snagged 1/4 of the global GEO market with that RLV, you'd still be up in the flight range necessary to start justifying a full RLV.But once you start talking gargantuan RLVs, the only way they're going to be cheaper than small RLVs is if the demand gets big enough to justify it. And that's going to be a huge increase in demand compared to today.~Jon
Many people seem to suggest that RLVs don't scale up well... I would rather suggest that the opposite may be true. RLVs may actually not scale down well at all. At least from an economic and practical perspective.
Quote from: Lars-J on 07/24/2017 12:08 amMany people seem to suggest that RLVs don't scale up well... I would rather suggest that the opposite may be true. RLVs may actually not scale down well at all. At least from an economic and practical perspective. That's true of any rocket. Larger tanks hold more propellant per lb and larger engines produce more thrust per lb - so as rockets grow they become more efficient. Falling from the sky as a RLV, a larger rocket will also be less dense, decelerate more and be easier to control.While there may be a market for small launchers and/or RLVs, the economics will favor larger ones - which is why so many small-launch proposals fail long before testing is complete. Even Falcon1 died this way and I wouldn't expect current proposals to fair any better.
Smaller RLV may only reuse booster while using expendable US. Alot of smallsat LV companies are aiming for high production rates to drive LV cost down, making RLV less viable. ...
Same with aircraft. A 747 is cheaper/passenger mile than a 1920's Ford Tri-motor. Bigger is cheaper/lb.
Quote from: spacenut on 07/27/2017 12:47 pmSame with aircraft. A 747 is cheaper/passenger mile than a 1920's Ford Tri-motor. Bigger is cheaper/lb. Assuming a full load. If the market won't bear a large size it will look for a smaller size. It's why the big efficient widebody jets sell worse than the little inefficient regional jets.