Author Topic: CATS challenge  (Read 29873 times)

Offline tnphysics

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CATS challenge
« on: 07/03/2011 02:41 pm »
Suppose you are the head of a group somewhere with one goal: make orbital space flight within the reach of a thrifty person who is not necessarily a millionaire.

Ignore politics for a moment-only technical, safety, and economic issues matter.

How would you do it? Anything goes, so long as it:

-is sufficiently safe (safe enough you would put your child on it)

-is sufficiently cheap (see above)

-does not need "pie-in-the-sky" tech (space elevators need not apply, etc.)

-would be profitable at the allowable fares

Alternatively, is it impossible? Why?

Offline MP99

Re: CATS challenge
« Reply #1 on: 07/03/2011 06:49 pm »
How would you do it? Anything goes, so long as it:

-is sufficiently safe (safe enough you would put your child on it)

May I suggest that there are people who work in dangerous environments on the ground / ocean (wildcats, Alaskan crab fishermen, etc) where a child could not go.

Given this would be a commercial / non-Government enterprise, people can choose to undertake risky activities if the "danger pay" is high enough. Similarly, people undertake (and will pay for) risky leisure activities such as scaling Everest, where I understand a quarter of those who attempt the peak don't make it back down again. Again, not an environment for children.

ISTM there are valid intermediate steps before safe-enough-for-children systems come along.

cheers, Martin

Offline Andrew_W

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Re: CATS challenge
« Reply #2 on: 07/03/2011 07:15 pm »
Why should we assume chemically powered RLV's are any more dangerous than chemically powered airliners?
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
Wilbur Wright

Offline Andrew_W

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Re: CATS challenge
« Reply #3 on: 07/03/2011 08:04 pm »
Obviously I vote for APT  ;D  a 15 tonne P/L translates to about 40 passengers, if operator costs plus profit were two million a flight, tickets cost 50k.
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
Wilbur Wright

Offline Jim Davis

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Re: CATS challenge
« Reply #4 on: 07/03/2011 09:12 pm »
Why should we assume chemically powered RLV's are any more dangerous than chemically powered airliners?

Hardly an assumption, surely?

If one doesn't count the Shuttle as an RLV (as most space advocates prefer) then no RLVs have ever been built or operated while airliners have been built and intensely operated in large numbers for many decades. Certainly we can expect the much greater experience with airliners combined with the fact that RLVs are much more difficult to design and develop to result in an airliner being safer?

Or if alternatively we do count the Shuttle as an RLV then the accident statistics speak for themselves.

Offline Andrew_W

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Re: CATS challenge
« Reply #5 on: 07/03/2011 09:35 pm »
Valid point about the amount of experience we now have with airliners vs RLV's, but I was thinking more in terms of there being any inherent (if that's the right term) difference in how safe they are. if we look at why airliners crash it's actually rare for it to be anything to do with the amount of energy they manipulate to propel them, it's  pilot error, structural failure, hijack/sabotage and weather that bring them down.

RLV's spend less time where there's weather, pilots will be at least as good as airline pilots, sabotage seems less likely (the saboteurs need access, and that's less likely at a few well secured spaceports than at thousands of airports, many in LDC's). So it's structural, and space only things like rocket engines and TPS that are balanced against the higher risk features of airliners.

I also don't think any conclusions can reached from the short one operator shuttle experience.
« Last Edit: 07/04/2011 01:51 am by Andrew_W »
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
Wilbur Wright

Offline tnphysics

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Re: CATS challenge
« Reply #6 on: 07/04/2011 01:45 am »
Okay supposed the safety standard is reduced in the near term, provided that it can reach this point in the future given sufficient experience. Are the other objectives feasible? How?

Offline colbourne

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Re: CATS challenge
« Reply #7 on: 07/04/2011 05:47 am »
The cheapest way per person would be a rotating tether, which will transport a passenger pod from a fast sub-orbital aircraft to orbit.
We can make the tether with todays tech and the length is short compared to a space elevator.
Docking will take care but with feedback mechanisms should be within our tech knowledge.

Offline Andrew_W

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Re: CATS challenge
« Reply #8 on: 07/04/2011 07:48 am »
The rotating tether option was something I was going to drop in at some point in relation to APT, combing APT with rotating tethers using existing tether materials the spaceplane delta V's can go below 3.5 km/s, mass ratios can be as low as 2.2, ie. a spaceplane that starts its ascent to the tether from 12,000M with a fueled mass of 400 tonnes can reach the tether with a mass of 180 tonnes, half of which could be payload.

If the SBP people are right, the cost of the energy to re-boost a tether using electric thrusters of Isp 4000s is less than $10/kg P/L.

If the whole system can be operated with airline efficiency you can in theory get ticket prices below 10k, freight below $30/kg.

http://nextbigfuture.com/2009/01/industrial-scale-production-of.html
« Last Edit: 07/04/2011 08:18 am by Andrew_W »
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
Wilbur Wright

Offline sarjil

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Re: CATS challenge
« Reply #9 on: 07/04/2011 01:48 pm »
well i am not a scientist or an engineer but from all the alternative launch systems i have seen and heard of, i think jp aerospace's idea would fit everything you have said, of course if it works.

basically i think its just an orbital airship.
http://en.wikipedia.org/wiki/JP_Aerospace
http://en.wikipedia.org/wiki/Orbital_airship
http://www.jpaerospace.com/

the bad part is with this idea they would be fighting with physics, at least thats the conclusion i came up with reading about this idea. but hopefully maybe one day they make it work somehow that would be great for spaceflight.
John Powell even wrote a book about the idea its on their website. anyways you guys here should know more about the technical stuff than me so hopefully you guys can elaborate more.

Offline Jim

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Re: CATS challenge
« Reply #10 on: 07/04/2011 02:59 pm »
Valid point about the amount of experience we now have with airliners vs RLV's, but I was thinking more in terms of there being any inherent (if that's the right term) difference in how safe they are. if we look at why airliners crash it's actually rare for it to be anything to do with the amount of energy they manipulate to propel them, it's  pilot error, structural failure, hijack/sabotage and weather that bring them down.

I also don't think any conclusions can reached from the short one operator shuttle experience.

Wrong, tact.  The whole flight regime includes energy management.  Reentry, docking, vacuum, etc.  Spaceflight will never be at the level of airline flight.

Offline Jim

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Re: CATS challenge
« Reply #11 on: 07/04/2011 03:07 pm »
Docking will take care but with feedback mechanisms should be within our tech knowledge.

Bad and unsubstantiated  assumption.  It is not similar to a space station docking, ABM interception nor an aircraft midair refueling.  This is constantly overlooked by tether advocates.


Offline Danderman

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Re: CATS challenge
« Reply #12 on: 07/04/2011 03:08 pm »
The title of this thread caught my attention, since there was a $250,000 CATS prize some years back, with the challenge being the first "amateur" rocket to reach 200 kilometers altitude. At the time the prize was first discussed, the consensus within the rocket community was that the prize would likely be won within a few weeks.

So, the lesson here was that translating from theory to practice is really, really hard when it comes to space access.

Offline Lee Jay

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Re: CATS challenge
« Reply #13 on: 07/04/2011 03:16 pm »
Why should we assume chemically powered RLV's are any more dangerous than chemically powered airliners?

Because airliners have a multitude of "intact abort modes".  In other words, a whole host of things can go wrong at almost any time during the flight (including explosive decompression, loss of engines, loss of many flight controls, etc.) and everyone can still survive.  That is a far more difficult thing to do with spacecraft because they are higher (safety is farther away in both distance and time - you can't get to 10,000 feet in 60 seconds from LEO), they carry more energy (the TPS has to be intact or they won't survive), and they are forced to carry lower margins during the critical stages of flight (ascent and entry) or else they will be too heavy to be practical.

It's not so much that airliners don't break or fail (they do), it's that nearly all the time they do everyone survives.

Watch this and imagine what would happen to an LV if an engine failure were to occur at the same moment (just as you're leaving the ground):



That airliner landed intact.

Offline Andrew_W

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Re: CATS challenge
« Reply #14 on: 07/04/2011 07:30 pm »
Quote
Watch this and imagine what would happen to an LV if an engine failure were to occur at the same moment (just as you're leaving the ground):

Well with a rocket propelled APT: it doesn't have air intakes so it wouldn't suck in birds, and it actually has higher reserves of engine thrust at T/O because it doesn't use most of that engine power till it starts its ascent after refueling.

Valid point about the amount of experience we now have with airliners vs RLV's, but I was thinking more in terms of there being any inherent (if that's the right term) difference in how safe they are. if we look at why airliners crash it's actually rare for it to be anything to do with the amount of energy they manipulate to propel them, it's  pilot error, structural failure, hijack/sabotage and weather that bring them down.

I also don't think any conclusions can reached from the short one operator shuttle experience.

Wrong, tact.  The whole flight regime includes energy management.  Reentry, docking, vacuum, etc.  Spaceflight will never be at the level of airline flight.

All forms of transport include energy management, other forms of transport have their own hazards, as I've said, airliners are exposed to some hazards to a greater extent than launch vehicles. We also need to take into account that there's a cost/safety trade-off, if it's deemed not safe enough, safety measures are introduced and the ticket price goes up.
« Last Edit: 07/05/2011 02:05 am by Andrew_W »
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
Wilbur Wright

Offline IsaacKuo

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Re: CATS challenge
« Reply #15 on: 07/05/2011 02:02 pm »
I don't have time to go into detail right now (I'm working on a 100y starship study propulsion system), but my answer to CATS is picokinetic pulse propulsion.

Picokinetic Pulse Propulsion uses streams of picosats in 4y solar orbits (perihelion 0.04AU, aphelion 5AU).  At 100km altitude, the relative velocity of the picosats is 44km/s, meaning it only takes 1 ton of picosats to boost an 11.5 ton suborbital RLV into LEO.

When scaled up to superheavy RLVs--like an ET sized 500 ton space liner between two SRBs--the cost per ton can be low enough for mass market space tourism.  Maybe less than $100 per ton, with ticket prices less than $1000.
« Last Edit: 07/05/2011 02:03 pm by IsaacKuo »

Offline Andrew_W

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Re: CATS challenge
« Reply #16 on: 07/05/2011 07:31 pm »
I've done a search on "Picokinetic pulse propulsion" and found no more informative than what you give here, which is even less information about how you arrive at a cost than I give for my idea. How are they launched? How are they accelerated? How are the guided? are they used just once or are they re-boosted somehow?
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
Wilbur Wright

Offline IsaacKuo

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Re: CATS challenge
« Reply #17 on: 07/05/2011 08:31 pm »
I apologize that I don't have time to go into much detail now.  The picosats are single use--they are vaporized in the process of imparting momentum to the client vehicle.  About 5000 of these picosats are consumed while boosting a client vehicle.

Each picosat is essentially a plastic water bottle with small steam thrusters for stationkeeping.  The control circuit is very basic--just a microcontroller, GPS style radio receiver, and a solar cell.  These mass produced picosats can easily be less than $10 each, and scaling up to large client spacecraft only requires increasing the mass of the water bottle.

The picosats are brought up to speed by a carrier bus spacecraft.

This bus spacecraft is first lofted into a suborbital trajectory, and then picokinetic pulse propulsion imparts Earth escape velocity with a v_inf of 20km/s.  This places the bus vehicle in a highly elliptical solar orbit, with aphelion at 1AU and perihelion at 0.04AU.  Picokinetic pulse propulsion is used again at 60 degrees from perihelion to boost the bus spacecraft up to the desired 4y parking orbit (aphelion at 5AU, perihelion at 0.04AU).  At this point, the carrier bus spacecraft can release some or all of the stored picosats depending on client demand.

Offline RanulfC

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Re: CATS challenge
« Reply #18 on: 07/05/2011 08:41 pm »
I've done a search on "Picokinetic pulse propulsion" and found no more informative than what you give here, which is even less information about how you arrive at a cost than I give for my idea. How are they launched? How are they accelerated? How are the guided? are they used just once or are they re-boosted somehow?
You can also look up "Externally Pulsed-Plasma Beamed Energy Propulsion" for similar but more "showy" ideas :)

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline IsaacKuo

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Re: CATS challenge
« Reply #19 on: 07/05/2011 10:35 pm »
You can also look up "Externally Pulsed-Plasma Beamed Energy Propulsion" for similar but more "showy" ideas :)

That's where I got the second part of the name.  The thruster pusher works in much the same way, but on a smaller scale and with little need for shock absorbers.  I also use a deep pusher nozzle rather than a shallow pusher plate to make the gas to escape rearward rather than off to the sides (this doubles the impulse).

Plastic water bottles are much cheaper than nuclear bombs, and they don't involve annoying radiation or treaty violations.  With a relative velocity of 44km/s, they still pack plenty of punch.

BTW--above I sketched an advanced "second generation" version where a picokinetic thruster is used to perform the near perihelion boost.  This is where the ultimate potential lies (it takes advantage of an awesome 177km/s relative velocity).  But it requires precision deep space encounters and it requires picosats to operate near the Sun.

A "first generation" version with less technology risk uses a solar thermal thruster at perihelion instead of picokinetic propulsion.  With a perihelion of 0.04AU, it doesn't even need a solar concentrator.  It does require significant amounts of LH2 to provide the 3.3km/s perihelion boost, though, which cuts into the ramp up rate (1.7x per year rather than 2.4x per year) and adds overhead.

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