Rocket thrust

[D Tibbets]

Why worry about ozone? So long as there were not to many space planes flying, some more ozone may be a good thing (if you do most of your accelerating in the stratosphere). Heck takeoff from Chile and fly over Antartica in polar orbits to fill the ozone hole Of course that would be somewhat inconvient for trying to get something to an equatorial orbit.

The concern is ground-level ozone. Large amounts of it near populated areas. We don't need that.

As far as conventional takeoff space planes, do the constraints concider cheating by using strap on rocket boosters like many Air Force planes have used in the past (like B47, C-130, etc)?

...

I'll just link you to this previous rant of mine, lest I spend all evening on a massive broadside:

http://forum.nasaspaceflight.com/index. ... #msg427616

The immediately ensuing discussion provides some elaboration if you want it.

You mentioned the takeoff run of a SSTO space plane as a critical facter. Boosters would ease this. Yes, it is a compromise, more structure and low efficiency fuel. But the problem at this point would not be thrust efficiency, but thrust power. Also, it could allow throttleback of the high ozone producing engines during initial climbout at low altitude. So, while a SSTO is more sexy, the technical and possibly enviornmentally friendlier 1.5, (1.25?) stage apporach would be easier and possibly cheaper in development and operation. In terms of adding mass the examples of military planes is even worse as I believe thay did not eject the spent solid rocket casings. But, again, takeoff power outweighed efficiency concerns.

Besides, how much ozone would be produced with such an engine. How would it compare to the Concod's ozone and NO output at low and high altitude? Concidering the frequency of flights, say 100 Concord flights (defore it was retired) per one SSTO flight, which would produce more NO and O3 pollution? For that matter, how would it compare to the Shuttle? or other rockets/ per pund of payload? How would it comepare to all the supersonic fighters flying? Wow would it compare to the amounts of qzone produced by lightning? Also, I would not expect SSTO spaceplane flights from urban airports.


Dan Tibbets

[DeltaV]

If it's not FULLY reusable SSTO and return with NO staging, throw-away mass, solid rocket boosters, etc., then it's not worth doing. Might as well stick with the current roman candle nonsense otherwise.

[MSimon]

If it's not FULLY reusable SSTO and return with NO staging, throw-away mass, solid rocket boosters, etc., then it's not worth doing. Might as well stick with the current roman candle nonsense otherwise.

I like a mag lev sled (Inductrack) for the initial boost of an SSTO.

[kunkmiester]

A magnetic track might be feasible.

As to throw away mass, as long at it's considered cost effective, it's on the table.

[KitemanSA]

A magnetic track might be feasible.

As to throw away mass, as long at it's considered cost effective, it's on the table.

Yup. A fly-back booster that lowers the cost to orbit is a positive. Fully reuseable, not necessarily SSTO. EVENTUALLY, SSTO will probably supplant all intermediate methods, but don't make the next step TOO high.

[DeltaV]

While Inductrack and flyback boosters (what the Shuttle should have used) probably (for now) make a lot of sense from economics and engineering perspectives, my independent streak demands zero reliance on any ground-based infrastructure, apart from fueling and required maintenance, repair and overhaul. I want my Polywell-powered VTOL space car/RV to be able to takeoff/land on any reasonably flat, dry land on the planet, and transit between any two such points in under 1 or 2 hours, with a trip to the Zero-G Diner thrown in if I happen to run out of groceries. Unfortunately, I probably wouldn't be able to afford lunch after paying for all the collision-avoidance avionics needed to prevent hitting one of the few billion other tourists, and the defensive weaponry needed to scare off flocks of pirates trying to steal my graphene superconductors*.

* [Edit] Actually, they'd be after the rhodium dopant, not the relatively far cheaper graphene.

[93143]

Did any of you follow my link? Did any of you read past my first post there?

Of course it's good if it lowers the cost to orbit.

The point is, it almost certainly won't. JATO canisters maybe, but anything bigger or more complicated is getting too far away from the ability to do routine operations with quick turnaround and minimal manufacturing or refurbishment. Maglev, on the other hand, is infrastructure rather than a stage, more like a runway than an SRB - but I still don't like it because it's a very expensive and specialized piece of infrastructure, and it complicates ground handling.

TSTO is right out. Stacking stages is completely incompatible with cheap and routine. And don't give me air-launch; air-launching something with even one 6 GW Polywell in it is going to be a gigantic pain in the ass. This isn't Space Ship One we're talking about. And if the air-launch vehicle actually imparts significant velocity, you've now got two fantastically expensive development programs instead of one...

Chemical is already on the edge of cheap, routine, fully-reusable HTHL SSTO. Witness Skylon. If you can't do better than that with a fusion drive, don't bother; it means it's not worth using fusion for space launch at all.

Also note that Skylon doesn't use JATO canisters...

I want my Polywell-powered VTOL space car/RV to be able to takeoff/land on any reasonably flat, dry land on the planet, and transit between any two such points in under 1 or 2 hours, with a trip to the Zero-G Diner thrown in if I happen to run out of groceries.

That might be pushing it a bit... High-thrust Mach-effect drives could do that, possibly within a normal person's budget (I had a back-of-the-eyelids design for a spinner-powered vehicle the size of a small RV, called the Prometheus; feature creep rapidly took it out of the range of plausibility for an ordinary salaried engineer), but Polywell-powered SSTOs are still going to be in the large-airplane class at least, unless Rick pulls a rabbit out of a hat with POPS, and even then you probably won't ever be able to afford one yourself...

By the way, I'm fine with VTVL SSTO if the reactor power-to-weight ratio is large enough to pull it off.

[DeltaV]

High-thrust Mach-effect drives could do that, possibly within a normal person's budget

Hopefully, cheap HT superconductors would make building a Polywell+Mach-Effect vehicle affordable for the ambitious, slightly crazy hobbyist/enthusiast, as long as nothing more complicated than coils, capacitors, vacuum chamber, structure, control electronics, software and a few other odds and ends was involved. Where it would get really expensive is in meeting future Federal Aerospace Administration requirements. This would argue for developing such a vehicle in secret, like the Wright brothers did, and worrying about Federal Aerospace Regulations after the media blitz had begun (lots of lawyers would probably volunteer to defend, for a cut). Overhead shielding during development, to prevent satellites from detecting any stray neutrons from Polywell trial runs, would be needed to avoid SWAT team visits.

[Aero]

Overhead shielding during development, to prevent satellites from detecting any stray neutrons from Polywell trial runs, would be needed to avoid SWAT team visits.

LOL You need to worry about more that neutrons. Unexplained heat will bring SWAT, too. They watch for heat from GRO lights used by under ground marijuana growers. Literally under the ground. But the heat escapes and SWAT drops by.

[KitemanSA]

Did any of you follow my link? Did any of you read past my first post there?

I didn't! I was just chatting with kunk, MSimon, and DeltaV.

[DeltaV]

Unexplained heat will bring SWAT, too.

Sounds like a job for one of MSimon's Polywell cooling systems, modified to distribute the waste heat over as large an area as possible, or maybe into a nearby river, while prototype vehicle development progresses.

[D Tibbets]

Did any of you follow my link? Did any of you read past my first post there? ....

Yes, and Yes.
Though I admit I ignored your mention of turojets on Bussards SSTO plane. I don't know how the numbers would work out- lighter solid rockets (or hybirds, etc) with low efficiency fuel; or heavier jets with more efficient fuel providing most of the thrust for takeoff and climbout. At some point there would a crossover in the advantages. If the rocket boosters are ejected while the jets are carried to orbit, there would have to be a heavy reliance on the efficieny of the fusion powered rocket engine to provide the nessisary excess thrust. Of course that is the whole point of the SSTO system in the first place.

Dan Tibbets

[DeltaV]

If Polywell is ready before Mach-effect, then:

Superconducting electric lift fans (VTVL) from ground to low atmosphere,
transitioning to superconducting electric turbines from low to medium atmosphere,
transitioning to ram-air arc-jet from medium to high atmosphere,
transitioning to onboard propellant arc-jet from upper atmosphere to orbit.

Modes blended where appropriate.

All powered by direct-converted alphas.

http://www.iop.org/News/news_22702.html
http://www.asdl.gatech.edu/teams/ureti/ ... skPlan.pdf
http://h2forum2008.ru/docs/pdf/abstracts/5e_3_02.pdf

[DeltaV]

The superconducting electric lift and electric turbine modes might be based on the same engine "core", similar to the STOVL F-35B, and the ram-air and onboard-propellant arc-jet modes might also share a core, connected to a variable-geometry intake and variable-geometry outlet. Ozone production would only happen at higher altitudes with this scheme. If the superconductors require LH2 maybe it could be the reaction mass for the onboard-propellant arc-jet mode. I'd rather not have to haul cryogenics, but in the interim, until real "high temperature" superconductors are developed...

[D Tibbets]

The superconducting electric lift and electric turbine modes might be based on the same engine "core", similar to the STOVL F-35B, and the ram-air and onboard-propellant arc-jet modes might also share a core, connected to a variable-geometry intake and variable-geometry outlet. Ozone production would only happen at higher altitudes with this scheme. If the superconductors require LH2 maybe it could be the reaction mass for the onboard-propellant arc-jet mode. I'd rather not have to haul cryogenics, but in the interim, until real "high temperature" superconductors are developed...

Actually if you are using enough liquid hydrogen for thrust mass, you would suffer little penalty in using it as your coolent for your superconducter moters and magnets before subsequently heating it for thrust. If you need to run the superconducter equipmet for longer times (deorbit and landing after up to several weeks in orbit) the increased storability and density and heat capacity (?) of liquid helium or especially liquid nitrogen might serve better.

Dan Tibbets