[CripDyke]

okay folks. I admit it. I'm a science geek...and aerospace tech thrills me.

So, the new Space Ship One (the first non-gov't vehicle to carry a human into space - and safely back, btw) fascinates me.

One of the things i'm wondering - but haven't found - is how the SS1 rocket engine (using Nitrous Oxide and HTPB as reactants) stacks up to the most efficient chemical propellant system, L H/OX.

Anyone got figures on the specific impulses of HTPB/NO & LH/OX?? I'm wondering if this is a viable fuel for orbital flight. I know SS1 can't just be scaled up (it wouldn't survive the faster reentry without new structure and TPS), but can the basic rocket engine be used in a new vehicle?

It would only have to be 80%, maybe 90% as efficient as LH/OX - or something like that - b/c the new SS1 style hybrid rockets don't require massive cryo-freezing/refrigerating machinery and insulation the way the Shuttle tanks do. (The NO does need that equipment, but it can be done more efficiently b/c of the higher boiling point & larger molecular size and general reduced reactivity that permits different types of tanks with less refrigeration - and that's just the oxidizer; the fuel doesn't need any of that at all).

But does it make it to the 80% level?

Anybody know? Anybody geekier than me?? C'mon, i know there's plenty of people outthere that have been thinking about high SI fuels and going radio-thermal and or fission based ion propulsion. Without VASIMR technology you can't get the thrust, but HTPB has the thrust...it just needs the SI.

[Qwyksilver]

Ughhhhh

You're making my head hurt at 7:30 AM.

I honestly have no idea, I just love the thought of how Science is catching up with Science Fiction. I was always more of the Biology geek. Subcellular is fun. Subatomic hurts my head.

[Orsino]

The kcal/mole yield has become less important than burn rates, as the necessary porting (to increase surface area) makes these motors way fragile.

Did you catch the Stanford article on paraffin fuels? This stuff burns three times faster than HTPB/nitro mixes, so it doesn't need to be swiss-cheesed to death. Apparently, this is the way to go for scalability. Look for a scheme like this to take the X Prize.

[CripDyke]

nah. X-prize will be won in 2 weeks by Burt Rutan using the HTPB/NOX system.

Paraffin - if it's more scalable - would be what's needed for orbital flights.

[Qwyksilver]

X-Prize. That's for the 1st privately funded and built space craft correct?

I can't remember the details, does it have to have re-entry and re-use capabilities?

[SaintRigger]

Qwyksilver, on Sep 14 2004, 07:50 AM, said:

X-Prize. That's for the 1st privately funded and built space craft correct?

I can't remember the details, does it have to have re-entry and re-use capabilities?

Yeah, it's a 10mil prize for whomever can launch a vehicle sub-orbitally with a cargo of 3 people. The important thing is it needs to be done twice in 2 weeks - to demonstrate a reusabilty factor as current launches drop and waste a considerable amount of resources.

Space Ship One shure am sexy.

[CripDyke]

QS - yes. But it only has to go up 100Km - which is between 62 & 63 miles.

So the reentry capabilities are not as difficult to engineer as those for an orbital vehicle (which is falling for 150 miles before it slams into the atmosphere).

As for reuse: it must be flown 2x in 2 weeks or less. Sep 29th is the first flight of SS1 to count towards the prize. SS1 can fly every 4 days, so they will have at least 2, possibly 3 tries to get that second successful flight, assuming the first one goes as planned.

They already flew SS1 into space once - but they didn't fly again within 2 weeks, so now that flight is irrelevant for the x-prize, but the test certainly helps the team know what to do & what to expect when they ARE flying for the prize.

Paul Allen (Bill Gates best friend from college & the 2nd biggest stock holder in Microsoft) gave 1/1000 of his fortune, $20 million, to bankroll this attempt to win the prize. Winning the prize would get back 1/2 his investment. He's hoping to get the rest back by selling tickets to ride into space.

BTW - mystery solved. That stanford article that Orsino listed had the Isp (sometimes called SI - Specific Impulse) as 360 for HTPB and 369 for Paraffin. These values are much higher than the solid rockets used for the shuttle. The SSME (space shuttle main engine) has an Isp of 400. These are all theoretical. In practice it's slightly lower in ever case.

In any case, the new Hybrid rockets - powered by Wax or by Rubber - are PLENTY strong enough to lift payloads into space.

YeeeeHaw!

The really cool thing about these technologies is that they are safe. Neither shuttle accident would have happened if using Hybrid rockets. (In the first case, the liquid fuel wouldn't have leaked - 'cuz there is no liquid fuel, only liquid oxidizer - and in the 2nd case, they would not have needed the same insulation, so it would not have fallen on the wing, thus wouldn't have cut the wing, so wouldn't have let in the super-hot reentry gasses).

I'm totally up on anything that makes space travel safer.

ALSO, it would make it cheaper, cuz there are fewer risky sub-systems to check, double-check, & so on. No x-raying the solid boosters, no checking the o-rings...it all adds up after a time....

Conversion to Hybrids could cut costs in half - easily. Using a "sky ramp technology" or something similar, could cut costs a further factor of 10.

Thus reducing the cost of flying to space from $10,000/pound down to $500/pound. That could revolutionize what we think space & space travel are good for...

I mean, how quickly would space hotels go up if they were 20 times cheaper, and tourists only had to pay $1million instead of $20million??

I'm not saying that just anyone could afford it, but there's a lot more people that would be willing to do it for $1 million than for $20 million. Exponentially more.

[Orsino]

CripDyke, on Sep 14 2004, 07:48 AM, said:

nah. X-prize will be won in 2 weeks by Burt Rutan using the HTPB/NOX system.

I will be very impressed if the current SS1, which made the first private space flight, also takes the prize by doing it twice within two weeks. I'm sold on the proof of concept, but their infrastructure's ability to turn it around quickly hasn't been demonstrated, to my knowledge.

It hasn't flown in more than two-and-a-half months, and their proud "X-flight date announced" link goes to a blank page. Have I missed something?

Oh. So I have. They just don't update their own website. Hmmm. That's not a very favorable omen, either.

The CNN story, however, speaks of significant engine upgrades. I guess, then, that it's not really the same vehicle anymore. I'll cool it with the nay-saying and wish them luck.

[CripDyke]

down time is because X-prize rules say you have to give the Contest Officials 60 days notice before you fly, & during that time they have to have full access to the vehicle to inspect it, etc.

So basically, they flew, spent a couple weeks figuring out exactly what went right & wrong, then they decided to fly for the Prize.

They announced without flying again (which would have been useless for contest purposes and no longer necessary for testing purposes, tho' perhaps a little helpful)...and then were immidiately prevented from flying.

So they used their downtime to get an extra 20% projected max performance out of their engines - this is 30%+ more than they actually used during their one flight above the atmosphere. (they also tested it by flying up to 50Km, then 80Km - both still in thin upper atmosphere - before the 100Km flight to space).

I think it was a good use of enforced downtime & feel pretty confident. I'm trying to get access to the testing grounds so I can road trip down & do a radio segment on being a lay-person witnessing history for the local NPR affiliate, Oregon Public Broadcasting. Still not sure if that's going to work out. But i'm sure trying!!