The Next Generation of Human Spaceflight

[GIThruster]

Have you heard about Boer’s plan on pace tourism?

Could you post a link?

[GW Johnson]

These discussions of an ejectable heatshield for a window are very enlightening. There are some creative people here. The idea of a stowable heat shield that works very much like landing gear doors is looking better and better to me, because of some practicality problems with the alternatives.

As for ejection charges, why not arrange the pyro as a gas push instead of a jet blast? Arrange the structure to "mortar-fire" away instead of thrust away. The RBOC chaff round on Navy ships works like that. It flies way up high off the ship, too.

I kinda like artificial vision, periscopes, and heat-shielded windows, all together. Sort of a "suspenders-belt-and-armored-codpiece" approach. The window heat shield might actually be a cooled thing, not necessarily an ablative. But if it needs to be an ablative, the "landing gear door" analog may well be the most practical. I dunno.

[rjaypeters]

Mortar charge works for me too. I went with a rocket because the initial accelerations are lower, with less shock to the vehicle structure and continued clearance from the vehicle (93143's comment about accelerated flight condition comes to mind).

[GIThruster]

I'm curious about the economics of a fusion spaceplane.

I was under the impression that in order to avoid all the expensive TPS maintenance we find in SSTS, you have to have very low thermal loading, and the only way to do this was with something like X-33, where you're flying a very large, light fuel tank back. Then supposedly you can use a metallic TPS.

If you build a reusable spaceplane of any sort that has higher thermal loading, can it compete with things like Zenit 2 and Falcon 9?

Here's a cost reference for most launchers:

http://www.spaceref.com/news/viewnews.html?id=301

Falcon 9 is supposed to launch for $40 million. It's smaller than Zenit by quite a bit, which launches for $35-50 million. Atlas V is likewise not on the list, but I believe it launches for more than $70 million.

But lets just take Zenit as a baseline since it's the most efficient to date, though lets note that in 2006, President and General Manager of Sea Launch, Jim Maser; left to become President and Chief Operating Officer of SpaceX:

http://en.wikipedia.org/wiki/Sea_Launch

http://en.wikipedia.org/wiki/Zenit_rocket

http://en.wikipedia.org/wiki/Falcon_9

These guys are flying cheap. Can any sort of spaceplane fly cheaper?

[Betruger]

Thanks.

[rjaypeters]

...The idea of a stowable heat shield that works very much like landing gear doors is looking better and better to me...

I'd be happy with a stowable heatshield except I'm not sure how well it (landing gear door-like mechanism) will work under high dynamic pressure just after the majority of reentry heating is complete.

Edit: We don't get to choose when the lights go out, so I'm looking for the solution that works across the broadest range of flight. I am hoping for a vehicle that more passively reenters and if the lights go out, the pilot has a chance to keep things on a even keel and pointed away from people on the ground while the crew completes their tasks (which may include bailing out). I'd even entertain an escape capsule.

End Edit.

BTW, is creative a good thing?

GIThruster,
I imagine you want numbers for your comparison of existing launch services v. new technology, which we don't have. Further, I expect you already know the hand-waving arguments about how not throwing away your hardware is cheaper.

So, what do you want from us?

[GIThruster]

GIThruster,
I imagine you want numbers for your comparison of existing launch services v. new technology, which we don't have. Further, I expect you already know the hand-waving arguments about how not throwing away your hardware is cheaper.

So, what do you want from us?

I want to know if there's a way to propose a cheaper launch system than Falcon 9 using a reusable.

If we're here considering a reusable spaceplane, then to make economic sense, it has to be cheaper than existing launch systems. If indeed low maintenance is based upon metallic TPS, then the plane has to use this instead of ablative or otherwise maintenance intensive TPS.

So what are we talking about here?

I'm all for a spaceplane, but it needs to be cheaper than anything it might replace. We have a baseline. $40 million/launch at SpaceX. If it costs more to launch reusable, then spaceplanes don't make much sense, do they?

This is BTW, why I couched the issue of future spaceflight in terms of egress from LEO. I'm not convinced current technology can lower the costs from Earth to Leo below those of Falcon 9.

If that's true, we cannot lower costs to LEO below those of EELV's and Falcon, then the debate becomes one of what it takes to go into deep space.

So I'm asking, is there any real hope to lower launch costs to LEO below those of Falcon 9, by building a spaceplane, or should we be looking at the second half of the task--what it takes to go where no man has gone before?

[Aero]

http://www.reactionengines.co.uk/skylon.html
The Skylon/Sabre has been discussed extensively over on the NASA spaceflight forum as a Single Stage To Orbit (SSTO) vehicle, but it's probably easier to dig out the information from the company web site above.

Right now, Skylon is projected to beat the Falcon 9 on launch costs but there is the thought that the Falcon 9 Heavy may beat Skylon. Of course if one compares the next generation of competition then one should see what a Skylon Heavy looked like. That vehicle is not yet conceptualized in the open literature.

[GW Johnson]

The main thing here is that Falcon-9, including the "-heavy", is all known, all-proven technology. Skylon is not yet known to work. The key item is its "Sabre" engine technology.

I have done some calculations myself, and so also have others, indicating that the spaceplane concept, especially single-stage versions, may be restricted to relatively low delivered payload masses. Cost per pound might well be low, but there's a low limit on pounds in any one launch. The true limiting factor is the big-airplane structural problem: part strengths scale as dimension squared, while part masses (and loads) scale as dimension cubed. Twice as big is half as strong, all else being equal.

On the other hand, nothing but price and political will prevent us from launching very large payloads with stage rockets. These could be augmented with all manner of strap-ons, including airbreathing. Most of the design trends are pointing to 2-stage, with a staging velocity around 10,000 fps. I see the possibility of reusability with first stages, much less so with second stages, due to the difficulties of the higher reentry speeds, and the enormous distances downrange.

[GIThruster]

On the other hand, nothing but price and political will prevent us from launching very large payloads with stage rockets. These could be augmented with all manner of strap-ons, including airbreathing.

Yeah. You're intimating an argument for a cheaper than Falcon launch system.

Cool.

But I'm not seeing promise for a launch system cheaper than SpaceX.

Show me the numbers. If you've got them, I'm sure Elon Musk will give you attention.

Even with a strap-on air-breather, if you can deliver the technology at market prices, you have a go. If you can't, you're looking at a solution without a problem.

Lets stop thinking that cool tech over-rides market economics. Simply--it just doesn't.

[93143]

Falcon 9 Heavy will not be cheaper than Skylon in a mature market. Skylon's initial price will be relatively high, but its reusability is pretty close to airline-like, and it is estimated that in mature service, ~$15M/launch (for 15 mT) would be the expected price.

If the market expanded substantially due to some killer app, Skylon could get down to a few million per launch. For 15 mT. You do the math.

As an aside, they've apparently got a plan for a reusable, refuelable upper stage for geostationary satellite launches...

The key item is its "Sabre" engine technology.

Indeed. They appear to know this; they've just finished their first production heat exchanger and plan to do a subscale test on an actual turbojet next year.

If the engines work, the rest of the vehicle is low-risk in comparison.

[GIThruster]

Sorry, but I've never seen anything that promised Skylon can return to Earth and be readied for the next flight so cheap. I think that's crap.

Skylon sounds like the same story we heard 3+ decades ago with the sales for SSTS. Shuttle was all crap. It was a bullshit story about how reusable would save the day, and instead it costs 5X more than the next worst competitor.

It all comes down to returning the craft through hypersonic re-entry. If you have thousands of tiles needing to be checked, maintained and replaced, then you have a VERY expensive "reusable" launch system.

Until I hear better, I'll wait for an M-E system. Rockets can't cut it.

What we need is fast in vacuum and slow in atmosphere--which is just backwards from what we have.

[Betruger]

Is TPS your contention with Skylon, or are you just saying that for Shuttle as a precedent?

If you just say Skylon's affordability's crap without giving even one specific way that that's guaranteed to fail, there's no argument. I don't recall exactly, but there's more than one scheme IIRC for Skylon. They're supposed to use liquid cooling for one part of the wings or fuselage, and I don't remember tiles (could be wrong) being their solution for the rest of the surfaces.

Don't have time to search for it, but one of the top google hits gives this, from last May:

Thermal Protection System

Perhaps the most challenging aspect of designing a SSTO space vehicle is that of developing a thermal protection system that can withstand the rigors of ascent into space and the even harsher environment of atmospheric entry. While the Shuttle’s TPS is a remarkable feat of engineering, it is also very fragile and expensive. Skylon’s lower wing loading allows it to employ less exotic materials, a decision that decreases the initial cost as well as well as the long-term support costs associated with refurbishing the TPS after each use. Skylon’s approach employs a silicon carbide reinforced ceramic “aeroshell” separated from the structure by titanium insulation. This system makes refurbishment and replacement of damaged panels easy and straightforward. Since the wings extend outside the Mach cone at high speed and thus experience high heating rates, the thermal protection also uses hydrogen in an active cooling strategy, circulating cold hydrogen through the hottest parts of the structure, then venting it overboard.

There ought to be much better sources for this info.

[GIThruster]

There ought to be much better sources for this info.

Actually that is much better than the last I read over at Skylon. Last i read a couple years ago, there was nothing but hand-waving about TPS. I'm wondering now whether I need to retract my rant.

2 years ago, the only real work I could find on Skylon was the engine. It really didn't look like they'd done any serious work on the craft itself and hand-waving TPS issues always frustrates me. Maybe they have a workable idea that's not just hand-waving. I certainly can't remember anyone else who has proposed cooling the ship with hydrogen and then venting it overboard. That might be a novel idea. . .

[93143]

There ought to be much better sources for this info.

There are. The documents section of REL's website has some interesting stuff. This one is a relatively recent example, and it has some TPS information. They've even got a trajectory analysis results spreadsheet for their old proof-of-concept configuration (the latest configuration, the D1, is a real design done from scratch, and the payload is 15 mT, not 12).

There are also a few threads on nasaspaceflight.com - RLV technical issues, Reusable Single Stage to Orbit Concept, and SSTO challenge - where Mark Hempsell has posted multiple times; his posts tend to be informative.

One point the thread seems to have missed is that the most important issue for the wing nacelle configuration is the shock/shock interaction that hits the wing and would defeat any passive RCS. This heating is very local and is handled with an active cooling loop.