Hypersonic suborbital transport market as SSTO enabler

[PB666]

4 hours ago, HebaruSan said:

747s used 4 engines with 200-300 kN each, so 800-1200 kN total. One SABRE supposedly has 1960 kN at sea level. I don't know how much capacity you lose by having to be hypersonic and vacuum-capable, but a naive ratio based on thrust would give 1633 passengers.

it would need all of that and more to take off from a stardard 2 nm runway,  d=1/2 a t ^ 2 and braking distance is the same no matter what. Therefore basically 1/3 rd of the runway is for abort, longer if yiu need a faster takeoff speed. 747 has a high wing span and the highest glide ratio of any 60- 70s era jet aircraft, these SST have high glide aspects only at near mach speeds. If you need 200 or 230 kt to take off and your thrust to weight is double then 

1/2 x ^2/a  = 1/2 y ^2/b  x = 220 and y =170 then x^2/a = y^2/b then a/b = x^2/y^2 which comes out to a thrust 1.6 times as much. That does not consider extrabraking distance needed to stop at 220 knots. But think about you paying passengers are going to have get an ekg before flying you are going to nail them to the back of their seats, and if you need to make an emergency stop, you are going to need seatbelts  with shoulder straps. 

I'm actually in favor of SST, i think there is a niche, particularly in the high end shipping stuff, but the problem is that you can't do the half-poophole like its now defunct predecessor, otherwise it will be doomed for the next hundred years. Runways are largely funded by cities and counties with federal support and gate usage fees. SST does not work well under that model it does work well under a regional model for specialty flight services that could invlude high value shipment of perishables. So for instance if you had an SSt runway in Denver or near St.louis that  served the entire US. This model would have to be much more efficient than package deliveries for most airlines that let perishables sit out on the tarmack for hours or that bump packages from flights, in addition it would have to have fast regional connections. And the competition has to be of concern, a flight from tokyo to new york following a jet stream might only take 10 hours, its hard for even SST to compete with that if transfers are involved. But not every market can have a 5 km runway in it. 

 

[Nothalogh]

10 hours ago, Kryten said:

supersonic air travel barely existed

Only because it was legally hamstrung into irrelevance

[PB666]

5 hours ago, wumpus said:

If I was part of reaction systems, I would certainly want to go this route.  It might be a long shot, but I'm sure it is a long shot that has a better chance than straight to SSTO.

I vaguely remember a claim from rec.arts.sf-lovers (an ancient sci-fi forum to you youngin's) that suborbital flights to Australia used less power than supersonic flights to Australia.  Anybody know how to do these calculations?  And is it feasible to do a "bouncing in and out of the atmosphere" flight profile with only mach 5?

I'm sure that SABRE can use kerosene.  I'm less sure that such a plane makes sense for flights where the mass of kerosene might not be higher than the the dry mass of the plane.  LH2 might make more sense.  Obviously you need LH2 if you want SSTO.

While the military does like "prompt global strikes" and can certainly sell the beltway on that, I'm less sure about the rest of the USA wanting to pay for "another F35 program".  It seems much more likely that when (and only when) B-52s start falling out of the sky, Congress will approach Boeing and ask/tell them to make a 777 or 787 that can drop bombs.

Anybody have a guess at how many seats a SABRE-powered "airplane" would fly?  Certainly a lot more than Skylon...

I've dabbled a bit in the usenet, ;^). It was alot better before google groups invaded. Deja-vu did not help it, it was curse by accessibility and popularity. 

Given they are still flying tail draggers for high value antartica supply miisions.... B52s have a whole desert of padts to utilize if they so chose, and in the day of 3d printers and lasre scanners it aint to hard to fabricate parts. Don't forget the F22 raptor one of the most capable fighters thrust to weight ratio exceeds 1 stealthy, fast as all giddap and has a high service ceiling, 

The days of the long range bombers are headed toward their ends, the current threats are not nuclear. The best tactics avoid cambodia styled carpet bombing missions. The b52 is being replaced by drones with 1 to 4 small footprint manned from little trailer homes in remote place USA.  jet powered drone. 

http://www.wired.com/2014/02/avenger/

payload 3500 internal, 2200 lb external, maximum altitude. 50000 maximum speed 500. While its not out of the range of all missiles, it is out of the range and detection limits of most surface to air missles.

[Nibb31]

I'm amazed that nobody has mentioned yet that REL does have a design for a hypersonic airliner, the LAPCAT A2 (I have to wonder where these guys pick their names), powered by a SABRE engine variant called the SCIMITAR.

Anyway, they proposed it back in 2008, but nobody seems interested. So I guess there probably isn't a market for it.

Edited April 23, 2016 by Nibb31

[Steel]

On 4/22/2016 at 4:51 PM, sgt_flyer said:

Reaction engines tought about the concept - they are stating a 20000km range for their mach 5 concept. (so a way greater range than concorde's 6200km)

https://en.wikipedia.org/wiki/Reaction_Engines_A2

now such a design would face the same problem as supersonic jetliners - you can't go supersonic above the ground - clearly limiting the avaible destinations. one of their idea was to propose to go from europe to australia by flying over north pole then above the pacific.

i'm not sure making a plane for such specific routes is going to see much buyers for that plane they would likely prefer more classic and more flexible designs that can be affected to other routes

in addition, the airports that would receive such a plane would have to build and maintain the infrastructure for storing and fueling the LH2 (+ ongoing costs to maintain the cryogenic temperatures). that'll cost a lot for 1 plane ! especially given the low density of LH2 and cryogenics, you won't be able to use a fueling truck - you'd need to bring the plane to the LH2 tank instead.

 

Edited April 25, 2016 by Steel

[sevenperforce]

On 4/23/2016 at 3:26 AM, Nibb31 said:

I'm amazed that nobody has mentioned yet that REL does have a design for a hypersonic airliner, the LAPCAT A2 (I have to wonder where these guys pick their names), powered by a SABRE engine variant called the SCIMITAR.

Anyway, they proposed it back in 2008, but nobody seems interested. So I guess there probably isn't a market for it.

No market as a separate vehicle, presumably. Doubling infrastructure and support costs is not really a great idea.

[shynung]

@sevenperforce

Separate vehicle, yes, but similar technology. A2's SCIMITAR engine is basically SABRE minus the rocket-mode parts. It still has the same precooler tech, and the same fuselage design, probably trading some tank volume for passenger seating areas. Presumably, support infrastructure for it can be shared with Skylon.

However, Nibb's probably more on-point about the lack of market for supersonic passenger transports. The last one that went into service did so at a loss, despite high ticket prices.

Also, I covered suborbital airliners before.  

On 3/3/2014 at 5:09 PM, K^2 said:

People who can afford sub-orbital aren't the kind of people who wait in lines to check in. They are the kind of people who are going to fly in to NYC or London on a private jet or a heli. Oh, and ICBMs from Russia don't take 2 hours to get to NYC. Sub-orbital to London will be under an hour with the takeoff and landing.

Cost is another matter. People who could afford this are also not the sort of people who are going to pack like sardines into tiny capsule like some sort of peasants that have to fly economic. Nor wait for a week for a convenient flight time. If you can't organize at least one flight a day with first class sitting for a reasonable price, it's not going to work.

With cryo LH2/LOX, composite tanks, composite structure, and something like an aerospike engine, preferably one that can run as a scram jet to improve efficiency, you might be able to just make it viable. But this is a huge risk on a fairly small and unpredictable market that no private company is ready to take.

There is some military interest in a similar vehicles. USMC has payed good money for various studies on the matter. A vehicle that can deliver a small platoon of Marines would be just perfect for such a venture. If they have actually started research on it and they go to building prototypes in secret right around now (this isn't something you can test without it becoming public) they can have one in, optimistically looking, a decade. If they are working with one of the aerospace contractor giants, like Boeing, and part of the agreement is them being able to make use of the tech, (not unprecedented, consider AgustaWestland AW609) we might be looking at private operations of sub-orbital shuttles within two decades. And that's a very optimistic prognosis for it.

Another route would be to try and use something like Falcon 9R first stage to get a boost for something with a much simpler build, and that can get you something like 20T sub-orbital, which can fit a small airliner-worth of people to make the whole thing relatively affordable, but we're back to the sardines scenario here, which I don't think people who can afford it would go for.

Edited April 25, 2016 by shynung

[cantab]

A promising market I think would be business jets. Some of the kind of people who already own or lease private jets, in part because they let you avoid the checkin and security waits, might be prepared to pay more for something faster. There are currently several supersonic business jet plans, though none yet in production.

[sevenperforce]

3 hours ago, shynung said:

@sevenperforce

Separate vehicle, yes, but similar technology. A2's SCIMITAR engine is basically SABRE minus the rocket-mode parts. It still has the same precooler tech, and the same fuselage design, probably trading some tank volume for passenger seating areas. Presumably, support infrastructure for it can be shared with Skylon.

However, Nibb's probably more on-point about the lack of market for supersonic passenger transports. The last one that went into service did so at a loss, despite high ticket prices.

Also, I covered suborbital airliners before.:)

They'd save some in common development costs, but not very much at all in construction or maintenance or support. Any differences between the vehicles is going to make for a huge support structure difference, rendering common support for orbital and suborbital flight impossible. Only a limited amount of common support would be possible anyway, but use two separate vehicles and it's utterly impossible.

The flight time reduction for supersonic travel is fairly meager compared to the flight time reduction for a hypersonic suborbital flight. So that might be a marked difference. What dV do you need for an antipodal suborbital hop?

The ideal scenario would be a wingless blended delta/sears-haack lifting body with horizontal-attitude VTOL, either via biaxially-ducted fans, rotating engine nacelles, or something similar. Kerolox. Constructible in various configurations, but all with the exact same frame and engine config:

• Small tank, 20-30 business class seats, small payload cabin
• Small tank, large payload cabin
• Large tank, small cabin (5-10 passengers)
• Large tank, small payload bay

The second two configurations are capable of reaching SSTO; the first two are not. However, all four configurations are equally capable of accepting a parallel first-stage booster, and all can return from orbital velocity. The booster allows the first two configurations to reach LEO and the second two configurations to have BLEO capability.

This way you can offer daily antipodal flights with half-hour flight times for a large set of passengers, or scheduled hypersonic payloads, or ISS crew ferry launches. With the reusable strap-on parallel booster, the first two configurations can take a large group of passengers into orbit or a large payload into orbit.