I read in the newspaper today that a Japanese company wants to build a Hypersonic passenger aircraft to carry 300 people at a time to replace Concorde. Anyone got any idea is this in any practical in the next 20 years without some major advance?

Practical - in what regards? Financial - simple economics for supersonic passenger travel says that it is not practical. Also consider Concorde cruising speed was approximately Mach 2. Hypersonic is usually considered above Mach 5. SR71 Blackbird only (only - like it was slow) flew at about Mach 3. Hypersonic passenger aircraft in 20 years - only in somebody's dreams!

Hypersonic offers some advantages over supersonic - in particular, there is the possiblity that the sonic boom problem might be eliminated due to flight at higher Mach numbers (i.e., smaller shock wave angles) and higher altitudes (e.g., 30 km for a HST vs. 15-20 km for a SST). Additionally, it is easier to justify higher ticket prices if you can decrease the flight time by 5x vs. 2x (imagine flying between Tokyo and New York in 2 hours).

For those technically inclined, check out my research...

http://sonic.t.u-tokyo.ac.jp/~marcus...aa20033804.pdf

My Ph.D. dissertation is focused on Hypersonic Transports, so I hope I am not dreaming about this stuff...

P.S. Anyone, if you can give me a link or reference to the newspaper article you saw, I would be interested in seeing it...

Interesting - nice paper. Even given technology advantages you point out, do you have a financial model for hypersonic travel? I.e., what would be the ticket costs. Yes, 2 hours Tokyo to NY sounds great!! But I would seriously doubt even that would justify the enormous ticket prices that I am imagining.

I haven't implemented a cost analysis model in my research (at this point), so I can't give you any hard figures... but I have given it some thought, and can sum up my ideas in a few points:

1) A main objective of my investigation into HSTs is to see if they can be developed and produced for costs relatively close to that of subsonic jets - this is why I attempted to minimize total take-off weight in my design method, as the take-off weight is frequently indicative (not always, but in general) of the total life cycle cost of an aircraft (i.e., development/maintance/production/operating costs). For a 250 passenger aircraft, a first-order design yielded a total take-off mass equivalent to that of a Boeing 777. Although technology requirements (thermal protection system, etc.) will require higher costs, these results do show that HSTs are promising.

2) Speaking of increased costs due to technological requirements, I will be the first to admit that a HST will require several relatively high-cost technologies vs. subsonic jets. This includes a dual engine system (turbojet and ramjet) and high-temperature materials (i.e., probably a lot of titanium and aluminum, with superalloys or refractory metals most likely required for some areas such as the leading edges). However, the fact that the HST only has to deal with conditions at Mach 5 (versus M>20 of the Space Shuttle), it can possibly use a variety of reusable/relatively-low-cost systems, including metallic thermal protection systems (versus carbon-carbon composites, ceramic tiles, etc.), and hydrocarbon ramjets (i.e., cryogenic fuels, scramjet/rockets are not required). These somewhat relaxed requirements indicate that cost increases vs. subsonic jets can be controlled to an extent.

3) It is hard to ignore the fact that there are no known aircraft out there than can sustain a cruise at Mach 5 for 2 or more hours. If a Mach 5 HST is actually developed, its high cruise speed and altitude, coupled with a large payload capability, will make it very attractive for military use also. In other words, developing variations of a HST for military use might help offset some of the initial development costs required for validating a variety of new technologies (e.g., metallic thermal protection systems, etc.).

4) On a related note, Mach 5 speeds will allow same-day delivery of goods to anywhere on the planet, so there is probably a market for cargo HSTs also (e.g., same-day FedEx). This will also help offset initial development costs.

5) One of the reasons that the Concorde was unsucessful economically was that the ticket price was >5x that of subsonic jets, with only a minimal (<2x) decrease in travel time. Looking at the example of flying between Tokyo and New York, one can surmise that a SST might make the trip in about 6 hours (vs. 12 or so for a subsonic jet). For a Mach 5 HST, though, this same trip might take 2-3 hours. Even if ticket prices are 2 or 3 times as much as that of subsonic jets, a lot of people (business travellers in particular) will consider it worth the cost to shave close to 9 hours or so off their travel time. So, it can be expected that there's a little more latitude for higher ticket prices for HST vs. SST aircraft.

--- Okay, so that came out a lot longer than I intended... Let me point out that the above is based on my research results and personal intuition. There are a lot of areas (e.g., control/stability, etc.) that I haven't really investigated in detail; these areas will definitely require further research before a real HST can be developed.

Anyway, I'm sure you can see my bias in the above comments - after all, my reasearch is focused on investigating the advantages of HST configurations. Plus, as I sometimes fly between Tokyo (where I'm studying) and the U.S. (where I grew up), I have a personal interest in seeing HST-type vehicles eventually enter service.

Hi,

I read it in the Metro newspaper...which is a free newspaper on the undergrond (tube) network in London. That is about 10 days or more ago now. Normally, if the story is in the metro it will also have been in the Times, the Daily Telegraph or the Guardian newspapers. All UK newspapers.

I am happy there are still people with dreams...

On a side note, if this was to be a commercial venture, I tend to think perceived safety may be the biggest issue, next to cost. How many shuttle flights could be sold right now at any price? Of course, this would not be an issue with the military...

Could you put up a satelite with a booster on the way to Tokyo?

I really like the way your design looks. Good luck.

Thanks for the comments about my research - the designs in the paper I linked above are actually about 6 months old; more recent ones include a lower wing anhedral angle (i.e., the wings are more "flat") and a more-accurate nozzle design/analysis, among other things...

I agree that safety would also be a big issue for a first-generation HST. Unfortunately, there's not much that can be done about this except to perform a lot of flight testing before going into operation. However, because a low-cost HST vehicle will most likely use a combination of hot structures and metallic thermal protection systems (TPS), hopefully it won't be that sensitive to TPS failures like the Shuttle was recently. It's hard to say anything concrete about this, though, until a detailed HST is actually developed.

Anyway, I am really enjoying my research into HSTs. As I'm approaching graduation, I hope that I can continue to work on these concepts in the future (hopefully at an aerospace company with an interest in actually producing a HST...). It would be nice to see Boeing (or someone similar) follow through with the development of a revolutionary aircraft concept (i.e., am I the only one disappointed that Boeing is now focusing on the 7E7? I understand the economics of the situation, but being an industry leader means sometimes pushing the envelope with revolutionary technologies and concepts).