Author Topic: Suborbital Atmospheric Bouncing  (Read 8955 times)

Offline SpaceGeek123

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Suborbital Atmospheric Bouncing
« on: 06/28/2013 11:53 pm »
It has been suggested that suborbital space-planes could preform a kind of Bounce/Skip on re-entry repeatedly extending the range of the vehicle and perhaps more interestingly the time in Zero Gravity.

I imagine such a capability would be an interesting growth on Suborbital Tourism, extending the time in weightlessness without needing to go all the way to orbit.


http://www.risacher.org/bh/analog.html
The idea even goes back to WW2 with the Silverbird

Offline sanman

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Re: Suborbital Atmospheric Bouncing
« Reply #1 on: 06/29/2013 11:08 pm »
Or be useful for sub-orbital trips to the other side of the world, skipping off the atmosphere like a stone across the pond, for rapid global travel. Just as long as you don't end up like that Lee Majors movie, where the airliner can't get back down.

« Last Edit: 06/29/2013 11:23 pm by sanman »

Offline Archibald

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Re: Suborbital Atmospheric Bouncing
« Reply #2 on: 06/30/2013 06:10 am »
It has been suggested that suborbital space-planes could preform a kind of Bounce/Skip on re-entry repeatedly extending the range of the vehicle and perhaps more interestingly the time in Zero Gravity.

I imagine such a capability would be an interesting growth on Suborbital Tourism, extending the time in weightlessness without needing to go all the way to orbit.


http://www.risacher.org/bh/analog.html
The idea even goes back to WW2 with the Silverbird

Being somewhat interested in suborbital refueling, I also noted that part of Clapp and Zubrin document.
There are not many ways of flying fast within the atmosphere. Scramjets or ramjets fly like aircrafts - flexible horizontal trajectories within the atmosphere. They also take severe heating in the process.

All-rocket vehicles are flying ballistic trajectories, and they are somewhat unflexible; a certain speed command a certain height, all this plotting against horizontal distance.

http://isulibrary.isunet.edu/opac/doc_num.php?explnum_id=95
 Page 28

Quote
It is apparent that to keep the insertion velocity from exceeding orbital velocities, ricochet trajectories are the only option to transport passengers across distances between 7,000 km and 20,000 km (where maximum altitude is limited to 500 km), and for cargo transport across
distances between 12,000 km and 20,000 km (no maximum altitude). In particular, for flights between opposite points of the Earth’s surface (antipodal flight), ricochet is the only suborbital
option.

There are two limiting distances: 7,000 km and 12,000 km; for distances close to these numbers,
ballistic and ricochet trajectories require the same amount of ΔV. For two major routes, London-New York (5,585 km) and New York-Tokyo (10,858 km), the distances are close to these numbers.
« Last Edit: 06/30/2013 06:10 am by Archibald »
Han shot first and Gwynne Shotwell !

Offline cordwainer

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Re: Suborbital Atmospheric Bouncing
« Reply #3 on: 06/30/2013 06:59 pm »
What would be the most durable or useful wing design for atmospheric ricochet? Lifting-body high-profile, box wing, delta-wing, reverse symmetry/cannard or some other design?

Offline Shevek23

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Re: Suborbital Atmospheric Bouncing
« Reply #4 on: 06/30/2013 07:45 pm »
I want to thank Archibald for that reference; there's all kinds of useful information there.

Having skimmed it I'd like to note they take 500 km as the maximum altitude to launch a suborbital leg to, in order to stay well below the inner Van Allen belt. I'm not sure if they take into consideration that the inner belt is higher and weaker at high latitudes, indeed vanishing completely at IIRC 60 degrees or so, whereas the three hub points they identify based on world travel patterns--London/Paris, New York, and Tokyo--as the best nexi for a world system are all pretty high latitude already so the triangle of routes connecting them peak in the very high latitudes. So it might be feasible to go higher on those routes without any significant increase in radiation hazard. Of course a higher altitude trajectory, while it will reduce the necessary velocity per hop, will increase the time required to traverse it, thus raising total exposure at a given rate.

Skip trajectories require one to launch at considerably lower angles than minimum-energy single arc suborbital paths, this means they have to be at higher velocities to achieve a given distance. Of course the idea is to lower the distance per arc. Coming into the effective top of the atmosphere at a lower angle allows the craft to redirect itself onto another arc with a minimum of both vertical acceleration and thus air drag. Essentially one has to reverse the vertical component of the velocity; a shallow angle is necessary to keep that minimized.

I'm pretty dubious about the concept; it seems to me that net delta-V comes awfully close to full orbital velocities and that one might as well just design the craft to go all the way to orbit at a modest altitude, say 300 km, and then deorbit to approach one's final destination, avoiding all need to have intermediate skip encounters. While the routes between the three regions cited above would have skip descents happening in Arctic regions where the sonic booms that result would raise minimal protest, as a general thing secondary routes developed later--to connect cities like Sao Paulo, Johannesburg or Cape Town, Sydney, and others into the network--would seem likely to sooner or later involve skips right over major inhabited areas. And the longer range routes would require many skips; since the paper Archibald cited assumed the craft would be re-boosted to regain full speed after a skip rather than allow each skip to decay the trajectory (which would lead to a very limited number of skips, each shorter than the one before) the total delta-V is going to add up, again raising the question of why not just aim for a low circular orbit in the first place.

Direct, single-arc suborbital trajectories would indeed save on delta-V, but as mentioned would raise the craft up to high altitudes that might well wind up cruising right through the lower Van Allen belt for trajectories with apogee in the low latitudes, as say New York to Sao Paulo or Tokyo to Sydney for instance.

The paper talks about single arc trajectories that stay under 500 km apogee and cover as much as 7000 km, approximately 60 degrees arc or 3600 nautical miles. I haven't worked out the orbital elements of that yet but I'm pretty sure the velocity is just barely under full orbital velocity.

For any great distance, going to full orbit and then deorbiting seems to be the smart thing to do to me.
----
As for Cordwainer's question, I suppose people have their opinions but the answer would depend on the design details and exact constraints of the mission I'd think. How many G's can a passenger vessel reasonably be designed to pull for instance? That has a bearing on how efficiently it will be boosted to its trajectory in the first place, then if we are doing atmospheric skips, the gentler you want the boosting glides to be, the broader they have to be hence the shallower the entry angle; you want less lift but also less drag since you'll be in atmosphere for longer. If the pax can take 3 Gs we get not only a different design but a different trajectory than if it has to be limited to 1.5! (Actually it's pretty hard to figure how the craft can be successfully launched at all with 1.5 G the upper limit on the acceleration).

I figure on a boring old delta with these sorts of musings myself. Of course a lenticular shape is also always fun! Practically speaking I'd expect some very wedgy sort of lifting body with sharp edges that at a glance would look like a delta, but with subtle details that make a big difference. If I could predict and sketch it in detail I'd be an aeronautical supergenius! Which I am not.

Offline gbaikie

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Re: Suborbital Atmospheric Bouncing
« Reply #5 on: 06/30/2013 09:03 pm »
Quote
I'm pretty dubious about the concept; it seems to me that net delta-V comes awfully close to full orbital velocities and that one might as well just design the craft to go all the way to orbit at a modest altitude, say 300 km, and then deorbit to approach one's final destination, avoiding all need to have intermediate skip encounters.
.

So you reach 300 km orbit, and immediately begin to deorbit, and if using minimal delta-v, you will re-enter on opposite side of the planet- a 20,000 km distance traveled. And if using more delta-v to deorbit you can land a shorter distance traveled.

Now, one doesn't need to go to 300 km orbit, one can go to orbit at 50 km height- there more orbital drag at 50 km, but this isn't a problem if the plan is to return immediately to Earth.

It seems to me the advantage of sub-orbital is you can have a lower re-enter velocity, but for long travel distance [+10,000 km distance] the suborbital would be a similar delta-v as something going into orbit.
So it's SSTO or TSTO reusable rocket doing sub-orbital flight.
A problem with reusable rockets is the lack volume of traffic, and with suborbtial could have more volume of traffic.

It seems a natural [or obvious] evolution of suborbital joyrides is longer and further distance of joyride. In other words, going up and down suborbital per seat is 100 to 200 K. And everyone suspects these cost will lower, and they may, but instead of lower price, one could also get possibility of more ride for same price [or even higher price].
So customer may have a choice of a 100 K up and down or "next step"
in suborbital of bigger jump at 200 or 400 K per seat.
So in the joyride department, as cost lower further, one could get to point of choosing the 10 K up and down, or the 1 million seat of traveling across a much larger chunk of Earth- or 10 to 20 million to go to orbit.

Edit: just because Virgin Galactic is starting with going and down, it does not mean, Virgin Galactic should continue to offer the same trip. Why remain at the same level as it easy for other start ups to deliver same product?
So this could mean a start up company may *have to* begin by offering a 500 km distance, at a future point in time, to compete a Virgin Galactic- which routinely offers a 500 km or longer distance traveled. Or public may willing to pay for the start up cost of a "inferior product" at the moment, but as industry develops, the public may will not be willing pay much for this type of ride. There isn't much of market for computers with capability of top end 1980 computers- and this general trend of new technology.
« Last Edit: 07/02/2013 12:23 am by gbaikie »

Offline R7

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Re: Suborbital Atmospheric Bouncing
« Reply #6 on: 07/01/2013 10:33 am »
What would be the most durable or useful wing design for atmospheric ricochet?

IIRC flat wing, as 2D as possible, is best super/hypersonic wing. See for example pegasus rocket, very flat 'wedgy' design.
AD·ASTRA·ASTRORVM·GRATIA

Offline rusty

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Re: Suborbital Atmospheric Bouncing
« Reply #7 on: 07/06/2013 09:10 am »
...
All-rocket vehicles are flying ballistic trajectories, and they are somewhat unflexible; a certain speed command a certain height, all this plotting against horizontal distance.

http://isulibrary.isunet.edu/opac/doc_num.php?explnum_id=95
 Page 28
Quote
It is apparent that to keep the insertion velocity from exceeding orbital velocities, ricochet trajectories are the only option to transport passengers across distances between 7,000 km and 20,000 km (where maximum altitude is limited to 500 km), and for cargo transport across
distances between 12,000 km and 20,000 km (no maximum altitude). In particular, for flights between opposite points of the Earth’s surface (antipodal flight), ricochet is the only suborbital
option. ...
I want to thank Archibald for that reference; there's all kinds of useful information there.
...
Skip trajectories require one to launch at considerably lower angles than minimum-energy single arc suborbital paths, this means they have to be at higher velocities to achieve a given distance. Of course the idea is to lower the distance per arc. Coming into the effective top of the atmosphere at a lower angle allows the craft to redirect itself onto another arc with a minimum of both vertical acceleration and thus air drag. Essentially one has to reverse the vertical component of the velocity; a shallow angle is necessary to keep that minimized.
...
For any great distance, going to full orbit and then deorbiting seems to be the smart thing to do to me.
...
So you reach 300 km orbit, and immediately begin to deorbit, and if using minimal delta-v, you will re-enter on opposite side of the planet- a 20,000 km distance traveled. And if using more delta-v to deorbit you can land a shorter distance traveled.

Now, one doesn't need to go to 300 km orbit, one can go to orbit at 50 km height- there more orbital drag at 50 km, but this isn't a problem if the plan is to return immediately to Earth.

It seems to me the advantage of sub-orbital is you can have a lower re-enter velocity, but for long travel distance [+10,000 km distance] the suborbital would be a similar delta-v as something going into orbit.
...
There's quite a bit of good reasoning above, but misses some fundamental points;

a) The concept of flight, or converting parabolic freefall into horizontal velocity via lift. It was addressed in the quote Archibald provided, referred to as "ricochet trajectories", and Shevek23's description of skip flight to "reverse the vertical component".

b) The second gbaikie touched on by noting one needn't reach 300km for orbit. The atmosphere shouldn't be thought of as a whole, but in fact density layers of which only the upper has been discussed here and requires not only extreme altitudes to reach, but extreme velocities to make use of.

Neither the extreme altitudes and velocities discussed, nor the requirement of unpowered descent are required for "skip flight". It seems far more efficient and faster to use medium altitude layers for occasionally leveling off (unpowered aka glide) or using the fuel saved by only achieving these lower altitudes for occasional powered ascents (sin wave flight). Taken into account, the concept of "skip flight" for transit is much more practical and closer when compared to ballistic or ricochet trajectories.

Thoughts, links or corrections?

Offline sanman

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Re: Suborbital Atmospheric Bouncing
« Reply #8 on: 07/07/2013 05:08 pm »
SkipFlight - I sense the makings of a good movie title. Now all I need is a script. Time to call George Kennedy.

Offline Chilly

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Re: Suborbital Atmospheric Bouncing
« Reply #9 on: 07/15/2013 08:23 pm »
SkipFlight - I sense the makings of a good movie title. Now all I need is a script. Time to call George Kennedy.

Must..resist..shameless..self-promotion...aw hell, I give up: http://www.amazon.com/dp/B006PNL48I

But can we get some better actors here? Anybody know Fred Thompson's agent?

Or anybody else's, for that matter?

P.S: I just called it "surfing."
« Last Edit: 07/15/2013 08:24 pm by Chilly »
Those who can't do, write.

Offline sanman

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Re: Suborbital Atmospheric Bouncing
« Reply #10 on: 07/16/2013 12:16 am »
Author in the house!

Ah, the techno-thriller -- my favorite kind of science fiction.

Chilly, just make sure you get nice fanfare theme music for it. It makes all the difference.




Meanwhile, more towards the topic - I'd wonder if this kind of aerospace craft would require special exemptions under existing missile international treaties. Would the sale of such aircraft constitute a violation of MTCR?
After all, this type of vehicle could be a pretty rapid delivery system if you packed it with a destructive payload.

« Last Edit: 07/16/2013 12:17 am by sanman »

Offline Elmar Moelzer

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Re: Suborbital Atmospheric Bouncing
« Reply #11 on: 07/16/2013 12:27 am »
Author in the house!

Ah, the techno-thriller -- my favorite kind of science fiction.

Chilly, just make sure you get nice fanfare theme music for it. It makes all the difference.




Meanwhile, more towards the topic - I'd wonder if this kind of aerospace craft would require special exemptions under existing missile international treaties. Would the sale of such aircraft constitute a violation of MTCR?
After all, this type of vehicle could be a pretty rapid delivery system if you packed it with a destructive payload.


I think there was a novel as the basis for the movie as well. The German title was "Orbit", not sure what the English title was. Orbit was very light on the science part, but a fun read for my early teenage self.
Wonder how Chilly's book compares. At that price, I might give it a shot.

Offline Chilly

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Re: Suborbital Atmospheric Bouncing
« Reply #12 on: 07/16/2013 12:28 am »
Author in the house!

Ah, the techno-thriller -- my favorite kind of science fiction.

Chilly, just make sure you get nice fanfare theme music for it. It makes all the difference.
...
Would the sale of such aircraft constitute a violation of MTCR?
After all, this type of vehicle could be a pretty rapid delivery system if you packed it with a destructive payload.

My favorite too, although I'm really enjoying the James S.A. Corey "Expanse" series, which is more space opera but it is FUN reading. It's my latest excuse for not having the sequel finished yet.

I generally listen to movie soundtracks when I need to get into the writing groove (i.e. drowning out the usual household noise).

Regarding MTCR (is that the same as ITAR?) I know that XCOR is fighting that battle right now over the Lynx being classified as a potential delivery system. Hell, they just want to sell rides over something more scenic than Mojave or West Texas!
Those who can't do, write.

Offline Chilly

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Re: Suborbital Atmospheric Bouncing
« Reply #13 on: 07/16/2013 12:34 am »

I think there was a novel as the basis for the movie as well. The German title was "Orbit", not sure what the English title was. Orbit was very light on the science part, but a fun read for my early teenage self.
Wonder how Chilly's book compares. At that price, I might give it a shot.
[/quote]

If it's the one I'm thinking of by Thomas Block, the US title was the same. Believe it or not, I haven't seen the movie everyone's linked to and didn't hear of that book until about the time I was finishing Perigee.

Far as I'm concerned my book holds up quite well, but don't take my word for it...
Those who can't do, write.

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