Realistic solutions to the difficulties of SSTO?

GCNRevenger · 2005-10-08 21:09:15

I think that a few meters will be a very difficult standard to achieve, on any regular basis anyway; space is a very big place, the tether will have an 80,000,000m orbit, and the spaceplane will have a pretty high vertical velocity before and after apogee. For a 100m target envelope, thats around a 99.999875% accuracy, and not counting the rotational synchronization nor lateral allignment.

One thing I know for certain, you will only get one pass

Oh, and I forget to state on previous posts, that I think small 500-1000kg payloads to the Moon aren't very useful, the Progress carries double that and it can barely sustain two men.

John Creighton · 2005-10-08 22:04:05

I think that a few meters will be a very difficult standard to achieve, on any regular basis anyway; space is a very big place, the tether will have an 80,000,000m orbit, and the spaceplane will have a pretty high vertical velocity before and after apogee. For a 100m target envelope, thats around a 99.999875% accuracy, and not counting the rotational synchronization nor lateral allignment.
One thing I know for certain, you will only get one pass
Oh, and I forget to state on previous posts, that I think small 500-1000kg payloads to the Moon aren't very useful, the Progress carries double that and it can barely sustain two men.

I’m curious about these accuracy numbers. I know when flying from earth to mars NASA uses the baseball analogy to describe the accuracy. But as with the journey to mars there will be some fuel used for corrections in the transfer orbit from the gowned to the tether. I understand there is a tradeoff between the mass fraction you can deliver and the amount of fuel you need for corrections. If too much fuel is needed for correction a useful payload will not be delivered if any payload is delivered at all.

So I guess it is not at all clear to me the feasibility of such a proposal. However, I do think that if the x prize is serious about reducing the costs to orbit they must add these accuracy requirements to the suborbital vehicle. Of course that only helps get payload to space but falls far short of the reentry issues that don’t even seem to enter the vocabulary of most x-prize competitors. If these altspace people are serious about reaching orbit there vehicles must be required to withstand reentry? If not why should we ever hope they will be able to utilize such a tether system.

noosfractal · 2005-10-08 22:19:36

As far as the position of the cable John, its all a matter of accuracy; how close is close enough? A suborbital spaceplane will probobly have to extend some hook or something that would pull the payload module off the plane, since the risk of losing the payload if it just "tossed" it to the tether would be too high. I think this will require accuracy within a few meters which is I think is unprecidented given the short amount of time you have to allign for rendezvous, the unknown/disruptive factors of (even rareified) atmospher and unsymmetric gravity, or the curvature of the trajectory. The problem is that there isn't a good way to know the position of either the tether nor the spaceplane with superhigh accuracy over the very short window for rendezvous. Even GPS has a pretty broad refresh rate I imagine.

I finally looked it up. You use Realtime Kinematic (RTK) Differential GPS (DGPS). Within 2 seconds from cold start you have 20cm 3D accuracy, if you have 2 minutes you can get that down to 2cm 3D accuracy. You can be moving at up to 9 km/sec. Once you have a lock you get a 100 ms refresh. You need access to the military frequencies for these figures. Being outside the atmosphere helps enormously. Ionspheric distortion is actually the biggest source of error for ground-based units.

Then, the cable-laying climbers will join together sections only with some of the matching flaps and anneal/irradiate them to induce crosslinking insitu. Additional cable sections would be attached to another set of flaps at the same sight in the same manner, and some flaps reserved for damage replacement.

I may not be understanding, but I think you're suggesting adding weight (extra ribbon layers) without strength (some left unjoined)? And I keep imagining that there is going to be some poor engineer at the bottom of the cable holding their breath every time a new join is retensioned. Even if you get full strength 99% of the time, after 50 joins you've got a 40% cumulative chance of breakage. I wonder how many 9s you'll be able to add for the procedure?

noosfractal · 2005-10-08 22:46:37

As for the timing I am not sure what the window is that the tether will be in a low enough orbit to hit. I am not sure also how many spins of the tether you will have as opportunities to make the catch. I am curious if you only have one opportunity what is the angular velocity of the tether.

If you miss in LEO, you have to wait 2.6 days to try again. If you miss in SO (i.e., abort because you didn't get a good enough lock - not lob your payload and miss) then you can theoretically re-try every 3 hours if your vehicle has that maneuverability.

mboeller · 2005-10-09 02:19:50

Here are e few other SSTO proposals:

microwave thermal thruster :

http://monolith.caltech.edu/Papers/ParkinLauncher.pdf
http://monolith.caltech.edu/Papers/ParkinThruster.pdf

combining an non spinning orbital tether with suborbital SSTO's ( sometimes called SSTT = single stage to tether ):

http://www.affordablespaceflight.com/
http://www.affordablespaceflight.com/howitworks.html
http://spacetethers.com/
http://members.aol.com/Nathan2go/

noosfractal · 2005-10-09 04:16:51

Site comparing laser and microwave launch ...

http://www.islandone.org/LEOBiblio/SPBI115.HTM

In brief: Lasers have ye olde cloud problem. Microwaves don't, but the transmission array must be large (>1 km). Hydrogen propellant may eat the ozone layer.

The rest of the site looks like a good resource as well ...

http://www.islandone.org/LEOBiblio/

http://www.islandone.org/Propulsion/

publiusr · 2005-10-13 10:48:00

It beats me how people fall all over themselves to find excuses to not build bigger rockets when these Rube Goldberg contraptions will cost 10 times as much.

The X-33 ruptured its fuel tanks just sitting there. What do you think is going to happen if you heat supercold tankage?

SpaceNut · 2005-10-17 11:48:17

I know that we have talked about the x43A Scramjet-powered aircraft and of its being cancelled along time ago as it did not fit into the plan. Though the ship has been flown a few times at incredible speeds.

This just in ATK Receives $15 Million NASA Contract to Continue Development of Air Breathing Hypersonic Propulsion

ATK to Build, Test and Analyze Scramjet Engines in Support of Mach 5-20 Flight Operations

So how can Nasa still be funding this?

John Creighton · 2005-10-17 12:24:39

I know that we have talked about the x43A Scramjet-powered aircraft and of its being cancelled along time ago as it did not fit into the plan. Though the ship has been flown a few times at incredible speeds.
This just in ATK Receives $15 Million NASA Contract to Continue Development of Air Breathing Hypersonic Propulsion
ATK to Build, Test and Analyze Scramjet Engines in Support of Mach 5-20 Flight Operations
So how can Nasa still be funding this?

I thought the air force was taking it over. However, we are only talking 15 million dollars here. I am not opposed to NASA spending that much on continuing the research effort.

RobertDyck · 2005-10-17 13:30:47

I know that we have talked about the x43A Scramjet-powered aircraft and of its being cancelled along time ago as it did not fit into the plan. Though the ship has been flown a few times at incredible speeds.
This just in ATK Receives $15 Million NASA Contract to Continue Development of Air Breathing Hypersonic Propulsion
ATK to Build, Test and Analyze Scramjet Engines in Support of Mach 5-20 Flight Operations
So how can Nasa still be funding this?

Yea! Yippie! Yahoo! Perhaps there will be a next generation spacecraft.

Ad Astra · 2005-10-17 19:52:11

To clarify a few points about the X-43:

1) X-43A was not cancelled; it was only budgeted for three flights, which were completed in fall 2004. The program was then set up for the near-term X-43C and far term X-43D and X-43B. These programs were cancelled in early 2004 with the announcement of VSE.

2) X-43C was an Air Force program with a hydrocarbon-powered scramjet. This was cancelled around the same time as NASA's X-43B&D.

3) The technology is certainly worth pursuing, but it has more utility for hypersonic passenger planes than for spaceflight. Seeing as how we lack a supersonic transport, it's premature to be talking about a hypersonic one. Until an economic case can be built, hypersonic propulsion will not see a high priority within NASA.

GCNRevenger · 2005-10-17 20:26:01

As nice as it would be to have a true Scramjet engine, NASA really doesn't need one right now. Considering the pretty bad state of American air travel economically, I doubt there would be a big demand for a super-fast passenger jet. About the only situation I could think of would be for a uber-elite business jet.

Later on, down the road, after we've got a Moon base and a start on a Mars base, then we ought to be thinking about a true space shuttle, almost definatly a two-stage vehicle (barring a fuel breakthrough), where a Scramjet might be ideal for the lower stage.

In the mean time however, the only people that need a Scramjet is the USAF and their hypersonic intercontenental bomber dreams.

Grypd · 2005-10-18 04:31:17

I Know it has been posted elsewhere but this refinement of rockets would make TSTO a lot easier and possibly put SSTO back on the table.

Spacedaily Article on new rocket engines

We have basically come to the end of substantial improvements in the fuel but if we can improve the rocket engine itself and gain improvements that actually allow a rocket engine to last longer but actually give more thrust per amount of fuel used then it does give spaceplane advocates a lot of hope.

GCNRevenger · 2005-10-18 06:11:41

Easier? Well, something like this isn't just nice for an RLV, its a downright nessesity.

However, unless engines better and cheaper then SSME or a pair of J-2S engines can be produced soon, then this program doesn't have much application for NASA any time soon. You've got to have a destination to fly your TSTO vehicle, which is best built with conventional rockets.

Don't let the article fool you though, such an engine isn't going to help much where it needs it most, the specific impulse. The maximum specific impulse of a given engine is limited by the energy liberated per mass of propellant, and NOT the engine. The best an engine can do is fully use this energy, it cannot find more energy then the fuel can produce.

Right now, the SSME has about 453sec of Isp, where the maximum theoretical efficiency of H2/O2 engines is around 550sec: some improvement could be made, but squeezing those last few points of Isp becomes disproportionatly more difficult and less practical. What we need an SSME-sized and efficient engine thats safer, more reliable, and less expensive to operate.

So, while it will make a TSTO true RLV possible , and give the USAF an easier means of building a suborbital space bomber, but the fuel is still the limiting factor to building a reasonably sized SSTO RLV.

RobertDyck · 2005-10-18 08:24:42

I think continuing SCRAM jet and hypersonic aircraft development is very important. That's how you will achieve a SSTO RLV. When I tried to design a reusable space taxi the result was a small shuttle sized for 4 astronauts launched off the back of a 747 with an expendable external tank. That expendable tank means it still isn't fully reusable. It's very hard to achieve full reusability without an improvement in engine technology. SCRAM jets will provide that.

As for not needed for the current path, why spend years and billions of dollars re-inventing the wheel? I've argued for rapid development of a Shuttle Derived Vehicle for heavy lift. GCNRevenger keeps claiming it takes much more development time, practically a develop-from-scratch time table. If it takes that much time and money to develop a simple SDV, then skip the whole thing and move on to something truly new. The Russian Energia is not any better than SDV, it's just cheaper. The current SSME can produce 453 seconds Isp in vacuum, RD-0120 can provide 455 seconds according to the manufacturer KBKhA. GCNRevenger has also argued for simplifying SSME to reduce cost; I've been sceptical you can do so but it turns out the RD-0120 is already simplified. It uses a single two-stage turbo pump and pre-burner instead of separate ones for hydrogen and oxygen. That must be carefully optimized for LOX:fuel proportions, but eliminates half the moving parts and the control system to balance the two systems during flight. The simplified exhaust cone of RD-0120 is already being implemented on SSME with the latest upgrades. Why not just use Energia?

In the "One man one way suicide mission..." thread I estimated cost of Energia. In my telephone conversation with Energia in year 2000, an employee told me NASA had contacted them a few years prior about using Energia for a manned mission to the Moon. They estimated it would cost between $60 million and $100 million to restore infrastructure. A NASA web page with international launch vehicles lists the Energia with the EUS as $120 million per launch in 1994. That tells me when NASA talked to them. Since then roof of building #112 collapsed. Based on Ontario estimates per square foot for constructing a new warehouse, and converting to US dollars the price for a new building that size would be $14.25 million. That's with a standard height roof and not including any internal equipment, but the concrete pad and most of the walls are still there. One of the walls is still intact but 3 walls were damaged down to the clearstory when the roof collapsed. I think using the price of a new warehouse with that floor area but standard height roof would be a fair estimate of the repair cost. Then applying accumulated inflation since 1994 for the higher figure to restore infrastructure plus building repair, we get $150 million. Applying accumulated inflation for per-launch we get $160 million. That means repair plus one launch has a total of $310 million for the first flight. That's half the cost of a single shuttle flight. NASA wants to spend how many billion to develop SDV?

NASA would be better off focussing development on a new lunar spacecraft, and hypersonic technology for a fully reusable space taxi.

SpaceNut · 2005-10-18 13:38:01

Here is another article on scramjet work.
Boeing Completes Successful Boost Test Of HyFly Hypersonic Demonstrator

A Boeing F-15E launched the HyFly vehicle during the test over the U.S. Navy's sea range at the Naval Air Weapons Center – Weapons Division at Pt. Mugu, Calif. The solid rocket booster successfully ignited and accelerated the HyFly to a speed of greater than Mach 3 – three times the speed of sound.
This test was the second of five HyFly flight tests that are scheduled from 2005 to 2007.

The ultimate goals of the program are to demonstrate a vehicle range of 600 nautical miles with a block speed of 4,400 feet per sec, maximum sustainable cruise speed in excess of Mach 6, and the ability to deploy a simulated or surrogate submunition.

Ad Astra · 2005-10-18 18:03:38

I fail to see what's so impressive about HyFly. Air-to-Air missiles routinely travel at Mach 3 and Mach 4.

Grypd · 2005-10-19 09:29:04

I fail to see what's so impressive about HyFly. Air-to-Air missiles routinely travel at Mach 3 and Mach 4.

Except we are not talking mach 3. That was just the basics this missile the HiFly will be expected to fly at mach 6 the next time and the eventual aim is for mach 7 to 8. At that speeds a missile would not even need an explosive ordinance its own speed would be enough to do extreme damage. A near miss would be just as bad as a hit. And the future of air war is that the ability to shoot at a target and hit before it can evade is essential to ensure survivability and controlling that sphere of warfare.

The future of air war is having more and more automation in fighters and bombers and as such the limitations imposed on the aircraft in taking evasive manouveres by having human crew will cease. We already have aircraft flying that can do manoeuveres that impose 20G but a human pilot cannot really take more than 10 G before blacking out even before this his reaction time is extremely debilitated. This is one reason so much money is spent on stealth as a modern aircrafts survivability is essentialy dependant on not being seen. If its seen by radar it will struggle to avoid a missile attack. Unmanned aircraft apart from having less of a radar cross section are able to use the aircrafts full capability and as such can survive by avoidance a hostile missile attack.

If aircraft are able to use there full capabilities then modern missiles like the AAMram and sidewinder would struggle to secure a hit simply being dodged out of the way. It will be essential for the future fighter aircraft to be able to fire its missile and to give as little time as possible for the target to be able to take evasive manouveres. And the HyFly will also cluster its ammunition so that if the target evades the main missile it may well be take out by the shotgun effect of the missiles "other" rounds.

SpaceNut · 2005-10-19 09:59:47

Of course engine research is also been on the back burned and is now coming to the forfront again.
NASA, Air Force Team Up on Next Generation Rocket Engine

The liquid-fuel engine, known as the Integrated Powerhead Demonstrator (IPD), was being tested at NASA’s Stennis Space Center near Bay St. Louis, Mississippi.

The IPD is designed to provide nearly twice as much thrust as current space shuttle engines and to do it safer and more efficiently. It does this by using unique "full flow" preburners that provide more thrust than traditional rocket engines while operating at cooler temperatures.
In current space shuttle engines, a liquid hydrogen fuel and a liquid oxygen oxidizer are both fed into a combustion chamber and ignited. The reaction produces a hot high-pressure gas that is pushed through a nozzle to create thrust.
The IPD works differently. Instead of only send small amounts of fuel and oxidizer to the preburners, the IPD engine sends all of the fuel and all of the oxidizer. This causes the turbopump’s turbines to spin more quickly, producing more thrust. It’s like a pinwheel spinning faster as more wind is blown through its blades.
When completed, the IPD will be capable of generating 250,000-pounds of thrust—double the performance of the most advanced booster engines currently available.

SpaceNut · 2005-10-19 12:47:46

Here we go again ATK To Continue Development of Air Breathing Hypersonic Propulsion For NASA

Alliant Techsystems has received a five-year, $15 million contract from NASA's Aeronautics Research Mission Directorate. Under terms of the contract, ATK will conduct hypersonic aero-propulsion research, test, and evaluation in specially designed wind-tunnels that replicate the atmospheric conditions aircraft experience if traveling at speeds up to Mach 20.

publiusr · 2005-10-21 15:24:44

Something else to go atop The Stick.

SpaceNut · 2005-12-15 13:53:05

We have seen the scramjet technology over the last few trips though the developement come with some success in the x43a that was built by ATK.

Now comes the Darpa version using JP-10 fuel or jet fuel with a top speed of mach 5.5.

ATK, DARPA and ONR Achieve First-Ever Flight Test of a Scramjet Powered by Liquid Hydrocarbon Fuel

The launch and flight test were part of the Freeflight Atmospheric Scramjet Test Technique (FASTT) program sponsored by DARPA and Office of Naval Research.
The FASTT vehicle was approximately 106" long and 11" in diameter. It integrated a Scramjet engine into a missile configuration. After separating from its booster rocket at more than 60,000 feet, the Scramjet engine ignited and propelled the vehicle at approximately 5,300 feet per second -- or Mach 5.5. Using JP-10 fuel, the Scramjet flew for at least 15 seconds while critical engineering data was captured via on-board sensors and tracking radars.
The FASTT program, ATK's Boost-to-Cruise initiative is developing hypersonic missile technologies capable of sustained flight at Mach 5 and delivering payloads on target more than 600 nautical miles down range.

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#101 2005-10-08 21:09:15

Re: Realistic solutions to the difficulties of SSTO?

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#104 2005-10-08 22:46:37

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#105 2005-10-09 02:19:50

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#106 2005-10-09 04:16:51

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#107 2005-10-13 10:48:00

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#108 2005-10-17 11:48:17

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#109 2005-10-17 12:24:39

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#110 2005-10-17 13:30:47

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#111 2005-10-17 19:52:11

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#112 2005-10-17 20:26:01

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#113 2005-10-18 04:31:17

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#114 2005-10-18 06:11:41

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#115 2005-10-18 08:24:42

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#116 2005-10-18 13:38:01

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#117 2005-10-18 18:03:38

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#118 2005-10-19 09:29:04

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#119 2005-10-19 09:59:47

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#120 2005-10-19 12:47:46

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#121 2005-10-21 15:24:44

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#122 2005-12-15 13:53:05

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