New Mars Forums

So you think the MiniMag Orion would be an ideal interplanetary drive, or?

Why do you see problems with the control of the orbiter after release from an 747 or An-225? The Space Shuttle was launched from the back of an 747 already. So I don't think this will be difficult.

On the other side, I agree about the problems with high-speed separation. IMHO hypersonic separation will be much more difficult. The spacebus concept for example avoided the problems with hypersonic separation with an altered flightpath. They designed the system so that the carrier aircraft would pull up to AFAIR 70-80° before release using rocket power. Therefore the dynamic pressure would be very low during separation.

One further remark to the low-speed carrier aircraft. According to t/Space and Molniya you can gain up to 570 m/sec due to the speed and reduced drag. So it could be worth the cost. When you use an really hugh carrier aircraft like this one [ http://www.buran.ru/htm/heracles.htm ] you should even be able to launch rather big payloads that way.

information about MAKS: http://www.buran.ru/htm/molniya6.htm
main page: http://www.buran.ru/htm/molniya.htm

Well;

I have found an interessting answer to the SSTO debate just yesterday.

Look here: http://www.astronautix.com/lvs/saturnvb.htm.

This is an 1.5 stage Saturn5. Only the booster engines with structure are recovered. But remember this is technology from the 1960s and uses only kerosin as fuel. So the system is imho rather impressive with an payload fraction of nearly 1%.

I wonder now if the original Atlas with 4 booster engines would have been able to reach LEO as an 1.5 stage system without upper stage too.

Oh, if you need more payload use an upper stage together with the 1.5 stage Saturn5 :  http://www.astronautix.com/lvs/saturnvc.htm

Hi Dook;

maybe this is something for your vehicle:

http://www.amminex.com/index_files/Page344.htm

Another article about this material:  http://www.physorg.com/news5890.html

No problem

OK, so you talk about the far future. I'm more concerned with the near future, cause NASA and ESA always seem to seek to master the problems of the far future and overlook the problems of the near future and so finally we have to stick to the same old V4-style rockets for ever.

So I try to figure out how to get into orbit ("LEO") now using available or nearly available technology. Therefore I reject fancy technology like scramjets which need; as I have heard after the last X43a flight " a hundred years to develop".

Ouch!
Well yes, this would improve the ISP but IMHO on the other side the vehicle would have to withstand even greater stress due to the depressed trajectory to get most of the acceleration within the atmosphere.

Well; IMHO your 1/4 - 1/3 more density seems to be a little bit much for Slush-Hydrogen. I have heard only two figures here, one being 10% from an NASA PDF and the other being more in line with your figures indicates AFAIR 85kg/m³ instead of the normal 70kg/m³, which translates to an improvement of ~21% in density.

Or do you mean "gelled Hydrogen"; using CH4 or even Al in the H2 to densify the fuel. Here the best seems to be up to 60% Al within the H2 to reach an density of ~170Kg/m³. Unfortunately the overall performance seems to be the same or even worse than with pure H2/O2, which I cannot understand but that's the conclusion of the http://gltrs.grc.nasa.gov/reports/1998/ … 206306.pdf from the NASA.

Have you a link for this. I don't know much about ceramics.

OK, you are basically talking about the MIPCC system as an pure plug on for existing turbojet engines. Well RTA will/wants to improve this even further and will/should result in turbojets being able to work at up to M4 - M4.5.
Other's like ESA-SART in Germany have studied the MIPCC approach too (but only PDF's so far)  using water, LOX or CH4 to augment the turbojets used in the first stage.

Maybe this PDF is something for you: http://hypersonic2002.aaaf.asso.fr/pape … 7_5148.PDF

So finally we are not so far apart. Well I don't like Sänger too much. It's an Highend-System with a lot of failure modes built in by design. The M6.8 ramjet/turbojet Booster is really complex and the Orbiter is far too small to have any useful payload (manned only ~3to) so every small weight gain during development would have wiped out large chunks of payload.
Because of that I "fell in love" with the SpaceJet study from the 1970's. The booster is rather simple and very small with only (then) off the self SST-derived turbojets, and the Orbiter/Shuttle would only use available technology already developed for the Space Shuttle. All this technology resulted in an remarkable system with an TOW incl. Booster of around 2.600.000Ib and an payload of 65.000Ib.
Well today such an big system is no longer possible due to the missing link, the SST. So we would have to do it with only fighter type engines with "only" 35000Ib. But despite this, IMHO CFK and advanced technology already in use would result in an fairly good shuttle with maybe 10000-20000Ib payload. So with present day technology using the "correct" system approach you could build an HTHL TSTO shuttle with an very good payload fraction. IMHO even with scramjets you cannot produce an better system with an higher payload fraction. 

NASA needs always a lot of money to do an simple job...unfortunately. This is not because the people are stupid or something like that, but because of the "system". So I don't expect something from NASA at all. The last and final clue for that was the Venture-Star-debacle. NASA back then didn't choose the "best" system for the job but the most complex system for the job. So the failure was built in from the beginning. This was IMHO an political decision and so technology were on the backseat.
So you will ask how I define the "best" system. Well for me the "http://www.spacefuture.com/archive/single_stage_to_orbit_vertical_takeoff_and_landing_concept_technology_challenges.shtml]Millennium Express" from General Dynamics would have been the best system cause it was the simplest system to do the job. VTVL + base first reentry + axis-symmetrical body would have resulted in the lightest vehicle with the highest payload.
But NASA decided otherwise. They wanted an Shuttle II and they got an Shuttle II. If you compare the old articles about the SSTO Shuttle II from the 90's with the final Venture Star then you can see that it is an close copy ( The Venture Star has only a more pronounced conic/wedge shape ). They even demanded that the Venture Star was man-rated with the capability to dock to the ISS....tsss and this from an first-gen SSTO barely able to even reach orbit. What about OMV? What about escape-rockets? How about using the rocket at first only as an "freight liner"?

Well, all the scramjet TSTO's studied at the moment have an max. payload of around 10MT, not more. This vehicles already approach the practical TOW-limit for HTHL-vehicles. For example look at this study: http://www.ssdl.gatech.edu/main/ssdl_pa … .pdf]Aztec: A TSTO Hypersonic Vehicle Concept

The TOW of this study is already at 314to this early in the development cycle. So you can expect that finally it will come in at maybe 380-450to (pure guess) and this is already close to the max. possible with HTHL-vehicles.
You can also see how slow the acceleration of the scramjet is compared to the ramjet. From M2.5-M6 =80sec  ; From M6-M8 =180sec. Also the ISP of the scramjet is not really great compared with the rocket(!). Only twice that of the rocket at M8. The thrust is even worse at M8 (maybe 1/8 of the rocket engine).

Also, only an 5x-10x reduction in payload prices per Ib. Why not more? If SpaceX can bring the FalconV to market this kerosene-LOX TSTO with simple rocket engines will bring down the cost toward US $900/Ib and this is already at least 5x lower than the cost of the Shuttle. 

So I don't think that we have to wait for exotic technology like scramjets to bring us "the future" but we can make it today with clever engineering and the "best" system.

PS.: here is the link to the comparison between PDE-rocket and air augmented systems. The weight of the pure-PDE-system was the lowest!:

http://www.ssdl.gatech.edu/main/ssdl_pa … 9-2354.pdf

Scramjets are useless for any orbital vehicle. Get over it. I have seen only one (!) scramjet based SSTO study which made sense compared to an pure rocket based SSTO and this vehicle used AFAIR acetylene instead of H2 and used the atmospheric heating to break the acetylene into H2+CO. This cooled the vehicle as good as pure H2 but due to the far higher density of acetylene and rather good ISP of the broken down acetylene the payload was reasonable.

Otherwise scramjet are useless for SSTO's.

How do you come to the conclusion that scramjet vehicles are easier to maintain? The opposite is true cause this vehicles have an far higher complexity than simpler rocket vehicles. Also the development costs are higher cause the empty weight is higher (which is an clear indicator for development cost) and the complexity of the structure and the systems is far higher compared to an rocket RLV.

Yes...and? I said above that I prefer other fuels than H2 for TSTO's cause here the ISP of H2 is not needed and using fuels with higher density reduces the vehicle size, weight and therefore development cost.
The all-rocket TSTO would be an pure VTVL-vehicle too, cause here wings are for wimps.

This is the option everyone tries. But than you increase the empty weight of both stages ( booster >>; shuttle > ) due to the higher complexity and therefore the development costs are higher. Also with more complex systems the development costs increase as well. If you increase the staging speed you will have to streamline the shuttle even more too and so the structure will weigh more too.

IMHO the SpaceJet-study is rather nice cause here you have two rather simple vehicles. A very compact booster using off the shelf turbojet engines and an pure rocket shuttle on top. The only drawback I see is that the available turbojet engines restrict the weight of the shuttle and so the shuttle has to use H2.

Not at all!  Read the links and maybe the PDF's of the HASTOL-study see:

http://www.niac.usra.edu]www.niac.usra.edu/

http://www.niac.usra.edu/studies/study. … 0.0]HASTOL Phase I

http://www.niac.usra.edu/studies/study. … 0.0]HASTOL Phase II

Well,

After reading most of the thread, I want to give you my opinion about the subject too.

IMHO SSTO is not possible due to the needed high fuel:structure ratio of around 10:1. Even then the payload is rather small, so you need a really large SSTO to overcome the problems and have an useful payload using the favorable scaling factors.

At the moment I prefer more than one approach:

1; pure rocket TSTO
2; Turbojet assisted SSTO
3; Tether assisted SSTO.

1; Pure rocket TSTO’s are well known so I will only briefly mention it here. Most people tend to think that “the highest ISP wins” and so they favor only H2/O2 as an fuel. IMHO this is not true for TSTO’s. Here Kerosin or other denser fuels (see http://www.dunnspace.com/alternate_ssto … lants.htm) work far better despite the far lower ISP.

If you need to stick to H2/O2 then use the engine which gives the most for the bang….PDE’s.
According to an older paper from http://www.ssdl.gatech.edu/main/publica … lications/  (sorry no direct link) which compared an RBCC-SSTO with an PDE-SSTO; PDE’S have an higher efficiency than normal rockets and can reach around 492.5 sec! Well AFAIR that’s the figure they used in the comparison. By the way, the pure rocket PDE proved to be superior to the RBCC-based SSTO regarding payload fraction and TOW. :)

2; At the moment this is my favourite cause in the last APR V5N5 (  http://www.up-ship.com/apr/v5n5.htm ) I have read an article about the “SpaceJet” developed in the lat 1970`s at Langley.
The HTHL-Spacejet uses an Turbojet-Booster stage together with an large Shuttle on top. The Booster accelerates the Shuttle to M3.5 and 50-60.000 feet (not sure at the moment). Due to this the Shuttle can have an mass fraction of around 0.20 cause it needs only around 7400m/s instead of the ~9350m/sec for an pure SSTO  (based on the mass-calculations in the article). 

I like this system cause with this approach you can get rid of the large booster aircrafts used for other HTHL-TSTO’s. The booster here is very small as can be seen in the link above.

Advantage:   
nearly SSTO operations with only an small and “simple” Booster.
Shuttle with only one type of engine
Booster with commercial Turbojets possible (military engines)
High performance ( 65000Ib payload with only 2.600.000Ib TOW including booster)

Disadvantage:   
The Shuttle needs large and heavy wings to lift itself and the booster from the Runway, but as an small bonus this reduces the reentry heating .
IMHO only suitable for H2/O2, otherwise the mass fraction would be too low.   
Needs a large amount of Turbojets if the Shuttle is heavy. For an small shuttle with around 180to you need already 4  35000 Ib turbojets found in modern combat aircraft. If your shuttle is as large as the one in the Langley-study then you need 8 turbojets with 85000 Ib each!

IMHO this system can be improved very easily compared to the old study done at Langley.
The Turbojets could be improved with the MIPCC-system in development for RASCAL and the SSME-engines could be replaced with rocket engines with an higher ISP ( 465-475 sec) and maybe use  an aerospike nozzle (if this is needed at all); or even with the high performance PDE-engines in development today.

The structure could be improved also cause they used pure 1970’s style systems and materials in the study (according to the article). So an heavy dose of CFK should lower the empty weight quite a lot.

3; tether augmented rocket.

Well I will not cover this at all, cause you can find a lot of information’s about this system on the web an it was already discussed here :

http://www.affordablespaceflight.com/ho … /home.html
http://www.spacetethers.com/]http://www … thers.com/
http://members.aol.com/Nathan2go/SPELEV … SPELEV.HTM

4; well you can also combine 2 and 3 to improve the system further. :)

Hope you like it.

Manfred

Well,

at first I was not sure if fuel-cells are an good idea or not, but after reading the following PDF's I'm sure that fuel cells are not the way to go. They waste far too much energy (3/4) to be useful.

Links:

http://www.evworld.com/library/carbdeto … detour.pdf
http://www.ilea.org/downloads/MazzaHamm … schlag.pdf
http://www.modenergy.com/BEVs%20vs%20FC … 120603.pdf

Why do You think that we need an larger launcher than an Falcon V?  IMHO the ~ 6000 Kg into LEO should be good enough for an decent capsule.

Well at least Gary Hudson from HMX thought back in 2000 that his company could build an reuseable capsule with 4 pax. max. for around US $145 Mio. The complete development cost + 4 flights would have been around US $145Mio if I understand the PDF correct. But this would have been unmanned capsules at first with only an light load of ~1000Ib. One launch atop an refurbished Titan2 would have cost around US $ 35 Mio

Link: http://www.hmx.com/AAS_Briefing_Edited. … Edited.pdf [5.5 MB]

Interview: http://www.hobbyspace.com/AAdmin/archiv … ...on.html

It should be possible to "surf" on mars. NASA already works on something like that, it's called Tumbleweed-Rover :

http://www.jpl.nasa.gov/news/features.c … eature=486

They have an lot of PDF's online. Search for "Tumbleweed" And "Rover"