Author Topic: Reusable single stage spacecraft  (Read 18396 times)

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25222
  • Likes Given: 12114
Re: Reusable single stage spacecraft
« Reply #40 on: 01/21/2017 05:23 am »
Better than scifi... Airplanes usually don't carry a payload equal to their dry mass.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Patchouli

  • Senior Member
  • *****
  • Posts: 4490
  • Liked: 253
  • Likes Given: 457
Re: Reusable single stage spacecraft
« Reply #41 on: 01/21/2017 10:30 pm »
I seem to remember years ago that an article on NK claimed that the Delta IV CBC had the ability to orbit several hundred kilograms as an expendable SSTO.

The S-IVB could could reach orbit with a payload of 10,0000 lbs if it was fitted with a SSME.

Recovery supposedly would cost about 6500lbs leaving around 4,000lbs for payload.

Ironically if Orion was the mass of Dragon  the SSME Ares I would not have even needed an SRB first stage.

If you put six SSMEs on a shuttle ET it not only could it fly into orbit but it also could also carry a 30 ton payload.

http://www.spacefuture.com/archive/a_single_stage_to_orbit_thought_experiment.shtml

http://www.thespacerace.com/forum/index.php?topic=2909.0

A single SSME SSTO built with modern materials in theory could actually be a fairly practical LV for Delta II class payloads.



« Last Edit: 01/21/2017 10:40 pm by Patchouli »

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25222
  • Likes Given: 12114
Re: Reusable single stage spacecraft
« Reply #42 on: 01/21/2017 11:12 pm »
Or a kerolox engined SSTO. I was just thinking about one based off of the Rd-181. They're less than $10m a pop. Just need to build balloon tanks, and you're in business.
« Last Edit: 01/21/2017 11:13 pm by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline HMXHMX

  • Full Member
  • ****
  • Posts: 1705
  • Liked: 2181
  • Likes Given: 659
Re: Reusable single stage spacecraft
« Reply #43 on: 01/21/2017 11:25 pm »
I seem to remember years ago that an article on NK claimed that the Delta IV CBC had the ability to orbit several hundred kilograms as an expendable SSTO.

And here we are still talking about the feasibility more than 30 years later.  I thought that paper of mine was forgotten.

 ;)

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25222
  • Likes Given: 12114
Re: Reusable single stage spacecraft
« Reply #44 on: 01/22/2017 02:56 am »
If you could get SpaceX to sell you a Merlin 1D for $1-2 million (slightly used), you could build a decent expendable smallest SSTO with it. It'd be cheap, too. And could probably place 2 tons in LEO with an upper stage.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Patchouli

  • Senior Member
  • *****
  • Posts: 4490
  • Liked: 253
  • Likes Given: 457
Re: Reusable single stage spacecraft
« Reply #45 on: 01/22/2017 05:06 pm »
Another idea use a TAN nozzle with the SSME in the case if it's a small space plane design like the Rockwell X33 the wings can may also be able to double as the RP-1 fuel tanks vs being dead weight on the way up.

« Last Edit: 01/22/2017 06:44 pm by Patchouli »

Offline Proponent

  • Senior Member
  • *****
  • Posts: 7276
  • Liked: 2781
  • Likes Given: 1461
Re: Reusable single stage spacecraft
« Reply #46 on: 01/22/2017 05:58 pm »
I seem to remember years ago that an article on NK claimed that the Delta IV CBC had the ability to orbit several hundred kilograms as an expendable SSTO.

And here we are still talking about the feasibility more than 30 years later.  I thought that paper of mine was forgotten.

Any chance we could get a link to the NK article or, better, still, the paper itself?

Offline Patchouli

  • Senior Member
  • *****
  • Posts: 4490
  • Liked: 253
  • Likes Given: 457
Re: Reusable single stage spacecraft
« Reply #47 on: 01/22/2017 06:51 pm »
Yah I'd like to see it too.
 I also read about an expendable SSTO that used a single pressure fed liquid hydrogen engine.
http://www.astronautix.com/a/aquarius.html
« Last Edit: 01/22/2017 06:57 pm by Patchouli »

Offline HMXHMX

  • Full Member
  • ****
  • Posts: 1705
  • Liked: 2181
  • Likes Given: 659
Re: Reusable single stage spacecraft
« Reply #48 on: 01/22/2017 09:32 pm »
I seem to remember years ago that an article on NK claimed that the Delta IV CBC had the ability to orbit several hundred kilograms as an expendable SSTO.

And here we are still talking about the feasibility more than 30 years later.  I thought that paper of mine was forgotten.

Any chance we could get a link to the NK article or, better, still, the paper itself?

Sorry; I mistakenly replied to douglas100's post and not Patchouli's which was reply #41.  I was commenting on my SSTO Thought Experiment paper.  I've never seen the Delta IV article.

Offline pippin

  • Regular
  • Senior Member
  • *****
  • Posts: 2575
  • Liked: 312
  • Likes Given: 45
Re: Reusable single stage spacecraft
« Reply #49 on: 01/22/2017 10:08 pm »
#42

Offline Proponent

  • Senior Member
  • *****
  • Posts: 7276
  • Liked: 2781
  • Likes Given: 1461
Re: Reusable single stage spacecraft
« Reply #50 on: 01/23/2017 02:09 pm »
HMXHX & pippin:  Thanks.  I see was being rather myopic in not noticing the links in Patchouli's post.

EDIT:  Corrected spelling of "Patchouli"
« Last Edit: 05/08/2017 07:33 pm by Proponent »

Offline DarkenedOne

  • Full Member
  • ****
  • Posts: 955
  • Liked: 58
  • Likes Given: 9
Re: Reusable single stage spacecraft
« Reply #51 on: 01/24/2017 03:13 pm »
Correction: the latest version of Merlin 1D has a thrust to weight ratio of about 200 due to thrust increases.

And if we're talking state of the art, that rules out every nuclear rocket.

Anyway, I was explicitly talking about what is possible, not just what we can do today. My point is that you can make huge improvements to mass fraction, so the fact that chemical has lower Isp does NOT mean that what I described can't be done.

Merlin 1D has performance that once would've been ridiculed as absurd and beyond the state of the art as well.

Alright lets see what falcon 9 rocket with a mass faction of 150 would look like with the Merlin 1D assuming the mass faction of 200.  According to wikipedia the mass of the Merlin D is 630, a thrust of 845 metric tones, and a mass of 630 kg.  Nine Merlin 1Ds would weigh 5670 and have be able to lift 1134000 kg.  For the entire rocket to achieve a mass ratio of 150 the dry mass of the rocket could therefore not exceed 7560 kg.  Subtracting the total weight minus the weight of the engines you get 1890 kg for the rest of the rocket.  The tanks, the avionics, the landing gear, the heat shield, the payload fairing, and the payload itself would have to weigh less than a Ford Edge.

I cannot prove that it is impossible.  There is no law of physics that says it cannot be done, but it is easy to prove that it is not feasible as it is far beyond the state of the art. 

As far as nuclear thermal and other nuclear technologies we cannot necessarily say that they can do better, but we do know that the limitations on what the technology can do are far higher.  If you just took the prototypes for nuclear thermal engines that were tested in the 60s and updated them with modern materials you would get likely get significantly higher T/W. 

In my opinion SSTO spaceships (not RLVs) are much more achievable with advanced nuclear thermal than with chemical rockets with insane mass ratios.

Alright lets see what a rocket with a mass faction of 150 would look like with the Merlin 1D assuming the mass faction of 200.  According to wik, a thrust of 845 metric tones, and a mass of 630 kg.  Nine Merlin 1Ds would weigh 5670 and have a thrust of 7605000 kg.  For the entire rocket to achieve a mass ratio of 150 the   

Offline DarkenedOne

  • Full Member
  • ****
  • Posts: 955
  • Liked: 58
  • Likes Given: 9
Re: Reusable single stage spacecraft
« Reply #52 on: 01/24/2017 03:20 pm »
And the theoretical basis for why NTR is fundamentally limited is due to the propellant, hydrogen. It has terrible density. And there simply is no possible material that could make the nuclear lightbulb work.

First of all, density is irrelevant.  Your spacecraft could be the size of a blimp.
Density does matter.  A vehicle the size of a blimp will suffer large drag losses.  Any given mass fraction will be more difficult to achieve with a propellant of lower density, because the tanks, the plumbing and the engines will all need to be bigger.  And if we're talking hydrogen, insulation needs to be factored in too.  John Whitehead wrote a nice paper (attached to this post) about SSTO mass budgets that illustrates the drawbacks of hydrogen (albeit lox-hydrogen, rather than hydrogen-NTR).

Spacecraft travel through the atmosphere very briefly.  The reason why they start by traveling straight up is to get out of it as quickly as possible. 

Offline DarkenedOne

  • Full Member
  • ****
  • Posts: 955
  • Liked: 58
  • Likes Given: 9
Re: Reusable single stage spacecraft
« Reply #53 on: 01/24/2017 04:02 pm »
I seem to remember years ago that an article on NK claimed that the Delta IV CBC had the ability to orbit several hundred kilograms as an expendable SSTO.

And here we are still talking about the feasibility more than 30 years later.  I thought that paper of mine was forgotten.

 ;)

I think everyone agrees that you can build a single stage to orbit expendable chemical LV.  The real question is should it be done.  Without much better mass factions on LVs than you probably will probably continue to see TSTO launch systems.  Reusability of course makes it much harder because all the components that are needed to make a system reusable add weight and reduce the mass ratio.  Given that first stage reusability is just start to come about, I think you can assume that reusable SSTO chemical launch systems are a bit far off. 

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25222
  • Likes Given: 12114
Re: Reusable single stage spacecraft
« Reply #54 on: 01/24/2017 05:20 pm »
Correction: the latest version of Merlin 1D has a thrust to weight ratio of about 200 due to thrust increases.

And if we're talking state of the art, that rules out every nuclear rocket.

Anyway, I was explicitly talking about what is possible, not just what we can do today. My point is that you can make huge improvements to mass fraction, so the fact that chemical has lower Isp does NOT mean that what I described can't be done.

Merlin 1D has performance that once would've been ridiculed as absurd and beyond the state of the art as well.

Alright lets see what falcon 9 rocket with a mass faction of 150 would look like with the Merlin 1D assuming the mass faction of 200.  According to wikipedia the mass of the Merlin D is 630, a thrust of 845 metric tones, and a mass of 630 kg.  Nine Merlin 1Ds would weigh 5670 and have be able to lift 1134000 kg.  For the entire rocket to achieve a mass ratio of 150 the dry mass of the rocket could therefore not exceed 7560 kg.  Subtracting the total weight minus the weight of the engines you get 1890 kg for the rest of the rocket.  The tanks, the avionics, the landing gear, the heat shield, the payload fairing, and the payload itself would have to weigh less than a Ford Edge.

I cannot prove that it is impossible.  There is no law of physics that says it cannot be done, but it is easy to prove that it is not feasible as it is far beyond the state of the art. 

As far as nuclear thermal and other nuclear technologies we cannot necessarily say that they can do better, but we do know that the limitations on what the technology can do are far higher.  If you just took the prototypes for nuclear thermal engines that were tested in the 60s and updated them with modern materials you would get likely get significantly higher T/W. 

In my opinion SSTO spaceships (not RLVs) are much more achievable with advanced nuclear thermal than with chemical rockets with insane mass ratios.

Alright lets see what a rocket with a mass faction of 150 would look like with the Merlin 1D assuming the mass faction of 200.  According to wik, a thrust of 845 metric tones, and a mass of 630 kg.  Nine Merlin 1Ds would weigh 5670 and have a thrust of 7605000 kg.  For the entire rocket to achieve a mass ratio of 150 the

I was referring to what's possible, not what is current state of the art. I thought that was clear?
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25222
  • Likes Given: 12114
Re: Reusable single stage spacecraft
« Reply #55 on: 01/24/2017 05:22 pm »
I have some ideas about how one could actually achieve such a mass fraction. But again, I was talking about what is possible, not what is state of the art.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Toast

Re: Reusable single stage spacecraft
« Reply #56 on: 01/24/2017 06:55 pm »
If you just took the prototypes for nuclear thermal engines that were tested in the 60s and updated them with modern materials you would get likely get significantly higher T/W.

I don't think so, in large part because we've already looked into it--in the late 80's and early 90's, project TIMBERWIND took a look at NERVA and tried to optimize it, and the best they could do was a TWR of 30:1*. We could probably push that a little bit higher, but to make it viable for a SSTO we'd need to push it a lot higher. Not to mention the political infeasibility of NTR's, especially as a first stage.

EDIT:
*And this may be highly optimistic--I don't think they ever obtained real-world thrust on this magnitude, but I could be wrong.
« Last Edit: 01/24/2017 07:07 pm by Toast »

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 10346
  • Everyplaceelse
  • Liked: 2426
  • Likes Given: 13596
Re: Reusable single stage spacecraft
« Reply #57 on: 01/24/2017 07:24 pm »

As far as nuclear thermal and other nuclear technologies we cannot necessarily say that they can do better, but we do know that the limitations on what the technology can do are far higher.  If you just took the prototypes for nuclear thermal engines that were tested in the 60s and updated them with modern materials you would get likely get significantly higher T/W. 
Opening up my copy of Sutton 4th Ed the Nerva Objectives were
Thrust 75Klb
Weight 14Klb
Pch 450psia
Nozzle area ratio 100:1
Isp 825sec.

That Thrust and weight gives a T/W of 5.35:1.
I'll note the SSME with a Pch about 5x bigger did not manage an expansion ratio above 77:1.
Quote
In my opinion SSTO spaceships (not RLVs) are much more achievable with advanced nuclear thermal than with chemical rockets with insane mass ratios.
Running the rocket equ with orbital velocity including losses to 9200m/s and the Nerva design (I'll keep the Isp of 825sec, even though a nozzle with that expansion ratio is unlikely with such a chamber pressure).  That means roughly 32% of the GTOW can be structure, including your engine.
Quote

Alright lets see what a rocket with a mass faction of 150 would look like with the Merlin 1D assuming the mass faction of 200.  According to wik, a thrust of 845 metric tones, and a mass of 630 kg.  Nine Merlin 1Ds would weigh 5670 and have a thrust of 7605000 kg.  For the entire rocket to achieve a mass ratio of 150 the
Using an average value of 320secs for a Merlin 1d that needs a mass ratio of 18 or roughly 5.35% of GTOW for the whole of the structure and payload.

I've no idea where you get a mass fraction of 150. You seem to be confusing it with T/W ratio.

BTW SSTO has acquired a lot of subconscious assumptions about it. People forget to mention they are only talking about VTOL SSTO's and extrapolating results from that.

If you choose to do something in the hardest way possible you should not be surprised if it turns out to be hard to do.  :(
« Last Edit: 01/27/2017 02:05 pm by john smith 19 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25222
  • Likes Given: 12114
Re: Reusable single stage spacecraft
« Reply #58 on: 01/24/2017 07:33 pm »
He got it from me. I suggested it is possible, and it is. Well beyond the current state of the art but still possible.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline DarkenedOne

  • Full Member
  • ****
  • Posts: 955
  • Liked: 58
  • Likes Given: 9
Re: Reusable single stage spacecraft
« Reply #59 on: 01/24/2017 10:24 pm »
If you just took the prototypes for nuclear thermal engines that were tested in the 60s and updated them with modern materials you would get likely get significantly higher T/W.

I don't think so, in large part because we've already looked into it--in the late 80's and early 90's, project TIMBERWIND took a look at NERVA and tried to optimize it, and the best they could do was a TWR of 30:1*. We could probably push that a little bit higher, but to make it viable for a SSTO we'd need to push it a lot higher. Not to mention the political infeasibility of NTR's, especially as a first stage.

EDIT:
*And this may be highly optimistic--I don't think they ever obtained real-world thrust on this magnitude, but I could be wrong.

Remember the Delta IV booster we were talking about that could supposedly be an expendable SSTO.  The RS-68 has a T/W of just 45, which is OK because according to the rocket equation you only need a mass ratio of 11.2 if when your ISP is 414.  That is just 50% better.  A nuclear thermal rocket with an ISP of 800 only needs a mass ratio of 3.5 to get to orbit.  If you have a NTR with T/W of 30 your doing pretty well.  If you assume the rest of the rocket has comparable weight than an SSTO with such an engine would be able to make it to orbit with plenty of payload. 

Of course you are right about the political challenges particularly in western countries however I think the real reason why NTR development ceased is that expendable NTR just do not make any sense.  Chemical engines are much cheaper if you intend to just throw them away.  With an NTR each flight will consume only a small portion of the nuclear fuel. 

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
1