The airship provides little benefit. launch velocity is more important than launch altitude
SAAOPL is designed to replace expandable launch system mostly using existing technologies. While SpaceX is taking VTVL approach, SAAOPL is based on HTHL but combined with stratospheric launch.
Aye, the only meaningful advantage of launching from altitude is the ability to use near-vacuum-optimized engines from the start
Quote from: sevenperforce on 04/04/2017 05:29 pmAye, the only meaningful advantage of launching from altitude is the ability to use near-vacuum-optimized engines from the startAre there any advantages to having a much more benign aerodynamic environment (e.g., far lower max Q)? Would that allow a lighter structure for the actual vehicle, and thus better performance? If one doesn't have to worry about dense atmosphere, and thus streamlining, does that allow different form factors for the vehicle rather than a slender tube?
Short launch cycle: the next mission can be ready in 8 hours from the starting point of current mission, if using the same system.
The airship round trip flight is going take more than that
Best quote I've heard lately is "Fall in love with your customer's problems, not your own solutions."
whether you launch the rocket from an altitude of 0km, or of 30km, it still has to go from 0km/s to 8km/s in velocity.
e.g. all the equipment you need to keep the liquid oxygen liquid is heavy
" it seems like...you're high up there and so surely that's good and you're going at...0.7 or 0.8 Mach and you've got some speed and altitude, you can use a higher expansion ratio on the nozzle, doesn't all that add up to a meaningful improvement in payload to orbit?"The answer is no, it does not, unfortunately. It's quite a small improvement. It's maybe a 5% improvement in payload to orbit...and then you've got this humungous plane airship to deal with. Which is just like having a stage. From SpaceX's standpoint, would it make more sense to have a gigantic plane airship or to increase the size of the first stage by five percent? Uhh, I'll take option two."
There was a Q&A at Aviation week some while back and this https://en.wikipedia.org/wiki/Air_launch_to_orbit was Elon Musk's response to another air launch concept involving a plane, but it could equally well apply to your platform:
Maybe replace the airship with this:https://www.nasa.gov/centers/armstrong/Features/TGALS_first_flight.html
Quote from: mikelepage on 04/06/2017 05:39 amThere was a Q&A at Aviation week some while back and this https://en.wikipedia.org/wiki/Air_launch_to_orbit was Elon Musk's response to another air launch concept involving a plane, but it could equally well apply to your platform:I actually shared Musk's view towards conventional air-launch approaches. In the AQ section of the following page, brief comments on two conventional air launch by plane and by balloon approaches have already been included.http://saaopl.net/index.php/features/One major reason that two conventional air launch are not promising, and yet to be mentioned by Musk, is that none of them are reusable, or neither of them can be an ideal candidate to develop a reusable launch system.
Quote from: saaopl on 04/10/2017 11:26 pmI actually shared Musk's view towards conventional air-launch approaches. In the AQ section of the following page, brief comments on two conventional air launch by plane and by balloon approaches have already been included.http://saaopl.net/index.php/features/One major reason that two conventional air launch are not promising, and yet to be mentioned by Musk, is that none of them are reusable, or neither of them can be an ideal candidate to develop a reusable launch system.Actually, if you'll read the quote above from Musk it doesn't mention reusability at all. Musk's point is valid even if you have full reusability.Musk's point is that an aircraft-launched system essentially makes the aircraft an additional stage. You have all the cost and complexity of an additional stage, but it's an additional stage that gives you much less benefit than a rocket stage. The same is true for an airship-assisted launch system -- the airship is an additional stage, but one that gives you much less benefit than a rocket first stage.You didn't address this point in your reply.
I actually shared Musk's view towards conventional air-launch approaches. In the AQ section of the following page, brief comments on two conventional air launch by plane and by balloon approaches have already been included.http://saaopl.net/index.php/features/One major reason that two conventional air launch are not promising, and yet to be mentioned by Musk, is that none of them are reusable, or neither of them can be an ideal candidate to develop a reusable launch system.
Quote from: ChrisWilson68 on 04/13/2017 09:32 pmQuote from: saaopl on 04/10/2017 11:26 pmI actually shared Musk's view towards conventional air-launch approaches. In the AQ section of the following page, brief comments on two conventional air launch by plane and by balloon approaches have already been included.http://saaopl.net/index.php/features/One major reason that two conventional air launch are not promising, and yet to be mentioned by Musk, is that none of them are reusable, or neither of them can be an ideal candidate to develop a reusable launch system.Actually, if you'll read the quote above from Musk it doesn't mention reusability at all. Musk's point is valid even if you have full reusability.Musk's point is that an aircraft-launched system essentially makes the aircraft an additional stage. You have all the cost and complexity of an additional stage, but it's an additional stage that gives you much less benefit than a rocket stage. The same is true for an airship-assisted launch system -- the airship is an additional stage, but one that gives you much less benefit than a rocket first stage.You didn't address this point in your reply.The cost and complexity of designing and constructing an airplane and an airship are at different level.
The launch platform used in SAAOPL system can be much simpler than a conventional HAA at the same level. Structurally, it is a mix of an airship and balloon, with the maximum speed close to 40m/s at approximate 22km altitude, which is substantially lower than the maximum airplane speed of 200+ m/s at 10km. This difference alone already can save a lot of aerodynamic complexities.
Another thing to be emphasized that SAAOPL is an unconventional launching system. It is not a wisdom choice to isolate each components in the system and compare with conventional stages individually, rather than comparing systems as a whole.
Taking the launch platform for example, if simply comparing it with conventional first stage in the scenario of launching an conventional upper stage, it doesn't worth at all, since it adds zero delta-V, lifts very limited altitude and doesn't boost reliability. However, within SAAOPL system, the launch platform brings SLSS out of dense part of atmosphere (significantly boost the performance of SLSS),
and provide the crucial altitude redundancy that SLSS needs to dump its fuel in the scenario of immediately-after-launch engine failure.
As a novel system, delivering a cargo to space orbit using SAAOPL system conceptually can be like sending a cargo to another continent using Boeing 747.
The design of SAAOPL system have placed reusability, reliability and short-launch cycle in the key positions since the beginning.
The cost and complexity of designing and constructing an airplane and an airship are at different level.......
How is this better than what DARPA is doing with the XS-1?
Quote from: whitelancer64 on 08/16/2017 09:15 pmHow is this better than what DARPA is doing with the XS-1?Not very familiar with technical details of XS-1. It seems XS-1 still is a vertical take-off vehicle, like what SpaceX did. SAAOPL is quite different. It is novel launching system which combines stratospheric launch and HTHL.
I'd recommend replacing RS-25 with either Merlin or BE-3 because RS-25 cannot do air-start or restart. If it could, Ares I would probably be flying today. XS-1 is ground launched (partly) because of this limitation.How do you propose to target the booster at a runway after separation? If it cannot restart, it will be limited to launch azimuths that are within it's crossrange capability to a runway, but that still keep the upper stage ground track away from populated areas. This might work for some launch sites and inclinations, but it is a significant limitation that needs analysis.I'd also recommend doing a detailed analysis to see how much larger the first stage (suborbital spaceship) has to be to do VTHL and put the same upper stage/payload to Mach 12 (por alternatively, what the payload reduction is with the same booster doing VTHL). This will give a mathematical basis for the claim that the balloon "stage" is worth the expense.
Most engine failures result in RUD.
Quote from: TrevorMonty on 08/19/2017 07:36 pmMost engine failures result in RUD.That is exactly what the design of SAAOPL system wants to solve. If an engine malfunction was detected, engine can be shut down immediately. SLSS will dump all its fuel into the air and glide back.
Even in the scenario of engine explosion, a layer of Kevlar between engine and SLSS can protect SLSS from serious damage. SLSS and its payload still can be survived and recovered.
SLP also helps SLSS start its engine before separation.
Quote from: envy887 on 08/18/2017 01:18 pmI'd recommend replacing RS-25 with either Merlin or BE-3 because RS-25 cannot do air-start or restart. If it could, Ares I would probably be flying today. XS-1 is ground launched (partly) because of this limitation.How do you propose to target the booster at a runway after separation? If it cannot restart, it will be limited to launch azimuths that are within it's crossrange capability to a runway, but that still keep the upper stage ground track away from populated areas. This might work for some launch sites and inclinations, but it is a significant limitation that needs analysis.I'd also recommend doing a detailed analysis to see how much larger the first stage (suborbital spaceship) has to be to do VTHL and put the same upper stage/payload to Mach 12 (por alternatively, what the payload reduction is with the same booster doing VTHL). This will give a mathematical basis for the claim that the balloon "stage" is worth the expense.Stratospheric launch platform (SLP) stables itself in the relative slow and steady airflow in stratosphere. Azimuth and pitch angle of SLP does not necessarily to be same as what are required by stratospheric-launched suborbital shuttle (SLSS). By controling length of tether cables beneath SLP, azimuth and pitch angle of SLSS is set to the predetermined values before separation. SLP also helps SLSS start its engine before separation.Given the chilly ambient temperature in stratophere, RP-1 is not ideal fuel for SLSS. Comparing with vertical lift-off rockets, One advantage of SAAOPL system is its reliability. SAAOPL has conceptual goal 1000 launches per year for single SAAOPL system. Hence, engine failure is a scenario that the design of SAAOPL must consider. If engine failure occurs soon after lift-off, both vertical lift-off rocket and its payload will be lost. However, that would be different for SAAOPL system. If engine failures occurs after being launched from SLP, SLSS has sufficient altitude redundancy, which is provided by SLP, to safely dump all its fuel and glide to an airfield nearby with its payload.
Firstly, I should put a note here that this is more a conceptual representation than a detailed design. Secondly, SLSS, as the third word of its name (Suborbital) states, doesn't reach orbital speed. For example, in a sample simulation for regional flight profile, SLSS reaches around 15 Mach speed and 112 km altitude at burn-out. Thanks for your interest and question!
Quote from: saaopl on 04/03/2017 01:26 amFirstly, I should put a note here that this is more a conceptual representation than a detailed design. Secondly, SLSS, as the third word of its name (Suborbital) states, doesn't reach orbital speed. For example, in a sample simulation for regional flight profile, SLSS reaches around 15 Mach speed and 112 km altitude at burn-out. Thanks for your interest and question!1 - the first time you mentioned SLSS was in this post in reply to mine, so how was I supposed to know it's suborbital?2 - actually, this is quite confusing, as the other name (your forum nickname) clearly has the word ORBITAL.3- so, is it ORBITAL or SUBorbital?4 - if itīs ORBITAL, how can it achieve a 30 km/s delta-v? Fuel tanks seem undersized by an order of magnitude at least.
Quote from: Tulse on 04/04/2017 06:23 pmQuote from: sevenperforce on 04/04/2017 05:29 pmAye, the only meaningful advantage of launching from altitude is the ability to use near-vacuum-optimized engines from the startAre there any advantages to having a much more benign aerodynamic environment (e.g., far lower max Q)? Would that allow a lighter structure for the actual vehicle, and thus better performance? If one doesn't have to worry about dense atmosphere, and thus streamlining, does that allow different form factors for the vehicle rather than a slender tube?There is a fairly large advantage, but only in one area with its own distinct issues: Small launchers. The smallest launcher that's feasible from the ground is around 10 tons.Let's give a hypothetical 30 ton 2-stage launcher a 1% payload mass fraction: It can launch 300kg to space. This isn't very bad - there are satellites in this size range which will pay some money for launch. Now scale that down by a factor of 10. A 3 ton 2-stage launcher suffers on a number of metrics that we can fix - Miniaturizing electronics and guidance and comms, a number of metrics that are inherently difficult - working with increasingly thin-walled pressure vessels, and some things we just can't touch - far proportionally greater aerodynamic losses, and thus (because greater aerodynamic force necessitates greater structural strength for the same velocity) a greater mass loss to structural reinforcement, and also a larger dV need & thus wet:dry ratio. This extends the amount of propellant that needs to be carried, and these effects compound on each other relentlessly. Long story short: You don't get a 1% payload mass fraction (30kg) out of a 3 ton vehicle of similar design. Nowhere near. More likely you'll just never get any kind of payload to orbit. Somewhere a bit under 10 tons, depending on what tech you use, the aerodynamic-related losses run asymptotic and you just can't make an orbital vehicle that launches from the ground.You can make one, though, that launches from somewhere above most of the atmosphere. If you don't have to deal with most of the atmosphere, you never hit the same compounding barriers, and you can scale that 30 ton launcher down to 3 tons without losing all that much payload mass fraction. You can hypothetically scale things all the way down to launching a single 1U cubesat.I would note however, that large launchers (EELV class and up) generally don't lose a lot to gravity+drag losses. The longer the rocket is, the easier it is proportionately to shove through the atmosphere. So you can't really compete by just using small launchers and upping the volume, without some kind of dramatic advance in mass production. Alternately, you could find a recurring payload from a paying customer that needs rapid response launches to a number of custom orbits.But we haven't yet. And so this sort of idea is not really a feasible business - in a world where there are cheaply reusable first stages and there exist few commercial customers for tiny payloads to custom orbits, a balloon or plane adds so little to the engineering picture that it's difficult to justify those forms of launch. We're going to be doing mass production of smallsats fairly soon once the LEO comms financing guys feel that launch is cheap enough, but large smallsat dispensers flown from an F9 are likely much cheaper, for a single plane, than custom launches. Few large constellations will need only one bird per orbital plane.
Quote from: aceshigh on 09/08/2017 02:52 amQuote from: saaopl on 04/03/2017 01:26 amFirstly, I should put a note here that this is more a conceptual representation than a detailed design. Secondly, SLSS, as the third word of its name (Suborbital) states, doesn't reach orbital speed. For example, in a sample simulation for regional flight profile, SLSS reaches around 15 Mach speed and 112 km altitude at burn-out. Thanks for your interest and question!1 - the first time you mentioned SLSS was in this post in reply to mine, so how was I supposed to know it's suborbital?2 - actually, this is quite confusing, as the other name (your forum nickname) clearly has the word ORBITAL.3- so, is it ORBITAL or SUBorbital?4 - if itīs ORBITAL, how can it achieve a 30 km/s delta-v? Fuel tanks seem undersized by an order of magnitude at least.The spaceship in this concept is suborbital, with a expendable orbital upper stage.It's basically XS-1, but launching from a giant balloon.
If you use BE-3 or Merlin it can have engine-out redundancy for most of the flight. And you really don't want to start an RS-25 while dangling on cables under a hydrogen balloon... there is a good reason all air-launch vehicle drop first, then fire. The RS-25 is a difficult engine to start even on the ground. If you drop it, there will be times where a abort on the pad is a lot safer. I'd wager the increased risk of the engine not starting and having to abort is greater than the reduction from having abort capability for a small part of the flight trajectory where the vehicle is within gliding range of a runway.You still haven't clarified how the suborbital booster returns to a runway. There are a very limited number of sites and launch azimuths where both 1) the ground track of the launch trajectory is acceptable and 2) the booster is within gliding range of a runway when it reenters. Most launch locations and azimuths will require a boostback/diversion burn - but RS-25 cannot RESTART, even if you get it to air-start. You could hot-stage, but that adds a whole 'nother set of complications.RP-1 freezing isn't really an issue, the booster would need insulated tanks anyway - to prevent solid air buildup on the LH2 tanks.Again, to convince anyone that air-launch is a good idea, you will need to calculate exactly how much booster cost you are saving by adding the expense of a air-lift stage.
but XS-1 is orbital, and it's almost like a payload.it's launched inside a 60 meters tall Falcon 9 rocket, first stage and second stage reaching 30 thousand km per hour. Then the XS1 is delivered already in orbital velocity.so, again, how exactly do you plan to reach orbital speeds?please, describe what is envisioned as the COMPLETE spaceship which will hang below the balloon. What will be it's size? How many stages? What will be it's fuel and amount of fuel? Payload capacity to LEO?
It's basically XS-1, but launching from a giant balloon.
Quote from: envy887 on 09/12/2017 02:04 pmQuote from: aceshigh on 09/08/2017 02:52 amQuote from: saaopl on 04/03/2017 01:26 amFirstly, I should put a note here that this is more a conceptual representation than a detailed design. Secondly, SLSS, as the third word of its name (Suborbital) states, doesn't reach orbital speed. For example, in a sample simulation for regional flight profile, SLSS reaches around 15 Mach speed and 112 km altitude at burn-out. Thanks for your interest and question!1 - the first time you mentioned SLSS was in this post in reply to mine, so how was I supposed to know it's suborbital?2 - actually, this is quite confusing, as the other name (your forum nickname) clearly has the word ORBITAL.3- so, is it ORBITAL or SUBorbital?4 - if itīs ORBITAL, how can it achieve a 30 km/s delta-v? Fuel tanks seem undersized by an order of magnitude at least.The spaceship in this concept is suborbital, with a expendable orbital upper stage.It's basically XS-1, but launching from a giant balloon.but XS-1 is orbital, and it's almost like a payload.it's launched inside a 60 meters tall Falcon 9 rocket, first stage and second stage reaching 30 thousand km per hour. Then the XS1 is delivered already in orbital velocity.so, again, how exactly do you plan to reach orbital speeds?please, describe what is envisioned as the COMPLETE spaceship which will hang below the balloon. What will be it's size? How many stages? What will be it's fuel and amount of fuel? Payload capacity to LEO?
Sorry for digging up an old thread but am i right in saying the main advantages of air launch are not efficiency gains but;A Very mobile launch pad (it literally flies)This allows matching of the target obit's ground track meaning no more waiting days/weeks for launch windows only hoursThis also allows launching into any inclination with the same "launch pad". (unlike SpaceX needing west and east coast pads)You can move your launch range to better ensure range availabilitySmaller benefit = being able to pick up payload from customer lowering transport costs/time for payloadProblems include developing expensive carrier vehicle (stratolaunch) but you could just use of the shelf vehicles for smaller rockets (VG) and having people near the rocket during fuelling and launch