• 0
Sign in to follow this  
KerikBalm

Do you SSTO anymore?

Question

So, in adpating to the recent changes, I've given up trying to SSTO everything.

The recent changes:

* Expanded physics distance

* Halved jet engine thrust

When trying to SSTO everything, I'd use big launchers to minimize the number of launches and re-entries I'd have to do...

As a result, my launch masses are often around 400 tons (and when actually near the payload mass limit, I'm getting >35% payload fractions)

The recent reduction to jet thrust makes the liftoff quite awkward. I also find that having to set a positive pitch angle with lower rear landing gear than front landing gear increases the risk of long payloads striking the ground.

The short burn time of the kickback SRBs + the increased physics draw distance means I can jettison them after burnout, and have them safely land on the runway

- full recovery cost for the decoupler parachute, and SRB itself - the only cost is the solid fuel, which amounts to 84 credits per kickback.

As a result, I'm now doing a lot of designs which stage while still over the runway.

8 kickback SRBs to help lift the nose, and then accelerate and climb above the runway really helps to get a 400 ton behemoth into the air.

Its equivalent to the thrust of >12 extra rapiers, or 10 extra turboramjets, and extra 3.26 m/s/s of acceleration (for a 400 ton spaceplane) on takeoff

All for the low low cost of 84*8 = 672 credits.

Considering the SSTO normally recovers with remaining fuel for >350k, and that fuel costs are about 15k for large payloads, its not much...

It only adds ~4% to the cost of fuel.

Is anyone else finding ways to make use of the longer draw distances to recover booster stages?

I can't manage anything like what spaceX wants to do due to physics limitations... but I find the short burntime of kickbacks to be perfect for 1st stage recovery.

Im also starting to try it out with vertically launched rockets, and I want to try out some RT-10s instead of RT-5s. Anyone tried this?

I'm worried their burn time is too long and they'll still be under parachutes when they get 22.5 km away, and they'll thus despawn.

I'd still like to have another stage, that I decouple on a suborbital trajectory, get the payload to orbit, and then switch back to the suborbital stage... but it will land so far away, recovery losses likely won't make up for the reduced fuel costs

(What I wouldn't give to be able to decouple a rocket from a plane at 30km going ~1,300 m/s surface velocity, and then be able to turn the plane around and land... or to make a 2nd space center to the east where craft could be landed for a higher recovery value)

Share this post


Link to post
Share on other sites

Recommended Posts

  • 0
What's wrong that you can't SSTO 200t? Admittedly, the biggest I've bothered to do is 130t, but it's all doable - ask any Whackjob.

Its not a matter of what i can or cant do, its that such scales are 100% not enjoyeable for me due to lag and the general sluggishness of such craft. this is the same reaosn all my "capital ships" are at a absolute max 350 parts, i dont want to deal with lag and well, anything that heavy without 30+ reaction wheels/LFO engines is gonna be painful to fly.

Anyways, this may very well change is U5 brings any performance boosts, right now the absolute max i can handle loaded is 1500, with anything above 600ish starting to get choppy especially in atmosphere. Yes i CAN play with so much parts, but its just not fun to do for me.

only time i can really accept lag is with carrier ops, carriers with 10+ fighters and alot of ammo thats ~800 parts in one spot is just too epic to not do.

Edited by panzer1b

Share this post


Link to post
Share on other sites
  • 0

Do I SSTO anymore? Hmmm...

If by "SSTO" you mean spaceplane, then 1.0 hasn't changed my use of them at all. I only use them as crew shuttles for permanent colonies on Laythe because unlike heatshields, SSTOs don't wear out over time, and are easier to land at very specific locations. I see no need for them anywhere else in the universe because there they offer nothing that appeals to me and come with several annoyances I'd rather not have to deal with. And if I was better at dropping conventional landers at specific places on Laythe, and if heatshields didn't wear out over time, then I wouldn't use spaceplanes even there.

If "SSTO" includes LFO rockets, then 1.x has actually increased my use of them. It's a lot easier to make a single stack fly straight these days than other configurations, they're quicker and simpler to build, are less prone to design/construction/staging errors, have fewer parts, take less of my valuable time to get useful payloads to orbit, and are just badass, especially when they're 5m :D.

But that's just how I play. To me, the game really begins once the tech tree ends and you can start using those top-end parts to build an empire, but on a budget. I make more than enough money doing contracts at other planets, that usually foster my own empire-building desires anyway (building bases and stations, for example), that I don't need to worry about whatever savings spaceplanes might give me. Besides, most of the stuff I send to orbit won't fit in a Mk3 cargobay anyway. So I don't even recover boosters and in fact spend $500 extra on each of them to blow them up with TAC Self-Destruct because explosions are cool :). And also, I value my own personal time above anything in the game and would rather spend it doing stuff out amongst the planets than spending huge amounts of time redesigning to improve launch efficiency, nursing a low-TWR spaceplane to orbit, recovering boosters, etc.

So here's how I use SSTO rockets...

1. Spend a reasonable amount of time designing the payload to meet mission requirements.

2. Spend the minimum amount of time slapping a transfer stage and lifter under it to give each the necessary dV with an acceptable TWR. The lifter is either a single LFO stage or has an initial SRB stage (thank the Dark Gods for Space-Y). Either way, the goal is to reach LKO with 300-500m/s left in the tanks.

3. Launch to an 85km parking orbit with the LFO lifter still attached some time before the transfer burn.

4. Create the interplanetary transfer node.

5. Burn the remaining lifter fuel at the node (but some number of orbits in advance) to create an elliptical orbit with the Pe at the proper ejection angle, then jettison the lifter and blow it up with TAC Self-Destruct. This lets me do a multi-pass transfer burn in advance so the actual transfer stage can have a lower TWR and still do the remaining burn in 1 pass.

Could I do things more efficiently? Certainly. Do I really need to? Absolutely not. Do I want to? Emphatically no. The above works quite well for me in terms of getting what I want out of the game. YYMV.

Share this post


Link to post
Share on other sites
  • 0
If by "SSTO" you mean spaceplane, then 1.0 hasn't changed my use of them at all.

No, I don't. Vertical launch SSTO rockets also seem like attractive candidates for recoverable strap on boosters to get your your first 150 m/s of dV.... which can really help payload fraction for non-airbreathers.

unlike heatshields, SSTOs don't wear out over time, and are easier to land at very specific locations

I assume you mean spaceplanes.... a SSTO can easily have a heat shield. Heat shields, even with ablator depleted, can still be quite useful. After you've done your interplanetary braking, ablator-less heat shields should be sufficient for just getting to and from orbit.

I see no need for them anywhere else in the universe because there they offer nothing that appeals to me and come with several annoyances I'd rather not have to deal with. And if I was better at dropping conventional landers at specific places on Laythe, and if heatshields didn't wear out over time, then I wouldn't use spaceplanes even there.

Well, the distinction between even a spaceplane and a rocket can get blurred.

personally, if the destination has an atmosphere, I stick some for of aerosurface on it to help adjust my trajectory - particularly so I can have a cluster of stuff to make a "base" or "colony"... I don't like to waste a lot of fuel, or reload a lot to get the deorbit burn precise enough.

That said... while my Duna landers have wings and are aerodynamically stable in horizontal flight... they pop chutes and come down vertically, and launch vertically into gravity turns like a rocket.

I'm not sure what I'll do for laythe, I don't think I can manage a pure airbreathing vertical launch without having a very large fraction of my mass being engines.

Detachable SRBs like I use on kerbin won't work more than once, so I'll probably use an aerospike or two to get into horizontal air breathing flight.

Sure... some areas of laythe are flat... but I'm not sure they'll have good ore concentrations, and I will want to supply an orbital fuel depot from laythe (Well, I'm assuming I can pull off good net gains due to use of airbreathers... I've also seen suggestions of mining on Val, and using that to supply an orbital laythe depot).

So... for laythe, I'm going to try and design 2 types of tailsitting VTOL spaceplanes (one "lander" for exploration and moving crew, one much larger "tanker" for fueling)

If "SSTO" includes LFO rockets, then 1.x has actually increased my use of them. It's a lot easier to make a single stack fly straight these days than other configurations, they're quicker and simpler to build, are less prone to design/construction/staging errors, have fewer parts, take less of my valuable time to get useful payloads to orbit, and are just badass, especially when they're 5m :D.

5m is meters? or million credits?

How much tonnage does a 5m rocket get to orbit?

Wouldn't you benefit from staging off some boosters that can be recovered?

For me...

"they're quicker and simpler to build" -> Well, fine, but I already built some very high capacity SSTOs in 1.02 that still work just about as well in 1.04.

They can take ~150 tons to orbit, payloads can be over 2.5x the length of an orange tank, and over 3x the width of an orange tank...

So now I just design a payload within those constraints, and stick it on my spaceplane.

If its smaller, I have already made some smaller spaceplane designs.

"take less of my valuable time to get useful payloads to orbit,"

This can be a bit of a problem... according to the ingame clock, it doesn't take that long... but when it takes 5 seconds for an in-game second to tick off... it takes a while.

My computer in particular doesn't like all the smoke effects of the exhuast hitting the runway...

The recoverable SRBs make that phase much shorter, and let me have less resting AoA, so the exhaust doesn't hit the runway as much.

"and are just badass,"

Personally, I find 400 ton spaceplanes (incuding payload) deploying 150 ton payloads pretty badass too.

Besides, most of the stuff I send to orbit won't fit in a Mk3 cargobay anyway.

Same here, which is why I made a spaceplane that can lift things a lot bigger than what fits in a mk3 bay.

5. Burn the remaining lifter fuel at the node (but some number of orbits in advance) to create an elliptical orbit with the Pe at the proper ejection angle, then jettison the lifter and blow it up with TAC Self-Destruct.

So you don't recover your SSTO lifter at all?

Why bother SSTOing it at all then? Staging is too much trouble?

Share this post


Link to post
Share on other sites
  • 0

Doh, I still haven't answered the the proper question, have I! So far I haven't found any useful boosters that burn-out, stop going up and fall back to the ground before my vehicles are more than 23km away (or whatever the distance is). Definitely something best for horizontal takeoff, I would think, as they don't have so far to fall so are on the ground again quickly.

Share this post


Link to post
Share on other sites
  • 0

*edited for bad math*

Well, so far, I've only done 1 design with a vertical launch using *fleas* (I just realized I've made the mistake of calling them "kickbacks" multiple times)...

It was an airbreathing spaceplane.... that pitched over and had only moderate acceleration

Lets consider just a simple vertical launch (no gravity turn)

The burntime is 8.9 seconds... Lets say the rocket continues accelerating after booster separation with a 2:1 TWR

1.5 flea TWR, 4.9 m/s/s net vertical acceleration... 43.61 m/s at burnout -> 194 meters high at burnout... suppose it gets to 250 meters before falling at 5 m/s

50 seconds to fall back down.

43.6*50+4.9*50^2 = 14,430 .... 14.43 KM Well within the limits

Suppose you only have a 2:1 TWR on the fleas... you get to 87 m/s before burnout..

Height at decoupling is now 388.13 meters... lets say it gets to 450, and descends at 5 m/s... Now they take 90 seconds to touchdown.

A rocket with a 2:1 TWR goes 87*90+ 4.9*90^2 = 47.5 km in that time... ok... too far...

It gets you ~44 m/s more... assuming a 2:1 TWR, that also saves you about 40 m/s lost to gravity drag... lets say 85 m/s total dV savings

not a huge increase when you're looking at 3,750 m/s to get to orbit...

Assume 315 Isp average for aerospikes, or 305 average for mammoths

Suppose you need 3750 dV to get to orbit

Subtract 85 m/s from that 3750 if using discardable boosters

3750 = 9.8*Isp* ln(mass ratio) -> mass ratio needs to be 3.37/3.51 aerospike/mammoth

3665= 9.8*Isp * ln(mass ratio) -> mass ratio needs to be 3.28/3.41

Assuming a 2:1 TWR in all cases(without boosters/after booster seperation), and the rocket dry mass(inc payload, not including boosters)

Per ton of dry weight:

Aerospike boosters/no booster, fuel tank mass: 0.263/0.253

Mammoth, fuel tank mass: 0.278/0.267

Engine mass, same order:

0.431/0.419

0.275/0.268

Leaving, per ton of dry mass, for for control systems/ power/etc + payload

Aerospikes: 0.306/0.328 -> a 7.14% increase

Mammoth: 0.446/0.464 -> a 4.04% increase

However, in both cases, the "core stage" sans boosters is lighter, if we keep the core stage the same weight, then the power/control/etc + payload mass is increased by 10.1% fo

Also... I wonder if a 1.5:1 TWR is better for a SSTO rocket... I don't know how much that affects the dV needed to get to orbit.

Edited by KerikBalm

Share this post


Link to post
Share on other sites
  • 0

Soo... I'm going even crazier....

I guess in the end, what would be best is an even shorter burn time, coupled with a higher acceleration...

Something that can shoot your rocket up in a short time, and then have the SRBs stop very fast due to parachutes, and land very fast.

Something to make it like your rocket is coming out the muzzle of a gun :P except we need to have really short burn recoverable boosters

If you could get your rocket to 150 m/s before reaching 150 meters, that would really improve the payload fraction of the core.

That requires an acceleration of 75 m/s^s and a burn time of 2 seconds

Since you're fighting gravity for 9.8 m/2... you'd need 84.8 m/s^s an 8.65 TWR... which would require about 25% of your mass to be fleas with their fuel tweaked down to 22.5%

Nearly empty Fleas have the best TWR@1 atm...except the launch escape system...

hmmmm.... a 0.53 second burn time and >60 TWR.... good Isp for a SRB too...

to get to 150 m/s in 0.53 seconds... you need 283 m/s/s acceleration... well 292.8 vertical... a 29.9 TWR....

If half your rockets mass is in the form of LES boosters... you'll make that TWR... and the boosters will burn out at 40 meters.... hmmm

I think just for fun, I'm going to make a LES boosted rocket... :confused:

Considering at a 2:1 initial TWR, to get to 150 m/s, I'm going to lose about another 150 m/s to gravity drag (@9.8 m/s/s it takes over 15 seconds to reach 150 m/s... and each second I lose 9.8 m/s to gravity)... reducing dV needs of the core stage by ~300 m/s

Yea... I'm going to do it... LES boosters... Gotta make sure the symetry is right and the thing flies straight.

To obtain attachment nodes for them, I think I'll add them on top of fleas with their fuel tweaked for 1.5 second burns...

This should be very Kerbal...

Ok, as a proof of concept... here you go, while the core rocket can SSTO by itself, launch is a bit cooler and more exciting with the fully recoverable boosters.

Drop this into your SPH:

https://www.dropbox.com/s/0zxv4728zhed0ol/SSTNope.craft?dl=0

Yes.. I said SPH, even though its a rocket, that way the boosters land for 100% recovery, instead of 98%

So, a basic flight profile that I've found works:

1) SAS on, throttle to full

2) Press spacebar... one second later you should be travelling over 100 m/s and the boosters' fuel should be gone, initial TWR is 20

3) Press spacebar again as soon as boosters cut out, TWR should now be 1.8

4) When apoapis passes 10km, switch SAS to follow prograde mode

5) cut throttle when apoapsis passes 80km (or whatever orbital height you want)

6) circularize at apoapsis, your TWR should be somewhere near 40, so it will be a short burn.

I invite you to remove the boosters and SSTO the core, and see what sort of benefit the boosters give you.

I tried tweaking the fleas to 20% fuel instead of 10%, but then the burn time was too long, and they went too high, and despawned before landing.

Edited by KerikBalm
add stuff

Share this post


Link to post
Share on other sites
  • 0

I almost never use SSTO. In fact I rarely ever use horizontal takeoff to orbit period. The only things that I build in the SPH are land vehicles (rovers, etc), atmospheric craft, and shuttles - the latter I save as subassemblies with a decoupler attachment as root, then take them to the VAB where I slap on a big LFO rocket and a pair of SFB's to get it to orbit.

Most of this is because I am limited on the amount of time I can spend playing KSP on a given day, so I tend to stick with what I know works. Currently, I'm building a refinery station in LKO, with a resuable lander and rover for a Mun/Minmus mining operation. The station core I put into orbit using a design inspired by NASA shuttles. However, since that design is remarkably inefficient, for everything else that goes on the station I use a three-phase rocket consisting of a multi-stage launch vehicle, a payload consisting of a dockable station part, and a command module/lander. The launch vehicle gets me to orbit and within docking distance of my station, at which point I jettison it to expose the rear docking port using a stack separator and use RCS to manuver into position and dock. Once I am docked I use a second stack separator that detaches from the payload. The payload stays docked to the station,and has a second docking port on the other end for future additions, while the lander vehicle uses radial-mounted ILX engines to burn retrograde and a combination of engines, airbrakes, and a drag chute to land safely back on kerra firma.

Share this post


Link to post
Share on other sites
  • 0

right now I'm working on a spaceplane that can get to orbit with a decent payload and +2000m/s of delta-v left over, i've nailed getting to orbit but cannot for the life of me design a plane that reenters without stalling all over the place around 30km. I use FAR for added difficulty :rolleyes:

Share this post


Link to post
Share on other sites
  • 0

In terms of planes, I've built two in my current game, a Mk2 and a Mk3, and not with stock parts. I've never used them outside the test flights to prove they would work, and I'm only just barely competent enough to build passenger SSTO planes. Cargo is apparently out of the question for me.

However, I have started using somewhat oversized but recoverable lifting stages for conventional orbital pods and such. Even put a station in orbit with a fully recoverable main stage. Costs more on the pad, but if you can land at least remotely close to KSC you get the majority of that back.

Share this post


Link to post
Share on other sites
  • 0
...How much tonnage does a 5m rocket get to orbit?

Quite a lot, especialy when combined with 3.5m SRBs. I love the Space-Y mod :)

Wouldn't you benefit from staging off some boosters that can be recovered?

...

So you don't recover your SSTO lifter at all?

...

Why bother SSTOing it at all then? Staging is too much trouble?

I find that I make so much money from contracts that I have no need to save money on launch vehicles. So once I was sure that was reliable, I abandoned all effort at making cost-efficient launch vehicles. The whole cost-efficiency thing involves a lot of hassle and consumes great amounts of time, whether you do it via reusable lifters (of whatever type) or refueling within Kerbin's SOI, or (shudder) both. But lifters and refueling infrastructure are merely support functions. The actual mission is about the payload. Therefore, the payload should get the bulk of my time and attention, which means quick and dirty launches instead of wrangling spent boosters, taking 20 minutes to get a huge spaceplane to orbit, or making innumerable tanker runs to and from Minmus. Without any of these things, I still make way more money than I will ever spend despite using highly extravagant, disposable rockets. So why should I bother doing any of these things?

Besides, I consider the entire "reusable space program" concept, as a way of saving money, to be ridiculous both in KSP and the real world. The Shuttle certainly didn't save money compared to disposable rockets and I highly doubt Space-X will, either, even if they someday succeed in recovering a booster. KSP doesn't even have refurbishing costs factored in so the savings it provides are not only unrealistic but exploitive. However, it's not enough of an exploit, at the bottom line, to be worth bothering with anyway.

Share this post


Link to post
Share on other sites
  • 0
right now I'm working on a spaceplane that can get to orbit with a decent payload and +2000m/s of delta-v left over, i've nailed getting to orbit but cannot for the life of me design a plane that reenters without stalling all over the place around 30km. I use FAR for added difficulty :rolleyes:

I and some of the FAR gurus might be able to help you out there - post some screenies of your plane on the Official FAR Craft Repository thread. I'ma guessing you probably just need to shift some mass (read: fuel) forward before you attempt re-entry but a screenie would help confirm that. I've got a cargo plane my own self that needs the fuel pumped forward or it flips out all over the damn place.

Share this post


Link to post
Share on other sites
  • 0
I don't SSTO anymore.

I'm SSTOing again. (I don't SSTO in my sleep....) :P

Share this post


Link to post
Share on other sites
  • 0

I think it depends on your game mode a lot.

I first played beta 0.9 in science mode. I didn't had to account for cash, so I didn't do SSTO at all. I preferred to build some complex asparagus staging which were quite fun to tweak.

But as 1.0.x, I restarted as Carrier. In mid game, your cash is quite low and your tech is high enough to build SSTO planes or rocket stages to LKO.

SSTO plane are fun to fly. I have one which I use to truck crew from my Kerbin space station. But that's more RP than really efficient. Sending multiple return pods to the station is much quicker and easy.

I use SSTO rockets a LOT. Once you have a neat design, they are highly scalable (there is no real limitation), easy to fly (due to no staging) and very cheap (once you get how to land less than 50km from KSC).

I'm now in late carrier game. I've so much cash, I'm nearly playing sandbox. SSTO aren't as usefull, but they are fast to build. I just create my ship and clip a pre-designed LKO stage on it, then launch. I don't even have to test the stage (but I test my ship staging on the pad without launch stage)

That's my SSTO stages program : http://forum.kerbalspaceprogram.com/threads/123195 . I even have a 400T and 600T. Both were variations of the 200 and 300T I designed in less than 10 minutes.

Share this post


Link to post
Share on other sites
  • 0

I SSTO as much as ever. Also, there's this to consider:

l03WwUvm.png

A lot of my SSTOs in old versions as well as 1.0 have used rocket engines in place of jet engines, so the jet engine nerf meant nothing in that regard. As far as spaceplanes go, things just changed a little. Now instead of spamming air intakes it's an issue of managing drag, etc.

Share this post


Link to post
Share on other sites
  • 0
I SSTO as much as ever. Also, there's this to consider:

http://i.imgur.com/l03WwUvm.png

A lot of my SSTOs in old versions as well as 1.0 have used rocket engines in place of jet engines, so the jet engine nerf meant nothing in that regard. As far as spaceplanes go, things just changed a little. Now instead of spamming air intakes it's an issue of managing drag, etc.

Another thing to consider in that graph, is airbreathing vs closed cycle.

You can have spaceplanes with no airbreathing engines, and you can strap some airbreathing engines on your rocket.

The Jet nerf affects airbreathers, which have a strong correlation with spaceplanes, but not neccessarily.

The physics extension range affects both.

Look at the craft file I provided in my previous post... It is neither a spaceplane nor an airbreather.

It could SSTO, but it doesn't, it takes advantage of the extended physics range, and thus get a couple hundred m/s extra dV from its 100% recovery boosters.

Its not a super practical design, just a proof of concept. The point is you could spam those boosters on any SSTO rocket to give it more dV, and you wouldn't lose any recovery cost.

It just becomes a question of fund efficiency - solid fuel is less expensive than LF (LF is 91.8/ ton, Solid fuel is 80/ton), but you use more of it due to lower Isp. However, the tyranny of the rocket equation means you'll get those back when your stage dV gets closer to the maximum limit

Share this post


Link to post
Share on other sites
  • 0
I'm just curious how I'm supposed to get back from orbit now with the re-entry effects. There's no heat sheilding on the Mk2 cockpits. Radiators?

Shallow re-entry with high drag.

I usually take about one third orbit and have nose ~30 degrees above horizon.

For more detailed info, you can check the Descent Profile section on the 2 SSTOs I posted on KerbalX.

Share this post


Link to post
Share on other sites
  • 0

From the opposite side of the planet from KSC, make your periapsis 30k. You come through the heating with the nose raised and will be nosing down heavily and once you get below the shock heating and then flare near the runway. It will feel like you are coming in too steep,

. The plane parts are about as resistant to heat as the command pods, but even the command pods don't need heat shields for a LKO re-entry. You really only need heat shields coming in from Minmus or further to a direct re-entry. While KSP does allow you to take planes out that far, it's not incredibly practical.

While we are on the subject though, I've recently started back on SSTO planes again and I'm having trouble with the new engine thrust at high altitudes. What is the flight profile? I mean, I can build a Jet powered craft with >1.0 TWR and get up no problem but then, why wings? My problem is needing to burn the rocket engines longer because I can't get up to speed with jets like I used to with 0.90 + FAR. What are you guys doing for ascent?

Edited by Alshain

Share this post


Link to post
Share on other sites
  • 0
From the opposite side of the planet from KSC, make your periapsis 30k. You come through the heating with the nose raised and will be nosing down heavily and once you get below the shock heating and then flare near the runway. It will feel like you are coming in too steep,
. The plane parts are about as resistant to heat as the command pods, but even the command pods don't need heat shields for a LKO re-entry. You really only need heat shields coming in from Minmus or further to a direct re-entry. While KSP does allow you to take planes out that far, it's not incredibly practical.

While we are on the subject though, I've recently started back on SSTO planes again and I'm having trouble with the new engine thrust at high altitudes. What is the flight profile? I mean, I can build a Jet powered craft with >1.0 TWR and get up no problem but then, why wings? My problem is needing to burn the rocket engines longer because I can't get up to speed with jets like I used to with 0.90 + FAR. What are you guys doing for ascent?

Instead of turning at 20 km, lower your nose around 13-15 km and try to maintain a 5-10 degree ascent, with enough patince I can get a plane (with nukes firing) to around 23km and mach 4.5 before turning on the jets

Share this post


Link to post
Share on other sites
  • 0
Instead of turning at 20 km, lower your nose around 13-15 km and try to maintain a 5-10 degree ascent, with enough patince I can get a plane (with nukes firing) to around 23km and mach 4.5 before turning on the jets
Did you mean turn them off?
...

While we are on the subject though, I've recently started back on SSTO planes again and I'm having trouble with the new engine thrust at high altitudes. What is the flight profile? I mean, I can build a Jet powered craft with >1.0 TWR and get up no problem but then, why wings? My problem is needing to burn the rocket engines longer because I can't get up to speed with jets like I used to with 0.90 + FAR. What are you guys doing for ascent?

I build up speed below 10 km. Usually between 8 and 9 km I build up speed to 1000-1100 m/s depending on how heat resistant the particular spaceplane is.

Then I nose up slowly, so I reach a 20 degree nose up by the time I pass 15 km.

Then depending on spaceplane:

  • If it has Nukes I engage them at 18-20 km.
  • If it has Jets and LFO Rockets, I engage the Rockets at 18-20 km, also.
  • If it has Rapiers.
    • And Nukes, I engage the Closed Cycle at 25-29 km.
    • And no Nukes, I engage Closed Cycle at 22 km.

At ~25 km I begin to nose down a little, so I'm at 15 degree nose up at 30 km. And I stay at 15 degree nose up, until AP is above 70 km.

For a Rapier/Nuke spaceplane with ~330 Oxidizer per Rapier, then this ascent profile will get even a craft with 0.25 TWR (after Rapiers shutdown) to orbit, if you're above ~250 m/s vertical speed at 30 km. Surface speed ~1250 at 20 km and ~1350 m/s at 30 km.

Edit: Fixed some errors.

Edited by Val
Additional info and fix typos

Share this post


Link to post
Share on other sites
  • 0
Instead of turning at 20 km, lower your nose around 13-15 km and try to maintain a 5-10 degree ascent, with enough patince I can get a plane (with nukes firing) to around 23km and mach 4.5 before turning on the jets

Not sure what you mean by "instead of turning".

- - - Updated - - -

Did you mean turn them off?

I build up speed below 10 km. Usually between 8 and 9 km I build up speed to 1000-1100 m/s depending on how heat resistant the particular spaceplane is.

Then I nose up slowly, so I reach a 20 degree nose up by the time I pass 15 km.

Then depending on spaceplane:

  • If it has Nukes I engage them at 18-20 km.
  • If it has Jets and LFO Rockets, I engage the Rockets at 18-20 km, also.
  • If it has Rapiers.
    • And Nukes, I engage the Closed Cycle at 25-29 km.
    • And no Nukes, I engage Closed Cycle at 22 km.

At ~25 km I begin to nose down a little, so I'm at 15 degree nose up at 30 km. And I stay at 15 degree nose up, until AP is above 70 km.

For a Rapier/Nuke spaceplane with ~330 Oxidizer per Rapier, then this ascent profile will get even a craft with 0.25 TWR (after Rapiers shutdown) to orbit, if you're above ~250 m/s vertical speed at 30 km. Surface speed ~1250 at 20 km and ~1350 m/s at 30 km.

Edit: Fixed some errors.

Wow, it can withstand that kind of heat? I'll give it a shot.

EDIT: Now that I think about it, I guess it really isn't that hot.

Share this post


Link to post
Share on other sites
  • 0
...

Wow, it can withstand that kind of heat? I'll give it a shot.

EDIT: Now that I think about it, I guess it really isn't that hot.

It does get hot. Usually when I pull up after building up speed, it's a very fine balance between ripping the wings off and parts exploding from overheating...

Share this post


Link to post
Share on other sites
This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this