FREQUENTLY ASKED QUESTIONS
Below we are collecting a series of common questions regarding the DIRECT Concept:
Question: What is the maximum performance for the different variants of DIRECT?
Answer:
The performance figures are:
Jupiter 120 (2x 4-seg RSRM, 2x RS-68) Crew Launch Vehicle:
- 102,812lb (46,635kg) to 42x120nm @ 28.5deg for LEO missions.
- 90,563lb (41,079kg) to 100x220nm @ 51.6deg for ISS missions.
Jupiter 120 (2x 4-seg RSRM, 2x RS-68) Cargo Launch Vehicle:
- 116,245lb (52,728kg) to 44x120nm @ 28.5deg for LEO missions.
- 104,333lb (47,325kg) to 100x220nm @ 51.6deg for ISS missions.
Jupiter 232 (2x 4-seg RSRM, 3x RS-68, 2xJ-2XD) Crew Launch Vehicle:
- 227,829lb (103,342kg) to 119x120nm @ 28.5deg for Lunar missions plus 31,669kg of EDS burnout mass.
- 202,855lb (92,014kg) to 100x220nm @ 51.6deg for ISS missions plus 31,669kg of EDS burnout mass.
Jupiter 232 (2x 4-seg RSRM, 3x RS-68, 2xJ-2XD) Cargo Launch Vehicle:
- 233,458lb (105,895kg) to 30x120nm @ 28.5deg for Lunar missions plus 31,669kg of EDS burnout mass.
- 198,294lb (89,944kg) to 203x220nm @ 51.6deg for ISS missions plus 31,669kg of EDS burnout mass.
NOTES:
All ESAS margins and GRA's achieved.
All versions assume the following:
- The 4-segment SRB used on Shuttle is retained without changes.
- RS-68 engine performance is 751,000lb vac thrust, 409.0s vac Isp - identical to the existing Delta-IV, and is not the "upgraded" version proposed by NASA for the Ares-V - which is planned to be operated at 106% maximum power level. The DIRECT proposal does not use this higher performance setting and thus reduces the stress on the engines which maximize safety and reliability. Upgrades like this are still possible in the future, but are unnecessary to achieve the stated performance figures for the Jupiter launchers in this study. DIRECT also does not require the more expensive 418s Isp regenerative cooled RS-68A upgrade engine being built by Pratt & Whitney/Rocketdyne for the Delta-IV Heavy launch vehicle. These enhancements all remain "future growth options" for the Jupiter vehicle.
- J-2X used on the upper stage is not required to be operational until 2 years later than currently planned (2017, not 2015).
- J-2X performance only requires the lower specification of the J-2X "D" variant: 273,500lb vacuum thurst and 448.0s vacuum Isp. DIRECT v2.0 Study has conluded the Jupiter launchers do not require the additional performance of the fully upgraded engine (the "J-2X") which NASA has requested already for Ares-V. If these upgrades still do become available and 294,000lb vacuum thrust and 448.0s vacuum Isp are achieved in the future, Jupiter's performance can take advantage of these enhancements - but they are not requirements in the critical path to success and the additional investment capital is not required to achieve higher levels of performance.
Crew Launch Vehicle Solutions Assume:
- Launch Abort System (LAS) massing 14,473lb (6,565kg), is disposed of 30 seconds after staging events, or at T+305s. This is conservative and can be refined further to improve performance.
- Payload Fairing (PLF) massing 11,759lb (5,334kg), mounted under the Orion is carried to orbit.
Cargo Launch Vehicle Solution Assume:
- Payload Fairing (PLF) massing 13,188lb (5,982kg), is disposed of at 75nm (139km) altitude. This is conservative and can be refined further to improve performance.
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Question: Isn't this performance a little excessive for Crew Launch flights?
Answer:
No. It is certainly more than enough to lift the 22mT Orion CEV. But, having the ability to also bring up a further 20mT to 80mT of additional payload creates the option to launch more cargo to space than Shuttle can with every crew. This is an ability the US will completely lose otherwise after Shuttle retires in 2010 because the Ares-I is unable to lift any additional payload at all.
This extra performance can be utilized by the Lunar missions, where the Crew Launch can bring up additional propellant for the Lunar Surface Access Module (LSAM). A two-launch strategy using this technique is capable of placing a 75mT Lunar Lander into Lunar orbit on every manned mission - nearly twice the size of the 38mT lander being planned to fly with the two Ares vehicles.
For ISS flights, the Crew Launch can bring up large quantities of spares, supplies and scientific equipment, all for no extra cost. It could even bring up sections of the ISS which have been cancelled due to the Shuttle's early retirement, such as:
If no additional payload needs to be lifted with an Orion CEV spacecraft, the additional capacity could be utilized to fly a ballistic shield under the spacecraft as an extra layer of safety between the launcher and the crew. Should the worst happen, a 20 ton water tank would absorb a lot of the debris and shockwaves of any catestrophic failure and add to the safety margin of a crew module trying to escape off the top of the booster. Such a water tank shield is demonstrated in our Video of the DIRECT launch.
Further, there is simply no way Ares-I could perform any future servicing missions to the Hubble Space Telescope without launching a "mission module" on a separate launcher first. The Jupiter 120 does have the lift capacity to launch the very heavy cameras and sensor packages which would be required to keep the telescope operating for a long time to come.
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Question: Why do we claim "Safer, Simpler, Sooner" for the DIRECT Architecture?
Answer:
Safer:
For launching crews, Jupiter-120 is safer than Ares-I. According to NASA's standard "Loss of Crew" (LOC) analysis dated 8th November 2007, Ares-I's LOC is 1:1256, which would result in one crew loss event every 314 years at the currently planned flight rate of 4 per year. Jupiter-120's 1:1465 LOC is 16.6% higher and would result in one loss of crew every 366 years. NASA specified in the ESAS Report that anything above 1:1000 would be acceptable for LOC, so we already exceed that requirement by more than 45%.
But that is not the end of the story. There are other factors which are much harder to quantify. Because Jupiter's all have significantly extra launch performance, this allows CEV's to fly with extra safety systems otherwise impossible to fly on Ares-I. Safety systems such as a hardened ballistic shield (weighing tons) can be mounted under the Orion spacecraft. Acting like a bullet-proof vest, this would offer signifcant additional protection to any crew attempting to escape from the launcher in the event of any catestrophic accident during launch.
Further, the launch is only a small part of the overall safety of any mission. With Jupiter's additional lift performance yet more safety system can be included which massively improve safety during the rest of the missions NASA is planning - systems such as radiation shielding for the Crew Module and significant micro-meteroid protection and more redundant/backup systems can be included on the CEV. Ares-I though, is incapable of lifting the extra weight of any of these systems. Jupiter wins hands-down for mission safety.
Having said that, "safety" also applies to program risk reduction too. Being a single LV, Jupiter is a whole lot "safer" in economic terms and in cancellation terms than Ares-I & Ares-V together. By requiring only the J-2XD to be developed "new" and only two new liquid stages (instead of three new engines and four new stages), the "safety" benefits to the schedule is also significant.
And "safety" can also be applied to workforce retention and politically sensitive spending around the nation. Because of it's much closer relationship to the existing STS systems, and because the "gap" is reduced by two years, Jupiter helps to guarantee to preserve the STS workforce far more effectively than Ares-I will, given that Ares-V will not follow for almost 10 years after STS is retired.
Simpler:
Is it simpler to build two new launch vehicles instead of one?
Is it simpler to build an all-new 5-segment SRB instead of retaining the 4-segment SRB's which have a 100% successful flight history of more than190 flights under their belts since they were re-designed following Challenger?
Is it simpler to re-design, re-develop and re-qualify the Apollo J-2S engine, while increasing its power by 26% to get the needed performance for Ares-I's J-2X engine, or simpler to require only a 14% increase in stress levels by only requiring the J-2XD variant?
Is it simpler to require new versions of the RS-68 which must be improved to have 6% more performance and internal stress or to just use the already-flying versions?
Is it simpler to require an all-new SRB-based First Stage and a cryogenic-based Upper Stage for Ares-I or just a single cryogenic stage for Jupiter-120?
Is it then simpler to require two more cryogenic stages (Core and EDS) for Ares-V or just build the EDS and use it on the same vehicle you have already built?
Sooner:
A first manned Orion CEV flight in September 2012 is two years sooner than the current September 2014 plans.
A first manned Lunar Return mission in June 2017 is also two years sooner than the current June 2019 plans.
Possibly even more importantly, having Heavy Lift launch capability to lift 40mT cargo's to orbit in 2012 is a massive improvement over NASA's risky plans today hoping to build the next real Heavy Lift vehicle (Ares-V) seven years later - in 2019.
DIRECT: Safer, Simpler, Sooner.
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Question: NASA has a "rebuttal" to the DIRECT Proposal - What is the story behind that?
Answer:
There is a "rebuttal" to v1.0 of the DIRECT proposal. It was released internally in October 2006 by Phil Sumrall, manager of Advanced Planning in NASA’s Exploration Launch Projects Office at NASA's Marshall Space Flight Center (MSFC) in Huntsville, Ala.
To be precise, it is specifically this document, combined with comments made publicly by Dr. Doug Stanley, head of the Exploration Systems Architecture Study (ESAS) Group, made at the end of 2006 which resulted in our team revising our v1.0 proposal into what we are presenting here as the v2.0 Architecture.
Specifically, Sumrall and Stanley's criticizms of the DIRECT proposal fell into two categories:
- Our criticizm of the Ares-I
- Our choice of a higher performance variant of the RS-68.
To address these two points, we began by largely removing criticizm of the Ares-I. While we do not believe it to be the right path, we do believe the "1-launcher, 2-launch solution" DIRECT Architecture stands head and shoulders above the Ares-I and Ares-V "2-launcher, 2-launch solution" on its own obvious strengths and there is nothing to be gained by our small team joining the growing criticizms already emanating from the majority of the US aerospace industry.
More importantly, almost every one of Sumrall's concerns with the v1.0 DIRECT concept revolved around the single issue that we had baselined a highly-evolved variant of the RS-68 main engine into the v1.0 designs. The specific engine in consideration here was a 435sec vacuum Isp variant of the RS-68 which would have utilized a Regeneratively cooled nozzle specifically optimized for post-SRB separation operations for use on DIRECT. Stanley/Sumrall's data never factored-in the optimized nozzle and instead simply assumed the Sea-Level optimized Regenerative nozzle already planned for the First Stage of the USAF Delta-IV launcher - an engine not optimized for near-vacuum operation, but instead optimized for maximum performance at liftoff. The DIRECT RS-68 variant also assumed a corrected injector/combustion chamber which would fix the existing RS-68 problem regarding LH2 entering the combustion chamber approximately 20 degrees too cold - a problem which reduces efficiency in the existing engines (specifically the C Sub Star portion of the Isp equation) and which was only discovered in the later stages of testing for use on the Delta-IV launcher. It is interesting to note that Pratt & Whitney, Rocketdyne do now believe that 430s vac Isp is possible from such an optimized RS-68, although the development costs are as steep as the J-2X development program. While our reasoning differs from Sumrall, we have still agreed with the fundamental assessment that this engine is not suitable. Our reasoning however is that it would be more difficult (read: expensive) than it really needed to be and thus we have completely deleted this requirement from v2.0 of the DIRECT proposal.
The DIRECT v2.0 proposal has taken this "rebuttal" document and re-worked the architecture to baseline absolutely zero performance upgrades to the existing RS-68 engines as flown on Delta-IV. No re-optimized nozzle, no regenerative cooling, no fixes to the injector/combustion chamber. We are not even using the higher specification engine which NASA is still planning to use for Ares-V. DIRECT's Jupiter launchers do not require the additional 6% increase to existing RS-68 performance (nor the additional stresses) currently baselined for use on the Ares-V.
To explictly head-off any similar complaints with the J-2X engine powering the Jupiter upper stage, we have also baselined to NASA's considerably lower specification J-2X"D" variant with 274,000lb vacuum thrust instead of the 294,000lb vacuum thrust which NASA is today baselining as the minimum requirement for both the Ares-I and Ares-V.
In practice, what this means is that both the main engines and the upper stage engines for all Jupiter vehicles will be safer because they operate at lower stresses. Because they do not need to be operated at such higher pressures they will therefore also be somewhat cheaper to develop and will also take a shorter time to field compared to NASA's equivalent engines for Ares-I and Ares-V. It also means that, although the extra performance is not a requirement, increases to Jupiter's performance are eminently possible at some point in the future - but the extra performance is no longer a hurdle which must be climbed before success is achieved. Such upgrades can simply wait in the wings until NASA has spare cash available at some point in the future and are simply not required to accomplish the ISS and Lunar missions which NASA is currently planning. This approach certainly fits far more neatly with NASA's important strategy regarding "Pay As You Go" instead of being forced to develop all the new, costly, technologies right at the inception of the new Ares program.
We thank both Mr. Sumrall and Dr. Stanley for identifying these concerns with the v1.0 version of our proposal and allowing us the opportunity to fix all of these concerns and thereby improve our v2.0 proposal enormously at the same time.
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Question: What do the people behind DIRECT personally expect to get out of this?
Answer:
As the front-man for this, I Ross Tierney, don't want anything for myself - not even recognition. The work is not mine, I just can't be fired by NASA for speaking out against the current plans, because I don't work for NASA at all. Most of the contributors to this project don't want to be fired for speaking out, so they wish to remain anonymous. Their primary goal is a more robust US space program than currently being planned. They want something which will provide a better return for the massive investment.
Most people don't believe that we are totally benevolent though, so if there has to be a "price"; I certainly don't think anyone involved would turn down VIP tickets to go watch the first manned launch of a Jupiter launch vehicle. So I will set 50 such tickets as a "fair price" for the work we have done to put this proposal together. Any takers?
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