Northrop says Air Force design changes drove higher Sentinel ICBM cost

A Northrop Grumman official on Monday attributed the explosive projected cost growth of the U.S. Air Force’s next intercontinental ballistic missile to the service’s design changes, including to the nuclear missile’s silo and connecting cables.

The Air Force’s original plan for modernizing its ICBM enterprise included keeping nearly all its existing copper cabling in place to be reused for the upcoming LGM-35A Sentinel. That’s roughly 7,500 miles’ worth of copper cabling, connecting 450 half-century-old Minuteman III ICBM silos scattered through the Great Plains region with launch control centers and other facilities.

But the company official, who spoke with reporters on the condition that he be identified only as an official familiar with the Sentinel program, said the Air Force concluded it is necessary to upgrade the copper cables with a higher-performing fiber-optic network. That decision apparently came after the service awarded the engineering and manufacturing development contract to Northrop Grumman in 2020, and during the company’s work on the program’s early design phase.

The Air Force also realized that the original designs for Sentinel’s launch facilities — the massive concrete-encased silos from which the missiles would launch — would not work and had to be changed, the Northrop official said. Those original concepts were drawn up during the technology maturation and risk-reduction phase as well as the early engineering and manufacturing development step.

And with hundreds of launch facilities dotting the Great Plains region, often in 1-acre plots, and thousands of miles of cable stretching across farmland and other privately held property that now must be dug up, the cost of these changes swiftly added up, the Northrop official said.

“As we’ve worked through those changes. That’s led to a design that’s different than the one that they [the Air Force] started with,” the official explained. “When you multiply that by 450, if every silo is a little bit bigger or has an extra component, that actually drives a lot of cost because of the sheer number of them that are being updated.”

In a statement to Defense News, the Air Force said the Pentagon is still studying what exactly caused the severe cost overruns, which triggered a review process known as a critical Nunn-McCurdy breach .

“In accordance with statute, [the Office of the Secretary of Defense] will determine what factors caused the cost growth that led to a critical breach via the Nunn-McCurdy process, which is currently underway,” an Air Force spokesperson said. “Early estimates indicate that a large portion of the Sentinel program’s cost growth is in the command and launch segment, which is the most complex segment of the Sentinel program.”

‘Unknown unknowns’ on $96B program

Sentinel is a massive program to replace the Air Force’s aging LGM-30G Minuteman III ICBMs, which now make up the land-based portion of the U.S. military’s nuclear triad. In 2020, Northrop Grumman received a $13.3 billion cost-plus-incentive-fee contract for Sentinel’s engineering and manufacturing development phase.

The program was expected to run about $96 billion, with the total per-unit cost amounting to $118 million when its most recent cost, schedule and performance goals were set in 2020. But the price tag has skyrocketed at least 37%, and the per-unit cost is now about $162 million.

In a congressional hearing this month, Rep. John Garamendi, D-Calif., pegged Sentinel’s current cost at more than $130 billion.

That triggered the Nunn-McCurdy breach, and the Pentagon is now reviewing Sentinel to figure out how to get it back on track as well as where to find funds to keep it going. Top Air Force officials have publicly said that with Minuteman III well past its originally expected life span, the service has no choice but to replace it with a new, more reliable model — and will find money to pay for it.

Sentinel, which was originally supposed to reach initial operational capability in 2029, is now expected to fall two years behind schedule. The nuclear missile’s first flight test, which had been expected to take place in fiscal 2024, is now likely to come in February 2026, according to the Air Force’s budget documents.

The Air Force said in an email to Defense News that the Sentinel’s first flight was pushed back due to longer lead times for components in its guidance computer. But the delayed flight test is not a factor in the program’s Nunn-McCurdy breach, the service said.

In a March hearing held by the House Armed Services Committee’s sea power and projection forces panel, Garamendi voiced his displeasure to Air Force officials over the Sentinel’s cost overruns, as well as the service’s inability to explain potential “trade-offs” to keep the program alive.

Garamendi questioned the need for the United States to spend vast sums of money on Sentinel, arguing the belief that the nation must maintain a triad of nuclear weapons has become a “religious issue, having very little to do with the world in which we’re now living.”

The Northrop Grumman official told reporters Monday that the company’s work on Sentinel continues, despite the Nunn-McCurdy breach and ensuing review process.

“We don’t have a pause on our EMD [engineering and manufacturing development] work,” the official said. “We’re continuing to make progress on developing the missile and iterating the designs for all the facilities.”

Airmen connect the forward shroud to the aft shroud of the reentry system for the Minuteman III weapon at a launch facility in Colorado on Feb. 12, 2024. (Senior Airman Sarah Post/U.S. Air Force)

In a discussion last fall, Air Force Secretary Frank Kendall said given it’s been so long since the service created an ICBM, early cost estimates for Sentinel were based on “a huge uncertainty.”

“There are unknown unknowns that are surfacing, that are affecting the program,” Kendall said during a November 2023 event with Center for a New American Security think tank. Kendall also said the Sentinel program was “struggling.”

The Northrop Grumman official highlighted such comments — including Kendall’s about the uncertainty that went into the program’s cost estimates — and said some estimates that went into the 2020 baseline review turned out to be incorrect.

Northrop also said the company’s effort to game out how a conversion process might work also showed problems with the original plan.

Before it received the Sentinel contract in September 2020, the firm started building a full-scale mock-up of a Minuteman III silo in Promontory, Utah, which it completed in spring 2021. The project was a major undertaking, and on Northrop Grumman’s dime. But the company saw it as a worthwhile investment in its bid to win the lucrative Ground Based Strategic Deterrent contract, as the program was then known.

Northrop didn’t have direct access to the Minuteman III silos — and likely won’t until the government hands them over for conversion into Sentinel silos — since the missiles must remain ready for launch at all times. And so the company considered its construction project the best way to understand how the massive retrofitting process might work — and to find where the biggest risks might lie.

The company’s team, alongside the Air Force, pored through the nonoperational mock-up and started to lay out components akin to what Sentinel would require. But as they did so, the Northrop official said, the group found some of the original conversion plans weren’t going to work.

Other design processes, including computer-aided design work, also helped the Sentinel team map out how much square footage various configurations would take up. In the process, some of the unknown factors that led to the original shaky estimates were cleared up. Still, it became clearer that the costs would be much higher than originally believed.

“They learned, along with us, things that needed to be potentially different or changed from the design,” the official said.

Five programs in one

In January, top Air Force official Kristyn Jones compared the Sentinel project to five major acquisition programs rolled into one. But the nuclear missile itself “is not an area of concern,” said Jones, who is performing the duties of undersecretary of the Air Force.

The Northrop official said the Sentinel missile will not just be a new iteration of the Minuteman series of ICBMs — “it’s not a Minuteman IV,” the official said — but a brand-new weapon top to bottom.

Its solid-rocket motors will be made of composite materials instead of the steel used on the Minuteman III, he explained, and it will have a more advanced guidance system.

Its design also includes modular components that allow the Air Force and Northrop Grumman to more easily add new technology as it becomes available.

And airmen are expected to be able to more easily maintain the Sentinel than its predecessor, with key components accessible without the need to delve too deeply into the missile and bring along a massive security detail while it is opened up.

Maintenance personnel with the 321st Strategic Missile Wing guide the reentry system for an LGM-30 Minuteman III missile onto a missile guidance set in 1990. (U.S. Air Force)

Sentinel will be slightly larger and lighter than the Minuteman III, which will allow it to carry more propellant and payload, he said. And it is being designed to last until at least 2075 — far longer than the decade Minuteman III was originally supposed to last.

The infrastructure for Sentinel — including the silos themselves, the launch control centers where airmen control the ICBMs, and supporting infrastructure — will also be refurbished.

That portion — which Jones called “essentially a civil works program” — is especially challenging, particularly with issues such as inflation, the supply chain and labor force shortages.

The service and Northrop Grumman plan to reuse the existing Minuteman III silos as much as possible. But that will require a great deal of new construction and equipment updates to ensure the Sentinel silos can keep operating through disruptions such as power outages.

Old computers in launch centers — some of them 1980s-era terminals with green screens — will receive updates with modern equipment.

But not all Minuteman III silos were built in the same configuration, the Northrop official said, which will further complicate their conversions.

With the nation’s roughly 400 Minuteman IIIs spread out across nearly 32,000 square miles in Wyoming, Montana, North Dakota, Colorado and Nebraska, that makes the Sentinel program a massive real estate project, requiring the government to negotiate easements and, in some cases, property purchases with numerous landowners.

All of that adds up to “one of the most large, complex programs I’ve ever seen,” Kendall said of Sentinel in November 2023. “It’s probably the biggest thing, in some ways, that the Air Force has ever taken on.”

There’s also another factor at play: What happens if the Air Force and Northrop Grumman look deeper within the existing Minuteman III silos and find they’re in worse shape than expected?

The condition of the silos is a potentially high-risk area for the program, the Northrop official acknowledged, but the program still expects to be able to reuse existing ones. A “handful” of LiDAR — or light detection and ranging — scans of current ICBM sites already took place, he said, and there have been reviews of silos decommissioned in the 2000s.

But deeper, destructive testing — “breaking apart the concrete to see what’s behind it and what the conditions are” — has not occurred on existing silos, the official said, since they have to remain operational.

Minuteman III silos have concrete liners as well as mechanical launch tubes and missile suspension systems that hold the current ICBMs. The tubes and suspension systems will be replaced, the official said, and the concrete liners underneath will undergo inspection to determine if repairs need done and what is reusable.

The government has contingency plans if the silos’ foundations prove to be seriously cracked or damaged, the official said. That could include remediation work such as patching cracks or replacing portions of the concrete.

If a site is too far gone to fix, however, drilling may have to take place for an entirely new silo.

“There’s currently no plan to dig new holes,” the official said. “But given the site conditions of the land, [there is] certainly the potential that when they get to investigating more of the silos, they may find that [reusing] some of them might not be possible.”

Though the Nunn-McCurdy review process is still underway, the Northrop official said the company is talking to the Air Force about ways to bring down costs. One idea under discussion, he noted, is potentially changing the way mechanical rooms are constructed to build them in a more modular way, which could lower expenses.

But no matter how difficult or expensive Sentinel becomes, or what trade-offs are made to pay for it, the Air Force is adamant it must happen.

Lt. Gen. Richard Moore, the service’s deputy chief of staff for plans and programs, said at the January appearance alongside Jones that extending the Minuteman III missile significantly longer is “not a viable option.”

“We will find the money,” Moore said. “Sentinel is going to be funded. We’ll make the trades to make that happen.”

Stephen Losey is the air warfare reporter for Defense News. He previously covered leadership and personnel issues at Air Force Times, and the Pentagon, special operations and air warfare at Military.com. He has traveled to the Middle East to cover U.S. Air Force operations.

周一，诺斯罗普·格鲁曼公司的一位官员将美国空军下一代洲际弹道导弹预计成本的爆炸性增长归因于该军种的设计变更，包括核导弹发射井和连接电缆的变更。

空军最初的洲际弹道导弹现代化计划包括保留几乎所有现有的铜缆，以便为即将推出的LGM-35A“哨兵”导弹系统重复使用。这些铜缆总长约7500英里，连接着散布在大平原地区的450个已有半个世纪历史的“民兵III”型洲际弹道导弹发射井与发射控制中心和其他设施。

但一位不愿透露姓名的公司官员在接受记者采访时表示，空军认为有必要用性能更高的光纤网络升级现有的铜缆，以取代“哨兵”计划。这位官员要求仅透露其熟悉“哨兵”计划的情况。显然，这一决定是在空军于2020年将工程和制造开发合同授予诺斯罗普·格鲁曼公司之后，以及该公司参与该计划早期设计阶段期间做出的。

诺斯罗普公司的一位官员表示，空军也意识到“哨兵”导弹发射设施的最初设计——即导弹发射所用的巨型混凝土筒仓——行不通，必须进行修改。这些最初的概念是在技术成熟和风险降低阶段以及早期工程和制造开发阶段制定的。

诺斯罗普公司的一位官员表示，大平原地区遍布数百个发射设施，通常占地 1 英亩，数千英里的电缆横跨农田和其他私人土地，现在必须将其挖开，这些变更的成本迅速增加。

“随着我们不断进行这些修改，最终的设计方案与他们（空军）最初的方案有所不同，”这位官员解释说。“如果每个发射井都比原来的大一些或者多一个部件，那么乘以450，由于需要升级的发射井数量庞大，成本就会大幅增加。”

空军在向《防务新闻》发表的声明中表示，五角大楼仍在调查究竟是什么原因导致了严重的成本超支，这引发了一项被称为“关键的纳恩-麦克柯迪违规”的审查程序。

空军发言人表示：“根据相关法规，国防部长办公室将通过目前正在进行的纳恩-麦克柯迪程序，确定导致成本增长并最终造成重大违约的因素。初步估计表明，哨兵导弹计划成本增长的大部分都集中在指挥和发射环节，而这正是哨兵导弹计划中最复杂的环节。”

960亿美元计划中的“未知未知因素”

“哨兵”导弹系统是一项庞大的计划，旨在替换美国空军老旧的LGM-30G“民兵III”洲际弹道导弹，这些导弹目前构成了美国军方核三位一体陆基部分。2020年，诺斯罗普·格鲁曼公司获得了一份价值133亿美元的成本加激励费用合同，用于“哨兵”导弹系统的工程和制造开发阶段。

该项目预计耗资约 960 亿美元，在 2020 年设定的最新成本、进度和性能目标中，单位总成本为 1.18 亿美元。但成本至少飙升了 37%，单位成本现在约为 1.62 亿美元。

在本月的一次国会听证会上，加州民主党众议员约翰·加拉门迪估计，Sentinel 目前的造价超过 1300 亿美元。

这引发了纳恩-麦克柯迪协议漏洞，五角大楼目前正在审查“哨兵”导弹系统，以确定如何使其重回正轨以及如何筹集资金维持其运行。空军高层官员已公开表示，“民兵III”导弹系统早已超过其最初预期的使用寿命，空军别无选择，只能用一种新的、更可靠的型号来取代它——并且会找到资金来支付这笔费用。

“哨兵”导弹原计划于2029年达到初始作战能力，现在预计将比原计划晚两年。根据空军预算文件，该核导弹的首次飞行测试原计划在2024财年进行，现在可能要等到2026年2月。

美国空军在发给《防务新闻》的一封电子邮件中表示，“哨兵”无人机的首飞被推迟，原因是其制导计算机部件的交付周期较长。但空军方面表示，此次飞行测试的延误并非导致该项目违反纳恩-麦克柯迪协议的原因。

在众议院军事委员会海权和投送部队小组 3 月份举行的一次听证会上，加拉门迪向空军官员表达了他对“哨兵”导弹系统成本超支的不满，以及空军无法解释为维持该项目而可能做出的“权衡取舍”。

加拉门迪质疑美国是否有必要在“哨兵”系统上花费巨资，他认为，国家必须维持三位一体核武器的信念已经变成了一个“宗教问题，与我们现在生活的世界几乎没有任何关系”。

诺斯罗普·格鲁曼公司的一位官员周一告诉记者，尽管发生了 Nunn-McCurdy 泄密事件以及随后的审查程序，但该公司对 Sentinel 的工作仍在继续。

“我们的工程和制造开发工作并未暂停，”这位官员表示。“我们正在继续推进导弹的研发工作，并不断改进所有设施的设计。”

2024年2月12日，在科罗拉多州的一个发射场，空军人员正在将“民兵III”型导弹再入系统的前整流罩与后整流罩连接起来。（美国空军高级飞行员莎拉·波斯特摄）

去年秋天的一次讨论中，空军部长弗兰克·肯德尔表示，鉴于空军已经很久没有制造洲际弹道导弹了，哨兵导弹的早期成本估算是基于“巨大的不确定性”。

肯德尔在2023年11月与新美国安全中心智库举行的一次活动中表示：“一些未知的未知因素正在浮出水面，影响着该项目。”肯德尔还表示，“哨兵”项目“举步维艰”。

诺斯罗普·格鲁曼公司的一位官员强调了这些评论——包括肯德尔关于该项目成本估算存在不确定性的评论——并表示，2020 年基线审查中的一些估算结果被证明是错误的。

诺斯罗普还表示，该公司对转换过程可能如何运作进行推演的努力也表明，最初的计划存在问题。

在2020年9月获得“哨兵”（Sentinel）导弹系统合同之前，该公司开始在犹他州普罗蒙特里建造一个“民兵III”（Minuteman III）导弹发射井的全尺寸模型，并于2021年春季完工。该项目规模庞大，由诺斯罗普·格鲁曼公司出资。但该公司认为，为了赢得当时名为“陆基战略威慑”（Ground Based Strategic Deterrent）的利润丰厚的合同，这是一项值得的投资。

诺斯罗普公司无法直接接触“民兵III”导弹发射井——而且在政府将其移交给诺斯罗普公司进行改造为“哨兵”导弹发射井之前，可能也无法接触——因为这些导弹必须时刻保持发射准备状态。因此，该公司认为其建设项目是了解大规模改造流程运作方式以及找出最大风险所在的最佳途径。

该公司团队与空军密切合作，仔细研究了非作战模型，并开始设计类似于“哨兵”导弹系统所需组件的方案。但诺斯罗普公司的一位官员表示，在研究过程中，他们发现一些最初的改装方案行不通。

其他设计流程，包括计算机辅助设计，也帮助Sentinel团队估算出各种配置方案所需的面积。在此过程中，一些导致最初估算不准的未知因素也得到了澄清。尽管如此，成本远高于最初预估的程度这一点也变得更加清晰。

这位官员说：“他们和我们一起了解到，设计中有些东西可能需要做出改变或调整。”

五合一程序

今年1月，空军高级官员克里斯汀·琼斯将“哨兵”导弹项目比作五个大型采购项目合并为一个。但代理空军副部长职务的琼斯表示，核导弹本身“并非令人担忧的领域”。

诺斯罗普公司的一位官员表示，“哨兵”导弹不仅仅是“民兵”系列洲际弹道导弹的新版本——“它不是‘民兵 IV’，”这位官员说——而是一种从上到下全新的武器。

他解释说，它的固体火箭发动机将采用复合材料而不是民兵 III 型火箭使用的钢材制成，并且它将拥有更先进的制导系统。

它的设计还包括模块化组件，使美国空军和诺斯罗普·格鲁曼公司能够随着新技术的出现而更轻松地添加新技术。

预计空军人员将能够比维护其前身更容易地维护“哨兵”导弹，关键部件无需深入导弹内部，也无需在打开导弹时携带大量安保人员即可接触到。

1990年，第321战略导弹联队的维护人员正在引导LGM-30“民兵III”型导弹的再入系统对准导弹制导装置。（美国空军）

他说，“哨兵”导弹的尺寸和重量将略大于“民兵3”导弹，这将使其能够携带更多的推进剂和有效载荷。而且，“哨兵”导弹的设计寿命至少到2075年——远远超过“民兵3”导弹最初预计的十年寿命。

“哨兵”导弹系统的基础设施——包括发射井本身、空军人员控制洲际弹道导弹的发射控制中心以及配套基础设施——也将进行翻新。

琼斯称这部分“本质上是一个土木工程项目”，这部分尤其具有挑战性，特别是考虑到通货膨胀、供应链和劳动力短缺等问题。

美国军方和诺斯罗普·格鲁曼公司计划尽可能地重复利用现有的民兵III型导弹发射井。但这需要大量的新建工程和设备升级，以确保哨兵导弹发射井在诸如停电等中断情况下仍能持续运行。

发射中心的旧电脑——其中一些是 20 世纪 80 年代的带有绿色屏幕的终端——将通过现代化设备进行升级。

但诺斯罗普公司的一位官员表示，并非所有民兵 III 型导弹发射井都是按照相同的配置建造的，这将进一步增加改造的复杂性。

全国大约有 400 台 Minuteman III 型导弹系统部署在怀俄明州、蒙大拿州、北达科他州、科罗拉多州和内布拉斯加州近 32,000 平方英里的土地上，这使得 Sentinel 计划成为一个庞大的房地产项目，需要政府与众多土地所有者协商地役权，在某些情况下还需要进行土地购买。

肯德尔在2023年11月谈到“哨兵”项目时说：“所有这些加起来，使其成为我见过的规模最大、最复杂的项目之一。从某种意义上说，这可能是空军有史以来承担的最大项目。”

还有另一个因素在起作用：如果空军和诺斯罗普·格鲁曼公司深入检查现有的民兵 III 导弹发射井，发现它们的状况比预期的更糟，那会发生什么？

诺斯罗普公司的一位官员承认，导弹发射井的状况对该项目而言是一个潜在的高风险领域，但该项目仍然希望能够重新利用现有的发射井。他表示，目前已经对一些现有的洲际弹道导弹发射井进行了激光雷达（LiDAR）扫描，并且也对2000年代退役的发射井进行了审查。

但这位官员表示，由于现有筒仓必须保持运行状态，因此尚未对其进行更深入、更具破坏性的测试——“打破混凝土以查看其后面是什么以及情况如何”。

“民兵III”型导弹发射井内衬有混凝土衬里，并设有机械发射管和导弹悬挂系统，用于存放现有的洲际弹道导弹。这位官员表示，发射管和悬挂系统将被更换，下方的混凝土衬里也将接受检查，以确定是否需要维修以及哪些部分可以重复使用。

这位官员表示，如果筒仓地基出现严重裂缝或损坏，政府已制定应急预案。预案可能包括修补裂缝或更换部分混凝土等修复工作。

然而，如果场地损毁严重无法修复，则可能需要钻探建造一个全新的筒仓。

“目前没有挖掘新坑的计划，”这位官员说。“但考虑到场地条件，当他们进一步调查筒仓时，可能会发现其中一些筒仓可能无法再利用。”

尽管努恩-麦克柯迪审查程序仍在进行中，但诺斯罗普公司的一位官员表示，该公司正在与空军商讨降低成本的途径。他指出，正在讨论的一个方案是改变机械室的建造方式，采用更模块化的设计，这有望降低成本。

但无论“哨兵”系统变得多么困难或昂贵，或者为了支付其费用而做出怎样的权衡，空军都坚决认为它必须实现。

海军计划与项目副参谋长理查德·摩尔中将在 1 月份与琼斯一同出席活动时表示，大幅延长民兵 III 型导弹的寿命“并非一个可行的选择”。

“我们会找到资金的，”摩尔说。“哨兵计划一定会得到资金支持。我们会进行必要的交易来实现这一点。”

斯蒂芬·洛西是《防务新闻》的空战记者。他此前曾在《空军时报》报道领导层和人事问题，并在Military.com网站报道五角大楼、特种作战和空战。他曾前往中东报道美国空军的行动。